Two strings, solar inverter question.

bris

I just picked up a 3.9 kw kit, 20x 195w panels. When The seller saw my roof layout he informed me the inverter that was with the kit would not be suitable as the instalation was spread over two roofs at right angle to each other. The lay out will be 7 panels on the smaller roof and 13 on the other so he suggested i should get two inverters as it would need two strings and the inverter wouldn't handle the MPPT tracking well enough because the one string is much bigger than the other.
I am now back at the drawing board as far as inverters are concerened. Firstly is he right, is one tracker not up to the job.
Secondly I was thinking of the Sunny boy SB1700 for the smaller string 1365 watt and the SB2500 for the larger string 2535 watt would the SB2500 be enough for the bigger string, would the extra 35watt make a difference.
I don't mind having to get two inverters if it does a better job so it's not an issue if it works out better.
Finally, he gave me two AC isolators for the kit but only one DC isolator as he said the two inverters could go into the on DC as it was designed for two, should I use another one and keep them seperate.
Thanks for looking, ant answers are greatly appreciated.

zeupater

bris wrote: »

I just picked up a 3.9 kw kit, 20x 195w panels. When The seller saw my roof layout he informed me the inverter that was with the kit would not be suitable as the instalation was spread over two roofs at right angle to each other. The lay out will be 7 panels on the smaller roof and 13 on the other so he suggested i should get two inverters as it would need two strings and the inverter wouldn't handle the MPPT tracking well enough because the one string is much bigger than the other.
I am now back at the drawing board as far as inverters are concerened. Firstly is he right, is one tracker not up to the job.
Secondly I was thinking of the Sunny boy SB1700 for the smaller string 1365 watt and the SB2500 for the larger string 2535 watt would the SB2500 be enough for the bigger string, would the extra 35watt make a difference.
I don't mind having to get two inverters if it does a better job so it's not an issue if it works out better.
Finally, he gave me two AC isolators for the kit but only one DC isolator as he said the two inverters could go into the on DC as it was designed for two, should I use another one and keep them seperate.
Thanks for looking, ant answers are greatly appreciated.

Hi

Talk to the installer about a SB4000TL - It's got two MPPTs and will cope with a 13/7 split with the randomly selected 195W panels which I just tried in the SunnyDesign software ..... download the software from the SMA website and try your configuration out on two arrays with the panel make/model which you have ..... (http://www.sma.de/en/service/downloads.html)

HTH
Z

ps - You mention kit ... you do realise that it needs to be a MCS accredited installation in order to register for FiTs ??

bris

I am downloading it now. I was hoping to steer clear of a TL inverter because of the earthing needed for one, but I will let the electrician worry about that if I can't find an alternative solution.