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

[LawVal]

I note that in answer to another EV Charger question a member suggested a 40A breaker would be preferred to a 32A because of many hours at continuous full 7kW load. I am not an electrician but understand the reasoning.
I have a 7kW charger (which generally runs full load for a continuous 5 hours during the off-peak period) and note that the electrician has connected to a 32A type B breaker in the CU and issued his NICEIC Domestic Electrical Installation Certificate accordingly. The circuit conductors are noted as 6mm csa
I have not experienced any problem with the installation but would the general recommendation be to increase the breaker to 40A?

Thank you.

 

[LawVal]

32 A for 6 mm2 its ok. By the way , cable insulation is PVC or XLPE?

One of the previous helpers advised me that the cable type installed is ‘F’ so swa (steel wire armoured) with an installation method C (clipped direct). This is extracted from the installation certificate.

 

[Miguel Esteban-Perez]

Well, taking a look at BS 7671:2018 seems that for PVC , with Methods A,B,C ranges go from 32 to 47 A. Of course an isolated cable supports more , I think that in your country with less temperature and some more humidity and with your mass systems it could also work for 40 A, but as said, keep it up in 32 A for 6 mm2.

 

[brianmoooore]

Surely this can be considered to be a fixed load, or at least a fixed maximum load of 32A.

 

[Julie.]

Surely this can be considered to be a fixed load, or at least a fixed maximum load of 32A.

Unfortunately not.

It's for an EVCP which is basically a fancy socket outlet.

The EVCP tells the vehicle that it has a maximum current of 32A.

The charger within the vehicle then (if working correctly) will charge at the 32A rate - or a reduced current if the in-vehicle charger has a maximum of say 28A.

However there is nothing inherently limiting this current, if the in-vehicle charger goes faulty, it could take much more than it should.


A fixed load is only where it is not possible to take more than rated as an overload, other than for fault type conditions.

An immersion heater for example is limited by its internal resistance, it wouldn't be able to overload, only suffer a fault.

 

[brianmoooore]

An immersion heater for example is limited by its internal resistance, it wouldn't be able to overload, only suffer a fault.

I won't mention the one I came across once, then. The outer sheath of the element had dissolved and the element spiral had shorted to the sheath part way along. It enjoyed a significant, but brief life, as a 6kW immersion, before failing completely. No RCD in the circuit, of course, and TNC-S (or PME as it was then.)