Immersion heater thermostat electrical problem

[leonado2]

I've posted here as advised as well. My Immersion heater thermostat keeps vibrating like mad when switched on. Its shaking inside the element where it slides in. I have replaced the wiring and cleaned the contacts, but its still shaking. Is there a way to test if the thermostat is faulty with a voltmeter?

Never known this problem before.

 

[BS3036]

Well, there is. You could use a multimeter set on Ohms. It should read open circuit (too many Ohms to measure). Then put the end of the thermostat in a pan of water and keep measuring till it reaches around 60° when the resistance should go to around 0 Ohms. You should probably also check that there is a high resistance between the contacts and the metal body.

However, I've never met this before. A new one is so cheap that I'd do that first.

 

[bernardgreen]

Other way round.

Close to zero ohms below 60°C, so heating on ON

open circuit above 60°C. so heating is OFF

That is assuming it is set to 60°C

 

[BS3036]

Other way round.

Close to zero ohms below 60°C, so heating on ON

open circuit above 60°C. so heating is OFF

That is assuming it is set to 60°C

Ooops! Quite right. Sorry.

 

[ericmark]

I have never seen this but since pocket is normally attached to element it could be element!

If the insulation on element has failed and there is no RCD on circuit maybe this could be causing electrolysis and hence vibration.

I know when I put three earth rods into a drum of brine and connected them to the three phases it did shake a far bit. Was sinking 64KVA so only to be expected but that's only time I have banged three phase through water.

When I say I well really it was the boss. I was objecting most strongly at use of salt. I wanted to use acid.