Immersion heater not heating?

[UseLeSsDiYr]

Thanks John.

Does it matter where I place the meter's black and red leads onto the grey / brown / blue terminals?

 

[Burnerman]

No, when you measure resistance, the meter polarity doesn't matter.
By turning the wee dial on the stat, you can set the temperature at which it trips out, turning the element off. 60 deg is the usual.
John

 

[Burnerman]

The immersion switch should be dual pole, that is it switches both the neutral and the live, but lets play double safe by turning the thing off at the fuse box.
John

 

[UseLeSsDiYr]

Thanks John

I will have to give this a shot tomorrow when I get a chance to power down everything and perform the suggested tests.

Will I have to get a qualified electrician to change the stat (if that turns out to be defective - I hope the fault lies here as cheaper option?), or can I do it myself?

Thanks.

 

[Burnerman]

The stat just drops into its own pocket - dead easy to lift out when you have disconnected the wire from it!
It looks fairly aged, I must say - and with your meter connected, you can tell if its switching capability is working.
If you get full continuity always, then its permanently on and probably boiling your water ..... if you cant get continuity at any point of the dial, then its goosed. You'll need to replace it with one of the same length, and they are readily available from the DIY sheds.
John

 

[UseLeSsDiYr]

When I took the picture earlier, I did notice that it slides out quite easily (about an inch with the wires still connected).

When I switched it on earlier, it sounded as if it was boiling, but after half an hour, the water remained cold.

What exactly do you mean by 'continuity at any point of the dial' - going through the different settings on the meter?


Thanks.

 

[Burnerman]

Just leave the multimeter on the lowest ohms setting, and if you touch the leads together it will read zero, showing continuity. With the leads not touching, there won't be a reading - call that infinity.
To test the thermostat, fix the meter onto the terminals, and then turn the dial. You'll see the meter read zero and then infinity as the stat opens - just like an off/on switch. Hopefully the meter will continue to read infinity to determine the stat has gone AWOL!
John

 

[UseLeSsDiYr]

Cheers for your advice John - hopefully, it'll be the stat that's gone pop!

 

[UseLeSsDiYr]

Morning

I've used the following meter to test this morning (don't laugh please, I know it's old school!).

I mainly used the sections V--- and V~, as the ohm section produces some weird readings. Placing the leads on the grey and blue terminals (elements), returns some results in the region of 0.17 and upwards. When placed on the grey and brown terminals of the stat, the readings under the V sections are 0.00, but under ohms, the readings fluctuate.

Would this suggest the stat has gone?

Thanks

 

[Newboy]

OK - let's try again!

1) Turn off the power to the immersion
2) Set your meter to 200 ohms - dial pointing to the bottom of the meter
3) Touch the two probes together - your meter should display 0.000
4) Rotate the thermostat setting so that the arrow points to the dot next to 80
5) Place the probes on the grey & brown wires and note the meter reading
6) Rotate the thermostat setting so that the arrow points to the dot next to 180
7) Place the probes on the grey & brown wires and note the meter reading

Post back here with the readings

 

[UseLeSsDiYr]

Hi newboy

By turning the power to the immersion, do you mean from the main fusebox or is the switch to the heater in the OFF position OK?

Touching the probes when set at 200 ohms results in 00.4. When not touching, it shows 1 . .

I can't see the 80 and 180 points you're referring to?

Thanks.

 

[Burnerman]

On your first attempt, you were using the AC and DC voltage scale, which would give you all sorts of spurious measurements.
Your meter is off at 12 oclock - turn it to 6 oclock (200 Ohms) and bash on.
Keep the immersion heater completely isolated electrically!
John

 

[St0rmer66]

You will NOT get 0.000 by touching the probes together though. There is always SOME resistance. 1.6 ohms on mine, might vary slightly on different models of course but in that ball park. But that doesn't affect your other results.

 

[Newboy]

You will NOT get 0.000 by touching the probes together though

Well in that case you need to clean your probes - what's the point of a meter which always gives you an inaccurate reading? In your case, every resistance reading would be out by 1.6 ohms!

 

[endecotp]

By turning the power to the immersion, do you mean from the main fusebox or is the switch to the heater in the OFF position OK?

Turn EVERYTHING OFF.

Then TEST that there is no voltage present at the immersion:
- set your multimeter to a high AC volts range
- touch one probe to something that you know is earthed, e.g. pipework, or an earth wire.
- touch the other probe to each of the terminals in turn. Due to capacitive coupling and the fact that this is a high-impedance meter you will not see zero volts. If in doubt, assume that it is still live.

Then continue with your RESISTANCE (not voltage) tests.

If you're finding this complicated.... maybe it's time to call in an expert? You really don't want to electrocute yourself, burn your house down etc.