Immersion heater, neutral wire keeps burning

limakilo0 · 21 Apr 2010

Hello,

I have had 3 different electricians in to look at my immersion heater (it's a manco combination cylinder) but none have come up with a solution.

In July the water went luke-warm. Thermostat showed signes of burning. He replaced the element and thermostat. Since then, it heats the water properly but the neutral wire connection gets exceedingly hot within seconds of the immersion being switched on, which is why the neutral wire keeps burning off. Another electrician replaced the wire from the clock to the element but the neutral connection is still red-hot.

Any answers please? It's not nice being relaint on a kettle!

David

assured heating · 21 Apr 2010

Its a loose conection to neutral try posting this in the electrical forum and you might get more respnse

Boilerman2 · 21 Apr 2010

Try uprating the flex to 2.5mm/2 it is not un-common to find Immersion Heaters wired in 1.5mm/2 flex, which is getting near the mark for this size of cable, but nothing will cause a burnt neutral like a loose connection

TicklyT · 21 Apr 2010

You need mechanically sound connections between bright, clean metals at the terminals to carry the current.

Any discolouration of the wire or terminal is probably an oxide layer formed when the connection first started overheating. Oxides have a high resistance, and cause further overheating and oxidation of the connection.

Overheating also softens the copper in the cable, making it difficult to make a mechanically sound joint.

Cut back or replace any heat damaged cable, and thoroughly clean the terminals before re-making the connections.

flameport · 21 Apr 2010

Rather than clamping the wire ends directly onto the element terminals, crimp a ring terminal on the end first:

Untitled

flameport
21 Apr 2010
1

That way, the terminal can be tightened properly onto the flat surface of the ring, rather than the uneven multiple strands of the wire.

RF Lighting · 21 Apr 2010

Can we have a photo please?

ricicle · 21 Apr 2010

Any existing burnt wire needs to be got rid of back to clean, unaffected wire otherwise the problem will not go away. Also check that the connection is sound on the element post itself !

limakilo0 · 22 Apr 2010

Thanks for all your learned replies.

I abandonned my original plan to do it myself and got another electrician in yesterday and he has put a temporary new cable (2.5mm) in between the immersion clock and the element. This appears to work as I can now keep my finger on the neutral terminal when it's on (before it was scorching hot within seconds). He didnt have any flexible cable so he's coming back on Saturday to finish the job off and also to replace the acble between "the feed" and the clock.

ricicle · 22 Apr 2010

Two things, make sure he does come back ASAP as normal t+e cable is not heat resistant and should not be used to connect up such an item (and is also not suitable for flexibility purposes either)

Also it is not a good idea to put your finger on any terminal irrespective of it being Neutral, unless of course you are isolating first.

securespark · 22 Apr 2010

limakilo0 said:
I can now keep my finger on the neutral terminal when it's on

Nucking Futter!

He didnt have any flexible cable

So what's he wired it in instead?

EDIT: sorry, rice, I didn't read what you put.

Adam_151 · 22 Apr 2010

securespark said:
limakilo0 said:

I can now keep my finger on the neutral terminal when it's on

Click to expand...

Nucking Futter!

I had a college lecturer whose favorite demonstartion was to stand on a wooden floor and touch the busbar tabs on a live DB

limakilo0 · 23 Apr 2010

ricicle said:
Two things, make sure he does come back ASAP as normal t+e cable is not heat resistant and should not be used to connect up such an item (and is also not suitable for flexibility purposes either)

Also it is not a good idea to put your finger on any terminal irrespective of it being Neutral, unless of course you are isolating first.

I was just following the example of my neighbour (who is a trained electrician, so he told me anyway!) not sure what you mean by "isolating first".

I dont know what the temporary cable is. It's just grey coloured and quite rigid as it doesnt fold easily under the black cap that goes over the element and wiring.

kai · 23 Apr 2010

There is one neutral I can touch safely with the installation up and running - the combined neutral and earth terminal at the right hand side of the service fuse block (it sticks out of the side - to which the main earth is connected!)

RF Lighting · 23 Apr 2010

In theory at least

ricicle · 23 Apr 2010

kai said:
There is one neutral I can touch safely with the installation up and running - the combined neutral and earth terminal at the right hand side of the service fuse block (it sticks out of the side - to which the main earth is connected!)

As long as you haven't lost the network Neutral somewhere

diynot

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Immersion heater, neutral wire keeps burning

kai

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