2 x SB4000-TLs or 1 x SB7000HV on single phase supply

[stevie gill]

I have been asked to do a quote for an 8kWp system on a commercial building which only has a single phase supply.

After running different systems through various software it seems that I have 2 options;

1) Install 1 SB7000HV inverter

2) Install 2 x SB4000-TLs


Option 1 is the most cost efficient solution, but Option 2 gives a better overall yield and the cost difference is negligible.

Obviously Option 2 would be the best solution, but my only concern is regarding connecting the 2 SB4000's. Is it OK to run 1 AC supply from the DB and onwards as follows: AC isolator - Generation Meter - Junction Box. Then AC Isolator - Inverter 1 - DC Isolator and a repeat for Inverter 2? I have connected 2 SB1200's in this manner before, but wanted to check about the more powerful systems before proceeding with my quote.

If this isn't OK, what other options to I have - individual supplies to both inverters? How would you then connect the generation meter etc?


As ever, any help would be greatly appreciated!

 

[sedgy34]

Depends if you will be allowed to connect onto the grid ask DNO

 

[stevie gill]

Western Power have said I'm fine to install an 8kWp system

 

[Earthstore]

Make sure you have a very low loss on your AC cable or with two inverters as one kicks in it can trip the other out with overvoltage, and then visa versa and so that cycle can continue.

I hope this helps.

 

[BruceB]

The installation instructions for the 4000TL require each one to be on its own mcb

 

[stevie gill]

Thanks to Earthstore and BruceB for the responses.

If following SMA's instructions Re separate MCBs, how would you connect the generation meter? Main DB - AC Iso - Generation Meter - PV DB - 2 sub circuits to inverters c/w AC & DC Iso's etc ????

 

[Henryk]

I have done this on bigger systems. Just need a splitter board on the end of your supply to the two inverters.
At the mains you could have seperate DB to feed pv, this would up the cost but at least have a descent job.

 

[Worcester]

Thanks to Earthstore and BruceB for the responses.

If following SMA's instructions Re separate MCBs, how would you connect the generation meter? Main DB - AC Iso - Generation Meter - PV DB - 2 sub circuits to inverters c/w AC & DC Iso's etc ????

Yep, we did one just like that with 2 x 5000TL's.

We also added in a pair of rcbo protected sockets at the PV DB for maintenance purposes we really don't want them used as a 'nornal socket' as they would consume unmetered generated electrcity, often we plug the monitoring systems in there (rs485 sunny webbox , routers) as they really don't use a lot of power. (Suppose that's the difference between TIC and DNC )

 

[SibertSolar]

Monitoring units and data loggers are allowed to be plugged in on the PV circuit - they're classed as "plant" dontchaknow.... ;-) (kidding about the plant bit...)

OP - could use a single Eltek 7000TL 3R or 9000TL 3R maybe? If all panels are on same pitch/orientation?

 

[danesol]

After checking with your DNO that you can connect 8kwh, I would think the most obvious thing to check would be if your local environment would benefit from using two inverters should you say have part shading at different parts of the day or using direct roof sections in different directions - if you are, I would say you may well would gain alots by using Option.2 otherwise option.1 ignoring costs for now.............