heating element problems with economy 7

[Deleted member 112031]

Sorry, that is what I meant by saying the thermostat was part of the element. Photo attached. If the elements are splitting though what good will changing the thermostat do?

 

[Taylortwocities]

The blue bit is the thermostat and just pulls out.

If the stat is faulty, it may be powering the element too much. If you turn the red temp control you should hear it click as it switches on and off.

 

[Deleted member 112031]

Thanks. I certainly think it possible that the stat has been faulty on the last two elements. Or at least unable to deal with the economy 7 being on all w/e. I started both elements at between 50 and 55 and as they reset gradually went down to 45. However by that time I think they had become faulty and the stat had completely failed leading to the splitting. That's my theory anyway.

Can you recommend a high quality element which the thermostat is less likely to fail?

 

[marconi]

I cannot find your system which you described as 'The system is a kernel direct plumbing unit produce code: 3396 installed in 2000.'
Some photos would be helpful.

 

[Deleted member 112031]

I couldn't find it online either. Photos are attached. There may also be some paperwork somewhere I could dig out.

 

[Taylortwocities]

Do you mean the reset button kept tripping. If so, the stat is definitely faulty, they operate at 90C to stop the tank boiling.

You have a standard thermostat. Pull it out and measure the length. You can buy a new one at most DIY sheds, Screwfix, plumbers merchants.
Make sure it has an over temp cut out included in it.

 

[marconi]

When was the last time the sacrificial aluminium protector rod was inspected and changed? See third image down.

 

[marconi]

When was the last time the sacrificial aluminium protector rod was inspected and changed? See third image down.

What kind of water do you have - hard or soft?

Is the tank copper or stainless steel?

What length elements have been used for top and bottom positions?

 

[Deleted member 112031]

Thanks for your feedback on the thermostat. I will bear that in mind in the future however at the moment a change of thermostat wouldn't suffice as I am pretty sure the element has split again.

In terms of the sacrificial aluminium protector rod - do you mean the piping impacting the corner of the sticker? Whichever one you mean I am pretty sure the answer is never though thinking about it a new one might been put in when I had a new pump installed last year.

I am in London so the water is very hard. I don't know if the tank is copper or steel.

I don't know the lengths of the elements. The first ones that survived for 15 years and their initial replacements were the same lengths and identical in all other superficial regards. The newer chrome ones were longer.

The top element is still functioning without issue and that was the case before, which makes me thing the thermostats of the bottom elements have been less than resilient and have been failing under approx 70 hours a week use.

 

[marconi]

I reckon you bottom element is sitting in/on or just above a thick later of limescale deposits . This means there will be insufficient convection currents of water around the element's surface area. Thus the immediate few centimeters of water around the element will be hotter and the surface temperature of the element will be higher. The overall result is that to achieve a heat flux of 3kW into the water the element will be operating at a higher temperature and for longer. Locally at the element the temperature is likely to be higher/or become higher than the boiling point of water (which is 100C at standard atmospheric pressure). The element is not designed to operate in this way for long.

I think (ie: what I would do) you need the tank draining of water, the bottom element removed and a torch shone through the boss to ascertain the limescale problem at the bottom of the tank. You can then scrape out/suck out with a wet vacuum cleaner the limescale and refit a hard water element of the correct length, or decide to replace the cyclinder in toto. Ask your plumber to cost for both repair and replacement before he starts.

And at the same time get the aluminium sacrificial rods replaced for new ones and record the date when this was done and when they next want replacing. I cannot see any flange in the images for something like these:

Protecting hot water tanks & heaters from corrosion - https://www.hamworthy-heating.com/Knowledge/Articles/Corrosion-protection-for-water-tanks-water-heaters