retro fit circuit breaker for shower circuit

[bennychops]

jst moved the shower in the bathroom. the shower is 9.5kw and is connected to the double pole switch by 10mm cable. the double pole switch then connects to the fuse box by 6mm cable (approx 30m away).

the fuse box is old fashioned and has a 45a cartridge fuse in it. should i replace the cartridge fuse with a retro-fit 45a circuit breaker?

also, is is safe that the cable changes size from 6mm to 10mm after the switch for shower???

 

[ricicle]

How is the cable ran from the CU to the pull switch?
Is there any 30mA RCD protection for the shower?
What type of CU do you have?

 

[bennychops]

cable is buried in walls from cu to pull switch. the cu is an old fashioned re-wirable fuse box, apart from the shower fuse which is a cartridge fuse.

 

[bennychops]

also, forgot to say, there is no rcd protection on the shower circuit

 

[ricicle]

30mA RCD protection is a requirement of the wiring regulations and most manufacturers for electric showers.

6mm² twin and earth is not rated for protection by a 45A protective device unless it is clipped direct or sheathed beneath plaster in a domestic situation.
If it is in a thermally insulated wall the cable must be de-rated which means a larger cable (or re-routing to the above conditions) for an appliance requiring a 45A protective device.

 

[Pensdown]

jst moved the shower in the bathroom. the shower is 9.5kw and is connected to the double pole switch by 10mm cable. the double pole switch then connects to the fuse box by 6mm cable (approx 30m away).

Because the shower is 30mtrs away from the CU the volt drop will exceed the maximum limits so it needs to be a minimum of 10mm all the way. If it passes through insulation it may need up-rating further to 16mm.

Can you post a picture of your consumer unit?

 

[ricicle]

Because the shower is 30mtrs away from the CU the volt drop will exceed the maximum limits so it needs to be a minimum of 10mm all the way. If it passes through insulation it may need up-rating further to 16mm.

9500/230=41.3A (7.3x41.3x30) / 1000 = 9.044V

5% of 230V = 11.5V so VD is not an issue.

 

[Pensdown]

That's because I set Amtech to 3% for final sub circuits to allow for the VD in the rest of the system.

But for a domestic shower you could use the full 5% so as you say, it's not really a problem.

 

[ricicle]

That's because I set Amtech to 3% for final sub circuits to allow for the VD in the rest of the system.

But for a domestic shower you could use the full 5% so as you say, it's not really a problem.

Unless we are in a huge great manor house where the shower IS fed from a sub-board......

 

[Spark123]

Just to make it a little bit more interesting, showers still tend to use the 240v rating - I take it that it is just a sales thing but would you like to buy a 9.5kw shower (240v) or an 8.8kw (230v) shower?