Gas central Heating

[graham14]

I have a fault on my heating system, hot water ok, radiators not getting hot,
Pump is working, thermostat appears to click when turned up, I suspect the motorised valve. What checks can I make.[/i][/b]

 

[breezer]

this

 

[ChrisR]

OPen the valve manually - with the lever until it stays on its hook, and make the hw come on. If the rads now get hot yes it's the valve , probably just its motor.

 

[graham14]

Thanks ChrisR did what u said and hey presto the rads got hot, they have now gone off, after about half an hour, turning the thermostat up does not fire up the boiler, It seems to click at about 14 although I have it at 20+ now as it is cold today.
Both the HW and CH are on.
I don't understand why the rads went cold, Although they are on hot again. and should stay hot untill, the thermo is turned down, the way we controlled the heat in the house before.

Should I be able to buy a motor for the M/valve or do I have to replace the whole unit.

Just checked the motorised lever is still hooked up ok.
System info:
Glow-worm Space-saver boiler
Potterton EP2000 controller
Grundfos pump
Honeywell motorised valve

Thanks again for your knowledge.

 

[ChrisR]

I don't understand why the rads went cold,

Because the HW cylinder was up to temperature and the boiler turned off!!! Turn the boiler thermostat down, the HW cylinder thermostat up. The boiler will stay on to heat up the HW but fail to reach the temp because of wot I just rote, and you'll have warm rads. Room stat will do nothing.

Should I be able to buy a motor for the M/valve or do I have to replace the whole unit.

You can get a replacement motor eg in Wickes for £12 or so. A bit fiddly but OK if access is easy. If not take the head off the valve first (2 screws).

 

[graham14]

Just turned the boiler thermo to min
turned the honeywell cylinder thermo up from 50 to 60 rush of water and the pump kicked in m/valve still latched on hook.

Rads are getting warm again.

Thanks still need to understand what I am doing and how the m/valve functions.

 

[ChrisR]

Simplified a bit:Valve at rest is in HW position. So Boiler is turned on by HW Thermostat. For CH , valve should move open then a switch inside turns boiler on. Your valve isn't moving cos motor is dead. Moving manually does not operate switch to turn boiler on but DOES open valve to heat HW and CH. Then call for heat has to be coming from HW stat for boiler to be on.

If you move the lever from Auto to Man very fast, you'll hear the clockwork run on to the position where the switch is operated and the boiler comes on, but it springs back so the boiler doesn't stay on.

Clear as mud?

 

[graham14]

Thanks ChrisR

Did what u said last night heating is staying on now.
It is a bit clearer also. Will replace valve top tomorow, and let u know outcome.

Can u suggest a Central heating Book that I can buy for future ref incase u not on the net. Thanks