Immersion Heater but Tank is Half Cold.

harryhound

I have a traditional hot water tank about 35 years old.
It is a cylinder about 3' (1 meter) tall and just about thin enough to clasp it in your arms (say 5' in circumferance).

In the winter it is heated indirectly from a boiler via a copper coil in the bottom of the tank.

Now, in the summer, it is heated overnight by a vertical immersion heater, about 30" long.

Though the time clock clicks to turn on the immersion and it definitely starts to draw current, the next morning only half the tank is hot.

Does this sound like a dodgy thermostat?

[Whoever fitted this tank did not allow for the regular failure of the immersion. I have to cut through the ceiling from the loft in order to get out the immersion element. Over the years I 've got through about 4 immersions but never had a thermostat go wrong. The hard water causes the element to erode and then the water shorts the element and the safety cut out next to the fuse box drops out.- but that is not happening this time]

Harry.

will-he-payitoff

The immersion will only heat the top half of the tank. as this is where the outlet is it should not be a problem.

HugoSP

I'm assuming the immersion heater is located into the top of the tank.

This problem sounds like the immersion heater is not long enough, but you say it is.

When it is heated the hot water will rise to the top of the tank thanks to the rules of natural convection.

I suspect that the immersion heater is not powerful enough to heat up the whole tank before it starts to lose heat through the sides. Maybe it's not that well insulated.

I would firstly look again at the hot water jacket. Cylinders these days come ready lagged in foam insulation and don't necessarily need a jacket. I suspect yours is not ready lagged and would need a jacket. If you can see copper then this is the case.

Once this has been discounted, I would consider replacing the cylinder with a ready lagged one of the same size, for two reasons.

Firstly the insulation would be more efficient.
Secondly a 35 year old cylinder may be coming towards the end of its life. Leaks can be troublesome and you would be dealing with this problem before it occurs.

If you do replace the cylinder, take the old one to a scrap yard. It's probably worth around £50 scrap.

EliteHeat

Assuming that you have used the correct 27" immersion heater then the problem will almost certainly be due to the bottom half of the cylinder containing limescale, a huge amount of limescale.

You could try to drain the HWC and remove the scale, but be ready to replace the cylnder as at 35 years old, it has had its day.

BTW, the current price for the cylinder is about £22, not £50 as previously stated.

HugoSP

EliteHeat wrote: »

BTW, the current price for the cylinder is about £22, not £50 as previously stated.

I got £40 for one a couple of years ago and the price has gone up since then, having said that the one I weighed in was heavier than normal, but we pearced the bottom to make sure it didn't have any water in it.

My local scrappy pays around £2 per kilo for copper