AC isolators - still required at CU?

[SolarCity]

It has been a long time since I installed an inverter in a loft. I'm doing one tomorrow and I can't recall whether an AC isolator would be required at the CU. Obviously it would be at the inverter but I seem to recall the rules being relaxed for the isolator at the CU?

 

[BruceB]

Have a look at 2.3.3 in the guide. It needs careful reading even though apparently simple. I am sure many would argue it is good practice that the 'main ac isolator' is NOT in the loft as that might not be considered 'accessible'. However, if you have a DP mcb or rcd in the CU dedicated to the PV then either could fulfill the 7671 and Guide requirements for an isolator.

Normally when I have done a loft I have done x2 isolators, one at inverter and one by CU, but where inverter is in garage or utility room and isolator is easily accessible then no need for another by the CU.

 

[SolarCity]

Thanks Bruce.

To be honest, I didn't think 2.3.3 was that clear to be honest.

It is a tough one as the CU is in a converted garage - it is now a kitchen - and AC isolators are pretty ugly things.
As you say, a DP breaker should satisfy the guide requirements.

 

[Gavin A]

As you say, a DP breaker should satisfy the guide requirements.

hmm, that's odd, I'd not noticed that revision from the draft, and had been assuming the wording from the draft had made it into the final version.

here's the draft version

An accessible means of isolation shall be provided to isolate the a.c. circuit. MCB’s, RCD’s and main switches installed in accordance with BS7671 and in an accessible location can be used to fulfil the requirements for an accessible means of isolation.

I also can't understand why it now has a paragraph instead banging on about unswitched fused connection units being acceptable. Seems very odd.

We've used dual pole MCB or RCD for the isolation point near the consumer unit / incoming supply connnection on virtually every install we've ever done without any problems. At the end of the day, it is complaint to BS7671 for the method of isolating a circuit, otherwise all other circuits would similarly need to have their own rotary isolators next to the CU.

 

[SolarCity]

I also can't understand why it now has a paragraph instead banging on about unswitched fused connection units being acceptable. Seems very odd.

Yeah, that part is bizarre.

We've used dual pole MCB or RCD for the isolation point near the consumer unit / incoming supply connnection on virtually every install we've ever done without any problems. At the end of the day, it is complaint to BS7671 for the method of isolating a circuit, otherwise all other circuits would similarly need to have their own rotary isolators next to the CU.

This is exactly how I see it. If it is to comply with 7671 then it is no issue - but is it there for DNO use?

 

[Gavin A]

Yeah, that part is bizarre.



This is exactly how I see it. If it is to comply with 7671 then it is no issue - but is it there for DNO use?

if it were then it would need to be in the meter cupboard, otherwise if they need to access the property anyway then they should be able to use an MCB same as the rest of us.