Mostly DiY Installation - options?

[JamesPa]

I am intending to install 4 panels in 2 arrays, one array of two panels on a flat roof, and one array of two panels at the apex of the pitched roof (of my 2 storey house).  This will add to my existing capacity, but as a totally separate system to preserve the FIT payments on the existing.  The DNO is happy with the proposed total 5.5kW peak (based on microinverters  - probably the best bet anyway as the array on the flat roof is subject to differential shading, so effectively there are 3 'strings' from a shading standpoint).  

 

With only 4 panels to install, the economics of a fully 'professional' job aren't great, and I'm anyway happy to do most of the work myself.   Im also installing an ASHP, so it makes sense to get an electrician to make the final connections into the CU for both and certify (actually, I cant see a reason why they cant share a connection - but that's a question for later).  It would be easy enough to find someone to do this alone at a sane price.

 

However I don't have the head for heights to climb on the pitched roof, and also export payment terms intervene.  I'm on octopus outgoing agile, and its a condition that the installation is MCS certified, which of course my existing installation is.  So in the ideal world I would find someone to do the work on the pitched roof (is this a task for a roofer or electrician?), make the connection to the CU for the new panels/ASHP, and MCS certify the new installation after I have done all the 'grunt work' other than high up on the pitched roof.  

 

Does anyone have any experience of a division of labour of this kind.  General electricians are used to 'first fix/second fix' and many are happy just to do second fix (its the high value and interesting bit after all).  However I get the impression that most of the (fairly few) MCS contractors locally are pretty much wedded to the idea of doing the whole job and charging an exorbitant amount for the privilege.  

 

Any suggestions here of how to avoid being totally ripped off?

[ProDave]

To claim an export payment the install has to be MCS, so that rules out DIY.  If your existing system is already getting export payments you could (cough) just install the extra and see if anyone notices the amount of export has gone up?

 

But my view is you already have (I assume) 4kW of existing PV so it will be hard to self use any extra above that, and funding it on export payments I don't think makes sense.  So I would be looking at the additional system being connected to battery storage entirely for self use outwith the times the main system is generating.

[Nickfromwales]

3 hours ago, JamesPa said:

I'm on octopus outgoing agile, and its a condition that the installation is MCS certified, which of course my existing installation is.  So in the ideal world I would find someone to do the work on the pitched roof (is this a task for a roofer or electrician?), make the connection to the CU for the new panels/ASHP, and MCS certify the new installation after I have done all the 'grunt work' other than high up on the pitched roof.  

You only need to meet this criteria if you export the extra ( new ) capacity. Why not fit a hybrid inverter, totally DIY it, and set the inverter to 0% export via limitation software?

You only need an electrician then who's done PV before.

[PeterW]

10 minutes ago, Nickfromwales said:

Why not fit a hybrid inverter, totally DIY it, and set the inverter to 0% export via limitation software?

Any of the micro inverters do that ..? Makes it even easier as the connection is then just into a rotary isolator. 

[Dillsue]

5 hours ago, JamesPa said:

This will add to my existing capacity, but as a totally separate system to preserve the FIT payments on the existing.  

The FIT rules have changed and you can alter a FIT system without losing your payments-

 https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.ofgem.gov.uk/sites/default/files/2021-12/Feed-in%20Tariffs_Guidance%20for%20renewable%20installations_V16.pdf&ved=2ahUKEwi91OP77aT8AhVHTUEAHebpBEoQFnoECBIQAQ&usg=AOvVaw3i84Pu-SO0Ibm-lhEjzfaT

[JamesPa]

11 hours ago, Dillsue said:

The FIT rules have changed and you can alter a FIT system without losing your payments-

 

Wow thanks for that, I was not aware (I wonder how many were).  

 

Its a lot of regulation to read, but on a skim it looks like extensions are allowed but the FIT tarrif claim must be prorated unless there is a separate generation meter.  That's fair enough, basically you still get paid for the original amount of generation but not the added amount.

 

Practically speaking how might it work though.  One could possibly add additional panels to an existing inverter if it has capacity, but how would it react to a mix of panel specs (12 year old 250W panels and new 400W panels). 

 

Or I suppose (if combining technologies is a problem) install a new inverter capable of multiple string operation and treat the old and new panels as separate strings?  Since the 'old' inverter is nearing the end of its design life (but, so far as I am aware still going strong), this might not be such an extravagant option.

 

 

[JamesPa]

13 hours ago, Nickfromwales said:

You only need to meet this criteria if you export the extra ( new ) capacity. Why not fit a hybrid inverter, totally DIY it, and set the inverter to 0% export via limitation software?

You only need an electrician then who's done PV before.

That's obviously a possibility.  To check my understanding (Im a physicist by training not an expert in the capabilities of currently available inverters) - to make this work I would need a CT on the meter tails so that the new inverter shuts down when it senses export, but does so without affecting export from the existing inverter? - is this correct?

 

Its certainly a simple solution (and maybe what I will ultimately do).  However I (and the planet) lose out on the potentially exported energy.  I'm not averse to having it installed to MCS standards, or to paying a reasonable fee for the installation, just to paying an arm and a leg.

 

16 hours ago, ProDave said:

But my view is you already have (I assume) 4kW of existing PV so it will be hard to self use any extra above that, and funding it on export payments I don't think makes sense.  So I would be looking at the additional system being connected to battery storage entirely for self use outwith the times the main system is generating.

16 hours ago, ProDave said:

To claim an export payment the install has to be MCS, so that rules out DIY.  If your existing system is already getting export payments you could (cough) just install the extra and see if anyone notices the amount of export has gone up?

 

I can't say I hadn't considered it the 'just install' option .  I have a solar DHW diverter so my current export will be below 'expectations', furthermore I've only just moved from deemed export to measured export, so I doubt the data to spot the difference exists.  However its not in my nature to do things 'improperly' if there is a sensible 'proper' solution.  Also there are probably people watching this forum! 

 

Re battery storage, I will do the sums, but so far have never been able to make them add up.  Local battery storage is, so far as I can see, negative environmentally where the alternative is export to the grid, so it would need to work financially to be justified. 

 

 

 

 

 

 

 

[Dillsue]

2 hours ago, JamesPa said:

Practically speaking how might it work though.  One could possibly add additional panels to an existing inverter if it has capacity, but how would it react to a mix of panel specs (12 year old 250W panels and new 400W panels). 

You were talking about a micro inverter solution so I assume that's what youve already got?? Solaredge optimisers deal with a mix of panel sizes and I assume micro inverters do too but that would be a question for the manufacturers tech support. It's the micro inverters that interact with each other, not the panels, so you can probably use whatever panels you want up to the limits of the micro inverters they are connected to. 

Plugging in 4 additional micro inverters into an existing loop shouldnt be a problem and if you use factory assembled and tested inverters/cables/plugs then its straight forward to connect up.

[Dillsue]

16 hours ago, Nickfromwales said:

Why not fit a hybrid inverter, totally DIY it, and set the inverter to 0% export via limitation software?

The DNO has said the extra panels will be ok so no need to limit export

[Dillsue]

2 hours ago, JamesPa said:

I have a solar DHW diverter so my current export will be below 'expectations', furthermore I've only just moved from deemed export to measured export

 

 

 

 

Not sure of your figures but if youve got a PV diverter wouldnt you be better off on deemed export??

[Nickfromwales]

3 hours ago, JamesPa said:

Its certainly a simple solution (and maybe what I will ultimately do).  However I (and the planet) lose out on the potentially exported energy.  I'm not averse to having it installed to MCS standards, or to paying a reasonable fee for the installation, just to paying an arm and a leg.

It is a contradiction to install additional PV that you won't use, so referring to not being able to give away ( for SFA ) the extra energy you pay ( a disproportionally huge amount ) to install is lunacy.

If you're getting the FiT payments ( a bloody grotesque scheme on a good day but staggeringly good news to anyone who adopted it ) then just leave this all well alone and enjoy the free money? The planet will not benefit, due to the processes to manufacture, install, and recycle these components.

 

This plan is ( IMHO ) a bad, and wasteful, idea.

Edited January 1, 2023 by Nickfromwales

[JamesPa]

1 hour ago, Dillsue said:

You were talking about a micro inverter solution so I assume that's what youve already got?? Solaredge optimisers deal with a mix of panel sizes and I assume micro inverters do too but that would be a question for the manufacturers tech support. It's the micro inverters that interact with each other, not the panels, so you can probably use whatever panels you want up to the limits of the micro inverters they are connected to. 

Plugging in 4 additional micro inverters into an existing loop shouldnt be a problem and if you use factory assembled and tested inverters/cables/plugs then its straight forward to connect up.

 

I haven't yet bought the micro inverters, my existing inverter is a string inverter. 

 

1 hour ago, Dillsue said:

The DNO has said the extra panels will be ok so no need to limit export

 

The export limit was suggested as a way to circumvent the requirement that, to get paid for export, you need an MCS install.  So by setting the new inverters to zero export Im not compromising the payments on the existing install

 

1 hour ago, Dillsue said:

Not sure of your figures but if youve got a PV diverter wouldnt you be better off on deemed export??

 

We haven't got teenage children so use only a sane amount of DHW!  On summer days the DHW is fully heated by 11am or even earlier and I export for the rest of the day unless we are doing something 'power'.  The panels are facing 25 degrees west of South to, so the rest of the day is actually most of it.

[JamesPa]

41 minutes ago, Nickfromwales said:

The planet will not benefit, due to the processes to manufacture, install, and recycle these components.

 

This plan is ( IMHO ) a bad, and wasteful, idea.

Only, I think, because of regulation.  If they can be installed for a reasonable price and I can get paid for the extra export then I think it benefits both me and the planet.  The exported energy will get used elsewhere down the road, with efficiency, presumably, very close to that of self use, because not many of my neighbours have solar panels.

 

Unless of course you are arguing that local solar is not good for the planet even if you self-use the energy harvested.

[Nickfromwales]

I'm just stating the facts.

Installing more PV should only be done if you are at sub zero export, eg still ( residually ) reliant on importing from the grid after the first installation.

Installing specifically to export is the least "helpful" thing you could possibly be doing with your money. Why not invest in installing IWI or EWI / insulating cavities / replacing boiler with a modern appliance & controls / upgrade to 3g glazing etc etc.

 

If you really want to help the planet, donate the funds to the WWF / other such entity that will put it to good use. You're not doing that afaic, sorry.

 

If, however, you go for a hybrid inverter and add batteries, ( so you do not need permission from the DNO ( as the battery system adds to your gross microgeneration figures for submission to the DNO )) then this may make sense. I would dare to say that you'd still be better off, at that point, in investing in a bigger battery ( instead of the additional PV ) and load-shifting off a ToU tariff to reduce reliance throughout the entirety of the year. I wouldn't be an advocate of just installing a battery for this purpose, but if it can be quickly and cost-effectively installed, to primarily harvest the export you already have, then it's a more viable consideration to do as I suggest above. 

Edited January 1, 2023 by Nickfromwales

[ProDave]

5 hours ago, JamesPa said:

I have a solar DHW diverter so my current export will be below 'expectations', furthermore I've only just moved from deemed export to measured export, so I doubt the data to spot the difference exists.

Why did you do that? deemed export assumes you export 50% of generation.  With a PV diverter you probably export less than 50%,  so you will loose out.

[JamesPa]

 

13 minutes ago, Nickfromwales said:

Why not invest in installing IWI or EWI / insulating cavities / replacing boiler with a modern appliance & controls / upgrade to 3g glazing etc etc

Pretty much all done already with the exception of triple glazing (but I have progressively upgraded the glass only in my double glazing as panels have failed, wow does it make a difference!)  Working also on a heat pump to replace aging boiler, if my LPA will allow it (see separate thread about the crazy noise constraint they have applied)

 

13 minutes ago, Nickfromwales said:

Installing more PV should only be done if you are at sub zero export, eg still ( residually ) reliant on importing from the grid after the first installation.

Over the year I currently use the same as I produce, however of course the generation and the use times of day don't coincide so, yes, I am reliant still on grid import.  With a HP the balance will of course change in favour of import.  The two initiatives are sort of linked, together they reduce my scope 1 and 2 emissions from my house (using the government reporting methodology) by 78%.

 

17 minutes ago, Nickfromwales said:

If, however, you go for a hybrid inverter and add batteries...

All my calculations to date conclude that batteries don't work financially, unless electricity prices go up again significantly and stay up (which I don't rule out).  If the alternative is grid export then they make absolutely no environmental sense at all because they consume scarce resources for no environmental gain. 

 

 

[JamesPa]

7 minutes ago, ProDave said:

Why did you do that? deemed export assumes you export 50% of generation.  With a PV diverter you probably export less than 50%,  so you will loose out.

Because my actual measured export is pretty much spot on 50%  (no teenage children so sane hot water usage!) and Octopus pays much more on measured export than on deemed export.

[Dillsue]

3 hours ago, JamesPa said:

 

I haven't yet bought the micro inverters, my existing inverter is a string inverter. 

 

 

The export limit was suggested as a way to circumvent the requirement that, to get paid for export, you need an MCS install.  So by setting the new inverters to zero export Im not compromising the payments on the existing install

Have a look at the spec for your existing inverter as you may well be able to have way more DC input from panels than the inverter rating. Our older 4kw inverter can accept 5.4kw of panels and our newer 3.68kw inverter can accept 5.7kw of panels.

Extending the system rather than adding a second system keeps you within the OFGEM guidance for pro rata payments and no worries about export limitation. If you put a second system in with DIY export limitation, you probably dont want to declare that to Octopus as Id be surprised if they'd accept a casual limitation set up that you could easily remove or alter yourself........unless anyone has done this????

[JamesPa]

53 minutes ago, Dillsue said:

Have a look at the spec for your existing inverter as you may well be able to have way more DC input from panels than the inverter rating. Our older 4kw inverter can accept 5.4kw of panels and our newer 3.68kw inverter can accept 5.7kw of panels.

Extending the system rather than adding a second system keeps you within the OFGEM guidance for pro rata payments and no worries about export limitation. If you put a second system in with DIY export limitation, you probably dont want to declare that to Octopus as Id be surprised if they'd accept a casual limitation set up that you could easily remove or alter yourself........unless anyone has done this????

That's rather a useful idea.  I have an SMA SunnyBoy 4000 with a total of 4kWp panels, not all at optimum angle so in practice I suspect the peak input is a bit less (I could check the logs I guess).  I think that in principle I could add 4*400W without breaching the input limits.  I imagine that I would need to put at least some of the panels on individual optimisers as they would be much newer and thus a different spec (and in some cases a different orientation) to existing.   Tigo seem to do optimisers which work with any inverter and (according to Midusmmer wholesale) aren't needed on every panel, only the 'out of spec' (ie new) ones.   

 

This is beginning to get interesting; the saving on inverters might pay for an MCS installer so I can still get the export payments on the whole combined array, as well as claiming the FIT payments on the original using the proportionating approach that is in the updated FIT document you referred to earlier.

 

There would, I suspect, be a period during the summer where the inverter (which is limited to 3.84kW o/p) clamps the output, but probably not for much of the day or for many months.  It needs a bit of back of envelope work to see if this limitation matters much.  I feel a spreadsheet and some downloads from PVGIS coming on.

 

 

[Dillsue]

The 4000tl spec Ive just looked at has max DC input as 4.2kw so quite limited. It also seems to have 2 MPPT inputs so if only one is currently wired you could hang your new panels on the free input.

 

PVGIS will give you hourly data which you can crunch in Excel. Put in all the panels facing the same direction AND inclination as a single array and down load the data for the best FIT generation year youve had. Repeat for the remaining panels grouping them in separate arrays by common direction and inclination. Once you've downloaded all the data put the date, time and kw from each dataset into a new sheet. Add all the kw values to give you total kw for every time period. Then sort the entire sheet by kw total column to see what your likely peak kw DC input is. If its 4.2kw or less then youre good to go, otherwise a bit more thinking.

 

Bear in mind that if your max PVGIS input is close to the inverter limit, then over time you might have problems with changing weather. Despite the fact that panel output is supposed to drop off over time, we've just had our best annual generation since 2015 on our FIT system.... climate change or a one off???

[JamesPa]

9 minutes ago, Dillsue said:

The 4000tl spec Ive just looked at has max DC input as 4.2kw so quite limited. It also seems to have 2 MPPT inputs so if only one is currently wired you could hang your new panels on the free input...

Im using both inputs so will still need some form of optimiser I suspect.

 

I crunched the numbers using the 2005 PVGIS data (which is the download it gives by default) capping the o/p at 3.84kWh in each hourly time period. The calculated aggregate 'sacrifice' because of the output power cap is just 47kWh!  I dont know whether 2005 is an average year or not, but 47kWh is small enough to be negligible.  

 

There are some periods where the peak input exceeds 4.2kW but neither the voltage nor the current will be outside the limits, so I wonder if the inverter will care?   Im guessing perhaps not, it may just operate slightly sub optimum.  I wonder how to find out - perhaps ask SMA..

[Nickfromwales]

You'd have to Tigo the lot most probably. FYI you can get Tigo's which go 1 unit per 2x panels, so may help out with economics, understanding their correct deployment of these units is of course critical.

 

Prob have to re-string also with that close a capacity vs what will end up installed, to split evenly across the two inputs.

Edited January 1, 2023 by Nickfromwales

[JamesPa]

12 hours ago, Nickfromwales said:

You'd have to Tigo the lot most probably. FYI you can get Tigo's which go 1 unit per 2x panels, so may help out with economics, understanding their correct deployment of these units is of course critical.

 

Prob have to re-string also with that close a capacity vs what will end up installed, to split evenly across the two inputs.

I will need to read up both on Tigo and on my current inverter!  The latter supports two strings, but has two inputs for each string, im not sure how these relate (probably just wired directly together internally).  The current array is anyway split 1.5kW/2.5kW so I think its might well work simply to add to the new panels (with optimisers) to the shorter string.

 

First step it to check that the SunnyBoy is happy if the maximum available power exceeds the spec, even though the voltage and current do not.  I'm struggling to imagine it would do anything other than operate slightly sub optimally under these conditions to throttle back, but Id better check before getting too excited.  

[Ronski]

On 01/01/2023 at 09:55, JamesPa said:

I was not aware (I wonder how many were). 

I became aware recently, so at some point I may replace my existing panels, and split it into two strings, with the second string on my Victron system. I'm currently DIY adding a Victron system to my garage, but the electrician is going to do the 240v work.

 

Strictly speaking you do not need MCS to get paid for exports, there are other 'bodies' that can check/approve, I can't remember the details but I think I may have a link saved at home. The main problem is just about everyone thinks you do need MCS, but those of us with existing MCS systems I can't see it being a problem.

 

I'm also fitting batteries, which means I should not use any grid power between March and September roughly, and we can charge the batteries off peak in the winter months greatly reducing our electricity costs.

 

I'm still on 50% deemed export for my FITS system, not sure yet if we'll change from that, will need to crunch some numbers once the additional system is added.

 

PS I don't think it's a good idea mixing different panels with different ratings on the same string, even with optimisers.

[JamesPa]

3 minutes ago, Ronski said:

PS I don't think it's a good idea mixing different panels with different ratings on the same string, even with optimisers.

I probably wouldn't by choice, but the panels I have are 12 years old and no longer available