Queries on a new PV installation

sampenfold · Nov 25, 2015

Hi all. I am looking for a 3rd opinion on a recently completed install at a friend of a friends property. I am PV installer (17th edition, Part P, 2394&2395, NVQ3), I did not install this system.

- The property has a 3 phase supply.
- The electrician has taken 25mm tails from the main fuses, through a 3 phase generation meter, to a 32A switch fuse... Seems ok so far.
- 6mm 4 core SWA (approx 20M) to the garage from the 32a switch fuse, into a 3 pole rotary isolator... Fine.
- There are two single phase inverters installed in the garage. One is a 5000W Growatt, the other a 3000W Growatt.

Now here's why I am writing this post...
From L2 in the rotary isolator a 2.5mm 3core flex goes to one inverter. And the same from L3 to the other inverter. Nothing from L1.

Thoughts?

plugsandsparks · Nov 25, 2015

Looks like L1 is ready for the third inverter...........

sampenfold · Nov 25, 2015

plugsandsparks said:
Looks like L1 is ready for the third inverter...........

Haha, yes but there isn't one!

Worcester · Nov 25, 2015

1) Does he have DNO permission to connect ? It is >3.68kW out of balance on one phase.

2) G83 or G59?

3) How are they achieving the fault disconnect requirements of BS7671

4) Cable looks undersized by MI's for the inverters

5) Why not have installed a small SMA tripower?

If I was only doing two phase, I would have put the 4 core SWA into a small db with 4 pole main switch and broken the three phase down into single phases, MCB on each phase, and then rotary isolators for each inverter, as each one is its own circuit.

Here's a small temporary installation using 3 single phase inverters - due to the weird configuration of panels on the roofs, we couldn't use a tripower, hence 3 single phase inverters configured as above, DC cables have got to be relocated in a month or so.

[ElectriciansForums.net] Queries on a new PV installation

sampenfold · Nov 25, 2015

Worcester said:
1) Does he have DNO permission to connect ? It is >3.68kW out of balance on one phase.

2) G83 or G59?

3) How are they achieving the fault disconnect requirements of BS7671

4) Cable looks undersized by MI's for the inverters

5) Why not have installed a small SMA tripower?

If I was only doing two phase, I would have put the 4 core SWA into a small db with 4 pole main switch and broken the three phase down into single phases, MCB on each phase, and then rotary isolators for each inverter, as each one is its own circuit.

Here's a small temporary installation using 3 single phase inverters - due to the weird configuration of panels on the roofs, we couldn't use a tripower, hence 3 single phase inverters configured as above, DC cables have got to be relocated in a month or so.
View attachment 30771

1) It was installed by a subcontractor for Project Solar UK. I am presuming that such a large company would have contacted the DNO.

2) I would presume G59. Certainly the 5000W inverter is more than 16A (so G59), and even says G59 on the side of it. The 3000W inverter says 13A, G83 on the side. As they are connected to one 3 phase circuit and one generation meter it must be G59.

3) The 6mm SWA is protected by the 32A MCB in the switch fuse near the meter. But the 2.5mm flex to each inverter is obviously not adequately protected.

4) Definitely.

5) Not sure why they have used these inverters, they could have got 2, 3 phase inverters or like you say 3 smaller single phase inverters to balance the load across all three phases.

I would have done it as you show.

sampenfold · Nov 25, 2015

Worcester · Nov 25, 2015

sampenfold said:
1) It was installed by a subcontractor for Project Solar UK. I am presuming that such a large company would have contacted the DNO.

Not an assumption I would make!

sampenfold said:
2) I would presume G59. Certainly the 5000W inverter is more than 16A (so G59), and even says G59 on the side of it. The 3000W inverter says 13A, G83 on the side. As they are connected to one 3 phase circuit and one generation meter it must be G59.

It can be G83 if <=3.68kW per phase
Being out of balance by > 3.68kW will need special permission from the DNO

What is your end game?

There's stuff wrong with it, I would tell your friend to get the installer back and get him to get them to provide all the appropriate documentation, there should of course also be an electrical test certificate.

Under new consumer law, they have only ONE chance to put it all right.

sampenfold · Nov 26, 2015

I just wanted further opinions before I advised them what to do.
The handover docs are all there, the electrical certificate leaves a lot to be desired. There's no mention of G59, but there is a G83 test report.

I don't hold much hope of them getting their FiT as it stands.

gnselectricals · Nov 26, 2015

The 2.5 flex is protected as the max load is 3kw therefore cannot be overloaded. Sounds a bit ruff but not dangerous

TedM · Nov 26, 2015

sampenfold said:
I don't hold much hope of them getting their FiT as it stands.

How many/what size panels are connected to each inverter?

What does their MCS certificate say?

Queries on a new PV installation

sampenfold

plugsandsparks

-

sampenfold

Worcester

-

sampenfold

sampenfold

Worcester

-

sampenfold

gnselectricals

-

TedM

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