Immersion heater on the blink

[Crofter]

Swift reply on this one would be appreciated- I have an angry SWMBO and an unwashed baby.

 

System is very simple, ancient copper vented tank with a loop to the defunct back boilers and a 3kw immersion. Photo of presumed offending article attached. There is power as far as the isolator switch. Is it worth trying to check the element with a MM? And are there different types of fitting etc, before I go buying a replacement element?

 

Thanks in advance... and I should mention at this point that I have always thought of the Welsh as our brothers and kindred spirits... splendid chaps one and all... cough cough @Nickfromwales

[Gone West]

My immersion thermostat packed up a few months ago. IIRC the resistance should be around 18 ohms. Might be that and not the element.

[Jeremy Harris]

I don't know much about Howden 6 bolt heaters, other than they are expensive to replace when compared to the more common threaded ones (around £80 to £90).  They do use a fairly standard short thermostat (the block where the line connection runs to) and you can check that with a meter, as my experience with immersions is that if they just stop working it's often the thermostat, if the blow the trip it's often the element itself.

 

Isolate the power, disconnect the cable and check for continuity between the thermostat output to the element and the line connection.  The thermostat switch should be closed when it's cold.  Try adjusting the temperature setting to see if you can hear a click, as very occasionally you can unstick a stuck one like this.

 

You can probably get a replacement thermostat that should fit the Howden sense pocket OK, I'm pretty sure they use a standard short thermostat.

[Nickfromwales]

If you have 230v at the live at the tank then do you have 230v coming out? If yes, element is fried, if no then stat is fried. 

And +1 to Jeremy's reply. 

[Crofter]

Thanks gents, will see if I can do a spot of troubleshooting.

[ProDave]

Do you have a multimeter?

 

If the element has gone, then to be honest I would get a new tank, it will not cost a lot more, will be better insulated, and will have standard cheaper elements for next time.

[Crofter]

Ok so I've now had a look and I think I can exonerate the element- getting about 20ohms on it. But the stat is giving me open circuit regardless of what I do to it.

I hadn't realised just what a simple little mechanism it was- I had assumed it would be electronic to some degree. Is it possible that it's something as simple as corrosion on a contact?

 

Also, I've had to gently explain to SWMBO why bypassing the stat may be a bad idea (does she want a shower badly enough that it's worth boiling the tank??) and then had to explain exactly what I was doing with the frozen waffles:

 

 

[ProDave]

just buy a new thermostat. Make sure the bit that goes in the pocket is no longer than the one you have.

[Jeremy Harris]

As Dave says, fit a new one.  They aren't that expensive, (around £10 or so, at least down here they are around that price) and with luck you may well be able to get one locally tomorrow (not sure whether you have a plumbers merchant on the island or not, though).  The one you need looks like a 7" one, best measure it to make sure.  They aren't repairable, unfortunately, as the failure is usually either the contacts burning out or the bi-metallic element that actuates them failing.

 

 

[Crofter]

Friendly local plumber had one in the back of the van. Now fitted and I will see if my shower tonight is hot or cold!

 

Oh and he's going to come and give me a quote for fitting a UVC. So all good really.

 

Thanks for the pointers everyone.