My System I believe is convetional and comprises of:
Boiler - Potterton Suprima
Programmer - Potterton EP2002
Valve - Potterton MPE322
Pump - MYSON Compact CP3
Thermostat - Drayton Digistat +3
The problem is that when heating is called for the boiler and pump cut in for 5 mins and then both cut out for 5 mins even though the radiators are only luke warm, this cycle appears to repeat all the time the thermostat is calling for heating. While the pump and boiler are running the heating LED on the valve turns from slight glow to bright but as soon as the bioler cuts out the pump stops and the valve LED returns to slight glow.
I have a similar problem, but my system is an (old) Potterton Netaheat boiler running hot water and radiators.
The thermostat is calling for heat but the radiators are lukewarm. The pump is running continually and the boiler fires up but runs for only a short time. Then the flame shuts off but the fan continues to run.
The radiators are all bled and working fine. The pump seems OK and is quite new.
It's an intermittent fault. Sometimes it runs OK. I wonder if it could be the boiler thermostat misreading the circulating water temperature?
The Potterton Suprima has a history of faulty PCBs on boilers around 4 years old which was hightlighted on the watchdog program. It would be worth having an engineer check it over and have the fault identified. The pcb is the worse case senario as they are quite expensive.
Is the water actually circulating? Its more likely that it isn't and that the boiler stat is working perfectly well and is shutting down the boiler when it reaches the required temperature which it will if the water isn't circulating.
Look for a blockage - where the feed from the F&E tank joins the primary is favourite.
No the the water is not circulating but that is because both the pump has stopped and the valve has shut even though the heating system is on and the thermostat is calling for heating. When I first noticed the problem I just thought it was just the boiler shutting down on the overheat stat.
At the moment the downside of this problem is that the radiators take at least 40 mins to come up to temperature when the heating starts. After that even though the bioler cycles the heating works well enough.
My question was is it circulating BEFORE the boiler shuts down and the pump stops?
Thats the point. If there is no circulation (when the pump is running) then sooner orlater the boiler stat will shut the boiler down and if there is no overrun circuit the pump will stop at that time as well.
When the signal from the programmer and thermostat is sent to the boiler the pump is signalled to run and will only shut down when the programmer times to the off period and heat in the boiler is dissapated.
"When the signal from the programmer and thermostat is sent to the boiler the pump is signalled to run and will only shut down when the programmer times to the off period and heat in the boiler is dissapated."
this same thing happened to me and i found out the answer of how to fix it. not sure if this is a current thread though so wont write it all now. if it is let me know and ill give you the details.[/quote]
Would appreciate knowing how you fixed this particular problem, I am having the same issue with my 'very old' central heating system and would like to be able to find a resolution to the problem.