HELP What to do with this shower??

[PaulWales]

My son, who currently rents his house, asked me to come and inspect his instantaneous electric shower as it has recently started to smell "fishy".

He had looked at the shower which seems to be OK and the main ceiling isolator.

This is the source of the smell. The last 3 cms of the "live" core to the T+E is charred with the copper core obviously black and oxidised.

The shower is fed from an RCD protected way and a 40 amp mcb. Though I am not sure of the model the shower is a 10.5 kw triton shower that looks fairly new. He tells me it was installed by the landlord when the bathroom was revamped prior to them moving in about 18 months ago. It certainly looked that new.

It would appear thet the cable feeding the shower is only 6 mm2. I do not have the dimensions to hand ( I had no vernieer caliper with me) but the earth is definitely single core and the line and neutral are multicore ( and in the old colours.

The "fusebox seems modernish I would guess 10 to 15 years old. It is a "split load unit with the main isolator and 2 of 6amp mcb on one side and the rest of the house rcd protected by a single rcd.

The shower mcb seems to be of the =same vintage as the rest of the "fusebox".

SO what to do.
First off:

Isolate the circuit (already done!!) and having checked for dead, replace the ceiling shower isolator (currently rated at 45 amp) with an MK 50 amp device. There is plenty of slack in the cable where it enters from the loft to shorten the feed cable and remove the obviously heat damaged end.

THEN do I:

i) Keep quiet about what appears to be an overloaded circuit
or
ii) Insist that he tells the landlord to change the cable and protection device (or the shower!!).

Is it possible to tell whether the cable has been damaged elsewhere by the long term overload that appears to have taken place?

Many thanks

 

[riveralt]

You should really have got the landlord involved at the very beginning since you may now be liable for any issues that follow. As a landlord myself I know that it is written in the contract that electrical and gas installations should not be touched by the tenant.

The problem you have is that Triton say for 10.5kw showers (which are really 9.6kw showers @230v) require 45Amp MCB and 6mm2T&E which in their manual is rated at 47Amps when clipped direct. They suggest 10mm2 T&E but do not make it a condition.
So while the mcb is lower than recommended it still will do its function and protect the cable in the event of a problem.

It sounds as if the cable temination isolator became loose and this caused the problem there. I hope when you made sure that you stripped the cable back to new copper before reconnecting.

Whether you tell the landlord is up to you but be aware of the first paragraph above.

 

[PaulWales]

Thanks for the prompt reply.

At the moment other than investigating on my way home form work (only just got in) we have done nothing.

After all not even "sheds" are open at this time of day!!

My son is planning to text the landlords to get "approval" for the work which will include the cost of the replacement switch (just under a tenner +vat from TLC). THey are often "out of the country with their work and manage their properties directly rather than use an agent.

My main concern was the "hidden" cable overload as I understood that 6mm2 was only good for 40 amps. continuous. Whilst I have general DIY kit including a reasonable multimeter I dont have access to "high" voltage IR kit if that was deemed essential.

 

[17thman]

There is the question of the 6mm2 cable probably not being clipped direct it is probably in trunking, or in plaster and possibly/probably within insulation or touching it. this will reduce the current carrying capacity.The fishy, smelly oxidisation is caused by an imperfect connection but 10.5kw or 9.6kw (converted) could have simply become overheated at it weakest point, you will not know without testing if the insulation of the conductors has been damaged elswhere through overheating. It is important that you get this professinally tested at the landlords cost.

You could tell the landlord that the smell was so bad that you turned off the mcb and opened the isolator as you were worried about a fire and just snipped the end off the live conductor as you did not want to it to comeinto contact with the terminal if someone inadvertantly turned the mcb back on.

 

[riveralt]

My main concern was the "hidden" cable overload as I understood that 6mm2 was only good for 40 amps. continuous. Whilst I have general DIY kit including a reasonable multimeter I dont have access to "high" voltage IR kit if that was deemed essential.

The On site Guide to BS7671 says that 6mm2 T&E when clipped direct or buried in plaster is rated at 46Amps. But this should be derated if, as 17thman highlighted if enclosed in conduit (38Amps) on a wall or enclosed in conduit in an insulated wall (32Amps). The derating is more severe if the cable passes directly through insulation which can reduce its rating by up to a half.
Strange as it may sound replacing the cable with 10mmT&E may be more expensive than just replacing the shower with a 8.5kw or 9.5kw rated one.

 

[PaulWales]

Not investigated the cable path, but the cable enters the isolator through the ceiling from the loft where there is certainly some insulation from what I remember about 100mm. I didnt ask whether the cable is on top of or underneath directly on the plasterboard ceiling and I cant recall from when I helped him move in - though I think it was under the insulation.

As to its route from the "fusebox" to the shower I can only guess. The house is a 1980's built timber frame with brick outer skin. THe fusebox is high on the ground floor "shared" wall at the bottom of the staircase so I assume (dangerous I know) that it travels up vertically into the loft passing though the party wall in the first floor bedroom. I dont know if there is (or is likely to be) any insulation in that wall. I assume that if there is then this would decrease the current carrying capacity of the cable.

 

[17thman]

An 8.5 KW shower usually requires a 40A mcb as per manufacturers instructions under the circumstances of trunking, insulation, cable installation method etc... A 40 Amp mcb would not protect that cable.

It would require a 7.5 kwatt.

 

[sparkybird]

It's really the landlords responsibility - and they sound a bit rubbish TBH. Is there a PIR (or EICR) for the installation - that's what I'd be asking. I also caution against undertaking the work yourself as you then become responsible and let the landlord off his/her responsibilities....