Immesrion heater / thermostat problem

marders

I'm having a problem with my boiler/hot water cylinder in that it seems to be heating during the day when it should only heat at night. I have check the off peak settings etc and it is from 2:15am to 7:15am. The boost is not on (and not set to go on). There are two black round covers (thermostat/element) on the outside approx 4cm in diameter. One at the bottom (off peak?) and one a bit higher (for boost?). The metal thread ring (whatever it's called - the bit where it attaches to the cylinder) on both of these are very hot. I'm led to believe that only one of these should be hot (the bottom I assume as no boost is being used). The thermostats seem to click on and off when I change the temp so the only other thing I can think of is somehow the elements and thermostats are not talking to each other properly, perhaps thermostat wired incorrectly? I have manually reset the thermostats (not sure what that achieves?).

Any suggestions on the problem or how to do some little tests to isolate the problem? I was thinking of turing the thermostats down to something like 20 degrees which should mean that the water is luke warm at best and then the metal rings should no longer be hot. If they are still hot then I guess it's a thermostat->element problem (like incorrect wiring?).

I notice on the manufacturer's site that it says "Standard Tristor products are supplied with one immersion heater for back-up in case of boiler failure. Models to suit electric only application are supplied with a second immersion heater". As it is electric only we have 2 immersion heaters (?the two round things) on the side and as stated above, these are both constantly very hot (the metal around them to attach to the tank).

Some technical details are as follows:
w w w . telford-group.com/tristor.php
The boiler is a Telford Copper Cylinder - Tristar 200. Max mains water supply pressure is 3 bar, max store pressure is 3 bar. Immersion heater power/voltage is 3kW(each)/230V AC.
The 4cm round black covers have on them: ThermTec Ltd Immersion Heater 2.75/3kW 230V/240V 50Hz.

penrhyn

Presumably the system is run off some sort of timer, you need to locate this.

marders

Yes it is run off a timer. I have reset this to default settings which means the off peak kicks in 2:15am to 7:15am and nothing else. It has the option of a timed boost or a manual boost. I have it set to manual boost so it should do nothing unless I press the boost button. There are lights on the timer unit to indicate when off peak and boost are in use and the only light that comes on is the off peak (as I dont boost). It's as if the elements are heating outside of off peak (as both are very hot on the outer metal ring) but the light indicators are not on.

Mynewt

If its not operating as it should, perhaps call the manufacturer or installer to have it checked out and repaired?

Fire_Fox

marders wrote: »

Yes it is run off a timer. I have reset this to default settings which means the off peak kicks in 2:15am to 7:15am and nothing else. It has the option of a timed boost or a manual boost. I have it set to manual boost so it should do nothing unless I press the boost button. There are lights on the timer unit to indicate when off peak and boost are in use and the only light that comes on is the off peak (as I dont boost). It's as if the elements are heating outside of off peak (as both are very hot on the outer metal ring) but the light indicators are not on.

It may be you have a problem with the elements or thermostats or it may be the timer itself is faulty. Either way if the tank overheats this may damage the elements or even be dangerous so you need to get the system serviced as mynewt says.

espresso

Your assumtion that you have a problem seems to be based entirely on:

marders wrote: »

The metal thread ring (whatever it's called - the bit where it attaches to the cylinder) on both of these are very hot. I'm led to believe that only one of these should be hot (the bottom I assume as no boost is being used).

You are not feeling the heat from the individual immersion heater elements which are in the centre of the tank. You are simply feeling the conducted heat from the hot tank to the large nut that holds the element into the tank boss. The tank is very well insulated and these are the only places that you are likely to feel any heat.

marders wrote: »

There are lights on the timer unit to indicate when off peak and boost are in use and the only light that comes on is the off peak (as I dont boost). It's as if the elements are heating outside of off peak (as both are very hot on the outer metal ring) but the light indicators are not on.

If your immersion was operating during the day, this would be reflected in your day rate meter usage. Read your meter!

You haven't got a problem, it's your lack of understanding that is the problem.

marders

A bit harsh espresso but what you say does make sense. The only reason I was basing it on the hot rings was because a plumber told me one should be cold and one should be hot. So both will be hot due to conduction and one will never be cold unless the other is?

I guess I should have mentioned the boiling sound I hear outside of off peak hours. Off peak goes off at 7:15am but having been home during the day I hear it boiling away for a good few hours more (even up to and past 2pm). It's not constant and seems to come and go so maybe it's not a boiling sound I'm hearing, perhaps just the tank refilling itself?

As for reading the meter, that can be a bit hard as I live in an apartment building and the meters are locked away somewhere though it should show up on the leccy bill.

Mynewt

It should show n the electric deinfatley but might be ahrd to detect. Do you have an owl or energy monitor or could you obtain the use of one. While you don't have the meter in your property there'll be a point in your property where the main supply cable enter's clip the monitor here and watch the difference in real-time consumption, between when you think it's defiantley off and might be on.

penrhyn

It sounds like the system has one timed feed for economy 7 to one immersion element and another directly connected feed to the second element. It should be possible to determine which circuit breaker in the consumer unit controls each feed, I doubt whether the mains feed into the property would be exposed to allow a current clamp to be used.
I would of thought that a resident would be entitled to be able to access their own meter.

Premier_2

marders wrote: »

A bit harsh espresso but what you say does make sense. The only reason I was basing it on the hot rings was because a plumber told me one should be cold and one should be hot. So both will be hot due to conduction and one will never be cold unless the other is?

I guess I should have mentioned the boiling sound I hear outside of off peak hours. Off peak goes off at 7:15am but having been home during the day I hear it boiling away for a good few hours more (even up to and past 2pm). It's not constant and seems to come and go so maybe it's not a boiling sound I'm hearing, perhaps just the tank refilling itself?

As for reading the meter, that can be a bit hard as I live in an apartment building and the meters are locked away somewhere though it should show up on the leccy bill.

It is essentially as expresso says. I think the plumber has totally misled you.

If the bottom immersion boss feels warm, then so will the top one. However, if you only use the top immersion then the top one would be warm whilst the bottom one would still feel cold. Hot water rises so an immersion only heats water above it.

The sound of water boiling is somewhat different to that of the tank refilling. Boiling water will be quite quiet and is the sound of gentle gentle burbling. Water refilling may be much louder; often it may be heard from outside the tank cupboard. The refilling should only occur when a hot water tap is on. The hot water is pushed out of the tank by cold water entering at the bottom, so in normal operation the tank should never be empty, even partially.

If you are hearing the water boil, even at any time of the day, then it sounds like your thermosat is set too high - this is quite a common fault especially with lower immersions on large tanks; 55 deg for the bottom immersion should be plenty hot enough - when the water gets that hot at the bottom of the tank, the water at the top will be much hotter.

marders

Misled by a trademan? Never! It's a shame I didn't think about it a bit more and took what he said as gospel, guess he was trying to get me worried so I'd get him in to "fix" things. Lucky it was over the phone and I was a bit slack so never called him back!

The sound must be refilling as I can hear it from the bedroom which is a good 20m away and it is more predominent in the morning to about lunch so makes sense with showers in the morning. Though if showers are the only hot water being used in the morning then I'd expect it to refill just once and not hear it come on and off a few time? I'll double check over the weekend - maybe run no hot water in the morning then I shouldn't hear anything? Though I know I've been in bed and heard it and no hot water had been run...hmmm.

As both of the immersion boss(es?) (thanks for the correct term for the metal ring thing!) are the same temp then I guess the bottom one is in use and therefore the off peak heater? It would make sense for the upper one to be for boost as that will heat less water so to speak. Maybe I could try turning the off peak off, wait for the bosses to cool and then use the manual boost and only the top should heat then.

So bottom should be 55, top about 65? If not using the top one (assuming it's for boost only) then I could set that to anything and it wouldn't matter as it's not in use, correct?

thanks everyone, I've nearly grasped the whole thing and I've gone from thinking I need to replace the whole thing to everything being as it should be (with a minor adjustment to thermostat and a very minor leak to fix).