Domestic and requirement for better than type AC or A RCD?

[ericmark]

I did not feel it was fair to talk about the problem in the thread where it started, the instructions seemed to ask for a type F RCD, but with a Domestic CU there is a problem with type F and B RCD's.

The problem is not done as a RCBO, type F two pole hard to get over 63 amp, type B two pole hard to get over 40 amp, type B often 4 module wide, and the price type F often over £150 and type B getting to £400 range.

It seems one can avoid the need for a type B by using a 6 mA DC detection unit to auto disconnect the supply, but only found them in electric car charging pods.

It seems not using type B can cause the RCD not to trip, but not using type F can cause it to trip when there is no earth leakage.

Not sure which is the worst? If a device needing a type B is fed from a type A as long as only that device and a TN supply even if it does not trip, is that really a big problem, only with a TT supply do we really rely on the RCD.

But type F is another question, clearly if high frequency causes a type A to trip, then no real away around the problem, or is there? Will a SPD help?

But if the electrician fits a type A then it keeps tripping he will be expected to correct the problem maybe free of charge, but to simply swap to type F in the consumer unit dropping to 63 amp with some manufacturers, some down to 40 amp, so it will likely involve a second consumer unit just for the item needing the type F RCD.

I personally feel disconnection devices and filters should be fitted to domestic appliances so nothing over type A is required. However This installation instruction set says

Make sure to use a dedicated power circuit. NEVER use a power supply shared by another appliance

When installing the earth leakage protector, make sure it is compatible with the inverter (resistant to high frequency electric noise) to avoid unnecessary opening of the earth leakage protector.

This raises two questions, 1) Can it share a RCD? 2) Will it need a type F RCD?

I would say it should not share a RCD and it does need type F, with a house with all RCBO CU it would need a separate enclosure, and likely also where just two RCD's again likely need a separate enclosure, with a high integrity consumer unit then maybe all the supplies from one RCD can be moved to RCBO's and that RCD changed to type F and a dedicated MCB.

However it seems to comply installation cost will be high.

So should any domestic appliance ask for better than a type AC or type A RCD?

 

[JohnW2]

There's no way I can vote - I need a "don't know" (or "haven't got a clue") option since, as I keep saying, despite an awful lot of trying I cannot find any particularly useful information about this issue.

Also although the title of this thread says ".. better than Type AC or A", the actual vote question just says "... better than Type A" - which makes voting even more impossible!

Kind Regards, John

 

[ericmark]

I do see your point, I no longer work as an electrician, so not a problem, however it is a problem for a non in house electrician, how do you deside if the client needs to fit rather expenive hardware?

 

[JohnW2]

I do see your point, I no longer work as an electrician, so not a problem, however it is a problem for a non in house electrician, how do you deside if the client needs to fit rather expenive hardware?

Well, it's not any use as advice for anyone else, but, as far as I am personally concerned, and assuming that you are referring to fancy types of RCD, having hitherto lived happily without them for longer than I care to recall, I personally wouldn't even consider "fitting rather expensive hardware" unless/until I had found enough convincing information to enable me to conclude that there was a 'need'!

Kind Regards, John