Powerbreaker socket query

[Chris Hogg]

When we first moved into this property, we had an old style wire fuse box and an ELCB. At the time I fitted two Powerbreaker sockets, one in the garage and one in the conservatory, (see

as example), for using extension cables for garden tools etc. Since then we have had a new consumer unit fitted, with MCB's and a 30ma RCD, as well as a whole house 100ma time delayed RCD (we have an overhead mains supply). The Powerbreaker sockets have a green test button which is supposed to be used regularly to ensure the Powerbreaker is working OK. This green button is also easily mistaken for an on/off switch as they don't specifically have one.

My problem is that pressing the test button frequently trips the RCD in the CU, which is annoying. Having replaced the CU with a modern version complete with RCD, are these Powerbreaker sockets really necessary, and can I revert back to the simple sockets of old?

[Invisible Man]

As long as the sockets are on circuits that are protected by 30mA RCD(s) I would have thought powerbreakes were unnecessary.

I have heard suggestions that you are safer with the current cut as close as possible to the appliance being used but I am not entirely convinced it would make a lot of difference.

Hopefully an expert will be along soon.

[Tabby]

If the socket circuit is covred by a 30mA RCD, which it presumably is, then the RCD socket gains you nothing in safety terms. The only advantage of retaining it is that sometimse when a leakage fault occurs, only the socket will trip rather than everything on teh CU's

30mA RCD. Losing stair lighting etc can have safety implications.

NT

[dennis]

The test button is showing that your 30mA RCD is working correctly.

However the 30 mA RCD offers the same protection as the powerbreakers so they aren't needed.

The 100mA RCD also appears redundant as the 30mA will trip first, unless its a split unit and only has one 30mA RCD.

[ARWadsworth]

The 100mA RCD is not redundant if it is a split load CU and the 100mA RCD is a time delayed unit (16th edition setup with the lights etc only fed via the

100mA RCD).

If the unit is not time delayed then any faults on the 30mA RCD side of the CU would probably trip both RCDs.

[ARWadsworth]

As long as the powerbreakers are fed via the 30mA RCD in the CU then use normal sockets. There is no advantage to be gained by keeping them.

[dom]

Nope.

The OP is probably on a TT earth, as he specifies overhead wires and a

100mA time-delayed whole-house RCD.

See:

?title=RCD#TT_InstallationsThe socket rcd's are however redundant.

[Chris Hogg]

Thanks for the replies. I'll change them back to normal sockets. Much less hassle.

For information, we have a TT system (couldn't remember the initials on my earlier post), with an earth rod (two in parallel, in fact). The CU is split, with the ring circuits and the electric shower on the

30mA RCD, and the cooker, immersion and lights on the other side with just MCB's, and both sides coming off the 100mA time-delayed RCD.

[dennis]

That's odd, you agreeing with what I said and in public too.

[John Rumm]

agreed.

It sounds rather like a traditional 16th edition cascaded RCD setup as was commonly used for TT systems. The 100mA unit will be in the main incomer switch posistion and is a time delayed. It is required since the earth loop impedance is unlikely to be low enough to open circuit protective devices on earth faults. The time delay ensures discrimination with the downstream 30mA RCD.