Inmersion heater

[North]

Hi all,

I am having the same problem from time to time with the connections to my hot water cilinder immersion heater
The cable attached to the pin seem to get burned over time with no apparent reason (see pic). This time the cable got detached from the immersion connector. Any one has got any ideas on why and how to avoid it?
Thanks!

 

[JohnD]

Your picture shows a charred green whisker seemingly in contact with the metal shell. Is this the brown L wire that should have gone into the thermostat? Or the black N wire? Was it trapped under the cover?

The wire that should be attached to the "pin" (the long threaded screw for the cap) is the Green and Yellow earth wire.

What is the fuse or MCB rating for this circuit? Do you have an RCD?

 

[North]

Hi no the damaged cable is attached to one of the terminals on the heater (the other one goes to the thermostat). The yellow and green is connected to earth correctly. I just moved into the place and found the installation like this.
Thanks!

 

[JohnD]

I am having the same problem from time to time with the connections to my hot water cilinder immersion heater
The cable attached to the pin seem to get burned over time with no apparent reason (see pic). This time the cable got detached from the immersion connector.

Your wording suggests it has happened a number of times. Is that true, or have you just moved in and only seen it once?

 

[North]

I keep in touch with the owner and he confirmed it has happened before

 

[JohnD]

cut back the old cable and remove any discoloured wire. If necessary replace it with a new length of heat resistant cable.

Show us a pic of the terminals showing the wires going into them (taken from above. The head of your thermostat obscures your earlier pic).

Sometimes this is caused by loose connections, or by re-connecting wire that has been softened through previous overheating.

You did not answer:

"Your picture shows a charred green whisker seemingly in contact with the metal shell. Is this the brown L wire that should have gone into the thermostat? Or the black N wire? Was it trapped under the cover?

The wire that should be attached to the "pin" (the long threaded screw for the cap) is the Green and Yellow earth wire.

What is the fuse or MCB rating for this circuit? Do you have an RCD?"

 

[North]

Hi the clables that go into the immersion heater are brown and blue (the blue one it looks green because of the burning) At the moment the brown goes into the thermostat and the blue to the other pin. The yellow-green goes to earth. None of the cables were traped
I do not know about the rating but it is connected to the RCD

 

[securespark]

That brown looks like it is stretched tightly round the N side of the element.

If so, re-route it.

The N terminal looks like it has suffered due to the loose connection. The element may need replacing.

 

[Echo the husky]

Looking at that photo, it looks like the flex could be too small. Looking at the genral colour of it I would replace it on sight with new heat resistant flex. The rule I use is 1.5mm² for immersion heaters used as a backup. 2.5mm² for immersion heaters in direct cylinders. Though I generally use 2.5mm² for everything now.

You will need to clean that neutral terminal so the copper wire is in contact with clean shiny metal. If it is in really poor condition you should replace the element, they are not expensive. If you just rewire it with the terminal blackened it will burn out agian. It is also a good idea to carry out an insulation resistance test on the element to ensure the copper sheath has not split open and is letting water into the element.

When connecting it is important that every copper strand gets connected into the terminal otherwise it will overheat again.

This is one of those small jobs that is so easy to get wrong.

 

[North]

Hi thanks for all your advice. I think you are right I need to replace the cable. How do I carry the insulation test? I have a tester but I am unsure how to do the test.
The RCD fuse also blowed up (the water tanks is in energy 7 and has got an independent fused RCD box downstairs. The fuse is a 15A and is a bit bigger than the usual ones you find in sockets, any idea where to get one of these?
Thanks!

 

[Taylortwocities]

I don't think that you really mean

RCD fuse

do you?

I guess that you mean that you have a fuse board that has fuse carriers. The immersion heater being 15amp? Like THIS

You can buy those in many places including Screwfix (see link) B&Q, Homebase, and many other.

 

[North]

Yes this is exactly what i mean thanks. I did not find it in the toolstation or screwfix website but found them in Maplins an hour ago.
I will put it back tonight.