Immersion tank not heating when central heating is on

P

PatriciaFox

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82
In the past few weeks our immersion tank has stopped heating water when the gas central heating is turned on.

Normally the water would heat up by default if the heating is on, but for no reason – no work done on central heating system etc, its stopped. When the switches are flipped to purposefully heat the water, the water does heat up.

Any idea why this might have happened?
 
See my first post here:

Draining and old (c. 1955) immersion cylinder

Your cylinder is probably like the one in the picture. If so then do the pipes into the coil heat up at all? Any chance that (assuming a two story house with cylinder upstairs in hot press) the upstairs heating has been switched off (e.g. isolated using a valve)? Do the upstairs rads heat up? If not then maybe there's a pump gone or something?
 
Yes the tank is upstairs, and the radiators are on and working as per normal, its just the tank that isn't warming up.
 
Can you check the pipes feeding the cylinder heating coil to see if they are hot when the heating is on? Basically the hot water in the central heating system should be pumped through the coil and should heat the water in the tank (unless you have some other arrangement but the one described should be common enough as far as I know).
 

Agree that this should be the first step. Look at this picture. http://www.lycrisbyrne.com/images/copper_direct-indirect.jpg You are looking for the pipes labeled coil fittings. One would normally be hotter than the other.

Once you have found the flow (top) and return (bottom) from the cylinder follow both those pipes and see if you can find a red valve or "a white box on top of a pipe" and take a note of where you feel the pipe warming up, if at all.

You say no work done but have you started using a room that you would not normally heat?
 

Will check to pipe once I get home and the heating is on.

No, no changes to radiators being turned on or off have been made. The immersion simply stopped heating when the central heating was on one day...there wasn't a gradual cool down period.
 
I had exactly same problem - CH not heating the HW Cylinder - got a plumber to take a look & found that the coil was 'silted up' (black gunk). My cylinder was the old uninsulated one so instead of cleaning it out I replace it with an new insulated one. Definitely worth doing as it saves me from using the electric shower in the morning- the waters still hot in the cylinder from the night before.
 
Yeah - a new immersion with a factory integrated lagging jacket is well worth it!
 
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