Replacing immersion heater controls

[SillyBilly]

Replacing immersion heater controls
My immersion heater no longer works. It has a 11" Shal SS11 thermostat which is fine as is the heating element with 19.3 Ohm resistance. The immersion has a separate cut out as pictured but no continuity so I suspect it has tripped or failed. I dont know the type but it looks like a Backer. It has a red or orange button with a black centre. I can read most of the code on it L88C 50809 36? 561348. Is this resettable like the ones on some other thermostats? I tried pressing it in.
If it isn't can I just replace the Shal SS11 with a Tesla 11" Control & High Limit Rod Thermostat for Immersion Heaters, Dual Thermo or similar and not wire in the existing cut-out

 

[mainline]

Replacing immersion heater controls
My immersion heater no longer works. It has a 11" Shal SS11 thermostat which is fine as is the heating element with 19.3 Ohm resistance. The immersion has a separate cut out as pictured but no continuity so I suspect it has tripped or failed. I dont know the type but it looks like a Backer. It has a red or orange button with a black centre. I can read most of the code on it L88C 50809 36? 561348. Is this resettable like the ones on some other thermostats? I tried pressing it in.
If it isn't can I just replace the Shal SS11 with a Tesla 11" Control & High Limit Rod Thermostat for Immersion Heaters, Dual Thermo or similar and not wire in the existing cut-out

To be honest, I would replace the element along with the stat as there maybe a problem with something else causing the high limit one to go open.

 

[Brother Blue]

Press the red button on the high limit cutout to reset it.

I assume from the thermostat we see in the background that this has an additional source of heat and the immersion is just for a backup/topup? If so its not uncommon for other sources of heat like that to upset the high limit cutout.

 

[SillyBilly]

Press the red button on the high limit cutout to reset it.

I assume from the thermostat we see in the background that this has an additional source of heat and the immersion is just for a backup/topup? If so its not uncommon for other sources of heat like that to upset the high limit cutout.

I suspected that this might be the case as the main source of heat has been the boiler. I put in two motorised valves to the top and bottom coils with separate thermostats.
The immersion is seldom used and I only found a problem when I checked it as I want hot water when I drain and move the boiler! I tried to press the red button in but it didn't move. Are they flush when not tripped

 

[SillyBilly]

To be honest, I would replace the element along with the stat as there maybe a problem with something else causing the high limit one to go open.

It is a 300L unvented cylinder and will be a pain to drain half of it and having to avoid it imploding

 

[Brother Blue]

I suspected that this might be the case as the main source of heat has been the boiler. I put in two motorised valves to the top and bottom coils with separate thermostats.
The immersion is seldom used and I only found a problem when I checked it as I want hot water when I drain and move the boiler! I tried to press the red button in but it didn't move. Are they flush when not tripped

Has the immersion heater ever been used?

Those little red buttons are annoying, they are usually just slightly loose and rattly and don't inspire confidence. There should be a slight click when it resets, if it had tripped, but a continuity test will confirm whether or not it has reset.

To answer your original question, if the safety cutout has failed then it would be ok to replace it with a combined thermostat and safety cutout unit if you cannot source a suitable direct replacement.

 

[SillyBilly]

Thanks for the reply. Yes it was used for a while.
I tried pressing the button in but no joy. No continuity. It is not easy to access the button so I have just bought a Tesla 48571 Dual Safety Thermostat 11" so if it trips again it will be easier to reset it. The two thermostats, top and bottom are set at 60 degrees but the boiler is set to 80 which means the flow through the two coils is at 80. The print on the original cut-out has L86C on it so that probably means that is the cut out. The max setting on the Tesla is 75 but I have set the thermostat at 60. If I set the boiler at 75 there is less likely there will be interference

 

[mainline]

It is a 300L unvented cylinder and will be a pain to drain half of it and having to avoid it imploding

Really, you should be getting someone competent and G3 qualified to work on unvented cylinders.
You should also be fitting original parts and safety devices.

 

[SillyBilly]

Still having problems. The surface mounted cut-out is faulty as the water temp is low and it should be normally closed. I haven't attempted to remove the cut-out. The Tesla dual thermostat arrived today but it is much bigger than the Shal single stat and fouls the positive terminal. I could bend the terminal over a bit but am concerned the insulation might break. Is that likely? I see someone on reviewing the Tesla on Screwfix had to bend it over and was worried!!
The issue of triggering the cut-out was mentioned in the Tesla technical page The new EN standard means that we cannot allow the upper limit of the control thermostat circuit to rise above 70 Degrees C as this will cause ambient temperature problems with nuisance trip outs due to interference with the secondary safety circuit
Otherwise is there a smaller 11" dual thermostat