AC Isolators

[SRE]

Could someone help me clear something up please? On the NICEIC training - don't groan, I know it was rubbish - we were told to use to ac isolators one either side of the generation meter but when I look at kits they always have just one isolator in them. So should it be one or two?????

 

[High Tower]

If your talking pv then it's a dc isolator pre inverter and a ac isolator post inverter

 

[edexlab]

( 1 DC isolator per string DC side)

1 Main AC isolator at origin of Ac circuit

DTI guide says;
If the ac switch disconnector and the inverter(s) are not in the same room
a local isolator should be installed adjacent to the inverter(s)
This is to facillitate maintenance of the ac cable run and inverter(s)

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[goodwilld]

If you have system where the inverter is near the mains board and meters, you only need one. If the inverter is in the roof you need 1 x AC Isolator in the loft space and one at the mains board, this is a safety measure so no one can turn the power on by mistake, they have to be lockable too.
Hope this helps!!!!

 

[jerriais]

Thanks, I was wondering about this too.

 

[GLES]

The system I've just done has two AC Isolators. One just after the inverter, in the loft, and the second one by the consumer unit downstairs. Obviously there is a DC Isolator just before the Inverter too.

 

[AC/PV]

Has anyone found a suitable alternative to replace the rotary AC isolator by the consumer unit? I have no problems installing one in the loft, garage etc, but quite a few customers I've encountered find them a little to industrial looking when their consumer unit is situated in their hallway, living room kitchen for example and I can't say I blame them!
Any suggestions?

 

[JulianC]

I have fitted a couple of Santon units like this. Still not pretty but a bit better than most:

Quite expensive and a bit cramped inside to work with, so I'll use something bigger and cheaper if possible!

 

[High Tower]

Do they have to be rotary isolators??

 

[edexlab]

Rotary switches are used as they can only be locked off, in the off position, ie can't use DP main switch for this reason .Also i can't think of another option ,there's probably several but why look when rotary's are stocked everywhere and they're cheap.
On our MCS inspection he said we could use 20A DP switch next to inverter but main ac isolator must be DP and lockable as above ie rotary

 

[AC/PV]

Thanks for the opinions people and thanks JCDC, I've looked at that isolator and as you mentioned it doesn't give you much room to work in! I think the problem is that this required degree of protection is not normally found within the domestic sector and we are therefore forced to use what is available currently on the market, namely big bright isolators designed to be easily identifiable in a factory! Not something that is adequate and will look nice on mrs Jones's wall! The search continues...

 

[Mark.W]

I put AC isolator in the loft with inverter and DC isolator. The circuit can always be isolated at the board via the MCB.

Mark

 

[Worcester]

We have an installtion to do where the inverter will be in the loft space just above the utility box and the only sensible thing to do is to install henly blocks, a garage consumer unit, the total generation meter and an isolator in the utility box - see photo below.

My Sparks has said that

it will be tight to get all this equipment in here, but we won’t know for sure until we try.

Just have a back up plan in case it doesn’t all fit in. may not require an isolator as the mcb in the garage unit would act as that, you would need to buy an mcb locking device and padlock

Has anyone used lockable MCB's yet? Why wouldn't it comply?

 

[edexlab]

Before you go ahead with this idea you need to check with the DNO as I'm fairly sure you are'nt supposed to put any equipment other than switch fuses in there although I have seen consumer units in them worth checking though as they all have different policies
I have done this and got the ok to do so ,and managed to fit in an AC isolator /meter and 3 mod CU in similar space to the picture, he'll have to lower the meter to make it easier

As for lockable Mcb's they should'nt be used as they can be locked in the on position

 

[JulianC]

As for lockable Mcb's they should'nt be used as they can be locked in the on position

Correct, and method of locking must be a standard padlock, not a special tool/key etc. See DTI guide pg.26

 

[Worcester]

Food for thought:

Just had an interesting chat with an NICEIC inspector about the above, (hes was doing the annual on my Part P sparks) and he confirmed two things:
1) To put it in the box I'll need DNO apporval as they ususally consider it theirs (wether it is or isn't seems to be irrelevant to them!)
2) Depending upon the earthing type and mcb rating, (no details given) then the mcb COULD be considered adequate as an isolar..... Mentioning that some isolators aren't switches (arcing distance) and depending upon the earthing type, breaking just the live and not the neutral will be Ok in some circumstances..

More questions, less answers!

 

[edexlab]

Mcb's can be locked in the on position, and so do not comply
also from the DTI guide and BRB mentions same requirements

A manual a.c. switch-disconnector must be provided located in an
accessible position within the Customer’s installation as in G83/1 (e.g.
adjacent to the consumer unit or main distribution board), which is:​

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in accordance with BS 60947-3
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must switch all live and neutral conductors.
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must be securable in the OFF position only.

It must be simple to secure using a standard padlock - devices that require a separate removable​

adaptor or special key to enable them to be secured are not acceptable.
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must clearly show the ON and OFF positions and be labelled as​

‘PV system – main a.c. isolator