immersion heater timer problem

[ample current]

Can some one help, i have been asked about an immersion heater which stopped working so she pressed the reset button on the temperature control, which worked for a while but now the timer has burnt out, any ideas what i should look be looking for when i go round to look at it. would a fault in the element cause this. and what would be the best way to test if the elem ent was at fault. I have a megger 1730 tester so could i use this to check the element. I am new to this especially heating.

Thanks in advance

Mark

 

[telectrix]

element should read about 20ohms L/N. then IR test to E. if any doubt, replace. if OK, could be timer has just given up the ghost, or a poor termination has caused overheating. make sure a replacement timer is suitably rated for a 3kW load.

 

[ample current]

Thanks :icon14: if it doesnt read 20 ohms is it likely to be a higher reading or a lower one ? and I take it you mean an ir test on the whole immersion heater circuit.

 

[Edd]

Thanks :icon14: if it doesnt read 20 ohms is it likely to be a higher reading or a lower one ? and I take it you mean an ir test on the whole immersion heater circuit.

If it reads higher (a lot higher)(using low ohm setting not IR) then its means its open circuit, element broken.. For IR you wana test the element to E as you could still have a 20ohm reading across L and N making it look ok, but a pin hole in the element shorting to E so test L-E at element..
If all reads out ok, I would fit new stat and time clock..
If heater looks down, then get replaced, fit time clock..

PS your reading may not be esactly 20 ohm.

 

[ample current]

i tested the element L-N and it read about 18.5 ohms, didnt check L-E across the element, and i take it ir means insulation resistance test.
The time clock had burnt on the load side on the live conductor at the connector.
I have to go back tommorow to install new cable from heater to timer so do I test using insulation resistance test (500v dc) across the terminals of the element (L-E) whilst its disconnected from the circuit and this should be a very high reading?
Thanks in advance
Mark.

 

[Edd]

Yep You got it.. 18.5 ohms is fine. but its best to do IR (insulation Resistance) from L or N of the element to E and as you say it should be a very high reading, if not >999

 

[ample current]

Thanks Edd

 

[telectrix]

The time clock had burnt on the load side on the live conductor

sounds more like the connection was loose and caused the damage, rather than an element problem. if there is an rcd in circuit, then a poor IR of the element would have caused it to trip.

 

[ample current]

You know i cant remember if there was an rcd on the cu or not now.... must pay more attention, the circuit is protected by a 16amp CB which was off when i first looked at it. I did an ir test across L-E and N-E both were >999 and the circuit to the outlet from the cu read >999 also. I thought it was a dodgy connection also when i saw the burn marks on the terminal.