Shower Wiring

[millarat]

I have a 10.5kw shower that was fitted over two yrs ago. Recently the pull switch stopped working so i replaced it. When i removed the old one it looked melted and black as if fire had started. The wiring is 10mm coming from CU 40amp RCD. in to a 45Amp pull switch. When the shower is run the wiring really heats up. Just looking for advice regarding this as the shower was fitted by a qualified electrician apparently.
I have also ran the shower then isolated and opened it. the wiring inside was really warm.
I am going to get qualified spark tae look at it but would like advise so i don't get ripped off.

Regards Alan

 

[ricicle]

If you did not strip the cables back to clean, bright copper and insulation then the same will happen again and again as the conductivity of the copper/termination is increased so causing heat and damage. Pull switches can and do fail due to poor connections and/or poor quality switches.
Where are you saying that the wiring heats up ?

 

[ericmark]

45.5 Amp is rather a large load and will need 10mm sq cable. It is possible the original was 7.5kW which only needed a 32 amp supply. I would be looking at the supply if I was the spark and if it is 6 mm then three options.

1) Change back to 7.5kW dribble shower.
2) Re-wire with 10mm sq cable.
3) Change to shower running of the stored hot water or water direct from a boiler.

I have the latter and heating by gas have 27kW available depends on rose size how much used.

 

[millarat]

I cut back the wire to clean copper and tightened up as much as possible. The wires are heating up in the switch.

But really heating up from the terminal block in the shower to the shower internals.

I do understand basic elec. just starting to wonder if 10.5kw shower is too much for circuit.

 

[millarat]

As for the wiring it is all 10mm the Consumer unit has 40amp RCD cable run is about 10meters and 1mtr from switch tae shower. the switch is 45 amp MK type so good quality.

 

[EFLImpudence]

As for the wiring it is all 10mm the Consumer unit has 40amp RCD cable run is about 10meters and 1mtr from switch tae shower. the switch is 45 amp MK type so good quality.

10.5kW @ 240V = 43.75A.

A 40A RCD is therefore not really compliant.
Also this is only a current carrying capacity and not an overload and short circuit protection.

You do not mention an MCB which is overload and short circuit protection.
It should have a 45A or 50A MCB.

Has someone fitted only the RCD without understanding what it does?
This happens quite often.


The MK switch should be alright but if it is overheating, this would suggest the terminals are not tight enough.

 

[millarat]

Sorry ma info was inaccurate. I have checked the consumer unit. The main supply is protected by 63Amp RCD and the shower is connected to a Clipsal B40A MCB.

 

[EFLImpudence]

and the shower is connected to a Clipsal B40A MCB.

Ok. That's better.
As I said it should really be 45A (or 50A as not all manufacturers make 45A ones).

This isn't too much of a problem because of the short time the shower is in use but it may cause it to be slightly overheated and after time it may become 'weak'.

 

[millarat]

As i said before the information is just tae stop me gettin ripped off. so thank you for all your help and information. I have ensured all the terminals are tight the ones inside the shower unit were a wee bit loose so tightend them up. I will get spark tae upgrade the 40amp mcb to 45/50.

 

[viewer]

The wires from the terminal block to the boiler will get hot as they are attached to 3 x 3 bar electric fires all in a cup.

 

[Porque223]

If you can't touch it for more than a few seconds it's at >50C. IIRC 70C will burn you immediately.
http://www.antiscald.com/prevention/general_info/table.php

 

[ban-all-sheds]

As for the wiring it is all 10mm the Consumer unit.

You do mean that it has 10mm² L & N conductors, not that it measures 10mm in one dimension or another?

 

[millarat]

Its 10mm² m8 just couldn't find the ² [/quote]

 

[riveralt]

Its 10mm² m8 just couldn't find the ²

Me thinks you have 6mm2 cable and not 10.
10mm2 refers to the size of the conductor

Nominal outside diameter 17.1mm x 10mm for 10mm2 T&E and the earth tends to be a stranded core
Nominal O.D - 13.5mm x 7mm for 6mm2 T&E earth tends to be solid core

 

[JohnW2]

Me thinks you have 6mm2 cable and not 10. 10mm2 refers to the size of the conductor
Nominal outside diameter 17.1mm x 10mm for 10mm2 T&E and the earth tends to be a stranded core
Nominal O.D - 13.5mm x 7mm for 6mm2 T&E earth tends to be solid core

You may, of course, be right - but, as a matter of interest, which part of what we have been told makes you think that it's probably 6mm²?

Kind Regards, John