Thermostat on water tank not working

[Supernatural323]

Good evening all,

I have a problem with my water tank. It does not switch off when it gets to the desired temperature, therfore I thought the thermostat was faulty. I got my friend to change it and it is still the same. So when I heated the water today I took the thermostat away from the tank and noticed the tank was cold. The theromstat is located at the corect position from the drawing of the thermostat instruction 1/3 from bottom. It is an old tank I imagine.

Can anyone enlighten me please?

Regards

John

 

[seco services]

Can't see how the cylinder can be cold if you have heated the water to 60c +.
How did you heat the water from the boiler or immersion heater ?
The stat is sitting on the copper cylinder and not the foam lagging ?

 

[Supernatural323]

The stat sit's on the cylinder. The water temperature coming out of tap must be 50 +. The water is heated from the boiler.

 

[D_Hailsham]

The stat sit's on the cylinder. The water temperature coming out of tap must be 50 +. The water is heated from the boiler.

Does the stat look something like this?

View media item 10596
Do you have any valves?

View media item 5946 View media item 11762

 

[Supernatural323]

Looks exactly the same, and yes I have the valves too.

 

[D_Hailsham]

Looks exactly the same, and yes I have the valves too.

How many valves do you have? One, as in the left pic (3 pipes connected), or two, as in the right pic (2 pipes connected to each)?

 

[Supernatural323]

I have 2.
One for the hot water and the other for the heating of the radiators.

 

[D_Hailsham]

I have 2.
One for the hot water and the other for the heating of the radiators.

Thought you might.

It sounds as if the HW valve is not working properly.

The valve has four wires: Brown (L) and Blue (N) are the motor connections; Orange and Grey are the auxiliary switch. The brown goes live when the HW stat is calling for heat. This runs the motor, opening the valve and closing the auxiliary switch. The grey wire is connected to a permanent Live supply and the Orange to the boiler's ON terminal. So when the switch closes, mains is sent to the boiler ON terminal.

You need to check:

1. When the HW stat is turned down: Brown has no volts; grey has 240V and orange has 0V.

2. When the HW stat is turned UP: Brown, Grey and Orange all have 240V.

 

[Supernatural323]

Think there is a misunderstanding. My water is heating up, but the copper tank does not feel hot 1/3 from bottom. Top of tank is hot. I was thinking I have an old tank or something and the water on heats top half of tank.

To re-confirm I have got hot water, it just doesn't switch off with thermostat due to the tank surface not warming up.

 

[Agile]

You may not be leaving it on for long enough!

What height is the top heating coil connection?

What height above this is tank hot?

What are the approximate temperatures of the pipes to the heating coil?

Why have you set the boiler flow temperature to the value its at?

Tony

 

[Supernatural323]

The heating coil connection is at the top of the tank.
The whole tank is insulated with some sort of foam. The only areas of tank I can touch is on the top and 2/3 of the way down when the thermostat is removed. Dont know temperatures of pipes, too hot to handle anyway.

Boiler flow temperature?

 

[Space cat]

This might be a stupid question but --

Is hot water constantly running away somewhere you don't know about? If it is, your cold tank will be forever filling to make up the loss.

 

[Supernatural323]

no

 

[D_Hailsham]

The heating coil connection is at the top of the tank.

Most HW cylinders have one connection at the bottom and the other about halfway up.

Can you post a pic of the HW cylinder?


PS sorry about the confusion, but you originally said

It does not switch off when it gets to the desired temperature

This can be caused by a faulty thermostat or by a faulty valve.