Shower Connections? estra rcd's etc..

[justinbowness15]

SORRY EXTRA RCD'S :rolleyes2:


Hi guys, i have been reading many other posts but as there are so many well trained sparks on here i thought id put my questions up.


I am having a shower installed in a recently revamped bathroom. Im no expert as you will soon realise but it will be installed by a part P pro.:frown:

The main in-house circuit board is the very basic 30+ year old 3 plugs/fuses type (operates plugs, lights and a previosly connect shower which has been removed)

As there already is a 6mm cable in the attic coming from the board which has a 45amp breaker for the shower, and i have an isolater switch to go in the bathroom, will i need an extra RCD in line from the switch to the shower?

So to try explain, Main board in kitchen with 45amp cut out plug - 6mm cable to loft - isolator switch - shower. This is how it currently was many years ago. I understand the max size shower which seems to be the smallest will be 7.5kw.

Hope you can help before i get over charged by a sparky. :sick:


Cheers

 

[electric will]

45a is pushing it on a 6mm cable if there is insulation in the loft which I guess there is, the cable is only rated at 32a

 

[malcolmsanford]

SORRY EXTRA RCD'S :rolleyes2:


Hi guys, i have been reading many other posts but as there are so many well trained sparks on here i thought id put my questions up.


I am having a shower installed in a recently revamped bathroom. Im no expert as you will soon realise but it will be installed by a part P pro.:frown:

The main in-house circuit board is the very basic 30+ year old 3 plugs/fuses type (operates plugs, lights and a previosly connect shower which has been removed)

As there already is a 6mm cable in the attic coming from the board which has a 45amp breaker for the shower, and i have an isolater switch to go in the bathroom, will i need an extra RCD in line from the switch to the shower?

So to try explain, Main board in kitchen with 45amp cut out plug - 6mm cable to loft - isolator switch - shower. This is how it currently was many years ago. I understand the max size shower which seems to be the smallest will be 7.5kw.

Hope you can help before i get over charged by a sparky. :sick:


Cheers

Well unless your cable is clipped on the surface this may be your first concern

Even if your not altering any wiring and just fitting a shower onto an existing supply ...........there is a better than even chance the showers manufacturer would want the shower to be RCD protected .................

As soon as you start to alter the existing circuit in any way what so ever you will have to supply that circuit with RCD protection

So there is a good chance that you will need to fit an RCD

 

[justinbowness15]

Will the RCD (what size) extra rcd in the attic be between the isolator switch and shower or before the isolator switch?

There are very few 7.5kw out there these days, anyone recommend one? i seem to like the MIRA zest (as i have been told MIRA are good) but does it really matter as there are a few out there.


I'm deffinately correct in saying 7.5 is the max then on a 6mm cable?

Should the 45A breaker in the kitchen board be lowered?


Thanks very much for your help.

 

[Octopus]

The only way to get accurate input into this would be to get a couple of local sparkies to have a look. Such "changes" often need additional changes too.

 

[malcolmsanford]

Will the RCD (what size) extra rcd in the attic be between the isolator switch and shower or before the isolator switch? If you are altering the circuit then the RCD will have to be ath the origin of the circuit. If your not altering the circuit and the manufacturer is calling on RCd protection then yes you can fit it where you wish. But putting protection devices in places where you don't expect them to be, or worse inaccessible to a degree is not a good idea

There are very few 7.5kw out there these days, anyone recommend one? i seem to like the MIRA zest (as i have been told MIRA are good) but does it really matter as there are a few out there.Mira are decent and a recognized make.


I'm deffinately correct in saying 7.5 is the max then on a 6mm cable? You cable will be rated by how it was installed. IE if it goes through insulation it can be 50% down rated. So we don't design circuits by can a 6mm take 7.5KW. All I can say that 7.5KW will pull a load of 31.25amps

Should the 45A breaker in the kitchen board be lowered? See above, but unless the cable is clipped surface, over it's entire run then yes it may have to be lowered


Thanks very much for your help.

........................................................

 

[Guitarist]

Agree with everything malc has said. If you google "7.5kw shower", there are literally dozens out there. Personally, I like the Triton range, though get a temperature stabilised model if you want to reduce the "scald effect" everytime someone flushes the loo
You may actually decide that now would be a good time to upgrade the old fusebox, rather than mess about with separate RCD units.

 

[justinbowness15]

May i just ask why it matters if the cable is clipped to anything? Heat?

I hope to have the 6mm cable clipped to a beam in the loft to keep it out of the way when someone is in the loft.

 

[malcolmsanford]

May i just ask why it matters if the cable is clipped to anything? Heat?Yes

I hope to have the 6mm cable clipped to a beam in the loft to keep it out of the way when someone is in the loft. That is ok but before it enters the loft and after it exits the loft how is it installed? If it is not clipped to the surface, ie it is in a trunking/conduit or buried in a wall, then you will need to down grade your protection device

.............................

 

[ayjay]

what about the length of the cable? it might be a really long run? or an i missing something

 

[tony mc]

As Murdoch has said get a few quotes and opinions of the sparks.

It could be that its not 6 mm and imperial cable installed IMO !

 

[Guitarist]

6mm T&E is not suitable for a 45A OCPD unless there are no derating factors whatsoever, which is highly unlikely.

 

[justinbowness15]

I have just spoken to a registered sparky. He has said put a separate small RCD box beside the current box, then go from that into the loft using the current wires, then to the isolator switch and then down through the ceiling to the shower. He said as i am getting a shower with both water and electric infeeds, the wire would be ok inside a metal chrome pipe identical to the water infeed aslong as it is earthed. But will try to find plastic chrome pipe.

He also said 8.5kw will be fine aslong as the mainboard and extra rcd are all correct ratings.

He also had a look at the gas and electric boxes, (maybe some earthing involved) and also under the sink?? not sure why though??

cheers guys for your help.

 

[telectrix]

sounds like your sparks knows what he's talking about. he has looed at gas and water supplies to see if they are bonded. if they're not, they'll need doing. if the cable to your shower is not covered in insulation, then 8.5kW on 6mm cable, with a 40A MCB is fine. RCD is essential as well.

 

[Knobhead]

Call me cynical if you like, but I think Mr. DIY is now off to do the job himself. Armed with all the expert knowledge he thinks he needs.
“I’ve just spoken to an electrician”, he must have been conveniently under the sink checking the earth.
This thread didn’t ring true from the outset.