Immersion Heater Timer Burning Out

[wolfie2010]

Hi All,

I've got a problem with my immersion heater timer burning out.

A few months the wires leading up to and inside the timer literally burnt/melted. A friend of mine who knows more about this sort of stuff went into the loft to push through some of the grey cable and he put in a new timer. Everything worked fine up until today when I noticed a burning smell again, this time the white cable coming from the immersion heater to the timer has burnt the live out and neutral out wires.

I've turned the breaker fuse for the immersion heater off in the CBU.

Question is could this be a problem with the element in the immersion? Also is it possible to get a timer with a higher resistance?


Many Thanks

 

[vsynth]

Either the cable is too small to carry the required current or you have a fault and the device protecting the circuit is overrated or faulty.

Can you tell us the rating of the fuse or circuit breaker supplying the circuit?

What are the contacts rated at on the timer and were the connections tight?

 

[wolfie2010]

Either the cable is too small to carry the required current or you have a fault and the device protecting the circuit is overrated or faulty.

Can you tell us the rating of the fuse or circuit breaker supplying the circuit?

Hi the cable installed from immersion to timer is a 2.5mm and the fuse is 16a.

 

[TicklyT]

The previous overheating may have led to some softening and oxidisation of the cable cores.

Softening (annealing) of the copper allows it to deform, so connections that were fully tightened when installed work loose and overheat.

Oxidisation leads to high resistance joints that tend to overheat, causing further softening and oxidisation

etc.

etc.

Until the connection fails.

.... Also is it possible to get a timer with a higher resistance?

It's high resistances that cause the problems. The higher the resistance, the more power dissipated as heat.

 

[wolfie2010]

Hello

I purchased one of these timers from a local electrical supplier

http://tinyurl.com/3al5fap

Just a bit baffled with the wiring as there seems to be no where to connect the earth cable from the immersion and from the mains to the timer?

Any help much appreciated!

 

[Steve]

Hello

I purchased one of these timers from a local electrical supplier

http://tinyurl.com/3al5fap

Just a bit baffled with the wiring as there seems to be no where to connect the earth cable from the immersion and from the mains to the timer?

Any help much appreciated!

What terminals are there? What are they labelled? If theres only two terminals its just live and switched live. You terminate the neutral and earths seperately.