New home PV Instal

[scotsparky78]

Hi all, I am about to embark on a mini PV install in my home to run my LED lighting - 200w max more likely to be 100w at any one time and would like your views before I go any further on what I have got / done

1. (still to buy) 2 x 100w Solar Panels - Run of 3m from PV to Charge Controller -
2. 20amp Solar Charger Controller - LCD - I have also incorporated charge indicators for volts etc
3. 2 x 125ah batteries deep cycle (wired in parallel)
4. 1 x 3PDT relay (240v Coil) - switch betewwen 240v mains and 12v (switched by 2 pole 20amp switch) - already tried and tested
5. PV to charge controller via 4mm cable and MC4 connectors, 20amp DC breaker before entering Charge Contoller & Main isolator switch
6. 20amp DC breaker from battery to inverter - ran in 8mm cable cable
7. Inverter incoming protected by blade fuses and the above dc breaker (20a)
8. Out put via inverter (13amp fuse plug) - Both 240 outputs to lighting circuit are protected by a 6amp MCB
9. From inverter output (plug top 13amp 2.5mm T&E) to a 30a joint box - From joint box to Lighting circuit - 6mm T&E (run is about 15m)
10. I am feeding my 240v coil from a singal radial circuit protected by a main RCD and a local RCD socket & I am feeding the lighting circuit from a singal radial circuit protected by a main RCD and a local RCD socket

That is it so far, just want to see if I have missed anything or going about it wrong?

Cheers

 

[EastAnglian]

I suggest you draw out the proposed installation if you want some objective critique of your plans. I'm surprised at the number of RCDs you appear to have in the "written" plans as its not clear how you plan to achieve the required discrimination between them.

 

[scotsparky78]

Hi EA, point taken on the discrimination, I have 30ma protection at DB so its pointless! Will upload drawing soon.
Cheers, C

 

[moggy1968]

you shouldn't be sharing the RCD on the DB.
solar should either go on it's own RCD or preferably not on one at all.
Don't know why you are fusing the DC. One wouldn't normally on a G83 installation.
I presume this is an installation under G83? if not you can't connect it to the grid at all. If it is why are you using batteries? It's rather confusing as this looks like a standalone system but you are talking about connecting to an RCD on your DB which would be completely wrong.
What inverter are you using?
Not sure why you are using such big cable, what length are your runs? Have you run this through a design package or calculated your voltage drops?
If this is a standalone then presumably all accessories run from it are completely seperated from the mains electrics.

 

[scotsparky78]

Hi Moggy, this will be a standalone system, not connecting to the grid purely using the batteries for storage to use led lighting at night. I mention RCD only as the 240v supply circuit when I hit the relay to switch from battery inverter supply to 240v mains supply.

I will be using a 300w inverter 12v-240v, lenght of run from PV to CC is 3m, cc to battery 1m- Big cable size- are you refereing to the 6mm? if so this was an old supply to the cooker ( cable run aprix 20m) which has been refitted so made sense to utilise it as the cable run is a nightmare back to the DB where I will pick up my lighting circuit outwith the DB in its entirety, all my solar instal is at back of the house (split level, nighmtare to get under the house for cable runs)

The accessories will be seperated via the 3PDT Relay - this way no 2 supplys will ever meet, I have not used any design software etc however i think my calcs work out ok - 120w of lighting in entire house

Is there another way I can do this without the batteies etc ? Complete novice with the PV side, Thanks for your paitence

 

[moggy1968]

Fair enough, no harm using an oversize cable if it's already there. You could use smaller DC cable. I would have thought 4mm would be ample. FUses on a PV system will tend not to operate as the fault current is only marginally above the operating current. How are you earthing the AC side? presumably via a spike?
I don't know how reliable your RCD will be on this set up. I have 240v power supply on my van and get a lot of nuisance tripping on my extension lead RCD, but they do tend to be very sensitive.
At that point I run out of knowledge. Idon't know about the legalities of having a system like this connected to the grid via a relay, but would be very interested to find out from those that might know.

 

[EastAnglian]

On the DC side have you factored the in-rush current of the LED lights? It will depend how many you turn on at once of course and the individual lights, but you don't want the inverter to die because it can't cope with the in-rush current.

Apart form being able to distribute the power over longer distances with smaller cables there is clearly an inefficiency in converting the power from 12V to 230V and then back to a lower internal DC voltage within the LED luminaires. Do you have the option of a 12V distribution system between batteries and lamps and if so have you considered using 12V LED lamps?

 

[scotsparky78]

Being honest I am not sure of the legal side on that either, I will need to get the old book out or start searching the net. Can anyone shine light on this? i have tested out the relay and it works a treat, although not tested it with a load just my trusty old meter. For more info the 3PDT relay is rated at 40amp, it was originally 7amp but due to the DC amps going thru the relay approx 12amps I had to upgrade.

 

[moggy1968]

intersting point, how about 12v downlighters for a boat?

 

[scotsparky78]

I didnt factor the inrush for the LED's, quick check on the net and inrush looks more attched to incadescent lamps although it is in LED but very minor, point taken as it is still a factor. Totaly agree on the inefficency, thats why i am stuck between 12v/24v as the factors are halved. My current LED lighting is 240v GU10 replacement so unsure where this stands, does my LED GU10 have a built in 12v transformer?

 

[EastAnglian]

Yes, the GU10 LED replacements have an LED driver in them - basically a tiny switched-mode power supply to convert 230V AC to a constant-voltage DC source.

In-rush current on mains-driven LEDs is a significant issue - I've often had to fit C-curve breakers in place of B-curve as these often trip when the light switch is turned on.

 

[EastAnglian]

Being honest I am not sure of the legal side on that either, I will need to get the old book out or start searching the net. Can anyone shine light on this?

I've not quite worked out how your relay is working in this arrangement but the wiring regs so far as I can make out would require the device connected to the 230V supply to be designed and approved for use on LV supplies. Presumably to BS EN60947-4-1 (Table 53.4, contactor) and suitably housed such that live parts are protected by a barrier/enclosure and cables are suitably restrained. You would also need to take heed of the need for electrical separation between the LV & ELV circuits and prove the isolation with an insulation resistance tester.

 

[scotsparky78]

Thanks EA, I suppose I will need to deal with this when I test out the led load on the inverter, finger crossed. If i need to fit a type C then fair enough, thanks for the heads up. I suppose my relay is working as a contactor, I have designed it in such a way that all live parts are protected - Garage CU 4way, din rail mounted relay with MCB, and cables glanded, all other connections would be via joint Boxes. I do need to look at seperation, I am very glad I posted on here as this is very much valuable info that escapes you when you have been in a desk job for 8 years and not on the tools!!

I will post the relay diagram on my PV install

 

[EastAnglian]

Sounds like you are thinking of all the right things

Been back on the tools for 2 years after far too many years of driving a desk and reporting to committees :rolleyes4:

Wouldn't swap back again!

 

[scotsparky78]

I so know where you are coming, i do miss the tools and keeping right up to date with the going ons but I am where I am and do try to keep my hand in at every opportunity!