immersion switch meltdown

Martron

well basically the bath/sink on/off switch cannot be flicked.

my theroy on it is that when the immersion is on heat travels up the wire and into the switch melting something in it preventing it from switching. i know this is not normal. but what is causing this?

surely there must be some sort of cut off if the immersion gets too hot?
i replaced the switch bepore but thought nothing of it.

now its happened again and i need to solve it. as these switches aint cheap.

any suggestions welcome.

Martin

Paddy McGinty

What do you mean by the "bath/sink" on/off switch? Is it definately an immersion heater (as opposed to say a shower switch which would be bulkier/bigger? (I ask as you say "these switches aint cheap").

Anyway..

Heat doesn't travel up the wire..at least not the heat from the immersion! It'll almost certainly be one of these things;

1. more often than not it's a loose wire that's caused arcing (wires into terminals probably burnt black and gone hard, insulation flakes off easily).

2. improperly connected e.g. if not enough insulation stripped off, then the screw may be partway on copper wire and part on insulation, symptoms maybe as above.

3. cable in use is too small for the job in hand.

post up here what sized breaker or fuse is protecting that particular circuit then it'll give us a clue ;O)

Martron

its definately the immersion. The wire that comes from the switch to the immersion gets hot and damagess the switches. There is no black arc marks on the switch. The wire coming from the immersion looks quite heavy( 5 core). The only fuse i can see is the breaker at the fuse board and it looks the same as the ones on the sockets. Its definately heat generated by the supply wire to the immersion. If i upgrade the wire will this solve that problem?

i also checked all the connection under the cap at the immersion. all is tight ans well insulted and clear of other wires.

Paddy McGinty

Well you've confused me Martin.. (though that's not difficult!)

Martron wrote: »

its definately the immersion. The wire that comes from the switch to the immersion gets hot

It could only get hot via load (or overload) or else conduction (heat directly transferred from the hot water cylinder - extremely unlikely I'd have thought).

Martron wrote: »

The wire coming from the immersion looks quite heavy( 5 core)

Doesn't make sense?.. you would normally have a 3 core (twin and earth) coming into the switch, typically 1.5mm cable. Then coming out of the switch the cable would (typically) be 3 core (L+N+E) white butyl rubber (or similar heat-resistant cable), which would go directly into the head of the thermostat at the cylinder.

The thermostat would generally be built-in with the cylinder, but as you've mentioned 5 core cable I'm wondering if there's some other arrangement?

1. Can you confirm it's a circuit-breaker at the mains? (as opposed to an old rewireable fuse board). If so this would (typically) be 16A.

2. Check what type of cable leaves the immersion switch. The switch will only have L,N+E out so I'm lost on where your 5 cores are coming from!

Maybe you could take pic of the inside of switch and post it?!

yuloni

This post has been deleted.

Martron

its a dual element immersion. the 5 core is between the switch and the immersion.

surely if it was any less than 16a it would trip?


anyway i was going though some other forums ( i know shame on me) and came across a thread with tthe same problem.

the comm at the top ( on the dual switch ) basically was not connected right. i used the same piece of wire from the previous switch that "melted"

anyway long story short that piece of wire was not making correct contact with the screws in the connectors. the copper was a bit grey anyway i fixed that and the immersion is now on to see if the wire heats up. so as paddy said the connection may have been faulty pulling more current on the wire.

Oh god what a ramble i hope it made sense.