Use RCD as main switch?

[Smugley]

Hi, doing some work in a bathroom at the moment - just on the lighting circuit. Ext fan & ELV lights. As the house has no RCD protection at all I'm obliged to add it. All circuits are split between two 8way consumer units, each with main switch and MCBs. My options for adding RCD protection are either:

1. Just replace the lighting MCB with an RCBO - my preferred option, although I don't think the CU will accommodate the extra height of the RCBO.

2. Add an RCD in it's own enclosure in front of the CU which includes the lighting MCB. Not ideal as there'll be a lot more testing of the other circuits involved to avoid the risk of nuisance tripping from circuits I've not touched. Also, no other point of isolation so will have to pull the fuse (or get DNO in to isolate)

3. Alternatively, I could replace the main switch with an 80A RCD, like you would see in many 16th edition CUs. I would put a MAIN SWITCH label under it.

Any reason why option 3 wouldn't be proper? It seems a bit regressive, but would be the neatest solution if the RCBO doesn't fit..

 

[Sintra]

An RCD should not be used as a main switch. 314.2

16th edition split boards have a main switch controlling all circuits & an RCD controlling split side.

 

[Smugley]

Okay, I had a suspicion this was the case, but thanks for pointing out the relevant reg. Sure I'd seen boards where RCD was used as main switch - maybe my imagination!
Thanks a lot sintra, much appreciated.

 

[Sintra]

You probably have seen them cause I know I have.

Best option as said would be to try and get an RCBO to fit cu.

 

[Hawk81]

you probably have seen it done in other boards. i have come across it many times and had to fix it. just because you've seen it done doesn't mean its correct.

 

[ghost]

In the late 80's/ early 90's a few housing developers installed CU's with an RCD as the main switch, I don't know how long it was done for, but I have seen it many, many times in properties built around that time.

 

[Spudnik]

In the early days of rcd main switches, they were normally 100mA, especially in the case of TT's.

 

[Smugley]

Just back from the customer and thankfully the RCBO fitted... just!

 

[Johno]

good, you could of put the lighting circuit through an rcd spur in the fuse board cupboard (crap i know, but it would do it) but rcbo best option i would say

 

[eskimo39]

http://www.screwfix.com/search.do;jsessionid=GR32KEQ2WFYJSCSTHZOCFGA?action=search&fh_search=2+way&fh_refview=search&fh_reffacet=categories&fh_refpath=facet_87316993&fh_location=%2f%2fscrewfix%2fen_GB%2f%24s%3d2+way%2fcategories%3C{screwfix_a131772_a231826}&fh_eds=%C3%9F&ts=59348

Consumer unit with RCD as main switch, although I would imagine to keep within the regs you would need to feed this from a CU via MCB.

 

[Sintra]

It is not described as a main switch but a 63A 30mA RCD incomer.

 

[elektrisien]

A RCD is not a overcurrent device, hence it should never used as that. An RCBo should be used, I would think.