Furnace/thermostat question

3 times in the past month I have noticed my house seems a little cool. I check the thermostat and it is set for 73 but the temp is 70. The thermostat says "Heat on" but the furnace is not on. If I just switch the thermostat off then back on the heat comes on and the house warms up. I have a Honeywell electronic thermostat. Is this a termostat problem or a furnace problem? Once I just took the thermostat off the wall (it sort of unplugs so you can change the batteries in the back.) and plugged it back in and the heat came on. I have seen igniters fail before but from what I can remember once it fails the furnace won't come on at all. Any ideas on this?
Andy Arhelger
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Can't see it from here(eyes squinting as I look), but this may be because of the batteries going bad.
Replace the batteries and if it still does it, call a tech.....

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Yeah, I forgot that. Mine needs batteries to work. And, turn the thing off (even for a second or two) may just enough rest to let the batteries do their job if low.
HeatMan wrote:

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There might be an anticipator circuit that you can play with. There is in my Chromlux 3. Your going to need a manual for your tstat and a real good understanding of your furnace. Might be worth a call to the local HVAC tech.
I doubt that the batteries have anything to do with it, but they are cheap to do if you do not remember when you last changed them.
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It seems that when you interupt the circuit temporarily by pulling the thermostat or turning it off, the furnace goes on. My first thought is that the mechanical jolt you're giving the thermostat is temporarily tightening a loose wire somewhere in the general area. Have you checked all your connections, upstairs and down, to make sure they're tight and uncorroded? Or maybe the contact points in the thermostat which complete the circuit are dirty or impeded by dust and need a slight jolt to make full contact.
The second thought is that restarting the current flow causes an electrical spike which is enough to trip a faulty relay.
Paul
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My Honeywell electronic thermostat always reads the same or at most 1 degree lower than the setting, which means that the thremostat regulates the temperature at the thermostat within one degree. The only time it ever reads more than one degree difference is if I manually turn it up and the time it takes for the furnace to come on depends on the amount you turn it up. It may wait 2-3 minutes for a 1 degree change but a 4 degree change is immediate, so if I want it on and it doesn't come on immediately with 1 degree increase I boost it up 5 degrees, it comes on, and then I lower it to where I want it.
I think it's your thermostat, if it normally is within one degree.
Andy Arhelger wrote:

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Sometimes when it is really cold my thermostat reads 18 or 19c when it is set at 21. Perhaps you have been experiencing cold weather and your system isn't keeping up? 19 is okay with me considering it is -25 to -30c outside.
Or maybe your thermostat is on a cold wall?

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I seem to recall a thread like this in the past where the OP had the same problem and ended up changing the batteries even though the indicator to do so was not lit, try that to see if it works, other than that, I'm just a spectator so keep up with the thread. nataS
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