help needed guys please regarding inverter choice

[Shirehorse99]

I'm still going to ask for a power one - if a cash adjustment is needed i will do it .
The job was a rush job - done in a day - so they could get as many in as possible. They just wanted to commission the job and come back to finish it off after the 12/12. They completed the flat roof last week ( panels have been weighted down on floor for 5wks)

Its a big company - part of carillon group - I don't really want to pay anymore than the 11250 I've paid now. I think after paying that amount of money I should have the system I specified

 

[FB.]

Sounds like incorrect advice to me.

The strings should be on the same angle and orientation as stated above by noddy. If there is a small difference this may be OK, but by your reply, there will be shading on one array when the other has direct sun. Also you would ideally have 2 balanced strings for the inverter, i.e. 2 strings of 7, not 1 string of 8 and 1 of 6.

You should have either two smaller inverters, or 1 dual tracking inverter. Bypass diodes will not help in this example. FYI the SB3000 is not a dual tracker, so would not have been appropriate either. Power One would be a good choice.

I am not sure how you will resolve this, as the initial suggestion of the SB3000 would have yielded the same result, unless you had been quoted on the SMA 4000TL for the Schuco panels, which is a dual tracker.

Hope you get things sorted out!

Have I misunderstood you or got confused?

Just the highlighted bits; I though that a Power One Inverter was capable of handling two unequal inputs in a more-or-less normal way, as long as all panels in each of the two strings were in the same lighing conditions (therefore bypass diodes not involved). ?
e.g. I thought that a Power One's dual inputs had no problems with (say) a string of four which get sun in the morning and a second string of six which get sun in the afternoon.

Sorry if I've misunderstood or misinterpreted your words.

 

[Shirehorse99]

Fb - is this post for me to answer ? - I haven't got a clue mate

 

[FB.]

Fb - is this post for me to answer ? - I haven't got a clue mate

Shirehorse -
No; the question was aimed at Spitfire - to clarify whether there is an issue with unequal strings going into a Power One inverter.

I thought that Power One inverters could handle two unequal strings - and that may be why Spitfire has recommended the Power One.

 

[Noddy67]

spitfire was just saying that it does need two strings... and then secondly that the PowerOne woudl be ideal because it has two strings which can be unequal.

I know Spitfire W and I know they know their onions / inverters.

 

[FB.]

spitfire was just saying that it does need two strings... and then secondly that the PowerOne woudl be ideal because it has two strings which can be unequal.

I know Spitfire W and I know they know their onions / inverters.

Thanks - that's what I thought, but I wondered whether I'd missed something.

 

[moggy1968]

A 400Tl is over rated on this system. A kostal pico 3.6 or power one 3.6 would be most suitable. neither the SMA or aurora are suitable.
HOWEVER you need to be sure the smaller string has enough voltage to power up the inverter. I don't have the specs of your panels or the inverter to hand to check.
Kostal may do a 3000 with twin MPPT but don't quote me on that. the other option is 2 inverters, but they won't like that!

 

[Noddy67]

Is over-rating isn't a problem as such? As long as you don't mind paying a little over the odds and the start up voltages are met it's not a problem. As such I think the P1 Aurora 3.6 is fine. It starts up at 120v so six panels is more than enough to fire that up.

No?

 

[cbw]

I LOVE the power 1.....Only downside is having to earth the array.

 

[Donavan Bangs]

you can have whatever inverter your heart desires , no sap calcs no contract

what if you think the sap calcs are off because they didnt calculate for a split system? and the azimuth was wrong?

 

[SolarCity]

First of all, make sure you don't get charged any extra. You asked for a professionally installed PV system and that's what you should be getting.

"Is over-rating isn't a problem as such?"

It's a good question. It is generally accepted that oversizing inverters is a bad idea as they won't work as efficiently as they might.

However, I have heard different from one other person. He told me that the only issue with oversizing an inverter is that you will pay more.

He is the Technical Service Support at SMA UK so I'm inclined to listen to him.

 

[Noddy67]

Hi Biggs,

Yes, I got my advice from the technical bloke at Powerone that oversizing (ignoring start up v) doesn't matter as such ... that's two heavy weight answers to the questions.

R

 

[FB.]

Re: over/under-rating an inverter:

According to the stats I've seen, it is only when the inverter is working below about one-third of potential (e.g. on dull days) that there is a modest loss of efficiency (a few percent) compared to a more suitably-rated inverter.

At the other end of the spectrum; an inverter with too much coming in from the panels is just wasting energy/overheating. Since quite a few people are finding that their PV is outputting 10-20% more than "the calculators" predicted, I'm not sure that it would be wise to have favourably-oriented (e.g. SSE, S, or SSW facing) panels too much greater capacity than the inverter.

Therefore, in view of both points I just covered; I would suggest a closely-matched inverter/panel setup.

 

[Shirehorse99]

Guys - I've been in work all day - so what is the general concensus about my system - power one 3.6 , sunnyboy 4000tl or what?

Im even more stumped now after reading through your posts

 

[Noddy67]

Ha ha, we've gone off-topic.

In a nutshell, either two seperate single inverters or a dual tracker is the bottom line... there are lots on the market but my preference would be a PowerOne Aurora 3.6.

good luck and let us know what happens.