I am a new PV householder - advice please. Unbalanced strings and wrong inverter

[juniperz]

When is your installation date

Well it was last Friday, but I stopped them half way through when I discovered the problem. I am waiting for them to come back with a proposal inorporating Solar Edge + optimisers today, then when I have made a decision (the alternative being to revert to the quoted Growatt inverter wired 8+8 or 6+10) I will ask for next Friday since I will be home then. Friday 13th. Gulp.

 

[sedgy34]

What modules have they given you, sorry I havnt been following what the issues were.

 

[juniperz]

What modules have they given you, sorry I havnt been following what the issues were.

It's in the first post:
"I was quoted for a Growatt-3600MTL with 16 Suntech STP 245S panels. We have a large roof, but it is hipped, so the installer proposed 12 panels on the house roof and 4 on a garage roof with same orientation and similar roof elevation. I did a bit of research on the inverter, even had a reply from Growatt saying that the panels should be connected 8 + 8.

So, today they came to install. The electrician has done all the internal wiring but they need to come back Monday to finish the panels and complete the electrical side.
2 Problems:
1) I just looked at the inverter in the attic and found it is not Growatt, but Samil SR4K4TLA1 (also badged Solar River and also known as Samil 4400w)......"

Might get back here at lunchtime

 

[sedgy34]

sounds like growatt prefer balanced strings for there inverters were possible, ive just seen some pics on here and i would make them re doo the work as they dont know how to install neatly!!! also we fit suntech 250s so why cant they 12 modules would get you 3kw but the 4 on there string not sure if that will work, also the board the inverter fixed too is not fire retardent is it, these clowns dont know how dangerous DC actually is.

you should speak to the manufacturer of the inverter to see if 1 string of 4= 980w will work


also dont pay them until everything is working and most of all LABELLED

 

[wstevew]

Is there a regulation thar says an inverter must be mounted on a fire retardent board.

I read a document from SMA that claimed that in theory the constant heat from an inverter will over time dry out wood and could cause a fire. But they concluded the heat from their inverters still would not be enough but were still concerned about wood dust which can ignite at lower temperature.

 

[Gavin A]

I believe it's a manufacturers instructions thing

 

[wstevew]

Thanks

 

[jerriais]

It is good practice to install on a fire proof board, especially when installing in a loft. We use it for every job except if we're on a non-combustible surface. Only trouble is it's not so strong so will usually need to be backed up with ply on the reverse side.

 

[juniperz]

I finally got a revised price from the installer - it was going to cost an extra 10% of the total cost to go for Solar Edge + 16 optimiers, so I have decided to stick with them removing the incorrect inverter and installing the one they quoted for - I don't think I would have got the return on that 10%. They are also going to mount on fire retardant board and do proper labelling.
I have given them this question (paraphrasing some of the advice from here - I hope I phrased it correctly):

"We will have 4 panels on the 35% garage roof and 12 panels on the 30% house roof. I know that we should not have these wired as 4+12 into the 2 MPPTs as the 4 would not generate enough voltage. We have talked about wiring the panels as 8 + 8, but with the roof pitch difference, I believe that it would be better to wire as 6 +10 as this would reduce the losses because 10 panels would not be affected by the pitch difference."​

 

[sedgy34]

If I were you I would check with inverter manufacturer technical helpline just for peice of mind as you seem to be doing the installers job for them

 

[juniperz]

Yes, I am doing that by email to Texas (Growatt is the manufacturer). They had suggested 8+8 before I realised that there was a roof pitch difference (picture me on a roof or two, with a protractor and a spirit level - much easier with scaffolding in situ!). The comment: "... 6 +10 as this would reduce the losses because 10 panels would not be affected by the pitch difference." actually came from Growatt, but I thought I would give the installer the chance to respond.

I do sometimes feel I am doing their job for them, and I thank you all here again, for providing me with (just) sufficient knowledge to do so.

 

[juniperz]

A new development - they have just told me that they cannot get stock of the originally quote Growat 3600MTL, and have offered "Power One Aurora PVI 3.6(16A limited), which (according to our design software) should be suitable to be wired either 4+12, 6+10 or 8+8, as this has a lower tracking voltage".

I remember someone on here suggesting Power One, so I am assuming I should say yes to this.
They send me a datasheet as PDF - I have found a link to it here.
COMMENTS APPRECIATED.

 

[jason121]

go for it beats the growatt

 

[Gary K]

Snatch his hand off for that offer.- Could be one of the most efficient inverters available

 

[jerriais]

How much is the pitch difference? I'm actually attending a Solar Edge technical conference today and would certainly say they are what you need in this case. Also I really doubt they would add 10% to the overall system cost.

Sent from my HTC Desire S using Tapatalk 2

 

[pww]

Actually this is about right. The solaredge inverter is similar in price to, say, an Aurora one. In this configuration you need 16 power optimisers which would make up most of the 10%, then you need to allow for the addtional back room work (solaredge registration etc). Still think the extra would be worth paying, but OP seems not to be convinced.

 

[juniperz]

How much is the pitch difference? I'm actually attending a Solar Edge technical conference today and would certainly say they are what you need in this case. Also I really doubt they would add 10% to the overall system cost.

Sent from my HTC Desire S using Tapatalk 2

Sorry, I have only just seen this.
"We will have 4 panels on the 35% garage roof and 12 panels on the 30%

Actually this is about right. The solaredge inverter is similar in price to, say, an Aurora one. In this configuration you need 16 power optimisers which would make up most of the 10%, then you need to allow for the addtional back room work (solaredge registration etc). Still think the extra would be worth paying, but OP seems not to be convinced.

Yes, this was their rationale - similar inverter prices plus the 16 optimisers.

 

[sedgy34]

they will have to change the startup voltage on the inverter for the string of 4 but still a result for you.

 

[babba]

yes looks like the four panels might as well not be there as they not going to start up the MPPT! as stated above .

Tricky one they should of either used a Mastervolt 600 for the four panels then a single tracker inverter for the other 12.

or gone for solar edge the dip sticks !!!

Makes me laugh really does

But we like a laugh.

 

[juniperz]

But we like a laugh.

Glad I caused some amusement! (I don't mean that is an offended way).