Problem with motorised valve??

[Graham22]

Hi,
My first posting although I have followed this excellent forum for a long time.
I have what I think is called an "open" system (Not a combi boiler).
The boiler is old but seems to work fine.
The radiators are on, but the only way I can get the radiator in the bathroom on (which is on the hot water system, so that it works in summer), is when I turn up the thermostat on the hot water tank, so that it calls for more hot water for the indirect heat coil in the tank. It then heats up the radiator perfectly, but later goes off again, I assume when the hot water tank has reached the new temperature.
Possibly a red herring, but last summer I drained the system to put in TRV's on radiators.

Is this likely to be a problem with my motorised valve? - It has three ports (I think, it looks exactly same as the one under item 10 in FAQ) and so if this is the problem, I assume I have to replace the whole valve and cant just change the electric motor on this one?

Many thanks

 

[Hugh Jaleak]

The rad in the bathroom wont work unless there is demand for the hot water. Once the cylinder has reached set temperature the valve will close to the cylinder circuit and thus bathroom rad. Nothing wrong with the motorised valve! If you want bathroom warm then the choices are either very hot water at the taps or replumb rad to CH circuit.

If you must have warm towels during summer months one option is to fit a towel rail in addition to the radiator. These can be heated with CH as normal when its on, and an electric element fitted for the summer months when CH isn't required.

 

[Graham22]

Thanks. So nothing wrong. If it aint broke, I wont fix it. Thanks for the help

 

[gaswizzard]

Or pipe the system correctly with flow to towel rail taken before motor valves , hot whenever HW/CH is called for.

 

[LetSearch]

One thing to try, is to turn the thermostat down on the boiler.

This will lower the temperature of the water coming from the boiler, thus making the heat transfer to the hot water a bit slower. Therefor, the bathroom rad will stay on just that bit longer.

Apart from that, you should turn the boiler stat down as low as you can tolerate anyway, in order to reduce your energy costs.

If you turn the boiler stat down, and the hot warer stat up, there is a point when the hot water stat is higher than the boiler stat and the radiator will always be on.

the big drawback, is that the rads may be too cool, as apart from being at a lower temperature, a significant flow of water from the pump will be going through the hot water calorifier, instead of going through the rads.

It's all a big balancing act. If you get it right, radiator may well be ok, the way it is piped.

 

[Graham22]

Thanks - this is all so very helpful. I have a much bettter understanding of what is going on now. Because the weather is cold, I had turned up the stat on just the boiler, which I now realise will have amplified the problem.
Many thanks