solar pv install on 3ph advice needed

[SPARKY51974]

Wondering if any of you guys could give me a bit of advice with this system as a bit unsure how to connect it as equipment that has turned up isn't what I expected. The system is on a domestic 3ph system. The DNO told us that we had to keep the system balanced across the 3 phases so as the system is only a small one for 3 phase due to roof area on garage and granny flat we have been supplied with 3 sunnyboy 1200 as apparently you cannot get a small enough 3 phase inverter. So here is my problem we were told we would receive 3 single phase sunnyboy 1200 inverters 3 DC isolators 3 AC isolators 1 3 phase generation meter and 1 3 phase 4 pole isolator and told what size 3 phase mcb to wire it to. I asked them for a wiring diagram just to confirm this set up and was happy enough. But when we received the equipment instead of the 1 3 phase generation meter and 4 pole 3 phase isolator, we received 3 single phase generation meters and 1 3 pole 3 phase isolator and told to wire same as previously on 3 phase mcb. My question to there technical was if wiring like previously told to 3 phase should the isolator not have been a 4 pole but also as they have supplied single phase generation meters should all of these system not just be wired as single phase units each on there own mcbs and just split evenly across the phases. Still waiting for an answer off them know how I would do it but just wondered if anyone could shed a bit of light as to how it should be done.

 

[karlb]

Sounds like they havent given you the

right kit. And what they are asking you to do is wrong imo.

You will need a 3phase meter to start with. I would the mount it into an adaptable box. From there run a 3 phase and cable to the meter and then split off out of the meter with 3 single phase cables to 3 ac Isolators.

 

[karlb]

Also I think provided it isn't a tt the neutral doesn't need to be switched so a 3 pole isolator would do and just join the naturals?

 

[SPARKY51974]

That's what I thought with one 3 phase meter and one 3 phase isolator on 3 phase mcb then split to single phase isolators .Why does it have to be a 6 pole isolator ?

 

[binky]

office wallah firk - up. no doubt couldn't get or didn't like price of proper kit so had brainwave.... :slap

Does this property have a 3 phase distribution board??

 

[SPARKY51974]

Yes it has a 3 phase distribution board why brand new property being built

 

[SPARKY51974]

Thought u went from inverters to single phase isolator then to generation Meter then to 3 phase isolator then back to 3 phase mcb that's how I was taught to connect it on solar pv course

Is that way incorrect?

 

[karlb]

If you want to meter each inverter separately that is correct. If you want to meter the system as a whole then that's wrong

 

[SPARKY51974]

Thanks for all the help and advice boys much appreciated so I will come from 3 phase mcb in distribution board to 3 phase meter then to 3 phase 4 or 6 pole isolator then to each inerter with a single phase supply. Am I right in saying that as all of this will be in a plant room on surface in trunking no RCD protection will be required. Do any of you boys fit surge protection at mains to protect the inverters

 

[kme]

Think of it like this:

IF you have a 3 pole MCB, then the load is going to be TP - so "one-for-all" isolation / metering.

If the MCBs were 3 x single pole; then individuate the inverters ( & metering!!!) - if there are three single phase loads, and/or 3 AC iso`s - then the metering would HAVE to be 3 x SP

Surge protection if required by mfrs` or clients` spec . RCD - that depends; we don`t have enough info yet ]

KME

 

[SPARKY51974]

Thanks kme get all that with isolators and meters and inverters just wanted to run it past people to make sure I was right before going back to supplier to get isolators and meters changed this is my first install with 3 phase . 3 phases isn't new to me as work on it nearly every week in some form or another. The inverters are sma sunnyboy 1200 and they will be located in same room as 3 phase db all wired in trunking on surface if that helps. Thank you again for all your help guys as new to the forumn and as I say a good tradesman learns something new everyday