RADIATORS ALWAYS ON PROBLEM

[gazza123]

Hi

I have a Honeywell ST699B 24-hour central heating controller with separate heating and hot water controls, and a three port valve system.

Unfortunately of late, I cant put the hot water on on its own........the radiators always come on as well. What is more, sometimes the radiators remain on even when I switch all the controls off. The radiators also sometimes get very hot even when the thermostat has been set at a moderate level.

Is this a problem with the Honeywell controller - I know they can be temperamental and its the second one we have had - or is it more likely to be a problem with the valve?

cheers

 

[D_Hailsham]

I cant put the hot water on on its own........the radiators always come on as well.

When HW only is selected the mid-position valve is not in action. The CH port is held closed by the spring in the valve. THe boiler gets its power directly from the HW cylinder thermostat.

If the rads are heating up when set to HW only the valve must be stuck in mid position. Try moving the lever on the side of the valve. It should be stiff to move as it is opening the CH port against the spring.

sometimes the radiators remain on even when I switch all the controls off.

Do you mean that the boiler is still running even when the HW and CH are OFF at the programmer? If so, the programmer must be faulty

The radiators also sometimes get very hot even when the thermostat has been set at a moderate level.

This suggest that the valve is not closing the CH port when the thermostat reaches the set temperature.

Turn the HW OFF and CH ON. Turn the CH thermostat down and check the lever on the valve as above. It should be stiff as you open the CH post. If there is any slack the valve is stuck in mid position. Try exercising the lever to free the valve.

Turn the CH thermostat right up and listen to the valve. You should hear the motor and the lever should be free all the way across.

 

[gazza123]

the lever on the head moves freely from side to side - there is no resistance at all.

re the boiler staying on................i switched off the controls last night but the radiators were still hot 45 minutes later

 

[D_Hailsham]

the lever on the head moves freely from side to side - there is no resistance at all.

Not even when CH and HW are turned off? Could be a broken spring.
Can you hear the valve working if you turn the room stat from low to high (two man job!!)

re the boiler staying on................i switched off the controls last night but the radiators were still hot 45 minutes later

Could just be taking a long time too cool down in the warm weather. Was the boiler and pump still working?

Which boiler do you have (Make and exact Model please)?
Which 3 way valve do you have?

 

[gazza123]

thanks for your replies

yes it probably is the warmer weather........the boiler is not working after switch off but the radiators are taking longer to cool.

re the hot water/central heating coming on at the same time......i think its all pointing to the three point valve diverter.......its a honeywell y plan type.

im on my own at mo so cant check the moving parts but have taken the cover off the y plan and the lever appears loose around the central rod and doesnt appear to be able to move or alter anything. springs appear intact so im not sure if its not all jammed and probably means a replacement.

 

[D_Hailsham]

the boiler is not working after switch off but the radiators are taking longer to cool.

If the valve is not working and the CH circuit is always open the rads will be getting hot all the time!

the lever appears loose around the central rod and doesnt appear to be able to move or alter anything. springs appear intact so im not sure if its not all jammed and probably means a replacement.

If you valve is the Honeywell V4073A1039, you can buy the actuator (box on the top with the motor etc) separately. If you have this valve, remove the actuator so the shaft of the valve is exposed then try turning this with a pair of pliers. It has a movement of about 10 degrees. If it can move easily, the actuator is u/s; though it could just be the motor in the actuator, which is available separately.

This is where you need a second person, though you may be able to check by leaving the actuator off, turning the wall stat up and then going back to see if the motor is working. (The motor runs all the time when the wall stat is calling for heat; this is one of the reasons why mid position valves tend to fail.)