timer on gas furnace?

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  #1  
Old 02-01-03, 02:39 PM
buzzojoe
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Question timer on gas furnace?

I recently put a Bryant residential type furnace in my metal building for heat.
It's a Natural Gas, pilot light style furnace and it works perfectly well to heat the building.
I only want to heat the building a few days a week, and don't care how cold it gets in between times.
I tried a programmable thermostat, but it only goes down to 45 Degrees. I noticed that when I shut off the 110V power to the furnace the gas valve shuts off and the furnace goes back to pilot on only.
What would happen if I used a 7 day timer to switch the furnace on and off and left the pilot light lit?
I would run an independent "always live" circuit to the blower so that if the timer shut off while the furnace was still warm the blower would finish it's cycle normally.
Is there anything wrong with doing this?
It would be great to have the building warm up early in the morning on the days that I want instead of having to let it run all the time.
Thanks in advance for any input!
 
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Old 02-01-03, 03:18 PM
hvac4u's Avatar
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go for it

a time clock with a programmable tstat would do just as you need
 
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Old 02-02-03, 09:19 AM
bigjohn
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The only thing I would like to add is have the timeclock switch open the W leg between the furnace and the thermostat. That way you don't have to worry about concocting a special circuit for the blower motor. In the event the furnace is running when the timeclock shuts the heat off, the blower will operate normally as though the thermostat had shut down the furnace.
 
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Old 02-02-03, 09:51 AM
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Exclamation I too would like to add some cautions.

buzzojoe:

I too had heated a building intermittantly with an LPG residential furnace.

One problem I encountered was that because the building would get to sub-zero temps, I found the gas valve would get sluggish upon opening and would start with a pretty good flame rollout.
I placed a 40 watt lamp on the bottom of the furnace, under the valve and eliminated the problem.
I'm not sure if the valve was just worn out or the temp was lower than it's design.

Also, the W terminal connected to a time clock is a good idea.
You have to use caution when you purchase the clock, that if it's 120 volt, you make sure you have a set of isolated contacts or use an additional high voltage relay.
 
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