HVAC Heat Pump Question

[davans]

I’ve had a few dual fuel heat pumps with gas as the emergency heat source.
I Replaced the all electric Heat Pump in our current home last year and stayed with all electric, with the strips for back up heat and believe I have an issue.

It will not transfer over to emergency heat unless you bump the thermostat 2 degrees up.
even when in the 20’s, like today, it just runs on regular heat. It will run for well over an hour at times maintaining temp but does not cycle much.

In my pervious home, there was a predetermind temperature, I believe it was 34 degrees, that when outside temps dropped below it ran on emergency heat only until outside temp rose above 34 degrees.

has technology changed recently or is there an issue with an ancient temp sensor?

 

[fast306stang]

Heat pumps aren't efficient below a certain temp. I am surprised at 20 degree temps that it didn't turn on emergency heat. That being said, if it's maintaining temps in the house, why would you want it to kick on the emergency heat? The heat strips will run your power bill up higher than the heat pump...

edit: now that I think about it, mine won't turn on emergency heat unless I bump up the thermostat a few degrees above the house temperature. I think my old house was the same way.

 

[Bass Akwards]

Hot goes to cold, heat pumps or any AC is moving heat from one place to another.

 

[davans]

Heat pumps aren't efficient below a certain temp. I am surprised at 20 degree temps that it didn't turn on emergency heat. That being said, if it's maintaining temps in the house, why would you want it to kick on the emergency heat? The heat strips will run your power bill up higher than the heat pump...

edit: now that I think about it, mine won't turn on emergency heat unless I bump up the thermostat a few degrees above the house temperature. I think my old house was the same way.

Mine runs excessively when it’s this cold, nearly non stop. I can’t imaging that, that is being efficient. Also compared to my previous homes. Emergency heat was controlled by outside temps. Perhaps technology has progressed with heat pumps and they are more efficient at lower temps. Just seems like something is wrong.

 

[fast306stang]

Mine runs excessively when it’s this cold, nearly non stop. I can’t imaging that, that is being efficient. Also compared to my previous homes. Emergency heat was controlled by outside temps. Perhaps technology has progressed with heat pumps and they are more efficient at lower temps. Just seems like something is wrong.

Curious what others say when they chime in. It's been so long since I worked in HVAC that I'm starting to forget things...

 

[Bass Akwards]

Is your system properly designed for your house? Seems like it is working, just cant keep up when its real cold. Also the tighter a house is, insulation wise and air leaks the better any system runs. Once you start hunting where possible air leaks (Open windows, door gaps etc) and you will find some, you will be surprised how many you find the more efficient your system will run.

 

[davans]

Is your system properly designed for your house? Seems like it is working, just cant keep up when its real cold. Also the tighter a house is, insulation wise and air leaks the better any system runs. Once you start hunting where possible air leaks (Open windows, door gaps etc) and you will find some, you will be surprised how many you find the more efficient your system will run.

The system is pared correctly for the house and the house is reasonably solid as far as insulation and seals go. It has something to do with what ever triggers Emergency Heat. Which I believe is driven by ambient, outside temps.

 

[JBWJr]

 

[MegaFan]

At 26 degrees outside early this morning, all three of my heat pumps were still putting out 90+ degree warm air. One unit (12 SEER) is 12 years old, the second one is also 12 years old (12 SEER) that had a new A coil (evaporator coil) installed in 2016, and the third unit (16+ SEER) is less than 2 years old, All three units still cycle but the new unit (16+ SEER) runs more than the older ones. However, on a positive note, it seems like the new unit can run all day with no meaningful impact on the electricity bill. For my 37 year old, 6,000 sq. ft. house, keeping the thermostats on 71 during the day and 68 at night, I am running at a $6.70 average daily cost in my current bill (not too bad, in my opinion). The only time the heat strips kick on are when I bump the t-stat up more than 3 degrees, which is a user-configurable setting in the programmable thermostats, and rarely, if ever, happens. Some units have heat pump lockouts based on the sensed outside temperature but that idea was "old school" thinking, especially with the newer, higher efficiency units.

 

[Dice]

if the house drops below 3 degrees of the sedt temperaturea the heat strips will automatically come on until the house temp gets back to within the 3 degree differential of the t'stat.