Heating Element Problem

[Latz]

Hi Guys

I know this isn't strictly electronics and more electrical but I'm hoping someone can help.

I've got a Tobi clothes steamer which, when switched on at the appliance switch, trips the main RCD of the house. This indicates a dead-short to me.

If it's plugged into the socket and then the socket switch is switched on, the RCD is fine so I know it's not the cord.

I've taken it apart and made sure there are no wires touching or fused together inside the unit, I've put a volt-meter on various places (set to continuity test) to see if there are any dead shorts anywhere, can't seem to locate one.

I've calculated the resistance of the heating element to be 35.27 Ohms (230v*230v/1500w). It measures 37 or so ohms out of circuit. I'm guessing it's not that. Have checked the switch and the wires on the back of it, have also checked there isn't any water anywhere that is creating a circuit.

It was working fine up until a day or two ago. I thought I had better top up the water tank. Put the water tank back in and that's when it stopped working (appliance was off at the time). I thought that perhaps I had dropped some water over it somewhere so I left it for 2 days to dry out. Still tripped the RCD so I took it apart.

Anyone got any ideas as to what I can try next?

Thanks!

 

[Colin Mitchell]

Just use the active and neutral

 

[Latz]

I don't understand what you mean? Just use Live and Neutral and disconnect the earth completely?

 

[Colin Mitchell]

Yes. Because it looks like a leakage problem.

 

[Latz]

Oh ok, is that safe to do? I can remove the earth from the heating element, everything around it is plastic so I won't be touching anything metal. Let me know if it's ok to do.. bit paranoid with these things especially with the voltage and current involved lol

 

[duke37]

It seems you have earth leakage. Measure resistance from live to earth, preferably with a high voltage.
The leakage from live to earth is the most likely problem but it can also occur if the neutral has deviated from earth.

If you find some leakage, disconnect each part and see where the fault disappears.

I would not disconnect the earth, that could be described as dangerous.

 

[Latz]

Thanks. I have removed the heating element from the circuit (but left it connected to earth) and measured the resistance from one leg to earth (the outer metal shell of the element). I got 4.1 Mohms. Measured from the other leg to earth, got 4.0 Mohms

What should it be? I'll keep probing to see what the other components are doing.

 

[duke37]

The resistance should ideally be infinity - but it never is.
You should be able to stand 10000Ω (10k) assuming that nothing else in the house is leaking.

Measure the resistance from line to earth at the plug without the heater connected to see if anything else is leaking.