immersion problems

[alexmurchison]

got called to a house saying immersion wasnt working....... simple, check electrical supply (none) replaced fuse and supply ok, but on inspection of immersion it was naff, so replaced with new superloy immersion, tested ...job done.
Couple of weeks later got a call saying there was a loud pop and immersion wasnt working again.. went back and sure enough the wires going into the spur were corroded. so replaced wiring and spur and another immersion as it too went pop. tested and got the customer to watch me show it working, left it working till water got up to twmp to make sure....
Then a few months later after winter got a call again to say it wasnt working again. went back and electrical supply was fine, looked at immersion and clicked the reset button and it worked !!
then she told me they hadnt used it since as they used the fire to heat the water. Then it dawned on me that the back boiler could be heating the cylinder to a temp that clicks off the immersion, i have tried turning the temp on the immersion higher but it still keeps clicking off,


so anybody had this issue and how did they over come it as all the immersions from the (plumb centre) are all the resettable rdt stat type ??

 

[Millsy 82]

There all like that now right pain but its better than them keep boiling. I have worked on some that will work fine for ages then lock out then reset them and they run for ages again then lock out makes no sense to me.

 

[lame plumber]

by pop do you mean the overheat stat has worked and just needed resetting? if so then the backboiler/fire heating the cyl is doing its job too well and water temp is getting too high and a heat dump is needed in the form of a rad on the primaries to the cyl.

 

[happyflyer]

I think they still make probe sensors without the trip unit that would stop it dead but you would have no limit stat, you could wire an external limit stat with a thermal reset, a strap on cylinder sensor would do but beware you are switching mains 3 Kw, make sure the contacts are rated that way and put some labels on the stats MAIN 240VAC

 

[alexmurchison]

hi yes, last time i went it just needed resetting via the little red button on top of the immersion, when she called me the other day to say it wasnt working again, to save me going back out, i said, get your hubby to (switch off the fused spur first before removing cover) then press the small reset button, she then switch it back on, she told me he did this but still wasnt working, so im going back tommorow to check for myself. It only clicks off if they have used the back boiler so like you both mentioned above, it must be the heat from back boiler over heating water in cylinder, even if i turn it to max which is 80 odd i think, it still clicks off, must be getting hellish hot.

I will mention a heat dump, but its always the same, they dont want that etc or the old one never did that, but like i said the older immersions werent resettable.

 

[lame plumber]

hw cyl probably thumps and bumps away when the fires on as well🙂

 

[thompsonbrown]

Agree with lame plumber system needs a heatsink.
could a bathroom rad/towelrail not be used for this.
Had a aga stove that kept boiling the cylinder, fitted a s/s towel rail in bathroom to resolve problem.

 

[jam1979]

just a thought shes not using the immesion in conjunction with the back boiler is she

 

[Millsy 82]

Is it a solid fuel fire/back boiler or gas? What system is it? Y plan s plan gravity? The temperature on the stat doesn't affect the lock out temperature as far as I'm aware I thought that was factory set. The only thing I can suggest is crank the cyl stat down a fraction if it has one. If its solid fuel I always though they had to have a heat leak on them as its an uncontrollable heat source ( but I don't touch solid fuel so I could be massively wrong. So stand to be corrected.)

 

[AWheating]

id be questioning why the hot water is overheating from the back boiler. Is it working propa?

 

[Howsie]

just a thought shes not using the immesion in conjunction with the back boiler is she

That wouldn't matter. Sounds lick a heat dump is required.

 

[lame plumber]

id be questioning why the hot water is overheating from the back boiler. Is it working propa?

seeing as the custard mentioned a fire to warm the water it must be solid fuel.