Small DIY (non FITs) grid-tie or off-grid PV questions

[siliconskum]

First off, I'm not a sparky, but I have done household rewiring, and I'm an electronics engineer, so I'm also used to dealing with AC / DC high current and voltage power supplies as part of my job. (I bet you hear stuff like this all the time right?)

I have several computer servers that are running 24/7, as you can imagine they are making my electricity bills somewhat buttock twitching. I would like to try to offset some of the running costs by using a small 600W PV setup, I'm not trying to entirely run them from solar, just reduce the mains load when possible. I enquired about a small non FITs install with a couple of local companies, but they were not interested in susch a small setup.
So, I looked up the various regs regarding solar installs, but they all deal with FITs / MCS approved installs. What information I could find was contradicting at best, and the part P regs seem to rule out anything other than a MCS install.

Is it possible for me to have a non MSC PV panel install connected with a G83 approved grid-tie inverter (I'm not interested in FITs, would not make sense with such a small system). I can easily get a G83 inverter (Mastervolt Soladin 600) which is perfect for such a small setup. I understand that this would need to be connected to the CU by a sparky, but could I use NON MSC panels (I allready have five new Chinese 12V 120W (TPS-105), the larger 36V versions of which are MCS approved (so safety wise they should be fine, and they are CE marked - though granted I doubt they will last 25 years... or even 10), and could I install these panels and the DC wiring / isolator / MCB etc myself (or would the whole lot have to be professionally installed)??


If that is not possible, the information I did find seems to indicate I can bypass most of the issues with an off-grid PV system, I was thinking of a grid-fallback type (runs via solar power, when solar drops it switches back to mains power). Basically the reverse of a standard computer UPS. I have an UPS that is designed for constant inverter running and a simple adjustment to the software will allow it to function in this manner.

Is this system OK with the same non MSC PV panels, and would it still fall foul of the part P regs (there are no electrial changes other than connecting the solar panels, and mains voltages are connected by standard IEC connectors for computer equipment).


Thanks for any help, I really need this explained.

SS

 

[Earthstore]

Why not have a decent system fitted, and produce a reasonable amount of power, you could borrow the money and use the FIT's to repay the loan, and yes it is still possible, but you now need an EPC (Energy Performance Certificate) for your property, and it needs to be a minimum of band D.

Most electricians would not certify somebody else's work, even though you may be an expert, what you could do is work with an electrician, run all the cables, fit all the boxes on the walls etc and then let the electrician connect everything up.

I hope this helps,

 

[oliver s]

Hi ss

I cant see any problem with this as long as you comply to the regs of installing the panels correctly, comply with part P, have someone who is qualified to deal with the DC side of things and also to notyfy your local DNO that you have a generator connected to the grid. As you say inverter has to be to G83. I might be tempted to install a slighty bigger system while you have all the scaffolding etc in place as the cost of the kit shoulnt be much more maybe double up and have two mastervolt 600 inverters. Im sure you will soon see a payback if you use quite a bit of electricity during the day.

Good luck , Os

 

[siliconskum]

Why not have a decent system fitted, and produce a reasonable amount of power, you could borrow the money and use the FIT's to repay the loan, and yes it is still possible, but you now need an EPC (Energy Performance Certificate) for your property, and it needs to be a minimum of band D.

Yeah, not worth it to me - my house is 110 years old and so is the roof structure (No way will it meet the modern building regs without major work),and no cavity walls etc. I would have to fight tooth and nail to scrape a band D (I've allready done this several times, I'm also a private landlord so I know whats involved). The money I would spend would NEVER get recouped this side of 40 years... I don't plan to be here that long.

Most electricians would not certify somebody else's work, even though you may be an expert, what you could do is work with an electrician, run all the cables, fit all the boxes on the walls etc and then let the electrician connect everything up.

I hope this helps,

Yeah, that would make more sense. I will probably take that route, assuming a grid tied system is even possible. I got the 12v panels because it was easier for an off-grid setup (UPS is 48V, MPPT controller would drop the five panels to the battery voltage).

I cant see any problem with this as long as you comply to the regs of installing the panels correctly, comply with part P, have someone who is qualified to deal with the DC side of things and also to notyfy your local DNO that you have a generator connected to the grid. As you say inverter has to be to G83. I might be tempted to install a slighty bigger system while you have all the scaffolding etc in place as the cost of the kit shoulnt be much more maybe double up and have two mastervolt 600 inverters. Im sure you will soon see a payback if you use quite a bit of electricity during the day.

Excellent. The part P side of things is what confuses me - it seems to indicate only MCS kit can comply. Is this the case, or would my panels be OK?

The five panels is the most I could install without the strength of the roof becoming an issue, 60Kg is not too much of a problem when spread out.

Cheers.

SS

 

[Earthstore]

One other thing, where do you intend to mount your panels?
and is the property listed?
Your panels would be 600wp, take into account some losses, so you will probably see a "peak" of 480w, and running at around 300w, do you think it is worth all that trouble to gain such a small amount of power?
I do understand what you are trying to do, but if you have the space, then why not ground mount something larger, you could always take it with you when you move.

 

[siliconskum]

The roof is slightly off east / west facing, so I intend to fit them on the west side (so not facing the highway, I'm not in a conservation area but RIGHT next to one... shouldn't be an issue though, plenty of PV installs around). Not listed property. House is also high up a wide valley, so this side is clear of obstructions. Roof sees sunlight from around 10-ish until sunset. Good for around 70% of expected output.

Yeah I allready factored in the losses, the computers average around 350W and about 480 full load (monitors tip it over 550W but they are not in continuous use together). Anything will be an improvement on my bills. And the panels were cheap.

The array size comes down to the roof strength. It's perfectly fine and fit for purpose, but I allready have a surveyors report, and know its state. This size is well under its maximum weight, so there should be no building control issues (and extra expenses). All I need is to to offset some of the computers use, the rest of my house requirements are cheap enough

*edit* Actually, I also have a smaller west facing roof on an extension, it's a little lower than the main roof, but it's also clear of obstructions (bar a phone line). It looses the sun a little earlier, and gets it a bit later, but I could certainly add another 2 - 4 panels there without issue.... I might look into that. Would mean another inverter, but I can live with that.

SS

 

[oliver s]

As far as i see it the Panels only has to be MCS approved to claim the feed in tariff, as long as the panel is manufactured to recognised safty standards i cant see any issue. Some panel manufactures that supply MCS panels also supply non MCS for off grid/ on grid systems so im sure they are made to the same standards. Part P is the electrical installation side of things only. I can see more people doing as you are as panel costs etc become cheaper and elec costs become higher. This is the idea behind the feed in tariff to encorage people to install pv to a point where it is viable to install without the FIT. But i would definatly try to install more than 600w this would only cover your baseline load of appliances then a further 600w would contribute to your computers etc. As earthstore said you will only get an avarage of around 350- 400w from a 600w system. Ideally to save the most you need to balance the output of your PV to your daytime load requirement.

OS

 

[siliconskum]

I see your point. My daytime power use is not much higher than the computers use, only a few intermittent running things (fridge, cental heating pump etc) roughly comes to 300W with everything running (minus occasional use of microwave). I just can't see that being worth the extra cost of the panels and inverter for a variable load of 0 to 300 watts. As I'm not claiming FITs or selling back to the grid, any excess power being fed back into the grid will be wasted, well not saving me any money anyway. 350 to 400W is quite a chunk out of the computers average useage.

I'm not ruling it out, but I need to think about that one. I may buy a few extra panels just in case.

SS

 

[moggy1968]

Your sparky will expect to run the cable, as he is signing to say they are correctly routed and installed to confirm they conform to all the relevant building regs (not just part P). it's not just a case of him doing the connection.
There is more to installing PV (and rewiring a house for that matter) than just making sure it works when you've finished.

If your sufficiently persuasive the sparky may let you work with him to reduce your costs but he will need to be sure your a help rather than a hinderance. I'm doing that with a customer rewire at the moment.

 

[danesol]

If this is of any interest..............

I too was running a SBS2003 server at home, which used far more that what you stated plus i also have 4 x 1.2kva UPS units looking after various devices. I've got rid of the SBS now in favour of a NAS system which doesnt the same job for me however what I wanted to point out is that buying and installing the system yourself in an economical house makes no real sense in my mind, when you can ofset your costs and profit against a proper installation in relation to a FiTs application.

For example at night - we consume now around 330watts and through the day until energy gussling devices are switched on 500-600watts, the real issue comes at night when we have two plasma's going and 1 x PS3 - you can see the bad side of 1kwh till midnight from school times. If and when the cooker or the washer, dishwasher or tumbler comes on thats another 2kwh plus each for an hour or two....

There are ppl who will check or sign your installed system off or ppl who will check your install for you, but in my mind, you would be best to invest in a proper PV system by a registered MCS installer especially if you are staying in the property for at least the next 10yrs, if not the argument for self installation may be warranted, but you need a good 3kw system to make any real gains especially when the weather is against you.....

Certain MCS installers are sending details of 4kw systems for around 6/7K fitted, signed and sealed with all paperwork done.

I would think that you would be able to fit your self for half that..... however as I stated above a proper system tied to a FiTs will serve your current purpose and make you money for years to come so why bother yourself ?

 

[siliconskum]

If this is of any interest..............
t..... however as I stated above a proper system tied to a FiTs will serve your current purpose and make you money for years to come so why bother yourself ?

As I explained, my house was built in 1901 and is a mid terraced slate roofed typical Edwardian property in the North of England. I'm also a private landlord, and have upgraded all (10) of my properties to meet an EPC band D or C. So I know FULLY the costs involved and what I need to do to get my house to comply with the FITs requirments. Basically the money I would have to spend would outweigh any cost saveings I would make from the solar for the next 7 to 10 years,possibly longer as I would need structural work to support a large install. I am unlikely to remain here for a full 10 years, and the property I will be moving to is a listed Victorian building, also listed with the local council as "historically or architecturally important" (and only two such buildings are listed as such for the county, the rest are monuments...), and there is a document I have that is nearly half a ream thick, which tells me what I can and cant have. A small solar install at the rear of the property (west faceing) is possible, but I need planning permission and to jump through hoops etc. Any thing bigger is just not going to happen. So I will likely to be taking my solar panels with me, and renting out a property that has solar panels installed, would be more hassle than I care to take on (trust me on that one - it is not worth my effort).

So, given that I only need to lower my bills where possible (and I've allready installed LED lighting in every room, remove all unneeded loads and reduced power demands by the computers), the best solution for me is a DIY small system.

In any other scenario, I would be agreeing with you.


Anyhow, thanx all. I have decided to add another install to the East side of the roof, though I may try some amorphous panels (probably around 400W due to size and weight). It's cheap enough for me to add in another inverter and swing the scaffolding to the front elevation (family of builders since 1880 - not a problem for me...)

SS