Little Clanger

Thank you both. Very useful

I seem to remember that the relationships between resistance, voltage, power and current are covered by the Ohms Law formulae, but what is the formula for calculating power required to heat a given volume of water through a given temperature change? Thanks

Again, thanks for the calculations, John

OK, thanks

So immersion can be on for even shorter length of time?

🙄

In answer to both these points, yes, I'm resigned to draining the tank and taking the element out

Thanks for the calculations. That's interesting. I usually leave the immersion on for the full Economy 7 overnight 7 hours, on the principle that as it is thermostatically controlled, it will switch itself off when the set temperature is reached. Now, I will reset the timer to the minimum time required and see if that makes any difference.

Voila encore

Initially, I'm renewing the thermostat in the lower immersion heater, with a different make (a Backer to replace a Tesla). A continuity test on the element gave me 21 ohms, which I understand is about right. Confusingly, it was working fine last night - heated a whole 162 litre cylinder without tripping. By the way, a note to NickfromWales - I haven't been able to follow your advice about returning the cylinder because I bought the cylinder without any immersion heaters fitted. I bought the immersion heaters from Screwfix, but didn't keep the receipt, so can't return them.

I've moved the thermostat from the bottom immersion into the upper immersion, and put it on 'Boost'. It hasn't tripped yet, but the upper immersion doesn't stay on for as long as the lower one, of course, because it reaches set temperature more quickly.

Voila

The limit stat is part of the control stat. It's set to about 60/65 now. Will send photo later. Thanks

😉

Good idea, I'll try that. Ty

The latter, John. The reset button on the immersion thermostat keeps popping out (but stays in for a while after being clicked back)

Thanks, Nick. So you think the element has gone?

The thermostat in one of my immersion heaters keeps tripping. Immersion element, thermostat and cylinder are about 9 months old. Thermostat is set to 65°. This is the lower immersion heater in a dual heater Economy 7 cylinder. I swapped the thermostat for the one from the upper immersion heater, but that tripped at some time during the night. These are Tesla units. I've ordered a Backer replacement, but does the fact that two thermostats tripped indicate that the element is at fault? We live in a hard water area, but the elements are incoloy-type, and nearly new. Any suggestions? Thanks

Again, thanks, John Well I can definitely push the pin in the body in with finger pressure, although with difficulty, and the pin springs out again OK. The fact that it shuts down on '0' setting but then opens on even the frost setting suggests the valve is opening and shutting properly. I've just had a closer look, with a torch shining though the vents in the head. With the adjacent air temperature 15o, when the TRV is set on '2' (15o - 17o), the expanding capsule is still loose in the head - there is a small gap between the top of it and the fixed bridge that it bears on, and you can wobble it with a knife. I would have thought that, considering the open/shut temperature range for this setting, it would at least be bearing on the valve pin and possibly starting to push it in to shut off the flow. This sort of confirms for me that the head isn't seating down properly and so increasing the distance between the valve and actuator pins. I tried tightening the collar with grips, but it didn't make any difference. The weird thing is all the TRVs are behaving like this!

Thanks. They are new TRVs and valves. The pin in the valve does push in when you put finger pressure on it. And anyway, it shuts down OK, when set to '0'. The pin in the head moves when heat is applied (when removed), so it's expanding OK. The total movement of the pin is only about 10mm from shut to fully open, so presumably only about 2mm of movement for each progressive setting. It's as if the pin needs to be fractionally longer, or the head screwed down tighter to shorten the distance. I've only done the collar up finger tight for fear of damaging it. Perhaps grips would pull it in a little more. Anyway, thanks again

Thanks. Yes, discovered that!

Thanks for your suggestions. Think the head is on OK. On these, there is a female hex on the head that fits on a male hex on the body. The expansion vessel appears to work - I took the head off and ran a hair dryer over it and the pin in the head definitely moved. Thanks again

I've fitted Pegler Bulldog TRVs to all my radiators, but they don't seem to be responding to room temperatures. On '0' they shut off the flow OK, but on any other setting they come on regardless of room temperature. For example, with the radiator turned off, I left a thermometer (on a Horstmann room thermostat sender), adjacent to the TRV. I left the thermometer to settle, which it did at 15o. According to the Pegler information, the TRV should have opened at this air temperature when set at '2' (15o - 17o), however, it opened as soon as I got to the frost setting, '*', which is supposed to be 7o. The thermostatic heads are seated down properly and the locking ring is tight. I've tried changing the heads, but same result. Any ideas, or have I misunderstood how they are supposed to function?

I've fitted Pegler Bulldog TRVs to all my radiators, but they don't seem to be responding to room temperatures. On '0' they shut off the flow OK, but on any other setting they come on regardless of room temperature. For example, with the radiator turned off, I left a thermometer (on a Horstmann room thermostat sender), adjacent to the TRV. I left the thermometer to settle, which it did at 15o. According to the Pegler information, the TRV should have opened at this air temperature when set at '2' (15o - 17o), however, it opened as soon as I got to the frost setting, '*'. The thermostatic heads are seated down properly and the locking ring is tight. I've tried changing the heads, but same result. Any ideas, or have I misunderstood how they are supposed to function?

OK, so as a temporary measure, I've decommissioned the TS and installed a Willis heater. Actually works really well for our limited needs and very simple - both pump and heater are controlled by the same time and thermostat switch. Reflecting on the relative failure of the TS, I realised that a lot of heat was being 'lost' by convection (and possibly expansion), with the TS on the ground floor and the 6.5 metre run of uninsulated flow and return pipework on the first floor. As HeatGeek point out, this heat isn't lost to the house as it is within the thermal envelope, but it still meant that it was a loss of stored heat energy. In the mornings, the one open radiator was hot even though it is on the ground floor, and the pipework was hot all day. Possibly explains why the thermometers on the TS and the flow pipe rarely showed more that 60 degrees, even with the overnight thermostat at 75. Now I'm wondering if I could have retained more heat in the TS if I had tried to break the convection by sweeping the flow pipe from the top of the TS downwards before looping back up to the existing pipework, but not sure if this would work.