Thermostat question


A couple of years ago the furnace was replaced and a new thermostat installed. The new thermostat is identical to the old one. The temperature never reaches the setpoint. Currently the temperature reaches about 70 degrees with the setting at 73. Also the new furnace seems to cycle on and off more frequently than the old one. The new one is a much higher efficiency. Should I try a new thermostat or reinstall the old one? Or just accept the bias? The old one had a wider "span" setting.
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If you're getting the room temperature reading off of the thermostat, and not a remote thermometer, I'd say you have a bad unit. I'd try the old one

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Ronald' wrote:

Depending on the thermostat, you may be able to adjust those factors. Do you have the manual that came with the thermostat? If not try the manufacturer's web site and see if they have a downloadable manual.
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Joseph Meehan

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If you have a Honeywell mercury thermostat, Make sure it is level. A slight "tilt" will change the settings.
---MIKE---

>> (44 15' N - Elevation 1580')
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On Feb 1, 8:36 am, snipped-for-privacy@webtv.net (---MIKE---) wrote:

Ever see a mercury thermostat with adaptive recovery?
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On Feb 1, 8:54 am, snipped-for-privacy@optonline.net wrote:

Ooops, wrong thread, my bad! But still, he said it was a new thermostat. They stopped selling mercury thermostats a long time ago.
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This is a mercury thermostat and was "new" with the installation of the furnace 2 years ago.
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I assume you spend more than fifty bucks for the new furnace? Why not spend another thirty bucks and get a thermostat using technology from this century? Why the eight dollar thermostat?
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It's the basic Honeywell round thermostat.
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The height of seventeenth century technology.
http://www.tecsoc.org/pubs/history/2002/nov7.htm
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Ronald' wrote:

I think I would opt for a more modern thermostat. However it is still possible to be a furnace problem. They will shut down if they sense an overheat situation in the furnance.
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Joseph Meehan

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Well, you learn something new everyday. I thought mercury thermostats had been totally phased out. But it looks like only some states have passed laws banning them and they can still be sold in other states. It amazes me that there isn't a FED ban on them by now, as mercury is a hazardous waste and this is an application where it can easily be replaced. Also kind of amazing that with a new furnace install, they wouldn't give you at least a cheap programmable.
So, I agree with Mike and would check that it's level, because if it is not, this is the problem that results.
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snipped-for-privacy@optonline.net wrote:

Yeah, but the OP might as well replace the existing thermostat with a programmable electronic one. Sensibly programmed, it will pay for itself in very short order. They're available at very low cost at many outlets including Walmart and Target. Just be sure to buy a unit suitable for your furnace/system.
This may solve all of his problems. If it doesn't, there may be a seperate issue causing the furnace to cycle and that will have to be investigated.
But there's a good chance a new thermostat will fix the problem and save money.
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It is also possible it is reaching the "set point" but not the indicated point. Some cheap thermostats never read quite right. What is the actual temperature from a real thermometer? Maybe it should be swapped out for a good programmable model.
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The actual temperature is exactly the same as indicated on the thermostat - measured with 2 different thermometers. The last I looked, this thermostat was commonly sold in stores. I called the outfit that installed the furnace. They now supply a different brand and type of thermostat. It seems that I will be crawling out of the dark ages.
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In that case, the indicator dial is probably off. Set it to 76 to reach 73. Problem solved.
Best bet is still a programmable if you want to save some heating money. In my house, they go up to 70 degrees first thing in the morning, then drop back to 68 for the rest of the day, then to 64 at night for comfortable sleeping. The heat comes on 15 minutes before I get out of bed. Works well.
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Programmable is the way to go. We had an old mercury t-stat when we bought our place and had problems getting the temperature set. It would usually get hotter than the preset temperature. The programmable we have now is dead nuts on. Very consistent. It's set for 68 when we're home and that's the reading we get on the t-stat unit in the hallway and on the thermometer in the living room. I love it. It pretty much paid for itself last year when natural gas prices were so high. Now we're looking at getting a new furnace this spring. Our current one is old (at least 20yrs.), but is very reliable. It's just not very efficient and I worry about the condition of the heat exchanger.
-Felder
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I bought a new one last year, Honeywell.
(---MIKE---) wrote:

Ooops, wrong thread, my bad! But still, he said it was a new thermostat. They stopped selling mercury thermostats a long time ago.
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Ronald,
You say that the temp never reaches the setpoint but you also say that the furnace is "cycling". What is causing the furnace to shut off before it reaches the setpoint? Remove the thermostat and jumper the heating wires. Does the furnace cycle or does it keep running. If the furnace shuts off call a furnace guy. If the furnace doesn't cycle then the problem is with the thermostat.
Dave M.
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