UK 3 Phase RCD?

JDD1991 · Jul 8, 2021

I have recently started on a site where there is a 16A 3 phase Atex socket which is supplied by a 16A 3 phase MCB. It was picked up on a recent inspection that it needs an RCD. For the life of me I cannot find a 16A 3 phase RCD. I started to think does it really need an RCD? The socket is only used for one piece of equipment which is regularly maintained and only used by trained operators. The building in which the socket is in is not used very often as it is a warehouse and power is off to the socket when the building isn’t occupied.
Any advice greatly appreciated

telectrix · Jul 8, 2021

found in 30 seconds.

Lucien Nunes · Jul 8, 2021

I cannot find a 16A 3 phase RCD

Are you looking for an RCD or RCBO? If RCBO then Tel has found you an example above. If you just want an RCD to use downstream of the existing 16A MCB then a 25A or 40A device will be much more readily available and probably cheaper.

JDD1991 · Jul 8, 2021

telectrix said:
View attachment 87499found in 30 seconds.

Thank you. Based on what I’ve said do you think it really needs one though? Could be risk assessed off?

loz2754 · Jul 8, 2021

Would it be possible to remove the socket and replace it with an isolator, thus removing the requirement for RCD protection?
A risk assessment would have to show a good reason why an RCD is not required in this case, documented and attached to the existing certification.
The Napit Codebreakers book has a whole 18 page chapter on the subject of risk assessments for the omission of RCDs:

e-spark · Jul 8, 2021

JDD1991 said:
I have recently started on a site where there is a 16A 3 phase Atex socket which is supplied by a 16A 3 phase MCB. It was picked up on a recent inspection that it needs an RCD. For the life of me I cannot find a 16A 3 phase RCD. I started to think does it really need an RCD? The socket is only used for one piece of equipment which is regularly maintained and only used by trained operators. The building in which the socket is in is not used very often as it is a warehouse and power is off to the socket when the building isn’t occupied.
Any advice greatly appreciated

Used 25, 40 and 63 amp 3 phase RCDs and then fitted fused switched isolators after the RCD so can downgrade to suit. This was in oil and gas industry too setting up life testing in workshops and also on sites.

JDD1991 · Jul 8, 2021

loz2754 said:
Would it be possible to remove the socket and replace it with an isolator, thus removing the requirement for RCD protection?
A risk assessment would have to show a good reason why an RCD is not required in this case, documented and attached to the existing certification.
The Napit Codebreakers book has a whole 18 page chapter on the subject of risk assessments for the omission of RCDs:
View attachment 87507

Needs to be a socket as the equipment does get moved about. Thanks for the info much appreciated

JDD1991 · Jul 8, 2021

e-spark said:
Used 25, 40 and 63 amp 3 phase RCDs and then fitted fused switched isolators after the RCD so can downgrade to suit. This was in oil and gas industry too setting up life testing in workshops and also on sites.

Appreciate the info, thank you.

Rockingit · Jul 8, 2021

telectrix said:
View attachment 87499found in 30 seconds.

Here’s a thing about those particular RCBOs….. the 4p neutral is just a dummy. So what that means is that inside a 3ph board you end up ‘losing’ 2 adjacent phases if you’re only populating with 3ph devices. AND - as I found to my distress on a recent job, they only do that on the right hand side - on the LEFT bus you end up with the N as L1 which means when you come to present cable you end with Blk-Gry-Brown, miss two, and it just looks so wrong!! ?