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Old 01-01-2012, 09:59 AM   #1
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oil furnace & programmable thermostat

To prevent the furnace from cycling on/off while we're away, I wondered about this idea: Can I install a programmable thermostat set at say, 70F, prgrammed to run for only two hours twice a day? I know the furnace will actually still be operating when the two hour heat on cycles are up. 1) Will the thermostat just shut off the burner, or will it stop the fan blower as well? 2) Will the furnace simply reset and start again normally the next time the thermostat two hour cycle starts 12 hours later? 3) If fan shuts off when the thermostst shuts off, should I be concerned about all that heat in the combustion chamber? Any advice will be much appreciated. Thanks.


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Old 01-01-2012, 10:19 AM   #2
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if you just have a generic stat non-programmable...just set it down to the lowest setting and the furnace wil maintain that 24/7....50F like on a round Honeywell T87 with a mercury bulb.on that fan cycle the fan is the last thing to come on when the stat calls and the last thing to go off after the stat is satisfied...and all is within the furnace the stat only controls the heat call the fan is controlled by the heat exchanger temperatures say on at 130F off at 80F.if you have a control board within the furnace then your working a fan delay(black relay cube on board) on a call for heat...if a new stat is digital you really don't/can't shut the heat unless you put the system in OFF at the stat ..it will maintain the modes of wake/leave/return/sleep with any settings from 50F to 90F if you set all the mode temps the same value it becomes a non-programmed stat seeing a constant setpoint thru the day...if you had return at 70F and sleep at 55F the furnace would shut down at sleep time but look at 55F..then if wake is 70F it would "anticipate"(what the room is and what the stat is set for)that at 6AM you want it 70F and slowly cycle the heating to be at that temp at that time...


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Old 01-01-2012, 11:40 AM   #3
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Just install a programmable thermostat to set the temp low while your away.
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