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We have a heat pump with electric furnace as the auxiliary heat source.

It's not extremely cold yet and the heat pump can get us to the correct temperature (without implementing auxiliary heat source) which means we will save money, but it does take a bit longer in the morning to get back up to proper temp.

At night we turn it down to 65, but during the day I would like it to get us back up to 68 (all degrees in Fahrenheit).

The Problem If I set the thermostat to go to 68 in the morning after it was set to 65 all night then the auxiliary heat kicks on immediately.

However, if I manually turn the temperature up 1 degree each time the heat pump kicks off then I can get it up to 68 without ever using auxiliary (more expensive) heat.

Why doesn't my thermostat do that for me?

Is this "slow movement to final temperature using only heat pump" a setting on my thermostat I don't know about?

Other Thermostat?

Do I need to purchase another thermostat to do this (for energy savings) or is this feature that I'm thinking of, just not a thing?

Here's a snapshot of the Honeywell thermostat that I have:

honeywell thermostat

Here are the only instructions I have for it:

honeywell thermostat instructions

Update - Wiring

I took the thermostat off the wall to examine the wiring underneath. I'm wondering if I have everything required to support this idea of a slow movement to set-point (without kicking on the auxiliary heat) if I install a new thermostat.

current Honeywell wiring

Would a Honeywell RTH2300B Work & Give Me Additional Options?

Here's a link to the manual.

Here's some hookup info from the manual. RTH2300B wire hookup diagram

However, I don't see that it states explicitly that the warm-up to temp functionality is definitely there. How can I determine if this thermostat has that functionality?

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    I have the same thermostat and it's dumb. The furnace doesn't know the temp or the thermostat settings. The thermostat just says "i need heat" or "i'm warm enough".
    – dandavis
    Nov 3, 2023 at 19:19
  • @dandavis yeah, I believe it is the thermostat causing the problem. It looks like there is supposed to be a threshold setting for temp difference so that auxiliary heat doesn't turn on unless the inside temp is at least X degrees different from the target set temp.
    – raddevus
    Nov 3, 2023 at 19:44
  • are you sure there's sperate wires broken out for that to the furnace? Mine only has one wire to control heat. There maybe be different versions that look the same, but if not, i'm pretty sure it has nothing to do with the thermostat.
    – dandavis
    Nov 3, 2023 at 19:52
  • I'm not sure about the wiring yet. I will be removing the thermostat to discover if that is true, but I was reading another question / answer here on Home Improvement SE that seems to indicate that it is the thermostat that would handle this: diy.stackexchange.com/questions/48956/…
    – raddevus
    Nov 3, 2023 at 19:58
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    Yes, that makes sense that ours doesn't work. Thanks for the discussion, you're helping me work thru this. I'm looking to get a new thermostat to resolve the situation, but I'm just trying to understand what I need to be looking for so I'm prepared to buy the proper thermostat.
    – raddevus
    Nov 3, 2023 at 20:02

1 Answer 1

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I discovered that the thermostat I was looking at RTH2300B does not support a heat pump with multistage (heat pump and auxiliary heat).

I found a doc on honeywell site that states:

does not work with backup heat

Once I got the terminology I was looking fore I was able to search for thermostats. I needed to know if the thermostat did multistage and heat pump.

I finally found this model : Honeywell Home RTH6360D 24-Volt 5-2 Day Programmable Thermostat

which supports the functionality that I need:

Stated on Lowes web site:

Compatible with: forced air (gas, oil or electric), hot water and steam, and heat pumps with electric backup

We have forced air, heat pump with electric backup so this model should work.

Company Attempts to Be Opaque

It seems as if the company attempts to be opaque about what the thermostat supports and how to wire it up. I'm guessing that they want you to get a "professional" installation.

I finally found a installation manual on the web site, but that manual doesn't even mention the heat pump and backup heat. Oy!

Here's another really confusing graphic that helps you sort out if you can use this thermostat:

(note that it says Heat pump with auxiliary heat: YES

Then next to it: With more than 2 heat stages: NO

A bit confusing, but I'm guessing I have only 2 heat stage so I should be ok, since I won't have "more than" 2 heat stages.

confusing thermostat graphic

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