Hot Water Too Hot

[dwbailey]

Hi Everyone,

I hope someone can help. I have a fairly new central heating system (about 1 1/2 years old) which I have never quite managed to get the hot water right on it.

It's currently coming out scalding hot, I've tried lowering my tank thermostat (it's now down to 45ish) and as far as I can tell the thermostat is functioning correctly (I've run the boiler and sat up by the tank and can shut the boiler off or on by lowering or raising the thermostat).

My common sense tells me that if I reduce the thermostat on the boiler itself then it shouldn't heat the water up so much. Would this be a correct assumption? I don't want to mess around with it too much if I don't need to. I have dropped it down a fraction but it doesn't seem to have made a lot of difference.

Any ideas or suggestions are gratefully received.

Cheers

Dan

 

[lagunaglen]

Is there an immersion heater fitted to the cylinder, and if there is,is it on all the time?
An immersion heater should just be used as back up on your sysem.

 

[D_Hailsham]

It's currently coming out scalding hot, I've tried lowering my tank thermostat (it's now down to 45ish) and as far as I can tell the thermostat is functioning correctly (I've run the boiler and sat up by the tank and can shut the boiler off or on by lowering or raising the thermostat).

Probably a motorized valve is letting water by. How many MVs do you have?
They look like this
View media item 800 or View media item 801
The MV should have a lever on the side marked Man and Auto. Make sure it is not stuck at the Man side. There may be a notch which the lever drops into to hold it in Man. If so. release the lever so it moves back to the auto end.

 

[dwbailey]

I do have an imersion heater as backup and it's definately not on.

I don't know about the valves, I will go and check in a bit and come back and let you know.

Thanks for the advice

 

[dwbailey]

Hi there,

I checked and I've got one MV which although is unmarked as to manual and auto seemed to be on the auto side (assuming that manual side is the one with the locking part for the lever). The MV is a Drayton MA1.

What I have just found on what I think are the hot water pipes is another thermostat (a Drayton PTS 1) which is attached to the pipes. This is currently set at 70 degrees. Would this possibly be the cause of my very hot water?

 

[steved101]

it is a possibility, where exactly is this other thermostat? who installed this - it makes no sense! this thermostat should not be there if you also have a cylinder stat!

 

[dwbailey]

it is a possibility, where exactly is this other thermostat? who installed this - it makes no sense! this thermostat should not be there if you also have a cylinder stat!

It was installed by a fairly reputable local company, unfortunately they're so busy that they are quite often hard to get hold of. What I forgot to mention (and also after checking out the model number of the second stat this is probably relevant) is that the boiler is outside housed in a small shed next to the house. From what I can tell, the thermostat might be in someway installed for some kind of frost protection. Would that make sense?

The thermostat is located on top of what I think is the main feed for the hot water after if comes out of the valve from the boiler and before it feeds into the house and up to the tank.

 

[D_Hailsham]

What I have just found on what I think are the hot water pipes is another thermostat (a Drayton PTS 1) which is attached to the pipes. This is currently set at 70 degrees.
What I forgot to mention is that the boiler is outside housed in a small shed next to the house. From what I can tell, the thermostat might be in someway installed for some kind of frost protection. Would that make sense?
The [PTS1] thermostat is located on top of what I think is the main feed for the hot water after if comes out of the valve from the boiler and before it feeds into the house and up to the tank.

If it is used for frost protection it will not be set to 70°C; 20-25°C would be more like it!

If the PTS1 is connected to the return pipe to the boiler, it is probably being used for frost protection. It is usually used in conjunction with a Drayton RTS3 Air Frost Thermostat. You can read about them Here

If it is on the flow pipe from the boiler, you need to find what it is wired up to control.

The Drayton MA1 valve is a mid-position valve. When you have HW only on the valve is not operational. It only comes into play when CH is called for. Water enters up the T and goes out the A port for CH and out the B port for HW. When out of circuit, a spring closes the exit via port A, so only the B port (HW) is open. Now the valve may have got stuck in the mid-position, so both A and B ports are open. The easy way to check this is to turn the electricity off to the system (this allows the valve to reset) then move the valve lever across to the catch. You should feel pressure as the valve is open against the spring. If you do not feel any pressure the valve is stuck. A tap or two with a blunt instrument may persuade it to free up.

If that does not work, remove the actuator (box on top which unclips) to expose the valve shaft. this can then be carefully turned with pliers etc to see if it is free. It will only turn through a few degrees.