RCD Connection Agnostic?

[DIYWell]

Double pole RCD module sitting in a standalone 2 way enclosure. Live on the left, neutral on the right. Supply connected to the bottom, load connected to the top.

But can it be connected supply to the top, load to the bottom? Once it's tripped, load is disconnected in either configuration. Or am I missing something?

 

[333rocky333]

Most i have seen you can wire top or bottom.i believe the only mark usually on them is an N for the Neutral side

 

[DIYWell]

Different manufacturers mark differently.

 

[DetlefSchmitz]

Without thinking too hard - doesn't it depend how the test button is wired?

 

[DIYWell]

I don't think so. The protection circuit monitors the L N bus bars in the module and flicks the switch if a fault is detected. The protection circuit doesn't care after that if it is powered or not; it has done it's job.

 

[JohnW2]

Without thinking too hard - doesn't it depend how the test button is wired?

I confess that was my immediate thought, too - but once I started scribbling, I decided that it was not the case.

If, as I assume is always the case, the test button effectively connects a resistor from the L on one side of the RCD ('input' or 'output') to the N on the other side, then it will 'work' with the RCD either way around/'up'. In one case the test current will go through the L of the RCD (but not its N) and in the other case it will go through the N (but not the L), but in either case it will create the same L-N imbalance current within the RCD.

Kind Regards, John

 

[EFLImpudence]

Isn't top supply the normal? So bottom supply should be the questionable way.

I don't think it matters which way it is connected.

 

[DIYWell]

In a domestic CU the live bus bar is at the bottom.

 

[securespark]

Remembering the RCDs I used to fit in the early days (Steeple brand), their instructions said it didn't matter which way round it was wired.

 

[ericmark]

Most 3 phase boards supply at bottom, most consumer units supply at top, however modern versions tend to be electronic, so the question is does the electronic board need power after it has tripped?

And where if any are the spark arrestors. Picture from Wikipedia 1) is supply so all electronics disconnected when it trips.

 

[DIYWell]

Surely to need power after tripping negates the principle of failing safe?

I also think if supply/load mattered, they'd all be labelled to avoid manufacturer liability.

 

[JohnW2]

.... however modern versions tend to be electronic, so the question is does the electronic board need power after it has tripped?

Need power for what? Until it is (manually) reset, it obviously doesn't need any power.

You surely aren't suggesting that it needs power to "stay tripped"? - that would be ridiculous! (and, since the 'tripping' will presumably be 'mechanical', impossible as well as ridiculous)

Kind Regards, John

 

[JohnW2]

Isn't top supply the normal? So bottom supply should be the questionable way.

Top supply is certainly the usual in (single-phase) CUs, but I think that 'bottom supply' may be more common (or, at least, at least as common) in the case of standalone RCDs such as the OP mentions - that is, for example, the case with the TD RCDs at the origin of my supply ...

I don't think it matters which way it is connected.

As I said, after a little thinking I agree.

Kind Regards, John

 

[SUNRAY]

around 2000-2002 I recall a problem with a brand which half tripped. IE after tripping they had to be manually moved to 'off' before resetting. The problem was the electronics were powered from the 'load' side and therefore powered down after tripping, if wired back to front the power remained on the electronics and the release magnet which overheated and burnt out if left like it or a prolonged period.

They had a rotary action rather than the toggle style.

 

[JohnW2]

around 2000-2002 I recall a problem with a brand which half tripped. IE after tripping they had to be manually moved to 'off' before resetting.

I think many are still like that - all of mine certainly are. It's sometimes possible to 'just reset' but, moreoften-than-not, it's necessary to 'push them right down' before they will reset.

The problem was the electronics were powered from the 'load' side and therefore powered down after tripping, if wired back to front the power remained on the electronics and the release magnet which overheated and burnt out if left like it or a prolonged period.

Leaving the electronics 'powered' after the device has tripped (hence the load disconnected) would surely not result in the release magnet remaining powered (unless the device were faulty), would it?

Kind Regards, John