UK 32A or 40A breaker for 7kW EV Charger

[Julie.]

Also fyi the cable type installed is ‘F’ so swa (steel wire armoured) with an installation method C (clipped direct) so therefore cable capable in this situation of safely pulling 53amps. So 40 amp breaker would be fine

I don't quite trust reports or EIs with installation methods, it's virtually impossible for the same method to be used all the way through the installation of a particular circuit.

It's usually a combination of clipped direct over most of it, a bit through duct/conduit and a bit behind insulation (thermal) etc - only the installer truly knows if the C is true in it's entirely, or just mostly true (and what the non-true bits are).

 

[LawVal]

Has this charger been installed to an existing split load board??
I.e. one which contains 2 RCDs protected half (ish) the circuits each??

Hello Bsharp thanks for the info and yes it is a newish (10 years) split board.
The circuit chart is as follows reading from the main switch on the right-hand side of CU.
100A mains switch
63A RCD 30mA
40A MCB, electric cooker
32A MCB, lounge, bedroom & hall wall sockets.
32A MCB, not used
32A MCB, not used
6A MCB, all internal lights
63A RCD 30mA
32A MCB, kitchen wall sockets + washing machine, oil-fired boiler
16A MCB, external lamp post
32A MCB, external car charging point
6A MCB, not used
6A MCB, not used.

 

[pc1966]

I don't quite trust reports or EIs with installation methods, it's virtually impossible for the same method to be used all the way through the installation of a particular circuit.

Indeed, in my own flat the RFC is on 20A because that is what it was on the original fuses. It ought to be OK for 32A but I did not put it in so have no knowledge of just how/where the cable runs.

It was probably done that way due to a high Ze originally, but I never had the chance to measure before the original cutout and MICC feed was replaced.

 

[Bsharp]

I don't quite trust reports or EIs with installation methods, it's virtually impossible for the same method to be used all the way through the installation of a particular circuit.

It's usually a combination of clipped direct over most of it, a bit through duct/conduit and a bit behind insulation (thermal) etc - only the installer truly knows if the C is true in it's entirely, or just mostly true (and what the non-true bits are).

Fair point, but you have to trust the installer at some point. My bet would be cable cleated externally from CU to EV charger in this case. But again without seeing the install you have to trust the installers reasoning.

 

[Bsharp]

Hello Bsharp thanks for the info and yes it is a newish (10 years) split board.
The circuit chart is as follows reading from the main switch on the right-hand side of CU.
100A mains switch
63A RCD 30mA
40A MCB, electric cooker
32A MCB, lounge, bedroom & hall wall sockets.
32A MCB, not used
32A MCB, not used
6A MCB, all internal lights
63A RCD 30mA
32A MCB, kitchen wall sockets + washing machine, oil-fired boiler
16A MCB, external lamp post
32A MCB, external car charging point
6A MCB, not used
6A MCB, not used.

I’d be slightly more concerned about the type of RCD present in the consumer unit.
If as you say it’s 10 years old then the RCD is more than likely going to be a type AC. Bs7671 requires a type A RCD to be installed for reasons which I won’t confuse with at this point.
Worth checking.

 

[Bsharp]

I don't quite trust reports or EIs with installation methods, it's virtually impossible for the same method to be used all the way through the installation of a particular circuit.

It's usually a combination of clipped direct over most of it, a bit through duct/conduit and a bit behind insulation (thermal) etc - only the installer truly knows if the C is true in it's entirely, or just mostly true (and what the non-true bits are).

What do you put regarding installation method on your reports or certs? I presume you trust these only joking I know what you mean though. Engineering judgment is needed if only running a couple of metres through thermal insulation wouldn’t make any difference tbf if the rest of install was say free air for the remains 25ms.

 

[westward10]

I’d be slightly more concerned about the type of RCD present in the consumer unit.
If as you say it’s 10 years old then the RCD is more than likely going to be a type AC. Bs7671 requires a type A RCD to be installed for reasons which I won’t confuse with at this point.
Worth checking.

Strictly speaking BS7671 does not require type A, type AC are still acceptable given the correct circumstances however in this case they probably are not.

 

[Bsharp]

Strictly speaking BS7671 does not require type A, type AC are still acceptable given the correct circumstances however in this case they probably are not.

Agreed. . I always install separate EV board spd and type A just my preference and I’m in no way claiming to be the any better than any other. Also just out of interest (maybe your not ) but I notice on the EIC posted by the OP the r1+r2 of the said EV circuit is 0.67ohms. 6mm2 swa with 6mm2 line and cpc as stated on cert would me the run is around 110m’s plus!! Big house that!!

 

[LawVal]

I’d be slightly more concerned about the type of RCD present in the consumer unit.
If as you say it’s 10 years old then the RCD is more than likely going to be a type AC. Bs7671 requires a type A RCD to be installed for reasons which I won’t confuse with at this point.
Worth checking.

Thanks Bsharp. Just checked and interestingly the two RCD's are different in terms of "numbers" ie.
The one next to the incoming switch is a BG CUR 6330 with IEC/EN 61008-1.
The one that does the car charger side is a BG CUR 6330A with IEC/EN 61008.

Perhaps the car charger electrician also changed the RCD on that side.

Whilst I was in there I tested the RCD's and I am pleased to say both tripped and reset!

 

[Bsharp]

Thanks Bsharp. Just checked and interestingly the two RCD's are different in terms of "numbers" ie.
The one next to the incoming switch is a BG CUR 6330 with IEC/EN 61008-1.
The one that does the car charger side is a BG CUR 6330A with IEC/EN 61008.

Perhaps the car charger electrician also changed the RCD on that side.

Whilst I was in there I tested the RCD's and I am pleased to say both tripped and reset!

He has swapped The RCD out for a type A so no issue there. Sorry for rambling on a bit but RE you actual op the EV will be fine on the 32 amp.