Central Heating Not Working, But Hot Water Is Working? Help and information on all topics relating to your central heating, air conditioning and ventilation issues.

[wokeye]

I have a pretty old heating system that I want to get replaced affter this winter, but would like to try and repair it if at all possible. The system is a Thorn EMI back boiler, hot water cylinder upstairs a header tank in the loft, and a 3 way honeywell motorised divertor valve. The water is working fine. However when I select heating the boiler starts but the I am getting no heating. I have looked at the way valve and pump which is located underneath the hot water cylinder. The valve is not opening at all when heating selected on the timer/programmer. The pump also does not seem to be running, as I thought I might have felt some vibration or something from it ? I replaced the syncron motor on the valve last year for a similar fault. Unfortunately it is an old motorised valve so I cannot replace the valve head without breaking the line, so a new valve will be required. Anybody any ideas, is it probably the valve? Just thought that I would be able to tell that the pump is running and I can't. I have tried a spare room thermostat and this has done nothing, although the boiler is running anyway. Thanks for any advice.

[Burnerman]

Pump probably doesn't run unless the valve has proved to be open in the correct position for heating, that's why you can't hear the pump running. Is the valve seized? May be worth giving it a hand, especially if it has a manual switch on it.

[ren]

Hi Wokeye,

Strangely enough, I am working on a similar problem in my home. I have an old Potterton Boiler and a Grundfos pump. The central heating works on the second floor of the house, but not on the ground floor. My research has revealed 2 things - If I turn the dial on the hot water cylinder to minimum and then max, and can hear the motorized Honeywell valve changing position, however, downstairs, at the boiler, I cannot hear the pump working. But then I dont know if the pump should make any noise. Further, I think I may be fooled into thinking the heating is working due to the natural rise of the hot water in our system, as the heating has to work with HW on. I am now thinking of draining the radiators as I suspect a blockage on the ground floor. Be great to see any replies you get, as it may help me to.

Cheers
Ren

[wokeye]

Hi thanks for the advice, I have fixed the problem in a manner. I shorted out the room stat on the wall. I linked out the red and yellow cables and now the pump, valve are operating correctly and I have heat :D So obviously I need a new wall stat. The current stat is an old Honeywell T6160B. It is wired Red to pin 1, Yellow to pin 4, Blue to pin 2. The thing is I would not mind trying a digital stat, but I am a bit of an idiot and do not know if it would be straight forward to wire up. Because I do not know what the 3 wires that I have do, and I do not know if a digital stat may require more wires. The easiest thing would be to get the same stat that I have as it would be cheaper, but a digital one may be more reliable. Anybody and ideas please??

[wokeye]

Hi thanks for the advice, I have fixed the problem in a manner. I shorted out the room stat on the wall. I linked out the red and yellow cables and now the pump, valve are operating correctly and I have heat :D So obviously I need a new wall stat. The current stat is an old Honeywell T6160B. It is wired Red to pin 1, Yellow to pin 4, Blue to pin 2. The thing is I would not mind trying a digital stat, but I am a bit of an idiot and do not know if it would be straight forward to wire up. Because I do not know what the 3 wires that I have do, and I do not know if a digital stat may require more wires. The easiest thing would be to get the same stat that I have as it would be cheaper, but a digital one may be more reliable. Anybody and ideas please??

[Steve the gas]

Ren hi,

Sounds suspiciously like sludge among a few other things. Check pump and drain a few downstairs to see what you get,then come back.

Hth

[ren]

Hi guys,

Managed to get all the radiators working now, by opening the Manual Restart screw on the Grundfos pump, and letting some air out. I then moved the speed switch between speeds, as I heard this may dislodge a blockage. Turned off all the upstairs radiators, and left one downstairs radiator on, nearest the pump and boiler. It got hot. I then opened up all the others. I now have a fully heated house. I still cant hear the pump though, but the thermostat does turn the heating down somehow.

Thanks very much for all the help.

/ren