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I want to do something that sounds really simple but cannot get a solid answer. I'm looking to set it and forget it. SW Pennsylvania sometimes one needs heat and cool the same day. I have a dog living in the house that likes normal temps. Here's what I want to do...

Set the thermostat at 70 degrees. When the temp reaches 68 - it heats to 70 When the temp reached 72- it cools to 70

Without the need to manually switch between heat and cool on the T stat. Is this possible? Will the heat and cool cycles constantly work against each other given my scenario?

Forced air gas furnace, High efficiency cooling.

Thanks for any help. Charles

isherwood
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notelano
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    Many thermostats have a heat or cool setting to keep the system from heating then 30 minutes later going into cooling. A thermostat that can be set to auto and a dead band, span or range programmed in is what you are looking for +2-2 is fairly tight control and may increase your power consumption but should do what you are asking for. Product recommendations are off topic but full auto with a programmable dead band or span is what you want. – Ed Beal Mar 15 '21 at 13:35
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    I'm surprised you have having a difficult time finding what you need, it's fairly common for a tstat to do both, you just set it to "auto". While product recommendations are frowned upon here in answers, I"m posting this as a comment. Here a a tstat that will meet your need with the added benefit of WIFI. I have one for my cabin and it's nice to be able to turn up the heat before we go there so it's warm when we arrive. https://www.honeywellhome.com/us/en/products/air/thermostats/wifi-thermostats/wi-fi-7-day-programmable-touchscreen-thermostat-rth8580wf1007-w1/ – George Anderson Mar 15 '21 at 14:27
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    Two separate "dumb" thermostats (one for heat, one for cool) would be the easy solution. I'll agree to disagree with George about WiFi being a "benefit" in a thermostat. – Ecnerwal Mar 15 '21 at 14:38
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    Yes, "Auto" is the feature you want. I have a non-wifi tstat sitting on the box waiting to get donated, so it shouldn't be that hard to find. – Duston Mar 15 '21 at 15:53
  • Your energy bills (and carbon footprint) must be enormous. It's going to be nearly constantly running to accomplish what you describe. Given temperature buffers built into any system, it's also nearly impossible to configure without having both systems running simultaneously, or some gap in between. – isherwood Apr 25 '22 at 14:00
  • @isherwood if DIYing such a system for comfort, rather than lab (sensitive equipment) use, I'd look at building in a time delay such that it can't cool within say 1 hour of the heat going off, and vice versa. There could be an exception for greater than say 5° out of band in case of rapid changes in uncontrolled heat sources – Chris H Apr 26 '22 at 12:12

2 Answers2

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These are very common, any thermostat that you can find that offers and "Auto" mode should be able to cool and heat based on what's needed without any action from your part.

However, the way you described the functionality is a bit different than what the thermostat will do. The auto feature will run a HEAT program along with a COOL program but they cannot be set to the same temperature otherwise the system will go crazy. For example, you could set the HEAT temperature to 70 and the COOL temperature to 74. Then as soon as the indoor temps goes to low 70 it would trigger the HEAT and stay around 70 until outdoor conditions are warming the house. At that point it will not activate again until the COOL set temperature is reached and will then keep it at 74.

You have to accept some variation in indoor temperature otherwise you system will just switch from HEAT to COOL all the time and you will be paying to cool down the heat that you also paid to bring into the house.

jmbouffard
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The term you're looking for is "Auto Changeover"

If the feature simply says "Auto" you're likely looking at a mode for the fan.

Auto Changeover

Changeover refers to the thermostat being switched from heat to cool as the air crosses a certain temperature. Auto changeover thermostats switch from heat to cool automatically while manual changeover thermostats must be changed by hand.

totalairep.com

System Changeover

Note: Thermostat can automatically control both heating and cooling to maintain the desired indoor temperature. To be able to select “automatic” system mode on thermostat home screen, turn this feature ON. Turn OFF if you want to control heating or cooling manually.

RTH5160D1003 Quick Installation Guide p9

Knowing the right term can save a lot of time and money.

candied_orange
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