Immersion Heater

[m4tty]

Hi,

The hot water is my flat comes from an Immersion Heater which is timed to come on twice a day so pretty old system but cant afford to upgrade boiler so have to make do with this.

Last night it packed up and on closer inspection after taking the lid off where the wires are terminated, the neutral was char grilled and had melted. The terminal had got so hot it had moved into the thermostat so gotta replace it today. Unfortunately the tank has to be un-plumbed and withdrawn from the cupboard then new element replaced then plumbed back in as the f&e tank is right above it and the element is quite long. (the flat is all on ground floor.. so no tank in loft).

Anybody got any ideas why the neutral wire had melted as it wasent a loose connection. Maybe airlocks in the cylinder causing early failure of the heater element???

Any pointers would be greatly appreciated

Thanks

Matt

 

[green-hornet]

Main reason would be overheating due to the heating element not having a thermal cutout. Are you sure the heating element has gone altogether? you could just replace the thermostat, the new ones come with an intergrated thermal cutout which is often user setable.

 

[m4tty]

Hi GH thanks for replying so quick mate

I replaced this element a year or so ago when the last one packed up so would have thought it would have had a thermal cutout but maybe not lol.

Is there anyway of telling if it had one?? and i wish i could post a picture but phone and laptop not bluetoothing at the moment ffs tried everything lol.

When I checked it after found out it wasent working then long threaded bolt which the earth wire goes to was live as when i put my meter near it i saw it arcing from the bolt to the meter probe. I know i shouldnt have tested it live but i didnt see the melted wire until i saw the arcing.

Cheers for helping us out here

Matt

 

[Apache]

Matty do you see the pic below? The blue thing is the thermostat.

the pic below shows just the immersion heater thermostat/cutout

They are easy to change - I have just done one! No need to drain tank or anything.

 

[Apache]

Some of the cheap ones don't have cut outs but AFAIK they are all supposed to have them now. See the page of the TLC cat - top ones no thermal cut out, bottom ones have. They are only a few quid so I'd chance changing it first!

 

[green-hornet]

Hi GH thanks for replying so quick mateI replaced this element a year or so ago when the last one packed up so would have thought it would have had a thermal cutout but maybe not lol.

Is there anyway of telling if it had one?? and i wish i could post a picture but phone and laptop not bluetoothing at the moment ffs tried everything lol.

When I checked it after found out it wasent working then long threaded bolt which the earth wire goes to was live as when i put my meter near it i saw it arcing from the bolt to the meter probe. I know i shouldnt have tested it live but i didnt see the melted wire until i saw the arcing.

Cheers for helping us out here

Matt

If there is any live voltage at the earth then the whole heating element will have gone. Again this could be due to overheating and a weakness in the element which then expands and effectively blows out.

 

[m4tty]

Hi and thanks for the replies everyone. The terminal where the neutral was terminated had moved over (through melting) and had burned its way melting the thermostat. The neutral wire was char grilled melting all the insulation off. Ive replaced the whole lot and for 20 quid so alls good. Thanks again

 

[PC Electrics]

I'd say you probably put the strands of the flex directly under the screw in the terminal. When tightened down, the screw cuts through some of the strands leaving you with a reduced csa and a high resistance joint which has subsequently overheated.

Use cord end terminals.