Immersion heater stopped working

[blackrose]

My immersion heater's just packed up. At first I thought it was the timer I recently installed but I bypassed it and tried to run the immersion direct but it still didn't work.

 

Could it be that the thermostat's gone rather than the element and is it possible to check which is broken with the AC meter on my multimeter?

 

I think it's got dual thermostats as a safety feature. Are these immersion heaters less reliable than ones fitted in houses? It's only 2 years old.

Edited May 12, 2009 by blackrose

[RobinJ]

Could it be that the thermostat's gone rather than the element and is it possible to check which is broken with the AC meter on my multimeter?

Make sure its isolated!

If you take the top off the immersion, you often find the thermostats are separate replaceable units. You should be able to check using the resistance/diode range whether the element or thermostat(s) are open circuit (provided the water is cold).

[MoominPapa]

I think it's got dual thermostats as a safety feature. Are these immersion heathers less reliable than ones fitted in houses? It's only 2 years old.

It's probably the same as those fitted in houses: the building regs mandate dual thermostats now.

 

The safety thermostat has to be a "trip". If the temperature gets high enough to activate it, it has to stay off until manually reset. The solution to your problem might be as simple as doing that.

 

MP.

[blackrose]

Make sure its isolated!

If you take the top off the immersion, you often find the thermostats are separate replaceable units. You should be able to check using the resistance/diode range whether the element or thermostat(s) are open circuit (provided the water is cold).

 

Thanks.Don't worry, I won't be prodding around down there unless the mains is switched off.

[blackrose]

It's probably the same as those fitted in houses: the building regs mandate dual thermostats now.

 

The safety thermostat has to be a "trip". If the temperature gets high enough to activate it, it has to stay off until manually reset. The solution to your problem might be as simple as doing that.

 

MP.

 

Thanks, anyone know how to reset it?

[chris w]

Usually it's a small red button.

 

Chris

[Strads]

Or you might be unlucky like us - only 4 years old but a failed element - came out covered in crystalised black stuff - probably 3mm plus thick...

 

and as the caloriifier is vertcal in a bay in the engine room - it meant draining the engine, central heating and disconeccting the in/out and yhe pressure vent..

 

that took about 30 mins.... unscrewing the element took 3 men an hour - stiff or what... and re plumbing it another 3 hours... "bl@@dy" hep conectors wouldnt re-connect - tried pushing the grippy bit sback - they wouldnt - meant disconecting more pipes and in the end switched to brass compression joints...

 

hope you have a an easier conclusion.

[chris w]

"bl@@dy" hep conectors wouldnt re-connect - tried pushing the grippy bit sback - they wouldnt - meant disconecting more pipes and in the end switched to brass compression joints...

 

hope you have a an easier conclusion.

Use "Speedfit" plastic plumbing or one of the other look-a-likes rather than Hep20. They all undo and reconnect easily, unlike Hep20.

 

Chris

[denboy]

Usually it's a small red button.

 

Chris

Or a tiny lttle black button that looks just like a bit of the moulding very very small had similar problem and all i had to do was press the button

[blackrose]

Or you might be unlucky like us - only 4 years old but a failed element - came out covered in crystalised black stuff - probably 3mm plus thick...

 

and as the caloriifier is vertcal in a bay in the engine room - it meant draining the engine, central heating and disconeccting the in/out and yhe pressure vent..

 

that took about 30 mins.... unscrewing the element took 3 men an hour - stiff or what... and re plumbing it another 3 hours... "bl@@dy" hep conectors wouldnt re-connect - tried pushing the grippy bit sback - they wouldnt - meant disconecting more pipes and in the end switched to brass compression joints...

 

hope you have a an easier conclusion.

 

I can't quite get my head around why you had to drain the coolant from the engine and the central heating?

 

When I fitted the immersion heater I only had to drain the calorifier itself - not the mixture from the coils.

 

Or a tiny lttle black button that looks just like a bit of the moulding very very small had similar problem and all i had to do was press the button

 

Thanks - I'll have a look for a red or black reset button when I get home this evening.

 

Mike

Edited May 12, 2009 by blackrose

[ChrisPy]

in a vertical calorifier you shouldn't need to drain anything - the immersion should be fitted in the top dome.

[blackrose]

in a vertical calorifier you shouldn't need to drain anything - the immersion should be fitted in the top dome.

 

Mine's fitted at the bottom.

[alan_fincher]

in a vertical calorifier you shouldn't need to drain anything - the immersion should be fitted in the top dome.

Not necessarily true.

 

I'd say 50% of vertical ones I have seen have the immersion heater boss at the bottom....

 

Like this.....

 

[ChrisPy]

then I'm the lucky one.

 

[denboy]

Mine's fitted at the bottom.

mine too

[ditchcrawler]

then I'm the lucky one.

 

No, the ones in the bottom heat more of the water in the cylinder, so you get more hot water out for the same size cylinder

[ChrisPy]

No, the ones in the bottom heat more of the water in the cylinder, so you get more hot water out for the same size cylinder

in my limited experience, immersion heaters are normally intended/used to heat some water quickly when the main system is warming up.

which is why in most places I have lived, the tank has had the immersion in the top, and I have never relied on it for regular hot water.

 

........... each to his own.

Edited May 12, 2009 by ChrisPy

[blackrose]

in my limited experience, immersion heaters are normally intended/used to heat some water quickly when the main system is warming up.

which is why in most places I have lived, the tank has had the immersion in the top, and I have never relied on it for regular hot water.

 

........... each to his own.

Immersions fitted at the top of a verticle calorifier will as you say heat a limited amount of water up more quickly than an immersion fitted to the bottom of the calorifier.

However the immersion heater fitted to the bottom will heat a whole tank more efficiently.

 

Since for many people including myself, shore power is the cheapst way to heat water (when neither moving the boat nor getting hot water as a by-product of heating the boat with a diesel heater or solid fuel stove), then for many of us it makes sense to use the immersion for our regular hot water supply and to have it at the bottom of the tank.

Of course the other advantage of an immersion at the top is ease of fitting and maintainence.

Edited May 12, 2009 by blackrose

[wonderdust]

I thought the type with 2 elements were used for different heating purposes, top one used for manual switch on for a quick heat up of water, second at the bottom connected to a timer to switch on overnight at the cheapest electricity rates, probably wrong though!

[blackrose]

I thought the type with 2 elements were used for different heating purposes, top one used for manual switch on for a quick heat up of water, second at the bottom connected to a timer to switch on overnight at the cheapest electricity rates, probably wrong though!

 

I'm pretty sure the dual thermostat is a safety feature. Not sure about a double element.

Anyway, the faulty immersion in question has been reset via a small black button on the thermostat and is working fine. Thanks to those who suggested this.

Is there any reason why this happens - overheating perhaps?

[denboy]

I'm pretty sure the dual thermostat is a safety feature. Not sure about a double element.

Anyway, the faulty immersion in question has been reset via a small black button on the thermostat and is working fine. Thanks to those who suggested this.

Is there any reason why this happens - overheating perhaps?

no idea why but i found the poxy button by accident when i drained mine down to change the heater as i thought it was knaced

[chris w]

I'm pretty sure the dual thermostat is a safety feature. Not sure about a double element.

Anyway, the faulty immersion in question has been reset via a small black button on the thermostat and is working fine. Thanks to those who suggested this.

Is there any reason why this happens - overheating perhaps?

Have you turned the (variable) thermostat up a bit lately? Perhaps its now getting too hot and the 2nd thermostat trips?

 

Chris

[blackrose]

Have you turned the (variable) thermostat up a bit lately? Perhaps its now getting too hot and the 2nd thermostat trips?

 

Chris

 

No, the only thing I did down there was install a thermostatic mixing valve.

If the engine and immersion were on at the same time could this cause the thermostat totrip?

[MoominPapa]

No, the only thing I did down there was install a thermostatic mixing valve.

If the engine and immersion were on at the same time could this cause the thermostat totrip?

It's possible that the engine could get the water hot enough to trip the safety thermostat. I failed with a quick Google to find the temperature required in the regs, but engine heated water certainly gets much hotter than is considered safe in the Brave New World.

 

MP.

[Keeping Up]

A few years ago I installed a thermostatic mixer on my system, it was a high-quality domestic model by Caleffi, but it kept giving trouble. I eventually discovered that it included a safety cut-out to shut off completely if the temperature of the incoming water exceeded 85 degrees, so when the engine was working well I kept finding that I had no hot water. Apparently all domestic mixing valves include this feature, so maybe the immersion cut-out is set to a similar value.

 

I replaced the mixer with one designed to be used on calorifiers, purchased from Midland Chandlers, which doesn't include the over-temperature cut-out; so I now have the first mixer bringing the temperature down to 65 degrees for general use, but with the second mixer to the washbasin tap set to a comfortably hand-hot lower temperature.