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Jerry, HVAC Technician
Category: HVAC
Satisfied Customers: 422
Experience:  Epa universal certification, hearth products specialized.
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There, I have a st9400c honeywell controller, and it is

Customer Question

Hi there, I have a st9400c honeywell controller, and it is not communicating with the boiler so when I put the heating on the boiler is not turning on
Submitted: 2 years ago.
Category: HVAC
Expert:  Plumberpro replied 2 years ago.
Hi it could be a motorised valve fault. Do you have motorised valves on your system . Google honeywell motorised valve images to see what they look like. They are normally situated by the hit water tank , if you have one
Customer: replied 2 years ago.
Hi, no motorised valves on the system. When the heating is turned on the controller, the boiler does not even start burning. I had the boiler serviced but this fault meant they could not check the heating. Hot water works fine, just the heating. the boiler is an ideal logic combi 24 if that helps.
Expert:  Plumberpro replied 2 years ago.
Hi, it may not be a programmer issue but a boiler fault. With a multi meter check for voltage in the boiler wiring centre at the switched live connection. If you dont have a multi meter put a link wire between both connectors labled room stat. If the heating runs ok , its a programmer issue, if the boiler doesnt run its a boiler fault. The boiler hit water can work when the heating side has a fault,ie diverter valve motor or heating thermistor