Honeywell ST6400C Programmer All aspects of plumbing questions and answers, help, tips and information

[margy]

On a fully pumped system, my boiler is running but there is no HW/CH. Someone said it could be the programmer not working and therefore not calling for CH/HW. My programmer is a Honeywell ST6400C. The CH/HW lights are on & I have it on 'continual' but nothing happens. Is there any way of testing the programmer to see if that is the problem?

[Dave From Leeds]

If the CH & HW lights are on it is likely that the programmer is working. From what you have said about the system being fully pumped but no hot water or central heating even though the boiler is running, my bet is on the pump either not working or being airlocked.

To answer your question about whether it is possible to test the programmer, if you have the installation / operation leaflet for the programmer that includes wiring diagram(s) and an electrical tester it is possible, but only if you know exactly what you are doing. Probably best left to an electrician.

[Dave From Leeds]

Another thought. You say your boiler is running. Is the burner firing up? If so, with no heat coming out of the boiler to the central heating or hot water systems, it should shut down on it's overheat thermostat. Does the boiler have a pilot light? If so is it lit?

[plumbersw15@talktalk.net]

[quote="margy"]On a fully pumped system, my boiler is running but there is no HW/CH. Someone said it could be the programmer not working and therefore not calling for CH/HW. My programmer is a Honeywell ST6400C. The CH/HW lights are on & I have it on 'continual' but nothing happens. Is there any way of testing the programmer to see if that is the problem?[/quote]

what makes the boilr run? turn the room stat down low to see if it turns the boiler off. then turn it up high see if boiler fires up. when it does work your programmer onn/off. then u know controls are ok. prob then into pump valves f& e on old systems ..