UK RCD sockets on RCBO protected circuit

[onlyhuman]

hi all
come across a new build commercial office where radial circuits feeding electrak power track was protected by 32A RCBO at dist board and the electrak tap off leads terminated into RCD under desk sockets
why install RCD sockets when circuit is protected by 32A RCBO
is this install correct or wrong

 

[newfutile]

It's not unsafe but I have had it where pushing the test button has tripped the rcbo, you also don't achieve selectivity

 

[Mikegh]

It's not unsafe but I have had it where pushing the test button has tripped the rcbo, you also don't achieve selectivity

Out of interest how would that occur ? I don't see an imbalance on the upstream rcbo ?

 

[mainline]

Out of interest how would that occur ? I don't see an imbalance on the upstream rcbo ?

Pressing the test button on a downstream rcd can cause the upstream rcbo to also see an imbalance.

 

[R-fur]

On some devices the test button connects a resistance between the outgoing live and the incoming neutral, this will not be seen by an upstream device.
On other devices the test button connects a resistance between the out going live and earth, this will be seen by the upstream device, but either device may trip because as newfutile said, there is no selectivity between devices.

 

[newfutile]

I actually had it happen after an mcb was upgraded to rcbo,this had a srcd socket that caused that to happen when I pressed the test button

 

[MDJ]

hi all
come across a new build commercial office where radial circuits feeding electrak power track was protected by 32A RCBO at dist board and the electrak tap off leads terminated into RCD under desk sockets
why install RCD sockets when circuit is protected by 32A RCBO
is this install correct or wrong

It isn't wrong, but they are better ways to do this, I have seen this many times, there can also be more than one desk connected to the electrak, so in theory a potential nusience tripping situation for the rcbo, this is quite common in a lot of offices though.

 

[littlespark]

Out of interest, I’ve been working in a double garage - come - man cave… supply from RCD side of a split board, out to the garage in SWA, and a 2 gang board with MCBs.

I’ve replaced the board in the garage to accommodate extra circuits and upgraded to all RCBO Fusebox on the thinking I’ll move the supply onto the non rcd side when the time comes.

Test button on RCBO and testing with MFT both trip just the RCBO….. but an actual fault (someone’s dodgy cheap and nasty battery charger) took out both the house and the garage circuit simultaneously.

 

[R-fur]

est button on RCBO and testing with MFT both trip just the RCBO….. but an actual fault (someone’s dodgy cheap and nasty battery charger) took out both the house and the garage circuit simultaneously.

As above, there is no selectivity between 30ma devices, it is pure chance which one will go first.

 

[EricMark]

I have used active RCD's in a FCU not as a RCD but as a no volt release for items like grinders. Cheaper than a proper starter with no volt release.

I also have a metal clad RCD 10 mA socket I had got with idea of using outside, but never got around to fitting it, mainly as I found test button not only would trip a 30 mA RCD but also a 100 mA RCD there was no on/off switch so only way to turn off was press the test button. An old MK one so not cheap and nasty.

 

[Rockingit]

Where are we up to these days on technical compliance of RCD sockets? There used to be an issue because their BS No. (which I’ll need a coffee to remember..) had been pulled from the regs, even though we all knew they worked fine.

 

[UNG]

An old MK one so not cheap and nasty.

I suppose alot depends on how you view MK's offering these days, MK are one of a number of companies that live off their long past reputation IMO

 

[Timbo]

Wouldn't touch MK rcd sockets.
Have a customer that had 3 MK Masterseal rcd sockets that were in an a/c compound for servicing use. Came to the 1st EICR and none of them worked.
Replaced with BG. No problem so far.

 

[loz2754]

Where are we up to these days on technical compliance of RCD sockets? There used to be an issue because their BS No. (which I’ll need a coffee to remember..) had been pulled from the regs, even though we all knew they worked fine.

They're back in since amendment 2. BS7288 SRCDs are recognised again.

 

[Mikegh]

Wouldn't touch MK rcd sockets.
Have a customer that had 3 MK Masterseal rcd sockets that were in an a/c compound for servicing use. Came to the 1st EICR and none of them worked.
Replaced with BG. No problem so far.

That's bad .
Did they work after testing when the mechanism was freed up