East - West Split - How many invertors???

[ian81]

Hi, my company have sent me to do an East West split with 18 Sharp 185w panels (9 on east and 9 on west) and one Sunnyboy 3800 invertor. Ive raised my concerns over having just one invertor and i feel that i need one for each side (without working out something like 2 x SB1700). Does anyone know if its advisable to have 2 invertors or even if it will work with one invertor???? im a bit confused any help would be great!!!!

 

[Energetic]

One for each side or a multistring (2 MPP trackers) inverter would do it. My understanding is the same as yours, different orientations should be seperate...

 

[Markc]

SB3800 is a single MPP tracker so the system is poorly designed. Certainly a much better yield from two inverters.

 

[ian81]

Cheers for youre advice im going to go back to the office in the morning and let them know 2 invertors would be best. Weve got PvSol but i think they need some training on it!!!!! i havent yet had a chance to go on it yet maybe this is my chance to have a play with it as ive heard its one of the best around!!!!

 

[claypole]

And even without the E/W split Sunny Design shows it won't work - unless they're NT panels, the only Sharp 185's that will produce the correct voltage range for a 3800. I received several quotes for my install based on SB3800 or 3300 that simply wouldn't work and in every case the reply was "our suppliers said it would be ok" but now we've checked it you're right, it won't work!

 

[Ramjam]

Why east west split? It's a good idea for solar thermal where you need it to work all day but with PV you'll get more by putting it all on the west side and it's easier of inverters. The afternoon sun is generally brighter than the morning sun so west works better than east (not according to SAP calcs but in reality it does!).

If you've got a small roof and that's why you've gone east/west then try an inverter like Steca 2010 with slave 2MPPs or I would go with two SB1700 then they can both talk to one Sunnybeam display.

 

[Noshocks]

go with the SB4000TL dual MPPT, the best inverter Fronius NEVER made

 

[claypole]

But would that be offset slightly by increased average ambient temperature in afternoons and therefore raised cell temperatures and reduced output? Anybody running equal split E/W with some comparison figures?
Or a SB4000TL with twin MPPT inputs, maybe cheaper than 2x1700 and still able to display seperate dc input from each string, plus bluetooth inc free, plus half the cost if you choose extended warranty route, plus arguably neater install. A little oversized but near identical predicted output as 2 x 1700 on E/W.

 

[Ramjam]

I'm almost with you but I steer clear of the TL inverters on account of the earthing and DC RCD requirements. I still haven't heard anyone explain how to wire TL inverters according to the regs and practically, the DC RCDs are apparently as rare as rocking horse manure?

 

[claypole]

See http://download.sma.de/smaprosa/dateien/7418/RCD-UEN103120.pdf
I understand the requirement for dc breaker on transformerless inverter but there is an exemption where the unit is proven to exclude dc currents from grid and SB4000TL complies with this. There's also an excellent chart somewhere on the sma downloads showing which panels require earthing with which inverters, and again the 4000TL is fine with most, one standout exception being the Sanyo hybrid modules. I must declare I have no electrical qualification so forgive if there other UK regs affecting this.

 

[ian81]

theres not much room on the west side for more than 9 panels due to massive shading the customer wanted the east west split. im going to go into the office this afternoon to discuss the options with them but after everyones advice im even more inclined to refuse to install the sb3800 !!!

 

[Worcester]

I just ran it through PV*SOL 2 off (1 x East, 1 x West) 9 x 185W sharp panels assuming a 40 degree roof slope and the only SMA inverter it recommedned / would allow was the SB3000TL-20 althought it has only one MPP tracker it does allow 2 strings to be connected.

The two inverter option it offered was 2 x SMA SB1700 (and it was a very good match)

It will be cheaper to purchase the single SB3000TL-20, - however see all the comments on grounding TL inverters and RCD devices

Then, if you choose two inverters the purchase cost will be higher, and then they will each need their own MCB which could be up in the loft and the connected to a single MCB on the main cosnumer unit (so only 1 cable from loft)

Whataver - by my recommemdation the SB3800 should go back to the stores .....

Pays ya money takes ya choice..

 

[edexlab]

I'm not saying this is wrong ,but as the 3000tl only has one mpp tracker then how can it be suitable for a E/W split?
if it was 2 strings same no modules same tilt/azimuth etc then I can see this being ok,
but I have to say I've not read anything about this inverter as its never been a match to any of the smaller jobs we've had

 

[edexlab]

See http://download.sma.de/smaprosa/dateien/7418/RCD-UEN103120.pdf
I understand the requirement for dc breaker on transformerless inverter but there is an exemption where the unit is proven to exclude dc currents from grid and SB4000TL complies with this. There's also an excellent chart somewhere on the sma downloads showing which panels require earthing with which inverters, and again the 4000TL is fine with most, one standout exception being the Sanyo hybrid modules. I must declare I have no electrical qualification so forgive if there other UK regs affecting this.

After seeing your comments on the hybrid's I had a good look through the Sma site and could'nt find any mention of this chart
could you post where this table was please
I did find the table re grounding modules but this can't be what you've found as there is no mention of Hybrids

 

[claypole]

Edexlab, thanks for this comment because I fear I may be at error. The table I had been looking at is here http://download.sma.de/smaprosa/dateien/7418/Duennschicht-UEN093821.pdf which I'm guessing is the same table you had found. It does not of course mention Sanyo Hybrid. At the time I was looking at it I was considering the hybrids but from their data sheet I understood them to have amorphous Si(superstrate design) which would make them unsuitable for the 4000TL. I should have re-checked the table before I posted because I realise I've written the comment incorrectly as if they are mentioned by name. If you also believe this is factually wrong and that they are in fact suitable please let me know and I'll edit the post.
Interesting material here too http://download.sma.de/smaprosa/dateien/7418/Ableitstrom-UEN092510.pdf