Which unit/enclosure to house upfront RCD?

[HappyHippyDad]

Evening..

Just looking at a CU change on a TT. I'd like to put a 100mA S type RCD before the CU. Is a 2 way (4 spaces) amd 3 metal board my only option? Its a bit big!

 

[Leesparkykent]

Why not replace the main switch in the board with an S-type?

 

[Welchyboy1]

If all circuits are 30mA protected why bother with an S type at all, just use an appropriate gland for the tails

 

[Leesparkykent]

If all circuits are 30mA protected why bother with an S type at all, just use an appropriate gland for the tails

Belts and braces I suppose with the links to the RCD's from the main switch.

 

[Risteard]

It's easily arguable that a self-contained RCCB within an enclosure is not a "similar switchgear assembly" to a distribution board. For a start it provides no overcurrent protection. Therefore it isn't clear that it must be made of ferrous metal, e.g. steel.

 

[davesparks]

If all circuits are 30mA protected why bother with an S type at all, just use an appropriate gland for the tails

Backup fault protection in case the 30mA doesn't operate.
I realise that everybody always follows the test quarterly instruction so there's minimal chance of them failing to trip when needed, but just in case the user of the installation forgets to keep up to date with pressing the test button a backup protective device might help.

 

[Octopus]

Why not replace the main switch in the board with an S-type?

Like that idea a LOT!

Got quite a few TT installs on my patch so this would be a very neat solution ........ unless anyone can give me a good reason it isn't!

 

[happysteve]

I realise that everybody always follows the test quarterly instruction so there's minimal chance of them failing to trip when needed, but just in case the user of the installation forgets to keep up to date with pressing the test button a backup protective device might help.

If you said that with a straight face, I wouldn't wanna play poker against you!

 

[HappyHippyDad]

Why not replace the main switch in the board with an S-type?

Could do, but at present the tails go into a Henley block and then to the CU, so it seems opportune to change to the RCD. Plus it will provide isolation for the board when required, plus give RCD protection for the one in a million time the tails come loose and touch the metal CU (TT).

It's easily arguable that a self-contained RCCB within an enclosure is not a "similar switchgear assembly" to a distribution board. For a start it provides no overcurrent protection. Therefore it isn't clear that it must be made of ferrous metal, e.g. steel.

Will be interesting to see if there are any more thoughts on this. I don't think there's going to be a right or wrong answer, just confusion!

 

[Leesparkykent]

Could do, but at present the tails go into a Henley block and then to the CU, so it seems opportune to change to the RCD. Plus it will provide isolation for the board when required, plus give RCD protection for the one in a million time the tails come loose and touch the metal CU (TT).



Will be interesting to see if there are any more thoughts on this. I don't think there's going to be a right or wrong answer, just confusion!

But the chances are you would have to house the RCD in a metal enclosure anyway so you would have just as much chance of that happening to the enclosure for the RCD. Imo thinking you would get away with housing the RCD in a separate insulated enclosure is wishfull thinking when it comes to an assessment from your scam. I would use a Hager design 30 board with the tail clamp, nylon tail gland kit, clip the tails entering the board and change the main switch for a 100mA time delayed RCD. On top of that I would ditch those Henley blocks and replace the tails from the new CCU to the meter.

 

[HappyHippyDad]

But the chances are you would have to house the RCD in a metal enclosure anyway so you would have just as much chance of that happening to the enclosure for the RCD. Imo thinking you would get away with housing the RCD in a separate insulated enclosure is wishfull thinking when it comes to an assessment from your scam. I would use a Hager design 30 board with the tail clamp, nylon tail gland kit, clip the tails entering the board and change the main switch for a 100mA time delayed RCD. On top of that I would ditch those Henley blocks and replace the tails from the new CCU to the meter.

I think that's all pretty spot on Lee, cheers

 

[HappyHippyDad]

It's easily arguable that a self-contained RCCB within an enclosure is not a "similar switchgear assembly" to a distribution board. For a start it provides no overcurrent protection. Therefore it isn't clear that it must be made of ferrous metal, e.g. steel.[/QUOTE]

I like the way even when speaking normally we sound like a regs book

 

[davesparks]

I would fit the RCD in one of those enclosures that the REC type isolators come in and list the plastic enclosure as a deviation from the regs as I would deem it to be a justified deviation in my professional opinion. Obviously using a good quality RCD and terminating it securely to prevent loose connections etc.

 

[Midwest]

Just to add my two pennneth and further this debate. I've asked my scheme - Elecsa - re housing RCD in insulated enclosure. Their interpretation is that a upfront RCD would need to comply with 421.1.201. When I fitted a Wylex A3 CU, it had a set of pics showing various installations, one of which showed a recommended install for a TT with a plastic enclosure for upfront S type. When I rang Wylex technical asking if they could explain, they batted me off to some sales guy, who said it was the lesser of two evils.

Think all will have seen the Elex at Harrogate 15 vid, and I seem to remember this was mentioned, with a 'we waiting further guidance' or something like that.

IMO is fairly easy to install a S type in a metal enclosure, using Wiska tails gland or similar & 6181y cable, which should make the possibility of shorting incoming mains almost impossible .

It's pretty damn annoying though, that prior to A3, you would have been strung up using a metal CU with a TT supply!

 

[sparksburnout]

But the chances are you would have to house the RCD in a metal enclosure anyway so you would have just as much chance of that happening to the enclosure for the RCD. Imo thinking you would get away with housing the RCD in a separate insulated enclosure is wishfull thinking when it comes to an assessment from your scam. I would use a Hager design 30 board with the tail clamp, nylon tail gland kit, clip the tails entering the board and change the main switch for a 100mA time delayed RCD. On top of that I would ditch those Henley blocks and replace the tails from the new CCU to the meter.

You been watching them videos I see!