Immersion heater problem

I had to replace the thermostat on the immersion heater on the water water tank at my parents' house recently as the thermostat decided that it didn't wish to switch off anymore, continuously heating the hot water to very hot levels.

The tank is a very old large one with an immersion heater mounted right at the very top facing downwards. I replaced the thermostat like for like with what was there before and now they have hot water without having to keep turning it on and off at the switch!

The cap on the immersion heater cover claims the element is 27" in length, but the thermostat that was already there was only 18" in length. Would this be right, or should the thermostat not be 27" also? That is assuming that the cap is correct and the element is actually 27" long... Don't know without removing the whole element from the tank - not something I want to do as it's actually working.

The problem is that although they now have hot water there is not much of it. The system used to be heated by a gas boiler which has since been condemed! That's why they since used the immersion heater as they have no desire to replace the gas boiler (as it only heats the water). The problem is that with gas heating (via coil inside tank) there was enough hot water for two baths, now there is barely enough for one full bath.

Any suggestions? Would I be able to just change the thermostat to a longer one, or would it not physically fit?

Reply to
Dane Koekoek
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I think 18" is the standard length for the thermostat.

Perhaps you have a fancy dual element heater and are using the short element?

Before the thermostat was fixed, did it produce enough water on electric heating?

Christian.

Reply to
Christian McArdle

Only one set of electrical connections to the element, so I doubt it. Looked fairly standard when I had the cover off.

Simple question, but I've asked that to my mum before, but she can't answer that! The element was replaced without my knowledge about a year or so ago at some exhorbitant cost by some electrical/plumbing firm when the old one went short circuit and tripped the MCB.

My parents both belong a health club where they go swimming and use the showers there virtually every day, so (bizarrely) hardly ever have a bath or shower at home! Mum says she thinks it worked okay before the element was changed, but can't say whether it's worked fine since due to lack of use other than for washing dishes or hands!

The tank is an old copper one with a lagging jacket (no foam insulation here!) You can certainly feel that only the top small portion of the tank is actually being heated. How can I improve on this? I know they should heat it by the coil inside the tank as this will heat the whole tank, but they don't want to go down this route - they say it's too much hassle replacing the old boiler!

Reply to
Dane Koekoek

Perhaps the installers were cretinous and replaced with a short element, although the fact that the thermostat was 18" might suggest otherwise.

However, the amount heated by a top mounted element is never likely to be good. I would recommend installing a new side entry element near the bottom of the tank.

Christian.

Reply to
Christian McArdle

So would you say an 18" thermostat is correct for a 27" element?

Would be simple if the tank accommodated this! What's the longest element that can be put into a tank?

Reply to
Dane Koekoek

I would.

Reply to
Christian McArdle

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Would be simple if the tank accommodated this! What's the longest element

The problem is that top mounted ones aren't very efficient at heating the bottom compared with a side entry. You can find longer ones, though, which may improve matters a little.

However, you can't beat a good old side entry. Your tank will accommodate it. You need to drain down and then drill the correct sized hole with a hole saw. The element can then be installed. This will provide more hot water than any top mounted device.

Christian.

Reply to
Christian McArdle

Sorry about this one. Don't you just hate the way Ctrl+Return always sends immediately. I'm always accidentally hitting it...

Christian.

Reply to
Christian McArdle

"Dane Koekoek" wrote | The tank is an old copper one with a lagging jacket (no foam | insulation here!) You can certainly feel that only the top small | portion of the tank is actually being heated. How can I improve | on this?

The immersion heater is only heating the water at the top of the tank because of it's length. It might not be possible to fit a longer one, as the coil inside may be a physical obstacle.

| I know they should heat it by the coil inside the tank as this will | heat the whole tank, but they don't want to go down this route - | they say it's too much hassle replacing the old boiler!

The *best* approach would probably be to replace the cylinder with a factory-insulated one with top and bottom heaters/stats, especially if the boiler is not to be replaced. The bottom heater can be switched on when a bath is required, and the top heater only is used for small quantities of hot water (washing-up etc).

An alternative would be to fit an electric boiler to the coil, on a pumped primary loop. They're 10kW (would require new circuit from consumer unit) and smaller than an instant shower over a bath. In some small, very well insulated new homes, they're used for the central heating radiators.

Owain

Reply to
Owain

It was somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Christian McArdle" saying something like:

Likely the cretinous installers had only a dual element one with them and used that.

The cretinous installers only wired up one element - the short one. I'd bet the feed isn't 4core and the old switch is merely on/off with no bath/sink.

He can connect the long element instead of the short one.

Reply to
Grimly Curmudgeon

Ahh, never thought of that!

Sounds a good idea, and would be something I'd do when the tank needs replacing...

Reply to
Dane Koekoek

Only one set of connections on the end of the immersion heater.

Reply to
Dane Koekoek

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