Junction box

[steamvalve]

I'm a little confused. I want to relocate my electric shower cable run. I therefore need to break the cable add two new junction boxes and extend the route. The shower is 9.5kW, the shower switch is 45 amp, the fuse is 30A at the consumer unit (old style with fuse wire). Am I OK with 30 amp junction boxes? The fact that the shower switch is 45 amp bothers me a little. Any advice would be much appreciated

 

[Steve]

Its the fact your shower consumes 41 amps that bothers me more, since its on a 30 amp fuse, on an old rewireable fuse box.

 

[JohnD]

9.5kW is about 40Amps. You are overloading your existing fusebox. One of that age will not be suitable for such a heavy load so you need a new one. Very likely your shower cable is also undersized and needs to be replaced. Junction boxes on a heavy and prolonged load like a shower are undesirable. If the cable passes through insulation (for example in a loft) it needs additional capacity.

If you are not ready to replace the consumer unit for the whole house, you can get a small "shower" CU installd with a 40A MCB and an RCD to reduce the risk of electric shock (which can be very severe when water and electricity meet wet and unclothed skin)

It is not a DIY job.