any ideas appreciated...... I have just installed 8 x 240w bosch solar panels on my house.They are to be used in conjunction with a 'sunny boy' 2500 inverter. However upon commisioning the voltage off the panels is not reaching the 300vdc required startup voltage to kick the system on. Voc = 30vdc per panel. The output of the string is between 240vdc and 287vdc. I have a dilemma - do i purchase a new inverter that will accept a lower startup voltage, or do i just put another 2 panels up to up the voltage from the string??? Does anyone know if the voltage drops once the inverter is grid tied - in that if i did purchase an extra two - would they be enough to keep the voltage above the 300vdc threshold. Or can the threshold be adjusted on the sunny boy 2500's? (My installer is also a little unsure what to do).

Is your installer mcs registered, if so he shouldnt be in the dark so to speak

Go to the sunny boy website, they have design software available.

what should the open circuit voltage of each panel be? sounds like a little design problem. If you have room for 2 more panels why didn;t you install them in the first place? I know money comes into it but the only way to make solar work is to put as many panels as possible up

If there is room, installing more panels will be better than buying a smaller inverter

Hes paying 5 percent vat on the inverter.
Your paying 20 percent!

Get your installer to ask sma for an installers code, he will need to prove he is an approved installed and using bluetooth to access engineers settings, I would check with SMA before doing this but input voltage can be altered slightly, from memory I think it is less than the 300v you say, I thought it was more half that for 2500.


Your inverter is two big for only 2 pannels

-------------------------
Dougie
Power Plus Electrical.co.uk

My mission is to live as long as possible......so far so good!

Thanks for info, I will speak to SMA this morning.

Are the modules the right ones ?
30 volts sounds rather low an open circuit voltage for large modules.
Some modules are effectively 2 lower voltage modules in the same housing, intended for series or parralell connection according to the required voltage. Perhaps you have this sort ?

Presuming that the modules are correct, then 8 times 30 is clearly 240, which is less than the inverter wants.
Adding 2 more modules will be marginal, I would go for 4 more if possible.
Once the inverter is running, then the array voltage will drop, but the inverter will accept a lower running voltage than it needs to start.

Actually FM the customer pays 5% whereas the installer pays 20% which is why the installer has to be VAT registered. As regards the original question, to get the FIT it must be installed by an MCS registered installer, to get the MCS qualification you must be able to prove competency. Whoever designed and installed this obviously isn't competent.

Apologies grumpy, i knew there was a 5 somewhere.
I have had pv for 18 months, but unlike others whonread their meters daily, i forget to read mine on the quarterly basis.
It really is fit and forget!

I've got to agree with that - I've got a SMA 2000 on 9x 240W panels - UK conditions won't produce 100% output from the panels and oversizing the inverter means higher losses.

I don't have the exact numbers to hand, but I'm sure mine runs on 200-300V on the d.c. side - I'm pretty sure it's just one string, so 30V per panel doesn't seem outlandish.

- Andy.

Your installation is badly designed. As existing, the next size up from 1500W for the inverter should have been specified. If you can fit two, or more panels, then you would have had a much better return if they had been fitted originally. If your installer isn't you then I would be having a very harsh conversation with him. However, if it is you, I would look in a mirror and have a very harsh conversation with your installer.