Water too hot

[Beagle1]

Hi

Our hot water is hotter than normal - too hot to keep your hands in but not scalding. I turned down the cylinder stat from 60c but it hasn't made any difference.

Turning it right down makes the boiler go off and right up makes it go on, so I'm wondering what else could be at fault?

Thank you.

 

[Space cat]

Do you hear a click as you turn it up and down? This should happen at or around the actual temperature of the cylinder. More precisely, it should happen at or around the temperature of the bit of cylinder it's attached to. Where is this exactly?

 

[sooey]

It sounds like the stat is working ok, is it still firmly attached to the cylinder wall? It should be about a quarter to a third of the way up from the bottom.

 

[Beagle1]

There is a click and the stat is firmly attached one third up.

The cylinder is upstairs in a bedroom and the system is gravity fed. The central heating can come on independently of the hot water, but the bathroom radiator comes on with the hot water. The boiler is a Potterton Prima F.

 

[Space cat]

Turn off the central heating at the controller and make sure the demand for hot water is On. Now turn the cylinder stat right up, make sure the boiler lights, then turn it down until you hear that click. Does the boiler go off? (The pump might run on for a few minutes.)

 

[muggles]

Have you been running your central heating recently? Did the problem start at around the time you first turned it on?

 

[Beagle1]

Turn off the central heating at the controller and make sure the demand for hot water is On. Now turn the cylinder stat right up, make sure the boiler lights, then turn it down until you hear that click. Does the boiler go off? (The pump might run on for a few minutes.)

The boiler did go off.

 

[Beagle1]

Have you been running your central heating recently? Did the problem start at around the time you first turned it on?

We haven't had the c/h on due to the mild weather.

 

[Space cat]

The boiler did go off.

So now we know that the cylinder stat can control the water temperature but maybe not to the temperature set on its dial. It could be faulty but, before you condemn it, make sure it has a good thermal contact with the cylinder.

Edit: Just a thought but --

Do you have an electric immersion heater in there?

 

[jerholdsworth]

thermostat could be turning off manually as described but not turning off automatically.
as long as there is no other heat source to the cylinder it can only be the thermostat,they are cheap to change as diy.

good luck.

 

[Beagle1]

There is an immersion heater in there.

Thanks to all who helped. I'm going to measure the water temp using an aquarium thermometer, just to rule out an incorrect perception.

Not being an expert, I'm puzzled why friends have suggested a faulty motorised valve. How would that make the water hotter if that were true?

 

[Hugh Jaleak]

The stat controls the valve, which in turn controls the boiler and pump. When the stat calls for heat it energises the valve to make it open. When the valve opens it then activates a microswitch within the valve housing which then energises the boiler and pump.

Should the valve be faulty it could be continuing to energise the boiler even though there is no demand from the stat. Hence boiler keeps running, and heating the water. However as you have said the boiler does switch off it seems to be working as it should....

 

[Beagle1]

Thanks for the explanation.

 

[doitall]

There is a click and the stat is firmly attached one third up.

The cylinder is upstairs in a bedroom and the system is gravity fed. The central heating can come on independently of the hot water, but the bathroom radiator comes on with the hot water. The boiler is a Potterton Prima F.

The system is an fully pumped S plan, not gravity

 

[Space cat]

There is an immersion heater in there.

Are you sure it's off?

Maybe the switch is faulty. Or maybe the light (if any) is faulty so you think it's off when it isn't. In all probability it's nothing to do with the heater but it pays to eliminate the obvious.