Heat pump / natural gas hybrid questions

[Max W]

My daughter needs to replace her natural gas hot air furnace and is looking at a hybrid heatpump / natural gas combination. It looks like a good choice with rebates and other incentives. Her condo in northern Massachusetts, close to NH, was built in the ‘80s with the building practices of that time. It seems from what I read these systems the heat pumps are generally designed to switch over in the 30’s. Why is this when todays heat pumps are being designed to heat efficiently to lower temps? Has this just got to do when the cost of heating with the heat pump becomes greater than that of gas? I 10 years of satisfaction with our mini split but just starting to learn about these hybrids.

Are there common pitfalls to be avoided when purchasing one of these hybrid units and getting it installed?

 

[begreen]

The switchover temperature should be configurable. Depending on the system configuration this could be at 10 or 15 degrees if the heat pump is very efficient and sized correctly.

 

[ABMax24]

Could be due to energy costs too. At 30f it could be that natural gas is just cheaper to heat with than the electric heat pump.

 

[bogieb]

Got curious so did a quick Google and found this

 

[Eman85]

We had a Comfortmaker package unit installed a couple of years ago. Switchover from heat pump to gas furnace is programmable, thermostat has an outdoor remote for temp/humidity info. Works great for us compared to the split system we had before with gas furnace and outside compressor unit.

 

[Whitenuckler]

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I watched this last night - Good info on keeping the COP high even in cold weather

 

[stoveliker]

I had a hybrid nat gas furnace/heat pump back in TN.
The heat pumps they install there are poor in the sense that they conk out at 40 F. They would go to "emergency heat", i.e. resistive heat coils in the air handler. Rather expensive to run even with the kWh prices there.
Moreover, and this is where the combo units shine, a heat pump will take quite some time to heat up a room/home when it's colder out (hence the advice to maintain temps rather than have them drop down during e.g. the night). Yet the gas furnace was fantastic, as it could heat our home by 10 F in 10 minutes when it was 20 F outside. (As compared to the emergency coils running for 2 hours.)

The air temp coming out of the registers was so much warmer - it was really nice waking up in a cold room, having the gas heat come on and feel that warm air (in the bathroom) and have breakfast in a normally warm room.

I loved the natgas/heatpump combo unit.

 

[begreen]

Our previous 2006 AmStd 2 stage HP would switch over at 25º to resistance heaters (no nat gas here). The replacement is good to -5º with a COP of 2.1 at that temp. With 15º being about the coldest we will see, I don't expect to need resistance heaters anymore.

Could be due to energy costs too. At 30f it could be that natural gas is just cheaper to heat with than the electric heat pump.

That is a good scenario to keep track of. Unfortunately, I expect nat gas prices to be on the rise in the future, so keep track of this if so.

 

[EbS-P]

Our previous 2006 AmStd 2 stage HP would switch over at 25º to resistance heaters (no nat gas here). The replacement is good to -5º with a COP of 2.1 at that temp. With 15º being about the coldest we will see, I don't expect to need resistance heaters anymore.

That is a good scenario to keep track of. Unfortunately, I expect nat gas prices to be on the rise in the future, so keep track of thi

I think we will keep installing resistive strips in the south for quite some time. For the simple reason that the heating needs are larger than cooling but they tend to size a system for cooling. Adding the resistive heat always them a cheap way to get that low end. There are a lot package units down here and there are not that many (or any ) inverter package units with variable output.

 

[Max W]

She went with a Bosch system. When I last talked with her about this the furnace was up and running and the heat pump was going in. She thought the heat was great. She lives out of state limiting how involved l can get. I would have liked to talk to the contractor to learn more but I guess it comes down to trusting my kid to make good decisions on things like this as she does on other things. I have two home owning daughters in different states. There have been times when I packed my tools and headed out for a big project or repair but mostly its just wishing we were closer when something comes up.