Why does my main house consumer unit trip when the inverter switched to AC backup?

Hello All

Can I say to start with I am not an electrician but used to be a heating engineer (yes I can hear the groans). I have wired the installation myself using the correct wiring and isolators, racking and trunking and it is not grid tied it is purely off grid with a separate input for a backup supply from a generator or the grid. The system does not feed back to the grid and when the mains is disconnected the system isolates the ac input internally in the cabinet with relays

In my solar setup I have a purpose built cabinet containing all protective devices, with isolators and an Axpert MKS V4 5.5kw inverter. The kit is housed in a fireproof cupboard outside the house. The unit is supposed to be a plug and play with 2 x us5000 pylontech batteries beneath the cabinet connected in parallel into the main input on the cabinet as well as AC input and AC outputs on the side of the cabinet. The PV goes into the cabinet and then into the appropriate connections fitted to the cabinet I have separate isolators external to the cabinet for both PV and AC and the supply for the AC backup in, runs off of a 32 amp line from the consumer unit.

The issue at present is that the main breaker in the house trips when the inverter switches over to utility to charge the batteries over night. The 32 amp m.c.b does not trip but the main isolator to the board does, I think it is an RDC isolator main switch ( I have attached a pic) The cabinet has a soft start relay for a generator but as the supply is from the mains the relay becomes active as soon as an AC supply is applied to the inlet socket.

Is there a device I could add to the line in before the solar cabinet and on the supply from the consumer unit in my house that would stop what seems to be a surge when the inverter calls for AC power.

My setup is that I have a separate solar supply to my house hold appliances via a new consumer unit next to the cabinet and then separate cabling to all outlets in the house.

I am trying to have a system where I power all of my regularly used stuff from the batteries and solar panels in the day and then just use the AC into the house as a way to supplement additional power to keep the batteries fully charged with cheap rate overnight electricity. At this time of year the solar gain will be fairly low, I am in the U.K.

Any suggestions would be welcome. I am new to solar and am finding my way albeit slowly.

Regards and thanks Tonyboy

A couple of possible causes:

• You have some sort of N-E fault in your installation and it is only on-inverter that enough difference is present to cause enough current imbalance (N not matching L) to trip things.
• You have something else fundamentally wrong with the inverter or its wiring (N not earthed when running, or L & N swapped wihch is very bad)
• It is simply the act of bringing the supply on quickly that trips the RCD. This is quite likely if it is a 30mA device for the whole installation. If you switch the mains AC on and off via the isolator switch (RCD on and ready to go, not enabling inverter at all) does it also trip? If so its down to the arrangement you have.

Just to add, a diagram would make it a lot clearer as to how things are wired up!

pc1966 said:

A couple of possible causes:

• You have some sort of N-E fault in your installation and it is only on-inverter that enough difference is present to cause enough current imbalance (N not matching L) to trip things.
• You have something else fundamentally wrong with the inverter or its wiring (N not earthed when running, or L & N swapped wihch is very bad)
• It is simply the act of bringing the supply on quickly that trips the RCD. This is quite likely if it is a 30mA device for the whole installation. If you switch the mains AC on and off via the isolator switch (RCD on and ready to go, not enabling inverter at all) does it also trip? If so its down to the arrangement you have.

Click to expand...

Hi pc1966
I am currently working through a number of tests to see what particular combination is causing the problem. This afternoon I set the inverter to u.s.b and set the time for utility to come on while I was standing next to it. I had turned off the p.v. isolator and when the inverter switched over it started charging the batteries with the 10 amp limit I have set. Tomorrow it is supposed to be sunny so I am going to seen if the P.V. on its own charges the system with no issue. I will leave the AC isolated completely.
I have turned the AC supply on and off a few times with the inverter not enabled and it did not trip, I will try it again tomorrow with the PV both on and off as well as with the inverter enabled and the pv on and off to see if there is something that sets it off in particular.

I should mention I had an F12 fault occur last week and it is a dc.dc overcurrent fault. The suppliers wants it back at my cost and says it is an mppt issue. I want to see if this is the case before I spend money getting a brand new inverter checked and probably charged for the privilege.
Initially I was concerned it was something to do with the pv. array being earthed to the battery earth and the ground rod so I disconnected the cable from the arrays to see if this solved the problem but it returned this morning when both ac and pv were connected to the inverter. Albeit the AC was the charging priority. Funnily enough though when the pv arrays were earthed to the ground rod the inverter never tripped the house at all. The only issue was when the earth was connected, the pv voltage measured at the connection to the cabinet went from 250v dc to380v dc and it was sufficiently close to the max pv input of 500 v to make me remove the earth cable, I wondered if the mppt was pulling voltage as a result of the earth connection in some sort of loop?
I will add more details when I have done some more tests.
This is from the suppliers site re the cabinet. I am not sure if this will conflict with my home system.
The unit is ready for direct connection to a back up source such as a diesel generator or the grid. The AC loads are connected a fully protected AC output plug , there is one 30mA 40A, RCD and MCB with TN-S earthing arrangement (common Neutral to Ground).
Thanks for taking the time to reply to my initial post I do appreciate it.
Regards

Tonyboy

pc1966 said:

Just to add, a diagram would make it a lot clearer as to how things are wired up!

Click to expand...

Just got this pc1966 I will sort out a drawing tomorrow hopefully, regards

Tonyboy

What does the inverter manufacturer say about supply RCD protection?

You would be well advised to clamp the tails supplying the board that trips with an ammeter that can resolve mA to see what leakage is present before and after the inverter is running. If it is above 10mA then tripping is quite likely (as "30mA" are specified to trip below 30mA but above 15mA)

This bit:

Funnily enough though when the pv arrays were earthed to the ground rod the inverter never tripped the house at all. The only issue was when the earth was connected, the pv voltage measured at the connection to the cabinet went from 250v dc to380v dc and it was sufficiently close to the max pv input of 500 v to make me remove the earth cable

Really does not look good! For a start, if you have an independent supply you must have an independent means of earthing! You cannot rely on the DNO still being connected during any outage. Also is it not the inverter that gets earthed, and the array of PV pannels is floating so it can check the insulation resistance? (at least a friend who has an ABB inverter works that way) Again, what does the manufacturer say?

Also 380V is nowhere near a 500V limit! I would expect an over-voltage error from the inverter if it were the case.

pc1966 said:

What does the inverter manufacturer say about supply RCD protection?

You would be well advised to clamp the tails supplying the board that trips with an ammeter that can resolve mA to see what leakage is present before and after the inverter is running. If it is above 10mA then tripping is quite likely (as "30mA" are specified to trip below 30mA but above 15mA)

This bit:

Funnily enough though when the pv arrays were earthed to the ground rod the inverter never tripped the house at all. The only issue was when the earth was connected, the pv voltage measured at the connection to the cabinet went from 250v dc to380v dc and it was sufficiently close to the max pv input of 500 v to make me remove the earth cable

Really does not look good! For a start, if you have an independent supply you must have an independent means of earthing! You cannot rely on the DNO still being connected during any outage. Again, what does the manufacturer say?

Also 380V is nowhere near a 500V limit! I would expect an over-voltage error from the inverter if it were the case.

Click to expand...

Hi pc1966
I will have to look into an ammeter to clamp the tails, I don't have one of them at present.
Re the earth, the batteries are connected to the earth rod next to the cupboard with 25 mm cables and I ran a separate 6mm from the roof to the earth rod to protect the arrays from lightning etc. The cabinet has its own surge protection on both the in and output of the ac and the pv but I have no information from the supplier regarding what earthing arrangement to apply to the cabinet. I initially ran 6 mm earth from both the arrays and from the metal cabinet and they all terminated on the 6ft earth rod installed adjacent the cupboard. This was tested and was 0.003 ohms if I recall correctly.
My concern was that the cabinet being wired as as TN-S adding an additional earth path may in some way cause an issue with the inverter and its wiring. This may well be completely unfounded so I am more than happy to be proved wrong on that. The voltage did spike a couple of time near to 480v on the pv supply input and I did notice when the earth from the array was disconnected it went back down to 258V or there about.
It was suggested that the whole of the system was best to be connected to earth via the Battery earth and therefore I had assumed this would also be accounted for in the way the whole cabinet was wired.
Does connecting additional earth cable to the chassis of the cabinet and to the earth input of the solar pv cause any kind of issue with the separation of the electrical side of things and the mechanical side of earth bonding the arrays and frames?
Many thanks and regards

Tonyboy

pc1966 said:

What does the inverter manufacturer say about supply RCD protection?

You would be well advised to clamp the tails supplying the board that trips with an ammeter that can resolve mA to see what leakage is present before and after the inverter is running. If it is above 10mA then tripping is quite likely (as "30mA" are specified to trip below 30mA but above 15mA)

This bit:

Funnily enough though when the pv arrays were earthed to the ground rod the inverter never tripped the house at all. The only issue was when the earth was connected, the pv voltage measured at the connection to the cabinet went from 250v dc to380v dc and it was sufficiently close to the max pv input of 500 v to make me remove the earth cable

Really does not look good! For a start, if you have an independent supply you must have an independent means of earthing! You cannot rely on the DNO still being connected during any outage. Also is it not the inverter that gets earthed, and the array of PV pannels is floating so it can check the insulation resistance? (at least a friend who has an ABB inverter works that way) Again, what does the manufacturer say?

Also 380V is nowhere near a 500V limit! I would expect an over-voltage error from the inverter if it were the case.

Click to expand...

Hi pc1966
I have done a rudimentary drawing showing my system overview, I hope it is sort of self explanatory.
I did have the earth connected from the bus bar to the earth rod but with it connected the voltage at the pv input in the cabinet was up to 450 + volts. since disconnecting it the reading is 252 v with the inverter off, and 350 to 400 with it on. I considered adding an earth from the consumer unit serving the house to the ground rod as this would then protect all of the house appliances and I was considering adding an earth to the cabinet as well as adding back the pv earth all to the ground rod.
I wondered if it was better to earth the pv rails and panels to a separate rod in a different part of the garden a fair bit away from the house so that this was not connected to either the battery earth or the ac earth to the consumer unit.
Currently I am trying to get information from the supplier but it is quite difficult, I had expected to receive a wiring diagram or at least a sheet showing the test results before the item was shipped but at present that has not been forthcoming either. If you have any suggestions please feel free to let me know. I want the installation to be safe and I am not using it to power the house at present so it is only running to test the p.v. charging and the a.c. charging.
Adding more ground rods and cable are relatively easy and would be better if that is what is needed.
Hopefully you can view the picture, many thanks and regards Tony

Please could you clarify the bit in bold in:

. The AC loads are connected a fully protected AC output plug , there is one 30mA 40A, RCD and MCB with TN-S earthing arrangement (common Neutral to Ground).

On the inverter load side including what you may have connected to it have you connected the Neutral and Ground/Earth together? This would be wrong to do if you are going to connect the inverter to the mains supply which already makes the N-E connection at or before your home's main fuse.

When the inverter output is supplied by the mains input, the presence of an inverter output N-E link after the house RCD, creates an alternative path for the neutral current to flow which is detected by the house RCD as a leakage of current to earth - so it trips.

marconi said:

Please could you clarify the bit in bold in:

. The AC loads are connected a fully protected AC output plug , there is one 30mA 40A, RCD and MCB with TN-S earthing arrangement (common Neutral to Ground).

On the inverter load side including what you may have connected to it have you connected the Neutral and Ground/Earth together? This would be wrong to do if you are going to connect the inverter to the mains supply which already makes the N-E connection at or before your home's main fuse.

When the inverter output is supplied by the mains input, the presence of an inverter output N-E link after the house RCD, creates an alternative path for the neutral current to flow which is detected by the house RCD as a leakage of current to earth - so it trips.

Click to expand...

Hello Marconi and thanks for the reply

The whole kit is in a purpose built cabinet, and the input and output are on the side of the cabinet with waterproof sockets. The main ac supply is via an isolator switch I installed outside of the cabinet at the end of swa cable and before the input socket, this is from a 32 amp mcb line from the consumer unit in the house.

The output of the cabinet goes to my separate consumer unit for the solar supplied sockets in my house. I have the line neutral and earth connected to the consumer unit and into MCB's and none of them are joined together. I was also going to be adding an earth from the consumer unit (solar) to the ground rod I have installed adjacent to the cupboard the unit is installed in, from the solar consumer unit so that in the event the dno power is cut off (which switches off and isolates the ac to the cabinet) I have a separate earth path as the dno's earth would effectively be removed also.
I am therefore assuming the output of the inverters AC arrangement in the cabinet is where the TN-S arrangement is carried out leaving the supply to be connected straight to the consumer unit (solar) in the manner I have described.
I have read a re read the description of the earthing arrangement (in bold) in the cabinet and can not see any other explanation for the assumption I have made.
That said I am at bit of a loss as to how I can get over this without having a separate small consumer unit fitted next to my current home mains unit with an mbc of 32 amp and then taking the supply to the cabinet from this.
Is that the only solution or is there a way to negate the issue by connecting the supply in a different way?
many thanks for taking the time to reply.

Regards Tonyboy

Have you an Ohmmeter/multimeter? Do know how to use it to measure resistance?

What disconnects the installation from the DNO supply when the inverter is connected?

Is this the boxed system you have or something similar?

davesparks said:

What disconnects the installation from the DNO supply when the inverter is connected?

Click to expand...

That was what I was asking about yesterday when I asked about relays and isolation. But I posted it in the wrong thread! Doh

marconi said:

Is this the boxed system you have or something similar?

Click to expand...

Hi Marconi and davesparks

Yes the cabinet is similar to the one in the picture, it is from the same people. It is connected to the mains via a side input and in the event the power goes of the soft start relay cuts off the power to the inverter. I disconnect it from the mains manually if I don't want utility power to provide any input but it can be left on and it comes in when the timer is set to use utility.
The battery will still supply power to the solar consumer unit via the inverter when it is set to in the program but it cannot go back to the main supply as this either disconnects when the power goes off, and as the output from the inverter only goes to the solar output consumer unit
In terms of it disconnecting from the main supply in normal use I think the supply side stays connected but not used and it only powers the inverter when the timer calls for ac from the ac input.
Yes I have a multi meter I used it to check the resistance of the earth cable to the rod when I installed that.
Tell me more please!
regards

Tonyboy

The switching inside the inverter box is normally done by solid state switches to ensure no-break of supply when moving between mains to output or inverter to output.

Tonyboy - where have you happened upon the term TN-S? I suspect what you have bought or set up is an off grid systemwith genie back up to the inverter mains input. This would require the inverter output to be made tn-s in order for automatic disconnection of the inverter supply to the output socket in the event of an earth fault. This would be done on the inverter output. For uk mains input in lieu of genie one cannot link the output N with Cpc/earth/pe for the reason I mentioned earlier.

marconi said:

The switching inside the inverter box is normally done by solid state switches to ensure no-break of supply when moving between mains to output or inverter to output.

Tonyboy - where have you happened upon the term TN-S? I suspect what you have bought or set up is an off grid input with genie back up to the inverter mains input. This would require the inverter output to be made tn-s in order for automatic disconnection of the inverter supply to the output socket in the event of an earth fault. This would be done on the inverter output. For uk mains input in lieu of genie one cannot link the output N with Cpc/earth/pe for the reason I mentioned earlier.

Click to expand...

Hi Marconi
The description of the inverter outputs says it has a TN-S arrangement and when I purchased it I was told it was suitable to connect the mains as a standby/ additional source of charging power for overnight cheap rate electric.
It is indeed an off grid solar supplied unit with either standby genie or mains power to charge the batteries overnight.
Is there a solution to the issue of the cabinet being TN-S and does it involve changing or adding anything else to the system to rectify the issue. Currently I am having an issue with the inverter showing an F12 fault so I think that it will be going back to the supplier next week, however given they are selling this unit with the specific option of direct connection to a mains supply I had really expected it to work once it was connected.
I am content to change things if it will sort the problem but I don't want to be having to alter stuff in the cabinet as it is all pre wired and supposedly plug and play.
Many thanks again

tonyboy

Please see attached electrical art. Please study and note my remarks beside the three balloons. The ohmmeter tests at A, B,C and D must be done with all sources of electrical energy ie mains, battery and pv panels isolated. With ohmmeter set to low range eg 0 to 200 measure between N and E/cpc and tell me results.

marconi said:

Please see attached electrical art. Please study and note my remarks beside the three balloons. The ohmmeter tests at A, B,C and D must be done with all sources of electrical energy ie mains, battery and pv panels isolated. With ohmmeter set to low range eg 0 to 200 measure between N and E/cpc and tell me results.

Click to expand...

Hi Marconi
I think this will take me some time to do, as I will need to get access to the mains in my house and I am assuming the insides of the cabinet trunking and connections. To be honest it may be more than difficult to start dismantling the internal components of the cabinet as its all concealed, I will get in the cabinet and see what I can access and hopefully get back to you soon, I am working over the next three days on odd shifts so it may not be until the weekend or Monday.
I am assuming I is the inverter and the consumer unit on the right is my solar out unit.
Thanks for taking the time to do the drawing, I am very grateful.
My fears at present are that I am going to have to do some serious alterations to the set up and that was why I got a self contained cabinet to avoid this.

Quick edit I measured the point (b and c) before and after the rcd and got 00.2 for both and the consumer unit (D) with feed unplugged and all both on and off and got no reading. The main consumer unit is in a built in cupboard over the door and will take some getting to, so it may take me a while to get reading A.

We will see.
Regards

Tonyboy

What literature do you have that you can send me or a link to? Do you have a circuit diagram for the cabinet?

If your cabinet has on one side as in the earlier video clip two c forms for mains in and inverter out then I can spell out a way to do the measurements at the socket or plug N and E pins without dismantling anything. But that will be tomorrow because I am starting to cook for visitors tonight.

marconi said:

What literature do you have that you can send me or a link to? Do you have a circuit diagram for the cabinet?

If your cabinet has on one side as in the earlier video clip two c forms for mains in and inverter out then I can spell out a way to do the measurements at the socket or plug N and E pins without dismantling anything. But that will be tomorrow because I am starting to cook for visitors tonight.

Click to expand...

Hi Marconi

I have done a couple of measurements but would be appreciative of a spelt out instruction, being a heating engineer and all. I have attached a picture of the cabinet and it looks like the inside of mine pretty much albeit they send it with a different inverter.

I have been trying to get any kind of information about my cabinet with little success from the supplier I can't even get test results of the product before it was shipped to me, It is a shame because to be honest the product does not seem too bad.

I realise you and others have lives outside of the forum and I am very grateful of the help and advice I have received, I am working for the next three days all over the place so I might be able to get back to you in the evening this week.
I hope your evening meal goes well.
Regards and thanks

Tonyboy

Thank you for image of inside. I ought to be able to fathom out the wiring diagram from it.

marconi said:

Thank you for image of inside. I ought to be able to fathom out the wiring diagram from it.

Click to expand...

I will try to get a pic of my actual cabinet and send that later, then at least it will be the actual item.

find attached mine.

regards

Tonyboy

Thank you for the readings at B and C which indicate that N and E are connected together at the output side of the inverter to create a TN-S earthing system. (Just to confirm I assume you are on the lowest Ohms range and 00.2 is 00.2 Ohms ie less than 1 Ohm. To be sure what reading do you get when you connect the Ohmmeter probes together? ).

The reading at A can be done at the cabinet - you do not need to gain access to your home's main consumer unit.

Again, with all PV and battery and mains isolators opened and the plug and socket on the side of the cabinet removed, take your Ohmmeter on the lowest Ohms range and do a) and then b) below:

a) To gain access to the ingoing E put a probe on the earth terminal of the cform plug. To gain access to the ingoing N, go to the AC in C40 MCB, turn it on and put the other probe into its N terminal. This measures between N and E at the input to the inverter.

b) Now would you keep the probe on the ingoing N at the C40MCB and put the other probe on the N of the outgoing RCD - this RCD to be switched on. If there is a mains input on/off switch on the inverter box then these needs to be turned on for this measurement and off for a). This measures between input N and output N.

What are these two readings please?


Please tell me the part number of the output 40A ABB RCD or post a closer picture of its front - I want to see if it is single of double pole.

marconi said:

Thank you for the readings at B and C which indicate that N and E are connected together at the output side of the inverter to create a TN-S earthing system. (Just to confirm I assume you are on the lowest Ohms range and 00.2 is 00.2 Ohms ie less than 1 Ohm. To be sure what reading do you get when you connect the Ohmmeter probes together? ).

The reading at A can be done at the cabinet - you do not need to gain access to your home's main consumer unit.

Again, with all PV and battery and mains isolators opened and the plug and socket on the side of the cabinet removed, take your Ohmmeter on the lowest Ohms range and do a) and then b) below:

a) To gain access to the ingoing E put a probe on the earth terminal of the cform plug. To gain access to the ingoing N, go to the AC in C40 MCB, turn it on and put the other probe into its N terminal. This measures between N and E at the input to the inverter.

b) Now would you keep the probe on the ingoing N at the C40MCB and put the other probe on the N of the outgoing RCD - this RCD to be switched on. If there is a mains input on/off switch on the inverter box then these needs to be turned on for this measurement and off for a). This measures between input N and output N.

What are these two readings please?


Please tell me the part number of the output 40A ABB RCD or post a closer picture of its front - I want to see if it is single of double pole.

Click to expand...

Hello Marconi
Thanks for the guide and for taking the time to help me.
Just as a double check the reading on the meter with the 2 probes together was 00.1 and 00.2
The earth on the plug to incoming N, I had no reading
The N on the incoming C40 mcb to N on the outgoing RCD no reading.
I have also attached a pic of the output Rcd as requested.

The cabinet does not have a main on off other than the Inverter switch, the input is cut of on the rcd/mcb and before that is a soft start relay that unless powered stays off. I have installed a double pole ac Isolator outside of the cabinet and for the solar input I have a double pole switch also.

I am still a bit in the dark about the earthing of the system in this respect. I realise the ecl device in my home supply unit senses the earth leakage caused by my powering the mains on to the cabinet and I can see that if the cabinet did not have an RCD, this I assume would stop the issue occurring. (or maybe not) I see also the need for an rdc on the solar output to protect anyone using the appliances supplied from the cabinet. However If the solar supply in the consumer unit was earthed to a ground rod would this be suitable as a means of earth protection for the solar output. And if this was the case would it then be possible to remove the rcd from the solar cabinet output.
I think someone else commented that the solar output should have its own source of earth separate from the dno in case of power failure in that if the L and N were disconnected so would the earth back to my consumer unit be as it is joined to the N of the house input.
I am sure there are like all things a multitude of reasons for and against different options and I am hoping that there is a reasonably simple solution to my issue. I am however somewhat disappointed that having purchased a plug and play unit that is sold as such I am in the situation I am now in.
Research was my topic for 4 months before I committed to get the kit and at no point did the provider mention I may have some issue with my supply to the cabinet. I am not pointing the finger at anyone as at the end of the day I purchased the whole thing, but it sure would have helped if I had been given a heads up.

If my measurements have not provided any answers I am happy to check and test as much as you wish if it will help.
I am as ever very grateful for the help.
Regards
Tony

Just to be sure - nothing you have done wrong - but would you measure the resistance between the two blue N connections at the bottom of the inverter box - see attached image and area circled in blue. If there are ac isolator switches on the the inverter box then please turn these on. As before all other power disconnected and isolated.

I am trying to establish whether the incoming N is permanently connected to the output N. (It may actually be a switched connection but at the moment I don't want to work on the cabinet when powered up.)

This link has a picture shwoing the internally linking of in N and out N:

Connection of Inverter Energy Systems to the Grid: New requirements surround residual current devices - GSES - https://www.gses.com.au/battery-storage-systems-what-are-their-chemical-hazards/

The tack I am following is that you have been sold a cabinet designed safely to take mains power from a generator which has an isolated neutral ie: not connected to earth E. When this generator is replaced by the UK mains supply the incoming mains N is connected to earth as the norm. Alas, your cabinet has an output N to E link as well which is troublesome when the inverter is in bypass/line mode ie mains supplying the output not the inverter. The effect of presenting your home's main RCD with an NE link before it and also after it is that not all the neutral current passes through it - some takes a different route via the two NE links. The net result is that the home RCD detects rightly a difference between the L and N and trips.

What some systems do is switch the output NE link in and out of circuit depending (respectively) on whether it is the inverter or mains supplying the output. At the same time the output has both L and N double pole switching between inverter LN and mains LN - at no time is the output connected to both Ns - that from the mains and that from the inverter. (Of course the switching also prevents both Ls from the mains and the inverter being connected to the output at the same time).

eg: Automatic Neutral-to-Ground Connection - https://www.sigineer.com/news/automatic-neutral-ground-connection/

Note that this is a US reference but it gives you the idea of what I describe.

What's important for safety is that for loads connected to the inverter cabinet output the N is always referred to E irrespective of whether the source of electrical power is the mains, a gennie or the inverter in order that fuses, mcbs, rcds, rcbos will operate in the event of an earth fault or earth leakage whether that be L to E or N to E.

AS this is a bought product, can you send me details of what you bought and from where and I while seek some technical clarification from the supplier/maker on what was intended in way of mains input.

Please do not change anything yet.

marconi said:

Just to be sure - nothing you have done wrong - but would you measure the resistance between the two blue N connections at the bottom of the inverter box - see attached image and area circled in blue. If there are ac isolator switches on the the inverter box then please turn these on. As before all other power disconnected and isolated.

I am trying to establish whether the incoming N is permanently connected to the output N. (It may actually be a switched connection but at the moment I don't want to work on the cabinet when powered up.)

This link has a picture shwoing the internally linking of in N and out N:

Connection of Inverter Energy Systems to the Grid: New requirements surround residual current devices - GSES - https://www.gses.com.au/battery-storage-systems-what-are-their-chemical-hazards/

The tack I am following is that you have been sold a cabinet designed safely to take mains power from a generator which has an isolated neutral. When this generator is replaced by the UK mains supply the incoming mains N is connected to earth as the norm. Alas, your cabinet has an output N to E link as well which is troublesome when the inverter is in bypass/line mode ie mains supplying the output not the inverter. The effect of presenting your home's main RCD with an NE link before it and also after it is that not all the neutral current passes through it - some takes a different route via the two NE links. The net result is that the home RCD detects rightly a difference between the L and N and trips.

What some systems do is switch the output NE link in and out of circuit depending (respectively) on whether it is the inverter or mains supplying the output. At the same time the output has both L and N double pole switching between inverter LN and mains LN - at no time is the output connected to both Ns - that from the mains and that from the inverter. (Of course the switching also prevents both Ls from the mains and the inverter being connected to the output at the same time).

eg: Automatic Neutral-to-Ground Connection - https://www.sigineer.com/news/automatic-neutral-ground-connection/

Note that this is a US reference but it gives you the idea of what I describe.

What's important for safety is that for loads connected to the inverter cabinet output the N is always referred to E irrespective of whether the source of electrical power is the mains, a gennie or the inverter in order that fuses, mcbs, rcds, rcbos will operate in the event of an earth fault or earth leakage whether that be L to E or N to E.

AS this is a bought product, can you send me details of what you bought and from where and I while seek some technical details from the supplier/maker and what was intended in way of mains input.

Please do not change anything yet.

Click to expand...

Hello Marconi

I measured between the two Neutrals at the input and output on the inverter and got no result at all.

The cabinet we bought is an SP5048 silent power plug and play 5kw that has an axpert MKS 4 inverter (5.6 kw) and not the voltacon V7 (yellow 5 kw inverter) that is in the product description. I am assuming that the actual cabinet layout and controls are the same for both model of inverter but I am by no means sure.
The company are Voltacon UK Ltd in Coventry
I believe I mentioned previously that the inverter has a fault F12 which is a dc/dc overcurrent issue that I have still to rectify possible by returning it to the supplier. Someone on another forum seemed to think that this is an MPPT issue.
I am hoping that this fault albeit on the P.V. side of things is not having any effect on the AC side of things.

I would be interested to see how forthcoming they are to you and that they can provide some sort of specific answer.

I will not be able to get back to you now until the weekend as my work commitments mean I am out of the house.

Many thanks for the help

Regards

Tonyboy

By way of clarification, that box marked Cronos Voltage is measuring the input voltage between L and N and checking it is within range ie say 230V +/- 10V, and if it is it then closes a contact which then applies power to the contactor next to it to supply power to the input of the inverter. If the voltage goes out of range then the relay contacts open, the contactor opens and thereby removes power from the inverter. There is a delay of 4s to close the contacts when the voltage is 'good' but they are opened instantaneously if not.

https://www.cronos-electronics.gr/faseon_en.htm

@Tonyboy
Has your electrical installation ever been inspected and tested and if it has was anything mentioned about low or unusual insulation resistance?

Have you had an electrician look at this problem?

It would be sensible to ensure that the RCD in the consumer unit is working correctly and that there is not a fault elsewhere in the installation that may be the underlying problem behind this issue.

I would also advise having an electrician look at the earthing arrangements for this system as you seem to be unsure about this. Poor or incorrect connection of the earthing, particularly as it sounds like there is a N-E link in this cabinet, may be causing your issues and may have resulted in there being unexpected dangers present.

Tonyboy: I have sent this to Voltacon:




To: [email protected];
17/02/2023 06:43
1

Silent Power SP5048-C-P, PLUG 'N' PLAY PHOTOVOLTAIC CONTROL CABINET Off Grid Inverter Charger Kit 5000Watt -

https://voltaconsolar.com/silent-power-sp5048-c-p.html

Dear Sir or Madam,

May I clarify something about the ac input to the Silent Power SP5048?

I have a client with this product which works fine until the ac input from the home mains is connected. When the domestic 230V ac 50Hz single phase supply is connected to the inverter the home consumer unit residual current detector trips cutting off this supply. I am helping him find out why. He tells me he bought the product from you with the expectation it could be connected to his home's mains supply, albeit he is not completely au fait with electrical jargon since he is not an electrician or electrical engineer so he may have misunderstood.

I note that the literature at reference describes the SP5048 as an 'off-grid' system and that pictorial schematic shows a generator providing the external 230V ac supply and not the mains. Indeed it also describes contacts and soft start for a generator supply.

I note too that the output ac is via an RCD and the supply is described as TN-S. This indicates to me that there is a Neutral to Earth link before the ac output RCD. I have measured with an Ohmmeter the low continuity resistance and thus presence of this link. The presence of this link would cause the domestic consumer unit RCD to trip because the mains supply already has its neutral connected to earth; the situation thus arises where there is a N-E link both before and after the home CU RCD with the inevitable result that it will detect an unbalanced current because not all the N current passes through the home RCD - some flows through the path created by the two N-E links.

So this seems to confirm to me - but I would appreciate your clarification please - that the SP5048 is not intended to be connected to the UK mains supply. It is as described in the literature, an off-grid system only meant to be connected to a back-up generator. Am I correct?

Yours sincerely


BSc(Hons) CEng MIET
Chartered Electrical Engineer

davesparks said:

@Tonyboy
Has your electrical installation ever been inspected and tested and if it has was anything mentioned about low or unusual insulation resistance?

Have you had an electrician look at this problem?

It would be sensible to ensure that the RCD in the consumer unit is working correctly and that there is not a fault elsewhere in the installation that may be the underlying problem behind this issue.

I would also advise having an electrician look at the earthing arrangements for this system as you seem to be unsure about this. Poor or incorrect connection of the earthing, particularly as it sounds like there is a N-E link in this cabinet, may be causing your issues and may have resulted in there being unexpected dangers present.

Click to expand...

Hi Davesparks
I have contacted a chap who is a solar installer electrician to see if he can have a look at things for me, he is away at present so in the interim I am trying to work through a number of tests with another member of the forum. I am grateful for your reply and hope in the next week to have had some response from the electrician. Regards and thanks Tonyboy

marconi said:

Tonyboy: I have sent this to Voltacon:

To: [email protected];
17/02/2023 06:43
1

Silent Power SP5048-C-P, PLUG 'N' PLAY PHOTOVOLTAIC CONTROL CABINET Off Grid Inverter Charger Kit 5000Watt -

Silent Power SP5048-C-P, PLUG 'N' PLAY PHOTOVOLTAIC CONTROL CABINET Off Grid Inverter Charger Kit 5000Watt - https://voltaconsolar.com/silent-power-sp5048-c-p.html

Dear Sir or Madam,

May I clarify something about the ac input to the Silent Power SP5048?

I have a client with this product which works fine until the ac input from the home mains is connected. When the domestic 230V ac 50Hz single phase supply is connected to the inverter the home consumer unit residual current detector trips cutting off this supply. I am helping him find out why. He tells me he bought the product from you with the expectation it could be connected to his home's mains supply, albeit he is not completely au fait with electrical jargon since he is not an electrician or electrical engineer so he may have misunderstood.

I note that the literature at reference describes the SP5048 as an 'off-grid' system and that pictorial schematic shows a generator providing the external 230V ac supply and not the mains. Indeed it also describes contacts and soft start for a generator supply.

I note too that the output ac is via an RCD and the supply is described as TN-S. This indicates to me that there is a Neutral to Earth link before the ac output RCD. I have measured with an Ohmmeter the low continuity resistance and thus presence of this link. The presence of this link would cause the domestic consumer unit RCD to trip because the mains supply already has its neutral connected to earth; the situation thus arises where there is a N-E link both before and after the home CU RCD with the inevitable result that it will detect an unbalanced current because not all the N current passes through the home RCD - some flows through the path created by the two N-E links.

So this seems to confirm to me - but I would appreciate your clarification please - that the SP5048 is not intended to be connected to the UK mains supply. It is as described in the literature, an off-grid system only meant to be connected to a back-up generator. Am I correct?

Yours sincerely


BSc(Hons) CEng MIET
Chartered Electrical Engineer

Click to expand...

Hi Marconi
Many thanks for the help in this, I will wait with interest to see what the reply contains.

I know this is a bit off topic from the one you are helping me with but I was wondering if you had any thought about this;
I am currently also faced with the prospect of taking the inverter back to the supplier myself, as it is not working correctly. On re testing the pv Voltage at the input to the cabinet I have now seen it peak from what was 258v DC which is what I get from the 7x 420 w panels as their VOC.

I checked this at the point before I connected the cabinet as it has an input limit of 500vdc and it was fine, then after the F12 fault occurred I checked it again and found it went from 350 to 450 or more at the connection to the cabinet. I have since disconnected the PV from the cabinet as someone else told me that this could be damaging my solar panels.
The response from the supplier regarding the F12 fault was it was an mppt issue and the inference was that I had somehow caused it. Since I have only connected the PV, the batteries and the two plugs I can't see how but I will have to wait until they test it to see what they determine the fault is.

I subsequently started the inverted connected to the batteries but with the external PV isolator off and measured the input voltage on the pv inside the cabinet. With the internal isolator off the was 0vdc but as soon as the internal switch was on the reading was 150-180vdc at the input which can't be right. I know mppt is designed to get the best out of panels and in particular to assist if a panel is part shaded but I can't really say with any certainty that this may be the cause of the increased voltage at the pv input.
Do you have any experience of inverter mppt issues and if so are you able to shed any light on what may be causing this problem too. If you would prefer me to start a new topic for this then of course I will as I don't wish to cause any issues on the forum particularly as you have been so helpful.

Frankly at the moment I am beginning to wonder what I have bough and if I would not have been better buying all of the parts separately and installing them on a board in the cupboard to my own design. I wanted a self contained unit as it negated the need to size and design the contents myself but as it stands it has not fulfilled the requirement of a "plug and play unit". Don't get me wrong I realise there may have been issues if I had done this the other way too and that the problem may be resolved some how with a relatively easy solution. I am waiting for a solar installer electrician to contact me next week as he is away at present. Hopefully he can have a look at my system and test the earth and the protection device in the house, who knows it may be my house that is the issue!
As ever I am really grateful for your time and assistance in this and look forward to hearing from you again and moreover what response you receive to your request.

Regards

Tonyboy

Tonyboy: I had a reply from Voltacon Conventry but it did not address my clarification with rigour so I have sent a further missive to them. Helpfully, they said they would study the wiring in of the cabinet so I have sent them your sketch with some additional bits by me and a drawing of how you have connected the cabinet into your home's consumer unit.

The detail of terminology matters. An off-grid system means exactly that; not at all connected to the nations electricity grid network. It may though be connected to a generator or other form of generation but not the mains electricity grid.

An on-grid system is connectable to the mains electricity grid, to provide back up, exploitation of off peak electricity and if arranged the export of surplus solar generation to the grid to earn payments from your mains electricity supplier.

Expanding on 'on-grid' a little, in order to export electrical energy to the grid, the inverter ac output technology has to be suited to connect in parallel with the incoming mains grid ac supply. The phrase 'grid-tie' is used for an ac connection between the mains and solar charger/inverter which facilitates a two-way flow of ac electrical power - from mains the mains to consume and to the mains to export. For safety reasons, a solar/charger inverter which is grid-tied has functionality to detect at all times the existence of the mains supply and in the event of a power cut it severs the grid-tie so that 240Vac 50Hz power produced by the inverter does keep (attempt to keep) the wiring in the installation and the mains distribution network your homes is connected to alive which would be hazard.

It is clear to me (at least for now unless Voltacon convince me otherwise) that your cabinet is an off-grid system. It is not intended to be connected to the mains. Indeed, as I have already pointed out, the cabinet and Voltacon too in their blurb describe it as an off-grid system. To do what you want to achieve - mains back up of the ac output and exploitation of mains off-peak electricity to charge the battery you should have bought an on-grid system. You did not require an on-grid grid tied system unless you wanted to export to the grid. On this point was it your wish to export to the grid to earn a feed-in payments? Feed in payment rates per kWh are quite low compared (pennies) with bought kWh (tens of pennies) so the best economic return is so-called self-consumption as solar power is produced or from stored power in batteries charged by solar (and wind) power.

Your current system is ill-suited to on-grid operation because in order to provide earth fault protection on the ac output side the neutral of the output must be connected to an earth reference. I will expand on this point about earthing in another post with some drawings to illustrate some current flows in neutrals and earth conductors and why the output rcd and mcb requires an earth connected neutral and why doing this on the output can causes the trip of an rcd present in the ac input feed.

I will ponder a work around for your current cabinet but just wanted to say early on you have mistakenly bought (in my opinion) an off grid system when you should have bought an on-grid one. You may have though a case for the mistake being with the supplier if you either asked for an on-grid system and they sent you instead an off-grid, or you described to the supplier what you wanted to achieve and they recommended sold you an off-grid system.

I will work up the diagrams over the next couple of days. Meanwhile have a look and read through this again and nota bene the absence of anything to do with connection to the mains and the schematic - concept of operation.

Silent Power SP5048-C-P, PLUG 'N' PLAY PHOTOVOLTAIC CONTROL CABINET Off Grid Inverter Charger Kit 5000Watt - https://voltaconsolar.com/silent-power-sp5048-c-p.html

A dead give-away that it is not meant to be on-grid is that the input ac power is via a c form plug. An on-grid system (which can operate in line/bypass mode ie output supplied by input grid mains) relies on an output earth referenced neutral derived from the input earth referenced neutral (and thus no need for an N-E link on the ac output side) the ac input must hard-wired in.

One can have systems which provide a switchable N-E link on the output depending on whether the system is in line/bypass mode - I introduced you to this idea earlier and this could - not saying it is right now - a potential solution but I need to check the UK regulations and of course locate where the link is made in the cabinet you bought.

My second email:

Thank you for your prompt response. I have attached two images. The DSC was produced by the client and shows in black how he has connected the SP cabinet. I have added to it in outline the connections to his home's consumer unit which is identified in this image as the two blue boxes. (A bit rough but I am sat waiting for my wife to have an XRAY so please excuse the standard of drawing).
In the second image - HOME CU - I have sketched how the ac supply is derived to feed to the SP cabinet. His home has the usual cutout, feeding a meter and main earth terminal. L and N from the meter and an E from the main earth terminal connect to the consumer unit. The consumer unit has a combined mainswitch and residual current circuit breaker which covers all the outgoing circuit breakers. One of these circuit breakers is a 32A one for the SP cabinet. Between the consumer unit and the SP cabinet is a 3 core cable with L, N and E which connects into a c form socket. This cform socket connects to the SP cabinet's ac input c form plug. There is an ac input isolator in this cable just before the c form socket - ie external to the SP cabinet.
Happy to amplify further when I am home but I hope these drawings give you the gist.

marconi said:

Tonyboy: I had a reply from Voltacon Conventry but it did not address my clarification with rigour so I have sent a further missive to them. Helpfully, they said they would study the wiring in of the cabinet so I have sent them your sketch with some additional bits by me and a drawing of how you have connected the cabinet into your home's consumer unit.

The detail of terminology matters. An off-grid system means exactly that; not at all connected to the nations electricity grid network. It may though be connected to a generator or other form of generation but not the mains electricity grid.

An on-grid system is connectable to the mains electricity grid, to provide back up, exploitation of off peak electricity and if arranged the export of surplus solar generation to the grid to earn payments from your mains electricity supplier.

Expanding on 'on-grid' a little, in order to export electrical energy to the grid, the inverter ac output technology has to be suited to connect in parallel with the incoming mains grid ac supply. The phrase 'grid-tie' is used for an ac connection between the mains and solar charger/inverter which facilitates a two-way flow of ac electrical power - from mains the mains to consume and to the mains to export. For safety reasons, a solar/charger inverter which is grid-tied has functionality to detect at all times the existence of the mains supply and in the event of a power cut it severs the grid-tie so that 240Vac 50Hz power produced by the inverter does keep (attempt to keep) the wiring in the installation and the mains distribution network your homes is connected to alive which would be hazard.

It is clear to me (at least for now unless Voltacon convince me otherwise) that your cabinet is an off-grid system. It is not intended to be connected to the mains. Indeed, as I have already pointed out, the cabinet and Voltacon too in their blurb describe it as an off-grid system. To do what you want to achieve - mains back up of the ac output and exploitation of mains off-peak electricity to charge the battery you should have bought an on-grid system. You did not require an on-grid grid tied system unless you wanted to export to the grid. On this point was it your wish to export to the grid to earn a feed-in payments? Feed in payment rates per kWh are quite low compared (pennies) with bought kWh (tens of pennies) so the best economic return is so-called self-consumption as solar power is produced or from stored power in batteries charged by solar (and wind) power.

Your current system is ill-suited to on-grid operation because in order to provide earth fault protection on the ac output side the neutral of the output must be connected to an earth reference. I will expand on this point about earthing in another post with some drawings to illustrate some current flows in neutrals and earth conductors and why the output rcd and mcb requires an earth connected neutral and why doing this on the output can causes the trip of an rcd present in the ac input feed.

I will ponder a work around for your current cabinet but just wanted to say early on you have mistakenly bought (in my opinion) an off grid system when you should have bought an on-grid one. You may have though a case for the mistake being with the supplier if you either asked for an on-grid system and they sent you instead an off-grid, or you described to the supplier what you wanted to achieve and they recommended sold you an off-grid system.

I will work up the diagrams over the next couple of days. Meanwhile have a look and read through this again and nota bene the absence of anything to do with connection to the mains and the schematic - concept of operation.

Silent Power SP5048-C-P, PLUG 'N' PLAY PHOTOVOLTAIC CONTROL CABINET Off Grid Inverter Charger Kit 5000Watt - https://voltaconsolar.com/silent-power-sp5048-c-p.html

A dead give-away that it is not meant to be on-grid is that the input ac power is via a c form plug. An on-grid system (which can operate in line/bypass mode ie output supplied by input grid mains) relies on an output earth referenced neutral derived from the input earth referenced neutral (and thus no need for an N-E link on the ac output side) the ac input must hard-wired in.

One can have systems which provide a switchable N-E link on the output depending on whether the system is in line/bypass mode - I introduced you to this idea earlier and this could - not saying it is right now - a potential solution but I need to check the UK regulations and of course locate where the link is made in the cabinet you bought.

My second email:

Thank you for your prompt response. I have attached two images. The DSC was produced by the client and shows in black how he has connected the SP cabinet. I have added to it in outline the connections to his home's consumer unit which is identified in this image as the two blue boxes. (A bit rough but I am sat waiting for my wife to have an XRAY so please excuse the standard of drawing).
In the second image - HOME CU - I have sketched how the ac supply is derived to feed to the SP cabinet. His home has the usual cutout, feeding a meter and main earth terminal. L and N from the meter and an E from the main earth terminal connect to the consumer unit. The consumer unit has a combined mainswitch and residual current circuit breaker which covers all the outgoing circuit breakers. One of these circuit breakers is a 32A one for the SP cabinet. Between the consumer unit and the SP cabinet is a 3 core cable with L, N and E which connects into a c form socket. This cform socket connects to the SP cabinet's ac input c form plug. There is an ac input isolator in this cable just before the c form socket - ie external to the SP cabinet.
Happy to amplify further when I am home but I hope these drawings give you the gist.

Click to expand...

Hi Marconi
As ever many thanks for the in depth reply. I do though need to tell you that the kit in the link you have above is not the one I purchased, (though I note it has the same reference and incidentally that there is also a third cabinet listed as an SP5048 too). As well as this the cabinet I received did not contain the inverter shown, but all the wiring and layout is the same. Also I need to clarify something regarding the drawings you have sent to Voltacon and the expectations of the system I purchased.

Firstly here is the link to the cabinet I purchased (stating that it can be charged from the grid) - Silent Power 5Kw Off Grid Inverter Cabinet 6kW Solar PV 48V/230VAC (voltaconsolar.com)
and here is a link to the (off grid) inverter that the cabinet actually contained when it arrived (though I have not raised this issue with them, as I believe the inverter supplied is a better model than that shown in the listed cabinet - Conversol VM 4. Solar Off Grid Inverter 5.6kW. PV Input 6kW. Wi-Fi, BMS & Wi-Fi (voltaconsolar.com)

In the many conversations I have had with the supplier for 4 months prior to purchasing the kit, I made them aware that I was intending to provide power to my home from a separate consumer unit unconnected with the grid and that I was going to store power in batteries when the solar was not producing power. I also wanted a means to charge the batteries in the event we had a long period with no solar, to this ends I was advised that the off grid cabinet was suitable and it could be supplied with supplementary power from either a generator or the grid. I told them I was not going to have a generator and was accordingly advised the system was fine to be connected to the grid via plugs as it has no means of returning power to the grid in the event of a power failure in the grid supply. I did challenge them a couple of times over this issue as I did not want something that would be a danger to anyone working on the incoming main supply in the event of a power failure. I am aware grid tied inverters have an islanding requirement and I think at the time I quoted this to Voltacon and the response was the system physically had no way to return power to the grid.

My system is this; I have the cabinet, batteries and solar panels connected to the SP cabinet in a purpose built fire proof cupboard outside of the house and I have a completely separate consumer unit in the cupboard that supplies solar only supplied power into the property via separate supply and power points in each room. The input to the cabinet is from a single 32 amp supply from the mains consumer unit in the house via an isolator in the solar cupboard then into the cabinet via the c plug.

In the picture of the cabinet and panels that you have sent I do not have the earth from the panels connected back to the incoming mains at the point it goes into the cabinet via the c plug. Currently I have the panel & frames earthed to the bus bar and am waiting to find out if it is better to run this to a separate ground rod in the garden for the purposes of the panels protection. I was under the impression that connecting the panels to the cabinet and equipment was not a good idea in the event of a lightning strike/induced current etc. I am not using the solar system at present so I have no issues with the earthing arrangement not being complete and will on advice do the best thing required. I have the batteries on a ground rod but am happy to put a rod outside in a separate location nearer the panels and frames.

The 32 amp supply from the incoming consumer unit has a line neutral and earth to the isolator in the solar cupboard outside and then into the cabinet via the plug with L,N and E.
I can see that given the issues at present, the earth is what I assume is causing the problems, as in the event of power failure from the grid there is still a connection via the earth through the neutral from the cabinet back to the incoming neutral at my incoming mains consumer unit.

In respect of the earth reference for the separate solar AC output to my home from the sp cabinet, I was also thinking that if I provided a ground rod connection to this, then the appliances in the home would not be connected to the grid other than through the c plug arrangement and would have a path to earth of their own.
I had initially considered if it was possible to remove the earth from the c plug out of the sp cabinet or somewhere else perhaps inside the cabinet and connect the solar consumer unit earth with a ground rod. This would then remove the connection between my solar consumer unit and the incoming consumer unit. I am not at all familiar with the requirements of this so it is only something I had thought about as a solution.

I am extremely grateful for the detailed help you are giving me, so want to ensure that the details Voltacon get are absolutely correct as any solution they may provide will be determined by the details they have to work with and given their quite unhelpful approach to me I do not want them thinking I have something that I don't. Moreover I don't want to waste your time working on inaccurate information. To summarize, all I am looking to achieve is an off-grid power supply to my separate off-grid sockets in the house, that can only when needed, have it's batteries re-charged from the low tariff night time mains supply.

Many thanks and regards

Tonyboy

I will mull over what have sent me which will make my rail journey North next week pass quickly. I was cooking a three course meal for 50 last night in our church social club so am a bit weary today for any serious thinking. But a quick question now - is the dedicated consumer unit for off grid sockets in the same building as all the other final circuits (ie sockets, lights, cooker etc) fed by your MEM Consumer Unit shown in #1? Do you have two types of sockets - 'grid' and 'off grid' and marked as such? And please post a picture of your cut out and the earth terminal so I can work out the earthing system. Is your supply overhead or underground? A few pictures saves me asking further questions.

Oh one more question- what ‘output source priority‘ option have you selected for the ac output‘s source of power Eg usb, sbu, sub? Is line/bypass mode enabled or disabled? Similarly what is the selected battery charging priority option?

ps: I have not yet read your axpert box‘s manual but would not be surprised if it is a standard white box akin to iconica and voltacon with an axpert badge stuck on. I have designed off grid solar systems with genie input and battery storage using the voltacon 5kW hybrid box.

marconi said:

I will mull over what have sent me which will make my rail journey North next week pass quickly. I was cooking a three course meal for 50 last night in our church social club so am a bit weary today for any serious thinking. But a quick question now - is the dedicated consumer unit for off grid sockets in the same building as all the other final circuits (ie sockets, lights, cooker etc) fed by your MEM Consumer Unit shown in #1? Do you have two types of sockets - 'grid' and 'off grid' and marked as such? And please post a picture of your cut out and the earth terminal so I can work out the earthing system. Is your supply overhead or underground? A few pictures saves me asking further questions.

Oh one more question- what ‘output source priority‘ option have you selected for the ac output‘s source of power Eg usb, sbu, sub? Is line/bypass mode enabled or disabled? Similarly what is the selected battery charging priority option?

ps: I have not yet read your axpert box‘s manual but would not be surprised if it is a standard white box akin to iconica and voltacon with an axpert badge stuck on. I have designed off grid solar systems with genie input and battery storage using the voltacon 5kW hybrid box.

Click to expand...

Hello Marconi
You certainly sound like a busy chap, I do hope that you get some rest before the trip tomorrow.

The consumer unit for the solar is in the external cupboard to be labelled as solar and not in the house. I have two types of sockets one for solar and one for the providers power, solar to be labelled as such when finished. I have attached a pic of the kitchen sockets) black is solar.
The incoming main supply is overhead and then in through the wall of the house to the meter and consumer unit. (also attached is earth arrangement in consumer unit).

I have output source set to SBU and I believe bypass mode must be enabled as when the timer is set to use the utility at night for charging it then makes power available to the loads as well as charging the batteries (albeit we would not be using any loads).
I have also attached a copy of the setup doc sent by the supplier with their recommended settings.

Battery charging priority is Solar only currently, recommended by supplier but I can set it to solar and then utility as I believe this is necessary to enable overnight charge from utility. This was set previously to solar then utility when we tested the utility charging timer on the inverter and it tripped the main switch in the house.

I am aware that you are busy so please reply when you have the time. I have to send the inverter back after it is removed next weekend so I am not in a rush as I doubt I will have the inverter back for a while yet.

As ever many thanks for the help and advice and have a safe trip.

Regards

Tonyboy

Very helpful information which casts much light on the problem. It says an up-front rcd is 'not recommended' - rather weak language methinks. It either is or is not required. Anyway, with more mental energy than last time I have the outline of a solution. But before I desrcibe it and also before you disconnect and return the axpert box, would you have time to do a simple test?

With solar, battery and mains all isolated first could you work through the next few steps?

What I want to establish is that it is the presence of an N-E link on the output which is causing your MEM CU RCD to trip when the box enters bypass and utility battery charging modes. To do this would you simply disconnect the line and neutral (coloured black and blue) from the output terminals on the Axpert box. Put each cable into its own connector to keep the bare ends covered.

With a multimeter on low Ohms range measure the resistance between the N and E ac output terminals on the Axpert box - I expert it to be very high resistance/off the scale. (#)

Now measure between the black and blue cables which are in the two connectors - with the output mcb on and the output rcd off. I expect the reading to be very low.

Now, set up the Axpert box so that you can charge the battery from the utility. You do not have to wait until the off peak tariff period - select a time during the day suited to the time you are going to do the test. The battery charging priority must be selected to put utility first.

Now, before the charging time slot period starts, power up the solar and battery and ac mains input. Keep the ac output disconnected. Wait till the charging time slot starts and see if the MEM rcd trips when the utility starts to charge the battery and bypass connected the ac input to the ac output(which of course is disconnected from any loads).

With this test there is no N-E link on the output, unless it is done inside the box but those two Ohmmeter checks will discover if this is the case if you find a low resistance reading between N and E at the box terminals - see # above.

I 'hope' we find the MEM rcd does not trip. If it does then it indicates another type of problem.

If this is not clear then I will amplify for you.

marconi said:

Very helpful information which casts much light on the problem. It says an up-front rcd is 'not recommended' - rather weak language methinks. It either is or is not required. Anyway, with more mental energy than last time I have the outline of a solution. But before I desrcibe it and also before you disconnect and return the axpert box, would you have time to do a simple test?

With solar, battery and mains all isolated first could you work through the next few steps?

What I want to establish is that it is the presence of an N-E link on the output which is causing your MEM CU RCD to trip when the box enters bypass and utility battery charging modes. To do this would you simply disconnect the line and neutral (coloured black and blue) from the output terminals on the Axpert box. Put each cable into its own connector to keep the bare ends covered.

With a multimeter on low Ohms range measure the resistance between the N and E ac output terminals on the Axpert box - I expert it to be very high resistance/off the scale. (#)

Now measure between the black and blue cables which are in the two connectors - with the output mcb on and the output rcd off. I expect the reading to be very low.

Now, set up the Axpert box so that you can charge the battery from the utility. You do not have to wait until the off peak tariff period - select a time during the day suited to the time you are going to do the test. The battery charging priority must be selected to put utility first.

Now, before the charging time slot period starts, power up the solar and battery and ac mains input. Keep the ac output disconnected. Wait till the charging time slot starts and see if the MEM rcd trips when the utility starts to charge the battery and bypass connected the ac input to the ac output(which of course is disconnected from any loads).

With this test there is no N-E link on the output, unless it is done inside the box but those two Ohmmeter checks will discover if this is the case if you find a low resistance reading between N and E at the box terminals - see # above.

I 'hope' we find the MEM rcd does not trip. If it does then it indicates another type of problem.

If this is not clear then I will amplify for you.

Click to expand...

Good morning Marconi
glad to hear you are refreshed.

I am just off to the hospital with my wife so I will not be able to do the tests until probably Wednesday am.
I am happy to do as requested and will work through the print out of these instructions as I go.

My only issue at present is that with the solar connected to the pv input on the cabinet I am getting 120 -200 v dc back out of the input terminals with the panels isolated from the cabinet and the pv isolator on in the cabinet. This has led me to some concerns over connecting the pv back to the input of the cabinet in fear of the increased voltage up around 450+ when last measured and the possibility of the added voltage causing damage to my panels.

If I can do the test with the pv isolated (running the inverter on the batteries) and it will yield the same results then I would prefer that rather than risk and damage to my panels.

Let me know if this will cause any issue and I hope to get back to you as soon as I return.

As ever I am grateful for your help

Regards

Tonyboy

Tonyboy said:

Good morning Marconi
glad to hear you are refreshed.

I am just off to the hospital with my wife so I will not be able to do the tests until probably Wednesday am.
I am happy to do as requested and will work through the print out of these instructions as I go.

My only issue at present is that with the solar connected to the pv input on the cabinet I am getting 120 -200 v dc back out of the input terminals with the panels isolated from the cabinet and the pv isolator on in the cabinet. This has led me to some concerns over connecting the pv back to the input of the cabinet in fear of the increased voltage up around 450+ when last measured and the possibility of the added voltage causing damage to my panels.

If I can do the test with the pv isolated (running the inverter on the batteries) and it will yield the same results then I would prefer that rather than risk and damage to my panels.

Let me know if this will cause any issue and I hope to get back to you as soon as I return.

As ever I am grateful for your help

Regards

Tonyboy

Click to expand...

Could you revise what you wrote in bold above please so it says what you meant a little clearer for me?

marconi said:

Could you revise what you wrote in bold above please so it says what you meant a little clearer for me?

Click to expand...

Hello Marconi

The issue with the pv input is this.

When I measure the pv input from the roof at the point it connects into the cabinet input connections (lower left in picture) I get the expected 253 vdc.
When the inverter is switched on but the isolator in the cabinet is off (lower right in picture), the voltage from the pv remains constant, when I then turn on the isolator in the cabinet for the pv, the voltage goes up to between 350 and 450 vdc.

When this happened I then isolated the pv supply using the external isolator I have fitted before the cabinet. Which effectively removes any input to the inverter from the pv, I then measured the voltage at the input connection to the cabinet and found the 100 to 200 vdc appearing at the input of the pv in the cabinet. If I turn off the isolator in the cabinet the voltage drops to zero, this led me to conclude that the dc voltage was coming from the inverter out through the input terminals in the cabinet.
Now I have no idea of how this is possible as this would indicate that the inverter is working totally incorrectly or that the inverter is somehow sending power to the point it is supposed to be taking it in.

When the inverter is on and working it only shows 252 vdc input from the pv (see Right hand pic) on the front panel of the inverter and it was not until I re measured the voltages of all of the terminals in the cabinet whilst trying to find any indication of what may be causing the problems I am having I discovered this issue.

I am somewhat concerned that this may be down to a wiring issue in the cabinet or the inverter but it is difficult to determine which without removing more wiring. Perhaps when I come to remove the inverter this weekend I will measure the voltage at the input connection to the actual inverter with all wiring removed to see if it is as above, when there are no other routes for the voltage from the inverter itself.

Feel free to ask for more information if this is required

Many thanks as ever and Regards

Tonyboy