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

[LawVal]

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.

Thanks Bsharp. I find this all very interesting so not rambling on at all. Thanks to all for the input.

 

[Risteard]

You work to manufacturers instructions.......If they say 32 amp then that's what you install

I'm not aware of any manufacturer that advises it. They typically state 20A for 16A, or 40A for 32A.

Not sure why a circuit breaker was used for this installation - typically a double pole switching RCBO should be used. What make/model of chargepoint is installed?

EDIT: It appears to be on a shared RCCB. An EVSE should be protected by its own dedicated RCD. Typically this means an RCBO, although it could be an RCCB supplying only one circuit.

 

[LawVal]

I'm not aware of any manufacturer that advises it. They typically state 20A for 16A, or 40A for 32A.

Not sure why a circuit breaker was used for this installation - typically a double pole switching RCBO should be used. What make/model of chargepoint is installed?

EDIT: It appears to be on a shared RCCB. An EVSE should be protected by its own dedicated RCD. Typically this means an RCBO, although it could be an RCCB supplying only one circuit.

Hello Risteard. In answer to what make:

The charger is an Ohme Home Pro 7kW and extracts from the website product manual are;
• Ohme units have PEN fault detection
• The RCD inside the unit is Type A and 6mA DC
*The RCD in the unit is certified as a RCD-DD, conforming to IEC62955.
*No overcurrent protection is provided in the Ohme Home Pro, separate provision is to be provided as part of the installation. We recommend a 40A Type B MCB.
*The Ohme Home Pro has a dynamic load balancing feature. A current sensor (CT) clamp is provided to measure the electrical demand of the property, or sub-board

I have sent an email to Ohme querying the 32A breaker installed by their appointed electrician whilst they recommend 40A in the manual albeit by feedback here the 32A seems to be OK (and is working fine)

 

[Bsharp]

Hello Risteard. In answer to what make:

The charger is an Ohme Home Pro 7kW and extracts from the website product manual are;
• Ohme units have PEN fault detection
• The RCD inside the unit is Type A and 6mA DC
*The RCD in the unit is certified as a RCD-DD, conforming to IEC62955.
*No overcurrent protection is provided in the Ohme Home Pro, separate provision is to be provided as part of the installation. We recommend a 40A Type B MCB.
*The Ohme Home Pro has a dynamic load balancing feature. A current sensor (CT) clamp is provided to measure the electrical demand of the property, or sub-board

I have sent an email to Ohme querying the 32A breaker installed by their appointed electrician whilst they recommend 40A in the manual albeit by feedback here the 32A seems to be OK (and is working fine)

I just had a read of their literature and as you say it “advises” 40amp.
So I wouldn’t worry.

 

[Risteard]

Hello Risteard. In answer to what make:

The charger is an Ohme Home Pro 7kW and extracts from the website product manual are;
• Ohme units have PEN fault detection
• The RCD inside the unit is Type A and 6mA DC
*The RCD in the unit is certified as a RCD-DD, conforming to IEC62955.
*No overcurrent protection is provided in the Ohme Home Pro, separate provision is to be provided as part of the installation. We recommend a 40A Type B MCB.
*The Ohme Home Pro has a dynamic load balancing feature. A current sensor (CT) clamp is provided to measure the electrical demand of the property, or sub-board

I have sent an email to Ohme querying the 32A breaker installed by their appointed electrician whilst they recommend 40A in the manual albeit by feedback here the 32A seems to be OK (and is working fine)

OK, when you refer to the RCD within the unit deriving from an RDC-DD (not RCD-DD) within the unit, then I am surmising that this is an electronic device within the unit and not actually an RCD complying with BS EN 61008 or BS EN 61009. As such, personally I do not feel that it is compliant to supply this without a dedicated double pole switching RCD upstream (realistically this being achieved with an RCBO which switches both poles). This should be of at least Type A. A Type B is not necessary due to the RDC-DD.

 

[LawVal]

OK, when you refer to the RCD within the unit deriving from an RDC-DD (not RCD-DD) within the unit, then I am surmising that this is an electronic device within the unit and not actually an RCD complying with BS EN 61008 or BS EN 61009. As such, personally I do not feel that it is compliant to supply this without a dedicated double pole switching RCD upstream (realistically this being achieved with an RCBO which switches both poles). This should be of at least Type A. A Type B is not necessary due to the RDC-DD.

I don't know the "technical" but the asterisk points in my above post are copied and pasted from the manufacturer's manual and I would have thought the manufacturer would have specified what was appropriate and compliant ie for overload protection they state "We recommend a 40A Type B MCB."
I don't know if the internal RCD is an electronic device or otherwise, they just say it is;
• The RCD inside the unit is Type A and 6mA DC
*The RCD in the unit is certified as a RCD-DD, conforming to IEC62955.

Do you think I should change the MCB for a RCBO?

 

[Bsharp]

OK, when you refer to the RCD within the unit deriving from an RDC-DD (not RCD-DD) within the unit, then I am surmising that this is an electronic device within the unit and not actually an RCD complying with BS EN 61008 or BS EN 61009. As such, personally I do not feel that it is compliant to supply this without a dedicated double pole switching RCD upstream (realistically this being achieved with an RCBO which switches both poles). This should be of at least Type A. A Type B is not necessary due to the RDC-DD.

I’m sure the op said that the electrician installed a new type A RCD in existing consumer unit, also as you say the Ohme charger does have integral RCD type A 30ma and
DC 6ma RCD biilt in. And as the method of installation was via swa then the charge point could arguably be connected via MCB. Although not the way I would as no real way of user testing the internal RCD in the ohme unit (I think)
As I said earlier I always supply sub board SPD type A RCD and that’s the way I’ll always fit as that’s what I feel comfortable doing.

 

[Risteard]

Although not the way I would as no real way of user testing the internal RCD in the ohme unit (I think)

Yes, and in my opinion strictly speaking does not comply with BS 7671 as the RCD-style functionality of the device is not actually achieved by the presence of an RCD complying with one of the listed Standards.

 

[Bsharp]

Yes, and in my opinion strictly speaking does not comply with BS 7671 as the RCD-style functionality of the device is not actually achieved by the presence of an RCD complying with one of the listed Standards.

Definitely, this is why I stick to the same install procedure every time.

 

[Miguel Esteban-Perez]

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.

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

 

[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.)