Immersion Heater - burnt out socket

[idj]

Hi, would appreciate any advice from electricians please.

My friend has an immersion heater which is wired via a normal 13A plug in socket and then a hard wired switched box with a neon light. The plug has been becoming hot while on and has failed to come on today. On opening the plug she found it had burnt out, suggesting that is the area of the weak link.

Searching the web suggests that most heaters are 3KW (I don't know if it is) and it should be hard wired through a 20A double pole isolator switch so i'm guessing the problem is likely to be that 13A is not sufficient. Would I be right or should 13A be enough & therefore it's possibly a faulty connection or something else?

I'm afraid I don't know the rating of the appliance or whether the box (coloured red with a red neon) is a 20A double pole isolator switch. Nor do I know if the supply is via 2.5mm 2 core & earth or the feed is via heat resistant 16A cable (I'm not an expert, I've just been googling).

I'm aware the work should be done by a qualified electrician but I'm trying to assess what is the likely extent of the work, i.e. might it be just a case of hard wiring the appliance to the ?isolator switch, & how much is it likely to cost.

Any advice would be gratefully received.

On a separate but related issue, before the burn out, if the plug socket was switched on after the hard wired one, the immersion didn't come on but the other way round it did. Does anyone know why that would be the case?

Thank you in advance.

 

[PrenticeBoyofDerry]

As stated most immersion heating elements are rated at 3kW. Although A 13A plug should be capable of safetly dealing with this load, it is not ideal and the immersion heater would be much better served via 13A FCU(fused connection unit). It is a simple swap, exchange the socket plate for a FCU.

 

[kai]

That is the safest way, buy a 13amp DP switched FCU (Example is MK K330 WHI) and swap the socket outlet plate with the FCU instead.

 

[bernardgreen]

It is a simple swap, exchange the socket plate for a FCU

If as is highly likely the cable behind the face plate has been affected by heat then cut back to clean bright copper before fitting the new face plate.

 

[idj]

Thanks all. So a 13A FCU is sufficient as opposed to a 20A? Just curious, why is a 13A FCU better than a 13A plug socket?

Incidentally, there is an FCU already as well as the socket so I guess we should just rewire from the appliance direct to the FCU, bypassing the socket. As Bernard says, the burnt out wire needs stripping back and so it wouldn't reach the socket anyway and will have to be replaced (unless we can put a junction box inbetween?)

Cheers...

 

[EFLImpudence]

I think, although it has not been asked, that everyone is treating this as if it is a ring final socket circuit.

However, if the immersion is on the usual 15A/16A radial dedicated circuit you do not need, and should not use, an FCU but should fit just the 20A switch you mention.

 

[idj]

Thank you. I don't know but I assumed it was on a dedicated circuit also. Not sure what the difference is between an FCU & a DP isolator switch or whether they are different but the last answer implies they aren't the same. I don't know what the one is that's fitted already in that case or what fuse rating it is. I'll try and find out and maybe obtain some photos.

Cheers.

 

[stillp]

Just curious, why is a 13A FCU better than a 13A plug socket?

There's some resistance in the contacts in the socket and the plug pins, that will add to the heat generated.

 

[EFLImpudence]

Thank you. I don't know but I assumed it was on a dedicated circuit

Is there a 15A fuse or 16A MCB in you consumer unit marked immersion or water heater?

Not sure what the difference is between an FCU & a DP isolator switch

A Fused Connection Unit has a fuse in it (rectangular pullout) and a switch.
If you have the above 15A/16A protection then this further fuse is not necessary.

A Double Pole (live and neutral) Isolator is just a switch.

Both may have a neon light indicator.

I don't know what the one is that's fitted already in that case or what fuse rating it is. I'll try and find out and maybe obtain some photos.

Photos would be good to make sure if you are still uncertain.

 

[idj]

Thanks stillp & EFLImpudence. I think it's a FCU but not certain as it's not mine and it's 250 miles away!I'll try and find out and get the consumer unit checked too and photos if possible

Cheers

 

[idj]

Just wanted to say a big thanks again to everyone that replied. Looks like the problem was the plug not being wired properly. Everything is sorted now and nothing gets hot. Cheers