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Honeywell ST6400C programmer doesn't switch off

Although at night we move the Heating and Hot Water sliders to Off and the red indicator lamp goes out, we find the radiators are hot in the early morning although the red indicator light is not showing.

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Re: Honeywell ST6400C programmer doesn't switch off

Since you have three on/off timing modes could there be an overlap in the times?
The wires in the unit might be crossed. (don't always assume the contractor who wired maintained the correct colors , I have a friend who blew out a heating pipe because when a replacement motor valve was installed it was never wired right and the plumber assumed the colors were correct so no overtemp shutoff created steam in PVC pipes, OPPS)
There fore maybe one is still coming on. Do you have more than one heating zone? IF so see below

I guess the main question is why manually turn it off? why not use the program.

I will assume your heat is know as forced hot water heating. My house is multizoned however when the zone calling for heat turns off (zone valve closes) I installed a bypass valve in the lowest zone in the house, and reduced the circulator low shut off temp to 130 F which means even though the heat isn't on my circulator will continue to run dumping this excess heat in the lowest part of house to rise through house. (the spring loaded water valve allows the heated water to flow into this zone )We do have two thermistats. And even though the lowest one is not calling for heat the radiators are hot when the excess is dumped into this zone. So investigate and see if your system might be similar. (multizone).

Investigate your wiring, reprogram, replace any battery backup.

Posted on Dec 19, 2007

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