50 Amp SG DP Wall Switch Required

[Jim Cooper]

Hi all.

Can anyone advise where I can puchase a 50 amp Single Gang double pole switch for mounting outside of an ensuite. This is for isolating switcihng of a 10.8Kw Mira electric shower, that requires a 50 amp MCB in a the CU.

Up to yet I can only track down a 50A double gang switch, which looks unsightly, as this is going in the bedroom next to the en-suite.

I do not want to have a pull cord, as all the wiring (10mm2) for the shower is in place for an external switch.

Any advice would be appreciated.

R

Jim

 

[Lurch]

Can't say as I've seen anything over 45A in single plate. If it's essential that there is a single plate switch on the wall how about a contactor in the loft with a standard 6A plate switch on the wall?

 

[Andy™]

all i can think of is a coooker switch, but they are normally 45A

in which case i would probably use that - 10.8KW is 45A at 240v - showers are usually their rated current at 240v, with a slightly lower rating at 230v - check the instructions/label on the shower for actual ratings

but i would also add that 2x 10mm

 

[Jim Cooper]

Thanks Lurch,

I will look into this option. Although, I would still prefer to go down the Single pate plan as wiring in place.

Thanks Andy,

The ratings for the shower are 10.8Kw at 240v & 9.9kw at 230v.

I have got a Crabtree 13 way dual RCD Split load CU, which C/tree do not supply a 45A MCB only a 50A. Therefore, I understood if the MCB is uprated to 50A, you need to match the isolation switch to 50 A.

I do have a 45A DP SG switch to go in, but would I have to scource an alternative make of 45a MCB (which might not fit the C/tree CU), or can I use this 45A switch with a crabtree 50A MCB.Pray

Replies appreciated.

R

Jim.

 

[NozSpark]

Personally I don't use 45A 1 gang isolators because they are such a pain to terminate.. (even with 6mm never mind 10mm)

 

[Lurch]

Personally I don't use 45A 1 gang isolators because they are such a pain to terminate.. (even with 6mm never mind 10mm)

Yep, double plate wall switches or Crabtree pull switches every time for me with anything 6mm or larger.

 

[Andy™]

Thanks Andy,

The ratings for the shower are 10.8Kw at 240v & 9.9kw at 230v.

I have got a Crabtree 13 way dual RCD Split load CU, which C/tree do not supply a 45A MCB only a 50A. Therefore, I understood if the MCB is uprated to 50A, you need to match the isolation switch to 50 A.

I do have a 45A DP SG switch to go in, but would I have to scource an alternative make of 45a MCB (which might not fit the C/tree CU), or can I use this 45A switch with a crabtree 50A MCB.Pray

Replies appreciated.

R

Jim.

just go with 45A switch and 50A MCB (unles you find a 45A one)

 

[bengie]

[quote name='Andy

 

[NozSpark]

^i agreei find the only time you can get 2x10mm cables into a single box easily is with a ceiling mounted switch where you can make the switch off with the cables 2-3 inches longer than required and lose the extra cable in the ceiling by pushing it back up but this is only possible if you put the cables into the box the right way round and with no twists at all, it has to be perfectly neat and the termination has to be spot on. 2x10mm can be awkward even into a double box, i try to use ceiling switches where ever i can.

Bengie

You should not be doing this... the cables sheath should be entering the accessory... If you dress the cables correctly then you should have no problem!!

 

[Lurch]

BengieYou should not be doing this... the cables sheath should be entering the accessory... If you dress the cables correctly then you should have no problem!!

I think the picture you linked to is a perfect illustration of exactly what was being described in the quoted text.

 

[bengie]

as lurch has said, that is exactly what i meant. i didn't mean strip the outer back a long way.

 

[NozSpark]

Sorry if I misinterpreted what you mean't, but you did say "loose the extra cable in the ceiling"BlushingBlushing

:coat :coat

 

[bengie]

no worries, i've seen a lot of diy sparking with that sort of thing done or missing sleeving etc.

i came across a shower isolator just like the one linked to but with no earth sleeving and connected up back to front(so the neon was on constantly), the tenants claims the electrician did it but i very much doubt it. without proof though we have to bite our tongue and put it right

 

[Jim Cooper]

Just to let yoiu all know, ended up using a double.as you guys advised.

Thanks,

Jim

 

[steptoe]

^i agreei find the only time you can get 2x10mm cables into a single box easily is with a ceiling mounted switch where you can make the switch off with the cables 2-3 inches longer than required and lose the extra cable in the ceiling by pushing it back up but this is only possible if you put the cables into the box the right way round and with no twists at all, it has to be perfectly neat and the termination has to be spot on. 2x10mm can be awkward even into a double box, i try to use ceiling switches where ever i can.

to the OP a fuse/mcb/rcbo is only there to protect the cable, nothing else. any switch gear on that circuit just has to be rated accordingly to the device it operates.

for future reference the specification of a circuit goes in the following order: load denotes fuse/mcb/rcbo required(always the next one up so a 41A load requires a 45A mcb), fuse/mcb/rcbo x any correction factors(due to installation method/grouping/insulation etc) denotes cable size required. sometimes due to installation conditions the size of cables can vary hugely, for example a 10.8Kw show as already mentioned is 45A so with a very short run going through no insulation(shower is back to back with fuseboard) the shower can be installed on 6mm cable with no issues but if that shower is is on the 4th floor of a town house and the fuseboard is in the basement with the cable passing through insulation for much of its run(installation method #105) then not even 16mm is of a high enough rating.

Switch gear has no correction factors normally and are sized according to load but personally i don't like to fit the minimum spec switch gear if i can help it(for example i wouldn't personally fit a 220W dimmer onto 4x50w halogen lights as i feel its pushing things and the life of the switch might be reduced, i would fit a 400w dimmer instead.).

HTH.

not sure I agree with that,

the MCB/RCBO must be of s smaller rated capacity than the circuit it protects,

surely the switchgear etc forms part of the circuit?

you wouldnt (physical restraints permitting) use a 6a switch to turn on a cooker.

 

[bengie]

thats just being silly there though isn't it.

 

[steptoe]

thats just being silly there though isn't it.

yes, it is, I agree, but the principle is the same,

you suggested it would be ok to protect a 45A switch with a 50A MCB.

code 1 PIR, oversize protective device.

 

[Blue Fox]

Can't say as I've seen anything over 45A in single plate. If it's essential that there is a single plate switch on the wall how about a contactor in the loft with a standard 6A plate switch on the wall?

Could you class this as isolation? I thought it would have to be a switch in the line - well does on the industrial work I have doine in the past for motors etc where a contactor definatly wouldn't have sufficed.

 

[Lurch]

Could you class this as isolation? I thought it would have to be a switch in the line - well does on the industrial work I have doine in the past for motors etc where a contactor definatly wouldn't have sufficed.

You could be right, if you are you could stick a switch inline with the contactor for isolation. The 6A switch and contactor would be for functional switching.