32A or 40A circuit breaker?

[HappyHippyDad]

A really simple question. I'm sat here with my coffee and getting confused by it!

7.4kW EVCP. Would I fit a 32A or 40A RCBO? Not concerned with anything else, as it's all sorted, but the fact that the 7.4kW equates to 32.17A has thrown me. I was just going to use a 32A RCBO, but really I should be using a 40A?

I realise a 32A RCBO is never going to trip at 32.17A, but it means it will be running at it's full capacity whenever the vehicle is being charged and I 'think' I remember @Lucien Nunes saying once (something along the lines) that a circuit breaker shouldn't be run at full current all the time.

Also, I will read all the spec when the charger arrives, but it hasn't yet and I cant find anything online. It's an Alfen Sline eve EVCP. It does mention on a number of sites 32A, but this is in relation to current used.

I realise the answer is simple. 6mm cable, ref method C, 40A RCBO, but I just fancied asking ?. I can then have a quick game a footy with the boy in the garden, make another coffee and then come back and have a quiet saturday morning read of the replies ?

 

[Strima]

32.17 is more than 32... ??

I'd be going with 40 amp as running the MCB on it's current limit will have long term effects on it's longevity.

 

[ipf]

If circuit capable, use 40, I'd always say.
If installation instructions say different, you can always change it.

 

[Soi disant]

Cable ratings have built-in tolerances which accommodate voltage fluctuations - not sure about protective devices.

I bet EV chargers are not simple resistive loads, and have some kind of switch-modery going on, so that 7.4kW could be 7.4kW at any voltage, so if the supply dips to 216.2V it's 34.23A.

 

[Soi disant]

I was just going to use a 32A RCBO, but really I should be using a 40A?

Interesting that they say Type A or Type B RCD protection.

If A will do, why on earth fork out the squillions for B?

 

[HappyHippyDad]

Interesting that they say Type A or Type B RCD protection.

If A will do, why on earth fork out the squillions for B?

Type A is only sufficient if the EVCP provides disconnection of supply in case of DC fault current above 6mA. See reg 722.531.2.101

 

[HappyHippyDad]

Cheers for all the replies guys?

 

[Soi disant]

Type A is only sufficient if the EVCP provides disconnection of supply in case of DC fault current above 6mA. See reg 722.531.2.101

The maker of that EVCP says that it needs type A or type B RCD protection.

If A will do for that EVCP, why on earth fork out the squillions for B?

 

[HappyHippyDad]

The maker of that EVCP says that it needs type A or type B RCD protection.

If A will do for that EVCP, why on earth fork out the squillions for B?

Not too sure where that questions comes from. Nobody would fit a type B RCD.
Ah, I see, they say type B 'can' be fitted. True, no reason whatsoever that I can see.