immersion won't heat above 50c

Cerco

Bruthal wrote: »

Its actually post 2 he mentions possible mixing valve.

When I read that I thought he meant a mixing valve on a tap because he was asking about measuring at a tap.

Bruthal

Can't see second heat source having much affect. What it does sometimes do is cause immersion overheat stats to trip, but shouldn't affect the immersion causing it to under heat water.

Cerco

Bruthal wrote: »

Can't see second heat source having much affect. What it does sometimes do is cause immersion overheat stats to trip, but shouldn't affect the immersion causing it to under heat water.

Suppose the other source was a coil in the cylinder connected to the a boiler. If the boiler was off and there was a circulating pump pumping cold water through the coil this would cool the water in the cylinder. However I would expect the element to be on to compensate.

CJ Haughey

Bruthal wrote: »

Can't see second heat source having much affect. What it does sometimes do is cause immersion overheat stats to trip, but shouldn't affect the immersion causing it to under heat water.

A second heat source can have a huge part to play for various reasons, no point in confusing the thread talking about possibilities that do not exist in this scenario.

Bruthal

CJ Haughey wrote: »

A second heat source can have a huge part to play for various reasons, no point in confusing the thread talking about possibilities that do not exist in this scenario.

Tell us how it will cause an immersion to under heat water just as matter of interest?

If the second heat source heats water to 70 degrees, the immersion won't come on since it's stat is now open.

If second heat source heats water to 50 degrees, immersion should still heat it the rest of way to 65 degrees.

There may be slight interference depending on immersion stat hysteresis properties and how close to 65 degrees the second source heats.

But causing a 65 degree stat to stop working at 50 degrees seems unlikely.

Dtp1979

CJ Haughey wrote: »

Already asked too.

I know ya did. I was re asking cause you didn't get an answer

CJ Haughey

Dtp1979 wrote: »

I know ya did. I was re asking cause you didn't get an answer

I did, see post 16.

Bruthal

meercat wrote: »

This is the most likely IMHO
The tube that the stat fits into may be slightly bent and touching the element preventing full heating of cylinder. That or there's a leak in your hot water system. Turn off inlet valve to cylinder and heat water overnight. Turn valve on the following morning and test temperature.

Yes thermostat tube actually touching or very close to element certainly would interfere with it's operation. When water is cold and element first switched on, it keeps stat cool enough for a while. But it might reach set point before the main water bulk reaches set point temperature.

Stoner

Mod Note:

Lads I killed some posts here, a bit of niggling going on. We can either leave them and be blamed for doing nothing, or delete them and be blamed for over modding.

Bruthal

Stoner wrote: »

Mod Note:

Lads I killed some posts here, a bit of niggling going on. We can either leave them and be blamed for doing nothing, or delete them and be blamed for over modding.

Seems OK to me anyway. Once Charlie is happy, all is well.

Bruthal

Cerco wrote: »

Suppose the other source was a coil in the cylinder connected to the a boiler. If the boiler was off and there was a circulating pump pumping cold water through the coil this would cool the water in the cylinder. However I would expect the element to be on to compensate.

Once the water is below immersion set point, it should come on. Particularly since this stat seems to be side fitted into the cylinder, so it's well below the heat trap at the top.

touchdown77

Originally Posted by meercat View Post
This is the most likely IMHO
The tube that the stat fits into may be slightly bent and touching the element preventing full heating of cylinder. That or there's a leak in your hot water system. Turn off inlet valve to cylinder and heat water overnight. Turn valve on the following morning and test temperature

.

Bruthal wrote: »

Yes thermostat tube actually touching or very close to element certainly would interfere with it's operation. When water is cold and element first switched on, it keeps stat cool enough for a while. But it might reach set point before the main water bulk reaches set point temperature.

I've a water meter fitted at the point of cold entry and its stopped when all taps are off, so there doesn't appear to be a leak.The house is direct mains, no storage tanks so its easy monitor if there is a leak with the meter.

Also I checked the hot water route out of the top of the tank and its straight to a manifold to all the hw taps, no mixer anywhere.

I went to buy a new element yesterday but didn't get one, however now that I see the posts above the stat tube being bent, I might get the element out first and examine it.
Given that the second stat behaves like the first, this theory would explain it.

I'll post a pic when its out.

touchdown77

If I end up replacing the element, whats the best brand to go for? (3kw 14" long)

Bruthal

touchdown77 wrote: »

If I end up replacing the element, whats the best brand to go for? (3kw 14" long)

It shouldn't matter too much about brand.

Sleeper12

I'm thinking if the element is caked in limescale then the heat could be transferred to the very top of the element or indeed to the thermostat. It's possible the stat is actually reaching the temperature required very quickly but the water is still only hitting 50. This is a wild guess as nothing else seems to make sense.

Bruthal

Sleeper12 wrote: »

I'm thinking if the element is caked in limescale then the heat could be transferred to the very top of the element or indeed to the thermostat. It's possible the stat is actually reaching the temperature required very quickly but the water is still only hitting 50. This is a wild guess as nothing else seems to make sense.

The stat sleeve touching, or very close to the element makes sense as a possible reason.

Element caked in limescale is possible, causing overheating of element and element head, and element pocket if that is also scaled up. Limescale insulates elements from the cooling effect of the water, so the element can overheat from it alright.

But cylinder is just 3 months old, and this problem is there since day one it appears.

Bruthal

If you are going to remove the element OP, mark it before hand so you know what orientation it was into cylinder. Might be helpful depending on how it looks, and how stat pocket looks in relation to element.

I know on some immersion installs, elements hit cylinder coils during install, bending them, which caused problems also..

Cerco

A few pics might help also. Like to see tank and manifold. Does manifold have manufacturer name and type shown?
Have you searched tank manufacturer's website for recommended element type?

Sleeper12

Bruthal wrote: »

The stat sleeve touching, or very close to the element makes sense as a possible reason.

Element caked in limescale is possible, causing overheating of element and element head, and element pocket if that is also scaled up. Limescale insulates elements from the cooling effect of the water, so the element can overheat from it alright.

But cylinder is just 3 months old, and this problem is there since day one it appears.

Ah, guess I wasn't paying enough attention when reading ops original statement.

Bruthal

Sleeper12 wrote: »

Ah, guess I wasn't paying enough attention when reading ops original statement.

Easily missed.

CJ Haughey

Bruthal wrote: »

Seems OK to me anyway. Once Charlie is happy, all is well.

Im happy Robbie.

Bruthal

CJ Haughey wrote: »

Im happy Robbie.

Great, glad to hear it.

2011

Ok guys we have all had a good laugh.
Please stay on topic.
No more snide remarks.

Thank you