Safe cable size for 3kw immersion heater.

Andystu · Posted: Wed Nov 05, 2008 1:13 am

Hi, all. A friend of mine has just had a new boiler and cntral heating system to replace his original one. For some reason, the old immersion heater was connected to 1.5mmT&E. The electrician that came to wire up the new system including the new immersion heater, said that the 1.5mm T&E cable was ok to leave in and wire up to.!. Is this the case or was he just being lazy not wanting to rewire with 2.5mm T&E. The cable is on its own circuit and the length is aprox 25metres. Also, I was wondering if the fuse fitted is ok at 16amps, i'm just a little concerned that the safety device i.e the circuit breaker can stand more than the cable?
Any advice would be appreciated.
Andy Stu

plugwash · Posted: Wed Nov 05, 2008 1:28 am

how is the cable run? In particular does it run through any insulation?

Andystu · Posted: Wed Nov 05, 2008 9:24 am

I believe it runs from the consumer unit which is located in the single storey garage, up through the garage lof space which has a small amount of insulation, maybe 50mm then under the floor boards and into the airing cupboard. If the route is vital for the calculation then I can find out exactly in more detail.

Thanks,

Andy Stu

Softus · Posted: Wed Nov 05, 2008 9:50 am

The route isn't vital - 1.5mm² T&E can safely carry more than 13A even if insulated and in conduit.

A 16A breaker is also fine, but the outlet in the airing cupboard should be fused at 13A.