Most heat pumps can be smaller than a furnace. My house for example, though I do not have a heat pump. My furnace is rated at 120,000 BTU’s. MY AC unit is 4 tons or 48,000 BTUs. If I were to replace both with a heat pump and wanted the same heating I would need a 10 ton heat pump, but that would be too large of a unit to properly air condition my house. A too large AC unit will not properly dehumidify a home. Also I probably would have to increase my electrical service. My other choice would be to replace them with a 4 ton heat pump and that would require a longer time to rewarm the house on a cold day.
As a disclaimer I have not ran a manual J on the house to see what the heating and cooling load would be. And I need proper insulation added to the attic, a project to do after I complete all the wiring corrections necesssary.
I think you may have to redefine your goals. Is it most important to you that a cold room be brought up to “room” temperature fast or that the hour-to-hour performance be constant so as to be comfortable?
My burner-fired furnace cycles on & off during the normal day, with a corresponding noise level fluctuation, and although the temp range isn’t more than 1.5F +/-, the cycling isn’t as comfortable to me as a heat pump would be with a steadier temperature and noise level. And some furnaces have wider swings than mine.
OTOH, it isn’t important to me that the house warm up quickly after a reduced thermostat setting. I can wait. Evenness is more important, personally. I think I would like a heat pump.
ETA: Are whole-house heat pumps made with auxiliary resistance heaters to give a boost when you want it? When I lived in Los Angeles, I had a large room that was entirely heated by a thru-the-wall heat pump. When the outside temp dropped below 45F (not often), the resistance heater kicked in. This would give you the best of both worlds.
This is not really the case with multistage heat pumps as they can run at a fraction of their max BTU’s.
It’s not a question of goals, that would be for IMHO, it’s a question as to why it takes longer, which is why I put it in factual questions (GQ)? Is there something inherent in a heat pump that could do the same thing just take longer, or is it in reality a less powerful heating device that we are being told to accept? Please note this OP paragraph which is speculation of a explanation that could answer it if it were true:
I guess if the output temperature of a heat pump is more dependent on room temperature input into the system than a furnace that sort of makes sense maybe. Like an extreme example, if a furnace output temperature is 150F no matter what, but the heat pump temperature is 20F over input temperature it would take longer for the heat pump to get up to it’s max. But that seems like a idealized example that only works with unobtainium.
Yes. Ours does that. Ours only comes on (I think) when we really crank up the thermostat (or, more often, something is wrong with out heat pump). Next time the temperature dips below 20, I’ll see if the auxiliary heat comes on automatically.
My house has two central heat pumps. The one downstairs is a Payne and the one upstairs is American Standard. Both have electric heating strips as well. I have Ecobee thermostats on both.
The Ecobee is key. It learns your schedule and can be controlled remotely. When we return from an outing, the volume we are occupying is warmed up within a few minutes. In our corner of the world, temps below freezing tend to be for a few hours at night, when we have the setpoint lower anyway. For those few days a year when temps are below freezing in the daytime or for many hours or days in a row, the electric heat comes on and keeps us toasty warm. (The defrost cycle on the Payne is either malfunctioning or inadequate, too, and the outside compressor becomes a block of ice. The electric heat keeps us toasty warm then, too.)
We’ve never been unhappy with the amount of time it takes to warm or cool the house.
1- Heat pumps are properly sized and can run continuously as part of that sizing. They are really designed and sized more to maintain temperatures.
2- Furnaces are somewhat oversized because it is cheap enough to add some extra to it, and unlike heat pumps, furnaces are not intended to run at 100% duty cycle, though they can and will in situations where more heat is called for, thus heating faster.
So a combo of oversizing a furnace and it’s ability to run at 100% duty cycle, though it’s sized for less duty, gives the furnace more heat to supply when called for.
Yes; you are agreeing with what I said. There is a minimum temperature the gas or whatever fuel you’re burning burns at, and it’s not just a few degrees above room temp. You can burn less of it and mix more cold air with it to make the output cooler, but it’s still warm compared to what you’ll get from a properly sized heat pump.
Heat pumps can extract and blow air really just a few degrees above room temp; you don’t get that big waft of warm air you do from a gas-burner, which I actually miss. You probably could if you grossly over-sized your heat pump, but that’s like buying a hot air balloon burner to toast marshmallows
That is very hot for hot air exiting from a vent. People can be burned by that temperature. It may be able to reach that temperature in the heat exchanger but the output into a room is usually only 15-20°F above room temperature. The main issue with heat pumps is the volume of air they can produce for a practical cost.
It would take a long time to heat a house if the temp was only 15-20 degrees above space temp. Or a very large volume. Most Gas furnaces have a high temp safety limit of 130 degrees, and operate at 120 degrees. If you do not insulate the ductwork it could then drop to 90 degrees but that would be a very expensive system to work.
Yes scalding will happen at 120 degrees. But the air registers on most systems are on the ceiling and would not be a threat.
I don’t know the details, but I do know that when we lived in Florida, the heat pump struggled to get things cold or hot. The old central air and heat units worked much quicker, and seemed “more efficient” in terms of heating and cooling. Didn’t see any difference in the utility bills from one to the other either. From what I read, heat pumps will not last as long as a central air/heat unit either, at least according to Trane and Carrier.
If you live in Florida, you want things to cool NOW. Seriously, that place is literally a swamp.
I don’t understand. An air conditioning unit is a heat pump that just works one way. It’s the same mechanism. Why would the “heating” heat pump cool less and break more easily?
It does make sense that a more complicated mechanism would have more potential for problems. Also an a/c usually has a much larger heat rejection coil than the cool side, something like 3:2 ratio or more (as the energy input into the system via electric power also gets rejected via that coil). With a reversible system you have to compromise between those 2.
But the main reason is that modern mini-split heat pumps they are just not being made to the same quality level.
As for why they don’t work as well, it could be just undersized for this application, and mini split systems don’t project air as far either, which causes short circuiting of air which lowers efficiency of heat transfer and that the heated/cooled air doesn’t travel too far from the unit, leaving the rest of the room less cooled or heated.