Immersion heater thermostat unresponsive
- Thread starter DIY10291
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So likely a 27” one, I’d personally measure the temp first, then you’ll know whether to adjust or if immersion has failed.
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If the thermostat fails there should be a second unit which either clicks open or fails to stop this happening where there are two forms of heating often re-settable if only electric non re-settable.
In the immersion heating housing there is a pocket (long tube) and the thermostat fits in the pocket, so can be changed without loosing water, with more sophisticated systems the water it taken you to 60ºC once a week, but can be cooler at other times, as any legionnaires protection, you can also get devices to mix water before it comes out of hot tap, used in old peoples homes a lot.
Central heating often installed following one of the honeywell plans, C Plan often no motorised valve, and the pump and boiler independently controlled so both run central heating and just boiler only heats water using thermo syphon. Then Y Plan and W Plan have three port valves and hot water and central heating both pumped, and S plan two x two port valves.
My problem is a C Plan and no cables between hot water tank and boiler, and the floors not easy access to lay them, so either need some wireless link, or use simple time, and at moment simple time, domestic hot water (DHW) can't get hotter than central heating (CH) water, but in winter really too hot, in summer the old timer was set 1 hour a day, this was far too long, so new Nest Gen 3 allows to be set down to ½ hour and select which days, so 4 days heated and 3 not is just about enough to wash hands in warm water.
In the immersion heating housing there is a pocket (long tube) and the thermostat fits in the pocket, so can be changed without loosing water, with more sophisticated systems the water it taken you to 60ºC once a week, but can be cooler at other times, as any legionnaires protection, you can also get devices to mix water before it comes out of hot tap, used in old peoples homes a lot.
Central heating often installed following one of the honeywell plans, C Plan often no motorised valve, and the pump and boiler independently controlled so both run central heating and just boiler only heats water using thermo syphon. Then Y Plan and W Plan have three port valves and hot water and central heating both pumped, and S plan two x two port valves.
My problem is a C Plan and no cables between hot water tank and boiler, and the floors not easy access to lay them, so either need some wireless link, or use simple time, and at moment simple time, domestic hot water (DHW) can't get hotter than central heating (CH) water, but in winter really too hot, in summer the old timer was set 1 hour a day, this was far too long, so new Nest Gen 3 allows to be set down to ½ hour and select which days, so 4 days heated and 3 not is just about enough to wash hands in warm water.
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Hot water should only be set to 55C otherwise the hot water will scald.
Competent plumbers can wire up heating systems. But many are not competent.
Only a very few electricians can confidently wire up heating systems.
What is needed depends on what has already been done. It is possible it hardly needs anything to be done.
Even electrically heated water costs depend on your water useage. A three minute shower is only about 90p. A bath about £4. But daily heat loss about £1 from the cylinder even if all HW pipes are lagged.
Competent plumbers can wire up heating systems. But many are not competent.
Only a very few electricians can confidently wire up heating systems.
What is needed depends on what has already been done. It is possible it hardly needs anything to be done.
Even electrically heated water costs depend on your water useage. A three minute shower is only about 90p. A bath about £4. But daily heat loss about £1 from the cylinder even if all HW pipes are lagged.
Is 55 degrees sufficient to stop legionella? I have seen various numbers, but most commonly 60-65
At the tap, which should be approx 50 degrees in abut 30 seconds.
20° or less – Legionella survives, but in a dormant state
20° to 45° – Legionella will grow rapidly
50° – Most Legionella bacteria will die within hours
60° – Most Legionella will die within minutes
70° – All Legionella bacteria will die instantly
But setting hot water at 55C should result in then dying and not multiplying. And it will not scald you too quickly.
20° to 45° – Legionella will grow rapidly
50° – Most Legionella bacteria will die within hours
60° – Most Legionella will die within minutes
70° – All Legionella bacteria will die instantly
But setting hot water at 55C should result in then dying and not multiplying. And it will not scald you too quickly.
as water in a cylinder is either fresh, or stored for hours, I am quite happy with a middle temp of 50C
A loft tank is much more of a worry.
Yet we never hear a peep out of anyone re tank fed electric showers which spend all their time heating water in the range 35C to 40C, depending on ones showering preferences and cannot be heated beyond 48C as the TCO (thermal cut out) switches off power to the heating elements.
What do you all make of this study? https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2094925/ -> "Electric water heaters already installed should be set at 60°C to limit the risk of Legionella contamination."
Do you have a source for this? I am seeing 60 degrees is necessary.
I know it probably won't make a massive difference, as we've had it set to 55 degrees for years with no problems, but I would like to get it optimal now that I have cleared all the crap out the way to access the thermostat.
Hi @Agile , just checking - are the contact details in your profile up to date? I have tried to contact you about attending to this, and I don't seem to be able to send you a private message. Thanks
There is a bit of a conflict - to kill off Legionella in stored hot water, then it needs to be set at >55C at least once per week. To be able to use hot water for hand washing, it needs to be around 45C. Most people would fill a wash-basin with a mix of hot and cold to hand wash.
Maybe like you, I prefer to wash my hand under running water - my solution on a hand wash basin, in the downstairs toilet, where I usually need to wash my hands, was to fit a thermostatic mixer valve. Hot and cold go to the valve and the valve then feeds to the tap. Turn the tap on and the hotest the water gets to is 45C. Stored water in the cylinder is at 60C.
I have seen 55C and 60C mentioned in various documents. Most stats have an hysteresis of 5C anyway.
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