Unvented Cylinder Immersion issue.

[GasValve]

I'm installing a new unvented cylinder.

Just filled it and tried the immersion which keeps tripping the RCD.
No trip unless the stat is adjusted to call for heat (so would that eliminate the cable?).
I bypassed the stat and connected directly to the immersion terminals with same result (so would that eliminate the stat?).

Resistance across the L & N terminals on the immersion is 20 ohms, the resistance between the L or N terminal and the E terminal is open circuit, but the resistance between the L or N terminal and the immersion base or the cylinder body is 1.8 M Ohms. Is 1.8 M Ohms enough to trip the RCD?

I've also tried powering it from three different circuits with the same result.

Any advice welcome please.

 

[jj4091]

No trip unless the stat is adjusted to call for heat (so would that eliminate the cable?).
No not nescasarily.
You can't test an element with a multimeter if that is what you are using, apart from finding an open circuit. Likelyhood the insulation is breaking down when supplied with 230/240v

 

[GasValve]

Thanks for the quick reply

Link just takes me back to this thread though..

 

[jj4091]

Thanks for the quick reply

Link just takes me back to this thread though..

Yes I don't know why it often does that when I try to quote something, obviously I am doing something wrong.

 

[AndyPRK]

you just need to delete the link it automatically inserts.

 

[ericmark]

To test for earth leakage we normally use 500 volt using a special meter, heating elements using mineral insulation are prone to damage on the ends, be it an oven or immersion heater, the mineral is hydrophilic that is it attracts water. So most likely it needs a new element.

However there is also a neutral - earth problem, if anything has a neutral - earth problem then no current will flow when there is no load as neutral and earth are the same voltage, but as the load increases the voltage between neutral and earth also increases, so for example the fault may be a bit of wet bread in the toaster, which is switches off but still plugged in, but it only trips when kettle is used, i.e. high load.

With a meter using 9 volt the reading should be infinity, if there is any reading likely the element is faulty, using 500 volt 1 MΩ is a pass.

 

[GasValve]

Many thanks for the detailed reply. Much appreciated.

Manufacturer is sending a replacement immersion. I hadn't expected a new unused element to be faulty.