How to control an immersion heater (Ed.)

[zakinho]

I need to control my water heating for the short term. I have a tank with an immersion heater that does not have a thermostat and runs 24/7 with the hot water at 75C . The heater is a dual element, each with it's own fused spur. Can I initially swap the fused spurs with these timers which will enable me to at least have it run for just a couple of hours per day?

https://www.screwfix.com/p/lap-digital-immersion-timer/1804r

Further to that, can I add in this strap on stat into the mix so that I can also keep the water at 60C ?

https://www.screwfix.com/p/drayton-hts3-cylinder-stat/95630

If this is possible what should the wiring configuration be?

 

[flameport]

I have a tank with an immersion heater that does not have a thermostat

All immersion heaters have thermostats, including that one. It's located under the black cover.
If there was no thermostat, it would literally boil the water into steam and be exceptionally dangerous.

The cylinder thermostat is NOT suitable for an immersion heater as it is only rated for 3 amps - far less than the 13+ amps that the immersion heater uses.

The timer could be installed, but in addition to the existing fused connection unit, not as a replacement for it.

 

[zakinho]

All immersion heaters have thermostats, including that one. It's located under the black cover.
If there was no thermostat, it would literally boil the water into steam and be exceptionally dangerous.

The cylinder thermostat is NOT suitable for an immersion heater as it is only rated for 3 amps - far less than the 13+ amps that the immersion heater uses.

The timer could be installed, but in addition to the existing fused connection unit, not as a replacement for it.

Thanks for the reply.... I was advised the same but there is no stat that I can see under that cover. I missed the 3A rating for the stat I was looking at.

 

[Harry Bloomfield]

I was advised the same but there is no stat that I can see under that cover.

Then you failed to see it, it absolutely MUST be there, no exceptions. Your electric bill, would be horrendous, were it no there.

 

[ericmark]

There are immersion heater timers designed for the job. Some have fuses built in, some can take duel supplies, the one I have does not run all the time at 3 kW designed for twin elements

although at around £300 this one is not designed for normal use, but for when one has solar panels. And I now realise was not really worth the money. However there are all sorts you can use.

That cylinder looks small, I would think it may just about fill a bath if you are adding cold, there are valves to mix hot and cold

you can't store hot under 60ºC and stop legionnaires and 60ºC is still too hot to put hands under it, so the mixer valve allows safe temp at taps and no legionnaires, and the water can be stored hot enough to fill a bath.

I from 2019 to 2023 when solar panels fitted, tried to heat my DHW using just time. I was told, which I found was incorrect, that to heat DHW with electric was more expensive to using the central heating, so I set in summer the boiler to run 4 times a week for ½ hour each time with a 20 kW boiler, when I moved to electric it told me how much I have saved, in other words how much used, typically 2.5 kWh per week, so it would seem turning on ½ a day would likely give you water at hand wash temperature, but you will not know it that is safe, and if you have the option of using the immersion heaters built in thermostat why take the risk.

 

[zakinho]

Then you failed to see it, it absolutely MUST be there, no exceptions. Your electric bill, would be horrendous, were it no there.

I’ll revisit today. The consumption so far IS horrendous, 110-180kw per day.

 

[Murdochcat]

I’ll revisit today. The consumption so far IS horrendous, 110-180kw per day.

That's a lot and highly unlikely to just come from a hot water tank unless its feeding your neighbours hot water too

Do you have storage heaters too?

You should also improve the insulation over that tank too

 

[zakinho]

That's a lot and highly unlikely to just come from a hot water tank unless its feeding your neighbours hot water too

Do you have storage heaters too?

You should also improve the insulation over that tank too

There is electric UFH which is taking a fair bit and easier to regulate but a simple measure of my meter from 11pm-8am I reckon 20kw was the immersion. I've started switching it off at the board but obviously am looking for a better solution. No storage heaters and agree re insulation, it's on the list.

 

[zakinho]

There are immersion heater timers designed for the job. Some have fuses built in, some can take duel supplies...

My plan would be to just replace the fused switches with a simple timer. There was an earlier comment that said I'd need to use a timer in conjunction with the fused switch but has that not been usurped by the breaker being an RCBO, i.e. isn't the fused switch a legacy item that they just didn't replace when installing the new consumer unit?

 

[Murdochcat]

There is electric UFH which is taking a fair bit and easier to regulate but a simple measure of my meter from 11pm-8am I reckon 20kw was the immersion. I've started switching it off at the board but obviously am looking for a better solution. No storage heaters and agree re insulation, it's on the list.

20kw is far more energy than it would take to heat up that tank from cold

I would look at your UFH settings - UFH consumes huge amounts of energy and is a expensive mistake if managed badly

 

[Murdochcat]

My plan would be to just replace the fused switches with a simple timer. There was an earlier comment that said I'd need to use a timer in conjunction with the fused switch but has that not been usurped by the breaker being an RCBO, i.e. isn't the fused switch a legacy item that they just didn't replace when installing the new consumer unit?

Waste of money. See my previous answer

 

[fixitflav]

20kw is far more energy than it would take to heat up that tank from cold

kWh, not kW (we've been here before)! -

 

[Johntheo5]

I need to control my water heating for the short term. I have a tank with an immersion heater that does not have a thermostat and runs 24/7 with the hot water at 75C . The heater is a dual element, each with it's own fused spur. Can I initially swap the fused spurs with these timers which will enable me to at least have it run for just a couple of hours per day?

https://www.screwfix.com/p/lap-digital-immersion-timer/1804r

Further to that, can I add in this strap on stat into the mix so that I can also keep the water at 60C ?

https://www.screwfix.com/p/drayton-hts3-cylinder-stat/95630

If this is possible what should the wiring configuration be?

View attachment 364139View attachment 364141

I have a immersion like that, its only 52 years old, a £7 Santon, that I installed when I bought this hose in 1972, it has a surface mounter thermostat (a Otterstat I think), that switches off at 60C/65C.
I also have one of those timers, 4 programmable times/day.

Difficult to imagine you using 20kwh/day, enough to supply ~ 360 litres of hot water at 60C or nearly 600 litres/day at 40C, do you have a small Hotel?.

 

[ericmark]

kWh, not kW (we've been here before)! -

Never understood why kWh rather than MJ, it is confusing as the seconds in the Joule per second are removed with the hour, leaving just the 3600 multiplier between seconds and hours, so 1 Wh = 3600 Joules.

But try explaining so some one, a unit with hour in the name, has nothing to do with time. But the one without hour in the name has. But the modern timer has a fuse built in, what you have to decide is do you want both elements through timer or one. There are timers designed for Economy 7 but can't remember which ones. And it seems there is a new Economy 7 now with 6 hours over night and 1 hour boost during the day, I would expect a tank like you show with the insulation part removed to use around 5 kWh per week, put a simple jacket over the cylinder and you can half that, but £1 or £2 a week is not that much anyway, with a timer at £70 which will only help with an off-peak supply. It takes my tank around 3 days to cool down, so does not matter when in the day it is heated, unless using off-peak.