Too hot water

[simond]

I have a customer whose hot water is too hot. He has a 15 yr old Copperform indirect foam insulated grade III copper cylinder.

Cylinder stat can be set at 50 deg, but it's still steaming. At around 70-75 degs.

We've done all the normal things like checking the 3 port valve, changing the cyl stat. But it was still getting too hot.

So out of desparation I moved the stat halfway up the cylinder - no change.

Finally, I checked the temperature up against the bare copper surface in the cylinder stat aperture - lukewarm. Same story for the old cylinder stat aperture. But when you draw water off, and there is plenty of it, it is around 75 deg C.

The only conclusion I can make is that there is a great deal of scale on the inside faces of the cylinder preventing heat transfer to the shell. Normally I'd expect this to be in the bottom and on the primary coil, rather than the circumference.

Any ideas, I haven't seen this before?

 

[clf-gas]

The only conclusion I can make is that there is a great deal of scale on the inside faces of the cylinder preventing heat transfer to the shell. Normally I'd expect this to be in the bottom and on the primary coil, rather than the circumference.

Any ideas, I haven't seen this before?

I concur Simon, but have you proved the stat to be working

 

[simond]

Thanks, and yes, we have proved the stat.

 

[sambotc]

Only thing i can think of is if there have been any alterations to the sytem for it to still circulate even if the 3 port is closed to hot water?

When you say you've checked the 3 port, have you made sure it fully closes 100%, it could appear to be closed, but still creaps round?

Chers, Sam

 

[gas4you]

off on a tangent a bit, but have you checked that immersion has not been left on? I know this is a basic question and no insult intended

 

[simond]

They are both fair and sensible suggestions, but it is the poor heat transfer through the wall of the cylinder which is the problem.

I checked the immersion (even though the spur was off) and it was dead....

I haven't seen a cyl before with such poor thermal conduction through the side wall. With the water coming out steaming I could easily touch the exposed area of the side wall with no discomfort whatsoever.

 

[Agile]

It may be a bit of a long shot but I have never encountered any serious scale on the walls so I dont see that as being likely!

Have you tried turning the boiler off and see if the water is still getting hot ???

I am suspecting an electrical fault!

Tony

 

[simond]

Me too, Tony, I've never seen scale on the cylinder walls either.

But I multimetered the immersion and that is definately off.

As I say, normally it would be painful holding one's hand against the copper in the cyl stat pocket, this one's lukewarm.

But the water coming out is bl**dy hot!

 

[Gasguru]

If your feeling very brave Simon you could risk rattling the sidewall with the radhammer/vibraclean - it might just work or rupture the cylinder

 

[sambotc]

can you remove the immersion and visually check with a torch?