help needed guys please regarding inverter choice

[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.

 

[wstevew]

I have 2 strings of 8 suntech STP240S in a 4000TL all is fine.

However 6 suntech panels will be about 182v (compared to my system).

Although the start up volts can be set for each tracker down to 125v I read somewhere the tracker range is 175 to 550v. Which may be a problem.

NEW SB3600TL?

 

[SpitfireW'sale]

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.

This has been covered by others since your post, but just to clarify: The Power One can handle two unequal inputs as you correctly say. The two inputs (strings) do not need to be in the same lighting conditions, as there are two MPP trackers which handle each string independently. In effect, a dual tracker inverter is similar to having two separate inverters. A problem can occur when you attach two strings, each with different light conditions, to an inverter which only has 1 X MPP tracker, as in your case. This will result in losses (and possibly significant losses depending on the difference in light conditions of each string)

 

[Shirehorse99]

hi guys after a few weeks of negotiation my installer agreed to a power-one 3.6 and had agreed to install in a couple of weeks at no cost to me . Today however after a phone call today he can only get a PVI-3.6-OUTD outdoor version.
When using the online string tool the inverter efficiency is now only 83.1% compared to 90.6% of the PVI-3.6.
is this OK ?

thanks again for your help - i'll be bloody glad to get this sorted!!

 

[babba]

try 3.0 OUTD

 

[Shirehorse99]

i looked at the 3.0 OUTD - but is 99% utilisation a bit too much - inverter working at full capacity?

 

[babba]

I would use 3.0 but its your install.

 

[Shirehorse99]

I would use 3.0 but its your install.

Will a 3.6 be no good then as he has ordered it now.
And why is the outdoor one different in efficiency to the indoor one

 

[babba]

If he has ordered it he can change the order. Look at the data sheet for 3.6 and 3.6 OUTD they are the same minus a fan.
People tend to go for the OUTD, never heard of anyone buying a 3.6...but I on a forum so we may get someone.

 

[Earthstore]

I think you may have answered the questions asked.
If the 3.6 OUTD does not have a fan, then it stands the potential to run hotter, which is why there must be a difference in output.
Now the 3.6 with a fan, is designed for indoor use to cool the inverter therefore giving better performance and probably longevity also.
This is not my field of expertise, however I think that makes sense.

 

[Shirehorse99]

If he has ordered it he can change the order. Look at the data sheet for 3.6 and 3.6 OUTD they are the same minus a fan.
People tend to go for the OUTD, never heard of anyone buying a 3.6...but I on a forum so we may get someone.

Although the 3.0 is optimum for the system - will there losses with the 3.6 given that they start at 120v