I currently have a 7.2 kW electric shower fed by 6mm twin and earth via a 30A breaker. The shower needs to be replaced but the lowest rating shower available now is 8.5kW which equates to around 35A. As 6mm cable is rated at 40A, would I be ok just uprating the MCB to a 40A unit to supply an 8.5kW shower?
Circuit rating
- Thread starter davecooper
- Start date
Sponsored Links
6mm² cable is not "rated at 40A".
A cable's current carrying capacity depends on how it's been installed, e.g. just buried in plaster, installed in conduit or trunking, running through insulation etc.
See http://www.tlc-direct.co.uk/Book/4.3.1.htm for more information on this (note - refers to an earlier version of the Wiring Regulations, and does not cover all of the currently recognised methods).
6mm² can be anything between 23.5A and 47A.
How is yours installed, and how long is it?
A cable's current carrying capacity depends on how it's been installed, e.g. just buried in plaster, installed in conduit or trunking, running through insulation etc.
See http://www.tlc-direct.co.uk/Book/4.3.1.htm for more information on this (note - refers to an earlier version of the Wiring Regulations, and does not cover all of the currently recognised methods).
6mm² can be anything between 23.5A and 47A.
How is yours installed, and how long is it?
As Bas as mentioned, you cannot take for granted the rating of 6.00mm T&E cable, as derating factors may need to be calculated in.
If a cable is run in conduit/trunking, in thermal insulation, grouped with other cables, a BS3036 fuse is protecting cable or the ambient air temperature differs from 30 degree Celsius and the length of the cable. Then the safe current carrying capacity of the cable will be reduced.
The maximum current a 6.00mm T&E cable can carry is 47A, but that can quite easily be drastically reduced be the above factors.
You say 30A breaker, I assume you mean fuse. Which would bring me to ask if there was RCD protection on this circuit? As it would be foolish not have it!
If a cable is run in conduit/trunking, in thermal insulation, grouped with other cables, a BS3036 fuse is protecting cable or the ambient air temperature differs from 30 degree Celsius and the length of the cable. Then the safe current carrying capacity of the cable will be reduced.
The maximum current a 6.00mm T&E cable can carry is 47A, but that can quite easily be drastically reduced be the above factors.
You say 30A breaker, I assume you mean fuse. Which would bring me to ask if there was RCD protection on this circuit? As it would be foolish not have it!
The cable is buried in plaster for about 1m then runs in air under a floor and up into a stud partition wall for another 3m. It is a circuit breaker, one of the push in type that replaces the fuse. I am getting a new consumer unit fitted but that can't be done for a few months. My plan was to run a completely new cable from the new consumer unit to the shower as it is a very easy route. However, I had wondered whether uprating was a possibilty as a stop gap.
Sponsored Links
Changing the size of the breaker is notifiable work. So you will need to either :
Notify your LA Building Control dept - be sitting down before looking up their fees for this.
Or get someone in who can self notify - this will almost certainly be cheaper.
If you get someone in, then he should be qualified to say whether it's OK or not.
Notify your LA Building Control dept - be sitting down before looking up their fees for this.
Or get someone in who can self notify - this will almost certainly be cheaper.
If you get someone in, then he should be qualified to say whether it's OK or not.
Thanks for the replies. We are now considering doing away with the electric shower and moving to a tap/shower combination. This has its own problems in our bathroom but it would solve a few problems such as years of dripping from the shower hose which has rotted part of the floor. If we do decide that an electric shower is still the best option, I am not going to fit a new one until the old consumer unit has been replaced and a new cable has been run.
Do you not have a combi boiler for a mixer shower or hot/cold tanks for a pumped shower ?
DIYnot Local
Staff member
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local
