consumer unit query

[steelman99]

Firstly not going to be doing anything myself , so dont need any sparkys telling me that i cant do it myself - I know that and dont intend to do so

present consumer unit has run out of space and we need an aditional circuit fitting for a car charger - had a few people look at the job , and im getting diffrent opinions/ answers

The existing unit is about 15 yrs old and the supply to the garage and shed has an RCD and a MCB protecting it -which takes up 3 slots in the consumer unit - some installers are telling me that we can take both out and replace with an RCBO and that will offer the same protection, and free up space in the consumer unit for the car charger - others are telling me that all whats there should be left alone and a seperate consumer unit should be fitted alongside the original consumer unit for the car charger. (there is a consumer unit in the garage with an RDC in it , if that makes any diffrence)

would prefer to go for the first option as the present consumer unit is fitted in a cupboard , and the extra unit would have to be mounted on the wall outside the cupboard , but also want it to be safe

any advice welcome

 

[JohnD]

Post some photos

 

[ericmark]

A car charging unit can require type A to type B RCD, depending on what is build into the EV charging point. I have not seen a type B or B RCBO, so it depends on what is being fitted, there is no single answer.

 

[JohnW2]

A car charging unit can require type A to type B RCD, depending on what is build into the EV charging point. I have not seen a type B or B RCBO, so it depends on what is being fitted, there is no single answer.

Indeed - and I think it's worth warning people about how they can be misled by the potential total confusion resulting from the ridiculous (IMO!) way in which the terminology has evolved.

There are countless devices being offered out there which are described as "Type B RCBOs". However, every one I have looked at turns out to actually be an RCBO with a B-curve, but of Type A or Type AC.

Like you, I have never seen a (truly) Type B RCBO on offer. If one needs such functionality, I therefore think one would have to use a Type B RCD (RCCB) in conjunction with an MCB.

Kind Regards, John

 

[JohnD]

I see TLC describes them as (e.g.) "40A 30mA B Curve Type A" or similar.

Mine are the old MEM MR30 type and the label is so tiny and difficult to read that I think I ought to find my label-maker and put info on the CU casing. (B Curve, Type A)

Edit
I've recently seen them described as "Tripping class - A"
Is that a common term now?

 

[EFLImpudence]

Indeed - and I think it's worth warning people about how they can be misled by the potential total confusion resulting from the ridiculous (IMO!) way in which the terminology has evolved.

Don't forget "Type tested" whatever that means.

 

[JohnW2]

Don't forget "Type tested" whatever that means.

Indeed - but it has to be said that "Type Test Certificates", such as this 18-page one (click here) , giove some insight to what is 'tested'

 

[EFLImpudence]

Yes , but do all manufacturers use the same criteria?


If they do then surely the devices must be compatible.

If they do not then some must be poorer and less safe than others.

 

[Murdochcat]

Post some photos

Essential before anybody can give really constructive answers

 

[steelman99]

sorry , but Im confused - the car charger is totaly irellivent to this question = all I want to know is can a RCBO be used to replace the existing RCD &MCB that protect the garage - if it can then theres enough room in the existing consumer unit for the guy to fit the car charger into it - just two diffrent sparkys are telling me 2 diffrent answers and i want to know what others views are

 

[JohnW2]

Yes , but do all manufacturers use the same criteria?

Presumably, but also presumably with the CU populated with their recommended devices?

If they do then surely the devices must be compatible.

Well, the theoretical (albeit seemingly incredibly improbable) argument is seemingly that, even if the devices of different brands are 'mechanically compatible' (which, of course, not all are), the results of the tests might be different if undertaken when different devices were installed.

If they do not then some must be poorer and less safe than others.

Again, although it seems to be a far-fetched suggestion, the argument appears to be that the devices are all 'perfectly safe' when installed in the intended CU, but not necessarily so when installed in something else. As I say, that sounds pretty far-fetched - not much different from suggesting that an accessory might become 'unsafe' if it was attached to a back box of the wromng brand