Rcd fused spur bathroom Fan

[nrg]

Hi All

I have a customer with a single rcd board, protecting the sockets and the garage only. They wanted a fan installing in the bathroom which needs to be rcd protected. I was going to pit and RCBO on the board for the upstairs light but crabtree have discontinued them. So I though I would install a RCD Fused spur.

I split the bathroom lighting circuit in the rose and did the following.

Ran a L N SL from the rose to the rcd using 3 core
Connected L N to rcd and SL to fan isolator switch
Connected L N from RCD to fan isolator
Connected bathroom light switch to L SL of isolator
Connected L N SL to fan

Basically what happens is the rcd unit trips out as soon as I turn the bathroom light switch on. If I remove the neutral from the rcd direct to the fan isolator everything works fine, but obviously the rcd is then useless.

I suspect a neutral issue but all lights have the same neutral. Any ideas?

Thanks In advance

 

[malcolmsanford]

Could you not transfer the lighting circuit onto the RCD protected side.

 

[Colin Integrale]

Surely that RCD is only on the permanent live and not the switched live...

Don't you want to put it on the feed to the 3 plate rather than after it?

 

[Colin Integrale]

Could you not transfer the lighting circuit onto the RCD protected side.

'Tis indeed the easiest option.

 

[nrg]

Thanks for the replies, the rcd is between the mains and the isolator thus protecting the lighting circuit and the fan. It might be an option to add to the rcd side of the board, however if there is a neutral earth issue it will then take everything out not just the bathroom lights

 

[Deleted member 9648]

Hi All

I have a customer with a single rcd board, protecting the sockets and the garage only. They wanted a fan installing in the bathroom which needs to be rcd protected. I was going to pit and RCBO on the board for the upstairs light but crabtree have discontinued them. So I though I would install a RCD Fused spur.

I split the bathroom lighting circuit in the rose and did the following.

Ran a L N SL from the rose to the rcd using 3 core
Connected L N to rcd and SL to fan isolator switch
Connected L N from RCD to fan isolator
Connected bathroom light switch to L SL of isolator
Connected L N SL to fan

Basically what happens is the rcd unit trips out as soon as I turn the bathroom light switch on. If I remove the neutral from the rcd direct to the fan isolator everything works fine, but obviously the rcd is then useless.

I suspect a neutral issue but all lights have the same neutral. Any ideas?

Thanks In advance

The way you have wired it the N to the light is not run through the RCD,causing an imbalance.....as above,ditch the spur and transfer the lighting circuit to the RCD side of the DB.

 

[nickblake]

I agree with malcome on this move the lighting circuit to the fused spur then from the fused spur to the lights / fan , fan isolator and put in a 2 amp or 3 amp fuse this way you will be giving extra protection to the fan due to the lower rating fuse

 

[ezzzekiel]

put the feeds for the light into the rcd fcu then to light, isolator fan

 

[nrg]

Cheers chaps, I'll have another look in the morning and determain Which neutral out of the 4 black wires going into the rose is the main one and then route through the rcd. I'm just concerned that the other neutrals will cause problems on the rest of the circuit!

Thanks for the help

 

[nickblake]

if you put the supplies loop in and out to the ingoing of the RCD fused spur and then a 1.5 to the light circuit for the bathroom , then pick up a 3 core from the light to the fan isolator then to the fan this way you can isolate the fan with out loosing the lights so at night if they dont want the fan on they can isolate it and still use the light and of course for maintainance purposes , and if you use a 3 amp fuse for that part of the circuit the fans better protected as well ,some fan manufacturers stipulate 2 or 3 amp fuses in thier fans

 

[nrg]

When you say loop in and out so you mean the live and neutral feeds?

 

[Deleted member 26818]

BS7671 requires that all circuits of special locations be RCD protected.
To my mind this requires the whole circuit, not just a part of it be protected.
Placing an RCD anywhere other than at the origin of the circuit would not meet the requirements of BS7671.

 

[nickblake]

When you say loop in and out so you mean the live and neutral feeds?

yes you say you have a single RCD board , do you mean a split load , and what crabtree model is it

 

[SMB]

Spin, thats got me thinking. Im not too sure if your right mate.

So.......if I added to a non-RCD-protected ringmain in a special location with an RCD socket it would not conform to BS7671 ?

I think it would. And I think that would also go for an RCD protected fused outlet for a fan.

Im not trying to split hairs mate, im just interested.

With respect.

 

[SMB]

put the feeds for the light into the rcd fcu then to light, isolator fan

Thats exactly the answer.

Find the feed to the light, redirect it to the RCD fused spur and wire from there.

 

[Deleted member 26818]

BS7671 only specifically refers to circuits requiring RCD protection in relation to special locations.
Other references refer to cables concealed in walls or socket-outlets.
RCDs only detect earth faults downstream from where they are placed.
So if as you suggest you were to place an RCD FCU on a ring main to spur off into a bathroom. Any earth fault on the ring main, or indeed in any appliance connected to that ring main would be able to be imported into the bathroom without causing the RCD to operate.

 

[SMB]

Thanks for the reply Spin, but im afraid I don't really understand. Sorry.

From my way of thinking anything fed from the RCD into that bathroom (regardless of what circuit its fed from) would be controlled via that outlet...ie it would be RCD protected.

Sorry to be thick.

 

[Deleted member 26818]

Yes anything after the RCD would be protected.
That isn't what BS7671 requires for special locations.
That aside whilst the RCD is protecting equipment downstream, it won't protect equipment upstream and it won't protect against voltage on the CPC from entering the bathroom.

 

[SMB]

Mmmm. I think I need to do some more reading then.

Thanks for the input.




Yours, rather confused,

SMB

 

[RogertheBodger]

Yes anything after the RCD would be protected.
That isn't what BS7671 requires for special locations.
That aside whilst the RCD is protecting equipment downstream, it won't protect equipment upstream and it won't protect against voltage on the CPC from entering the bathroom.

Thats an interesting debate.
Wouldn't it be true that any non RCD circuit could import potential via the cpc into the bathroom, all circuit cpcs are connected together.