System Question

[WRDEnergy]

Hey all,

This might be slightly weird but bear with me.


I am doing an install on Monday and I have designed it based on the SMA sunny design software, I saw that if i used 12 218watt hyundai panels I get a 99% efficency using a 2500HF-30 and if i use 6 220watt hyundai panels on a SB 1200 i also get a 99% efficency.


so i have 2 roofs 1 i was going to put the 12 panels and the other the 6 panels this is all on 1 house but has 2 sections to the roof... I know i have a almost perfect inverter choice but my questions is this.... can I combine the AC side from both inveters into the same generation meter... or do I have to use 2 generation meters ? parts for me are not a problem but I have never done a build this way.... I know techinallly both inveters will be giving out 230v 50 hz but like i say i dont know if its good to combine them

to confirm i will have both go into the generation meter then have just 1 go to the consumer unit (basically joining them in the meter)


Any advice on this would be great.


thanks

 

[wstevew]

Im not an Installer but when I was getting quotes there was a discussion about having 2 smaller inverters and they would have connected them before a single generation meter.

Im not sure if you can register more than one meter for the FIT.

 

[snoopdog]

Hi yes that sounds fine to me, when we have had two invertors in the past they have been in loft.

we had 1 AC PV isolator adjacent to the consumer unit, then via one self generation meter.

6.00mm T & E up to the loft feeding local AC isolator Invertor 1, Then loop off the live side of AC isolator 1 to feed AC isolator to Invertor 2

 

[Gavin A]

hi, I'm afraid you're misunderstanding sunny design.

You can never get 99% efficiency on any inverters current available, certainly not the SB1200 or 2500HF. The highest you'll get on the SB1200 is around 93%, and maybe 94.5% on the HF.

I think you're possibly seeing the capacity factor (or whatever they call it) and mistaking it for efficiency.

if I'm reading that right and you've got a 12 panels on one roof, 6 panels on the other, then the most efficient and most cost effective option in the SMA range will be either the 3600TL or 4000TL with dual MPPT. Unless there's some reason you can't run both arrays into a single inverter.

 

[WRDEnergy]

hi, I'm afraid you're misunderstanding sunny design.

You can never get 99% efficiency on any inverters current available, certainly not the SB1200 or 2500HF. The highest you'll get on the SB1200 is around 93%, and maybe 94.5% on the HF.

I think you're possibly seeing the capacity factor (or whatever they call it) and mistaking it for efficiency.

if I'm reading that right and you've got a 12 panels on one roof, 6 panels on the other, then the most efficient and most cost effective option in the SMA range will be either the 3600TL or 4000TL with dual MPPT. Unless there's some reason you can't run both arrays into a single inverter.

I was refering to power ratio when i said efficiency also acording to sunny design using a 3600tl would be worse than using a 1200 and a 2500 but my question was about combining them into 1 meter.

Max efficiency on the 2500HF-30 will be 96.3% and on the 1200 it will be 92.1%

 

[petex2416]

Personally I'd of gone down the Solaredge route on this one. One inverter, maximum possible efficiency...

 

[WRDEnergy]

Personally I'd of gone down the Solaredge route on this one. One inverter, maximum possible efficiency...

Thanks.... but I already have the parts and I already have the 2 inveters I know its easier to use just 1 inveter but using 2 will work better which is a fact and will be more efficent overall and produce higher yields I know its easier form an electical point of view to use just the one inveter but I am going to use 2 and was trying to find out if I could terminate them together on the AC side and then go into the Meter or CU as usuall.

 

[Gavin A]

I was refering to power ratio when i said efficiency also acording to sunny design using a 3600tl would be worse than using a 1200 and a 2500 but my question was about combining them into 1 meter.

Max efficiency on the 2500HF-30 will be 96.3% and on the 1200 it will be 92.1%

On this specific system, sunny design puts the average efficiency of the 2500HF at 92.6%, and SB1200 at 89.7% in that set up, with a combined estimated annual generation of 2884kWh / year

It puts the average efficiency of the 3600TL in that set up at 93.3% and the annual output at 2940kWh / year

In what way is a system that is more efficient, generates more through the year, costs less and actually complies with the G83 regs, the worse system?

 

[Gavin A]

to answer your question though, yes you can terminate them together on the AC side, as long as each inverter has it's own isolator.

 

[WRDEnergy]

Thank you for the answer, I must be using a diffrent version of the sunny design to you as the results It is showing to me is dirrent to what you have.


and they have a combined annual yield of 3462.80kwh prehaps you put the wrong hyundai panels into the system they have quite a few rated at 218watt and 220watts.

 

[Gavin A]

ok, I had only used 10 panels instead of 12 on one part of the system, and have now swapped to the 218 & 220Wp panels Hyundai are selling in the UK (the 1476mm versions)

3316kWh and 93.6% efficiency for the 3600TL

vs

3260kWh / year with 93.2% average efficiency for the 2500HF and 89.8% for the SB1200

the exact figures will be different to yours because I don't know the orientations, so have worked it on both systems facing south.

The difference between the 2 is fairly marginal, but it's simply not true to claim that the 3600TL would be worse than the 2 inverter set up. There could be other reasons for recommending 2 inverters, but performance is not one of them on a system that's right in the middle of the 3600's range.

In this situation a dual MPPT TL inverter is virtually always more efficient and more cost effective.

 

[WRDEnergy]

Right.... I explained the pros and cons to the customer of having 2 inveters vs 1 or vs a dual tracking the price is only £200 more for the 2 inverters vs the 3600 atleast from the supplier I use and they decided to go with the 2 inveters.

I agree with you there isnt much diffrent in terms of performance, well its a fact so dosent matter if i disagree or not thanks for your help though.

 

[Gavin A]

no worries, just correcting the mistaken impression you were giving of the relative merits of both options, as we would almost always recommend the opposite for the reasons stated.

on top of the £200 you've also got an extra AC isolator, junction box, extra cabling, extra fitting time, the extra cost of fitting the bluetooth piggy back unit if you're offering a sunny beam etc.

anyway, as you say, you've already bought the kit, I just didn't think others should follow that advice without seeing the counter argument.

 

[WRDEnergy]

no worries, just correcting the mistaken impression you were giving of the relative merits of both options, as we would almost always recommend the opposite for the reasons stated.

on top of the £200 you've also got an extra AC isolator, junction box, extra cabling, extra fitting time, the extra cost of fitting the bluetooth piggy back unit if you're offering a sunny beam etc.

anyway, as you say, you've already bought the kit, I just didn't think others should follow that advice without seeing the counter argument.

Yes I agree although in this case the only extra cost is £200 for the inverter and £20 for the isolator as 6 of the 18 panels are going on an outhouse in the garden so we would need the same length of cable same with fitting time etc... but I 100% agree with you if it was all on the same roof or one roof next to the other then it would be a waste of time, I would never have even suggested it to the client if that had been the case.... but as I said this post was about combining them together not to talk about weather using 1 or 2 would be a good idea as I understand that aspect (clearly I dont know everything as I wouldnt have posted here in the first place)


Thanks

 

[SolarCity]

I just thought I'd add that I'd be very surprised if the two inverter option gets even close to the yield of the TL inverter.

I know Sunny Design gives an approximate yield but apparently it uses a very vague method for working this out - it is more of a configuration tool than a yield estimator.

The reason I doubt that the two inverters option will do as much as the TL option is that our results are all showing considerable improvement from our installs using the transformerless option.