old (1991) Trane heat pump and "emergency heat"

[masraum]

The new-old home that we bought has what I suspect was a very nice HVAC back in 1991/92 when it was made/installed. It's a heat pump and the thermostat has "heat" and then a separate switch for "emergency heat."

The guy that sold us the house said that the emergency heat should be used below ~50º.

I'm trying to figure out the best/correct operation of the system to ensure that it lasts until we are ready to replace it versus having it die at an inopportune time.

I've seen some stuff online that says that heat pump systems will go into emergency heat mode when needed (~35º). But I'm not sure if that means modern systems will do that and whether mine would be considered modern or not. I know my parents used to have problems with their system when they got near or below 40º and their home was probably about the same age.

I'm curious, how cold should I let it get before I select "emergency heat" or if I should select that at all or if there's anything specific that I should do with/for this sort of system.

Our previous home had AC and a gas furnace, so the heat pump thing is new territory for me.




I don't have a photo of our thermostat, but it looks like one of these.

[legion]

Do you know if your emergency heat is natural gas or electric? I've seen heat pumps that use both.

When I lived in Atlanta it got down below freezing for about two weeks straight. Those with heat pumps with electric emergency heat were struggling (they'd have to wear coats indoors) and getting electric bills over $1,000. I had two regular natural gas furnaces and while natural gas was expensive (4x what I pay for it in Illinois), my gas bill was only $300 for the month and the house never felt any different inside.

When it comes time to replace and assuming you have natural gas at your home (I hear not all houses in the south do), I'd highly recommend natural gas emergency heat.

[LEAKYSEALS951]

Mine is about 91-92.

The heat pump works like this- with switches- cool- off- heat- emergency heat.
In the heating mode, the heat pump runs, but will auto kick over to propane when the temps get low. What specific temp that is, I don't know.

Emergency heat mode just bypasses the heat pump and runs straight propane.

I can always tell when the heat pump switches to propane, as the heat coming out of the vents will be warm, and will actually warm the floors, compared to the "cool drafty" feeling of the heat pump. I don't know what temp the device kicks over. I can also pull an upper cover off the indoor furnace itself, and you can feel/see the blue flames.

Perhaps at low temps, reverting to EH just reduces wear and tear on the heat pump, but when it's really cold, say 10- 20 degrees, I don't hear the outdoor unit cycling on / off. It does seem to cycle when it's in the 40-s- 50's, when it actually could be extracting heat from the great outdoors.

[masraum]

Originally Posted by legion

Do you know if your emergency heat is natural gas or electric? I've seen heat pumps that use both.

When I lived in Atlanta it got down below freezing for about two weeks straight. Those with heat pumps with electric emergency heat were struggling (they'd have to wear coats indoors) and getting electric bills over $1,000. I had two regular natural gas furnaces and while natural gas was expensive (4x what I pay for it in Illinois), my gas bill was only $300 for the month and the house never felt any different inside.

When it comes time to replace and assuming you have natural gas at your home (I hear not all houses in the south do), I'd highly recommend natural gas emergency heat.

The emergency is absolutely electric. There's no gas or any utility other than electric.

A lot of the homes in the rural areas have large tanks that they get filled from time to time. I'm not sure if they are propane or some other sort of fuel. I could see converting to one of those for heat since this home is farther inland from Houston and gets cooler weather.

[masraum]

Originally Posted by LEAKYSEALS951

Mine is about 91-92.

The heat pump works like this- with switches- cool- off- heat- emergency heat.
In the heating mode, the heat pump runs, but will auto kick over to propane when the temps get low. What specific temp that is, I don't know.

Emergency heat mode just bypasses the heat pump and runs straight propane.

I can always tell when the heat pump switches to propane, as the heat coming out of the vents will be warm, and will actually warm the floors, compared to the "cool drafty" feeling of the heat pump. I don't know what temp the device kicks over. I can also pull an upper cover off the indoor furnace itself, and you can feel/see the blue flames.

Perhaps at low temps, reverting to EH just reduces wear and tear on the heat pump, but when it's really cold, say 10- 20 degrees, I don't hear the outdoor unit cycling on / off. It does seem to cycle when it's in the 40-s- 50's.

Thanks, good to know. Then potentially, I can leave the heat in the standard position and it will kick the emergency on automatically. I noticed that when the emergency heat is kicked on, the fan blows all of the time and the air gets REALLY dry. I'll experiment some, thanks.

[Sooner or later]

I had a similar, possibly the same, system when I lived in Tyler. The very same thermostat and switch set up. Mine worked fine down to at least 40 degrees. My backup heat was electric. I can't remember if it turned on automatically or not. Seems like it did.

[LEAKYSEALS951]

I wouldn't sweat the hurting the heat pump too much. If the outdoor unit is original, it's probably on it's last legs anyway. In a worst case scenario (the pump fails) you'd just switch to emergency heat and bypass the heat pump. I've done this in the past. I don't think you'll get stranded heatwise.

[legion]

Originally Posted by masraum

The emergency is absolutely electric. There's no gas or any utility other than electric.

A lot of the homes in the rural areas have large tanks that they get filled from time to time. I'm not sure if they are propane or some other sort of fuel. I could see converting to one of those for heat since this home is farther inland from Houston and gets cooler weather.

Those tanks are propane. Natural gas appliances can run on propane but require an adapter to restrict the flow as IIRC, propane is more energy-dense than natural gas (methane). Everyone who lives out in the country here has propane for heat.

You might want to check if the electric heating coils used for emergency heat need to be replaced. Ones that are 30 years old almost certainly need replacing. My understanding is that they don't degrade so much a break. You may have had 5 coils 30 years ago and 3 may have worn out and snapped, limiting how much emergency heat your system can produce.

[flipper35]

Our geothermal heat pump switches automatically if it can't keep up. At -20* it still runs the normal pump and the temp out the vents is 90*.

You shouldn't have to worry about switching it.

[masraum]

Originally Posted by Sooner or later

I had a similar, possibly the same, system when I lived in Tyler. The very same thermostat and switch set up. Mine worked fine down to at least 40 degrees. My backup heat was electric. I can't remember if it turned on automatically or not. Seems like it did.

Cool, thx.

Originally Posted by LEAKYSEALS951

I wouldn't sweat the hurting the heat pump too much. If the outdoor unit is original, it's probably on it's last legs anyway. In a worst case scenario (the pump fails) you'd just switch to emergency heat and bypass the heat pump. I've done this in the past. I don't think you'll get stranded heatwise.

Yes, "last legs," while we are mentally preparing for that, we'd rather not rush into it.

Originally Posted by legion

Those tanks are propane. Natural gas appliances can run on propane but require an adapter to restrict the flow as IIRC, propane is more energy-dense than natural gas (methane). Everyone who lives out in the country here has propane for heat.

You might want to check if the electric heating coils used for emergency heat need to be replaced. Ones that are 30 years old almost certainly need replacing. My understanding is that they don't degrade so much a break. You may have had 5 coils 30 years ago and 3 may have worn out and snapped, limiting how much emergency heat your system can produce.

Good info, thanks. I'll see if that's something that I can easily check (resistance/continuity through the coils). Propane seems like a good way to go other than having the ugly tank sitting around.

Originally Posted by flipper35

Our geothermal heat pump switches automatically if it can't keep up. At -20* it still runs the normal pump and the temp out the vents is 90*.

You shouldn't have to worry about switching it.

I'd love geothermal. It sounds like a really good way to go, but I've heard that they are unlikely to work well around here. I guess we get too hot. That seems questionable to me, but I've not ever been prepared to replace a system so I haven't really looked into it.

[billybek]

Heat pumps have come a long way in the last few years.
There is a Daikin heat pump out there that claims to deliver 100%? of heat down to minus 10 deg F.
Not sure about the other manufacturers.

[id10t]

Ours kicks on automagically if it is cold enough. I wanna say when outside temps hit low 40s it kicks on ...

[Zeke]

I'd get a wood stove just for the charm. But it might come in really handy in the winter.

[masraum]

Originally Posted by id10t

Ours kicks on automagically if it is cold enough. I wanna say when outside temps hit low 40s it kicks on ...

Good to know, thanks

Originally Posted by billybek

Heat pumps have come a long way in the last few years.
There is a Daikin heat pump out there that claims to deliver 100%? of heat down to minus 10 deg F.
Not sure about the other manufacturers.

I'll keep that in mind and confirm when we're ready or forced to start replacing stuff.

Originally Posted by Zeke

I'd get a wood stove just for the charm. But it might come in really handy in the winter.

Yes, we'd love one. I suspect there used to be one. I'm sure since this place was built in 1924, and the central HVAC was installed in the 90s, that this place must have had some more primitive means of heating and cooking.

[peppy]

Our heat pumps kick to emergency heat when the temp differential is 2 degrees. We have electric$$$.

On a side note we have the boiler for when it's cold.

I know "cold is a relative term for VA"

[masraum]

Originally Posted by peppy

Our heat pumps kick to emergency heat when the temp differential is 2 degrees. We have electric$$$.

On a side note we have the boiler for when it's cold.

I know "cold is a relative term for VA"

Thanks.

It seems like the consensus is that it probably should automatically kick the emergency heat on if needed. The predicted lows for this Fri, Sat and Sun mornings are in the mid 30s. I'll have an opportunity to check then.

[A930Rocket]

I guess it depends where you live, but the propane tank can be buried. Most of ours have been, depending on available area and code.

[masraum]

Originally Posted by A930Rocket

I guess it depends where you live, but the propane tank can be buried. Most of ours have been, depending on available area and code.

Interesting and very good to know. I see them around here not buried, but then, due to "survivorship bias" or something like it, I probably wouldn't see them if they were buried, so I have assumed they only exist above ground.

I'm guessing cost is the biggest reason why I see so many above ground. I presume that's much less expensive than in-ground installation.

[LakeCleElum]

Originally Posted by Zeke

I'd get a wood stove just for the charm. But it might come in really handy in the winter.

After almost 60 years of splitting/lugging firewood, my Wood Stove has lost any charm it might ever have had..........I'm over it come this next spring...

[greglepore]

Originally Posted by masraum

Interesting and very good to know. I see them around here not buried, but then, due to "survivorship bias" or something like it, I probably wouldn't see them if they were buried, so I have assumed they only exist above ground.

I'm guessing cost is the biggest reason why I see so many above ground. I presume that's much less expensive than in-ground installation.

The propane companies rent them above ground, and inground 500 is around 2k to buy, and you need to install it, with appropriate anti corrosion control.