hot water tank immersion heater stat Q

[jives11]

hi,

I have a fully pumped gas CH + HW system, with a hot water tank. The tank has a topup immersion in the top, and a thermostat strapped to the outside, contacting the cylinder through a cut away in the foam insulation.

I also have E7 electricity which with offset washing machine + dishwasher works out fractionally cheaper if I can offset around 9% of total use. I'm experimenting with using the immersion for an E7 boost. My gas bill is very high and I think the efficiency of Gas heating of my water is compromised by too complex a layout and too many heated towel rails , also possibly poor insulation on the pipe runs

My question is regarding the immersion heater. I have noticed that if I turn it on after a while it appears to get turned off, or rather it is on but not drawing current. I can see this from one of those currentcost electricity monitors that measure the total mains. So If I get up at 6:00am and turn on the immersion, the house consumes around

3.5Kw, but after around 45 minutes it drops to around 400 watts.

I assume this is because the water is hot enough, and that is a good thing, but I'm curious what is doing that ? Is it the strap on tank stat ? If so the light in the immersion switch is still on ? Maybe there is a stat in the heater element itself ?

I'm not complaining, if the immersion cuts out when it's done it's job

- that's great , I'd just like to understand how .

[Trevor Smith]

The emersion heater has its own thermostat, if you remove the top cover you will see it and there will be a small adjuster with a temperature scale so you can alter the temp at where it turns off. The stat that's on the side of the cylinder is for the boiler and has nothing to do with the emersion heater. Trevor Smith

[Donwill]

Yes, you're quite right the immersion heater also incorporates a rod thermostat which is obviously doing it's job.

Cheers Don

[Calvin Sambrook]

Trevor is absolutely right but the tone of your original question (that is the fact you asked it at all) has me thinking that I should also add that with the top cover removed there are almost certainly exposed live terminals. *Only remove the cover with the circuit isolated at the consumer unit*.

If you can still read uk.d-i-y, great. If not, my words arrived too late!