New Heat Pump installation and expectations

wlee

We recently replaced the 25 year-old central air conditioning unit in our raised ranch style home in the Mid Hudson Valley of New York State with an air-to-air heat pump. The new installation re-used the existing A/C ceiling ducts in the upper floor for a 36k BTU attic air handler, and added three mini-split heads for the lower floor (consisting of 12k BTU and 6k BTU high-wall units and a 9k BTU floor console). These are connected to a single 48k BTU outdoor unit. I should also mention this is a dual-fuel heat setup, as we retained our existing oil-fired boiler and the hydronic baseboards throughout the house.

The installation did not go smoothly and we had to have repeated service calls over about six weeks to fix all the issues. We were told everything was now good to go. However, having never had heat pumps before, I do not know whether my doubts about their performance now are due to lingering problems or un-realistic expectations.

The split heads on the lower floor seem to work properly after some startup time…the floor console head has the longest run from the outdoor unit and takes the longest to heat up (especially if none of the other units are operating), but eventually it does provide heat. Note that so far I have only used the heat pump when the outdoor temperature is above 35F; at lower temps I use the oil boiler and baseboards.

One of the specific things both the various techs that came out to service the issues and the owner of the company told me was that heat pumps work best when they are turned on to a set point and left alone. However, I am operating under the belief that if I have head units installed in rooms I am not using, I can keep them turned off, and then only turn them on when I need to, essentially using them as space heaters. Is that unrealistic?

For the air hander in the attic that conditions the upper floor, this is set via thresholds in the smart thermostat to also only operate when the outdoor temp is above 35F. As temperatures recently moderated in NY, the air handler started operating. The air coming out of the ceiling ducts never felt hot or even very warm - it was tepid at best. And yet, it was able to hold the desired temperature set for the upper floor. The only comparison I have for ducted heat is a former home with a natural gas fired hot air furnace, and when it was running, the air coming out of the registers was very warm. I know this is influencing my judgement of the new equipment and need to understand if it's just a matter of resetting my expectations.

To their credit, the installer has been responsive and has given me no pushback in answering questions and correcting the original issues (and yes, this is how it should be, but I've heard lots of horror stories to the contrary), and I'm sure they would go through this with me yet again if I asked. I was hoping to get an outside opinion from the folks here as to whether I need to press them for further action or if I just need to educate myself on how heat pumps in 2026 operate (essentially, if I set it to temperature X and the unit keeps the house at temperature X, it's doing what its supposed to). Thanks in advance.

bjohnhy

It sounds like it is working appropriately for a heat pump.

"…the floor console head has the longest run from the outdoor unit and takes the longest to heat up (especially if none of the other units are operating), but eventually it does provide heat. "

How many hours is "eventually"?

Have you measured the air temperature coming directly out of the unit that you describe as tepid? This is where the efficiency of heat pumps is able to excel. instead of heating the air to >130F like a natural gas air furnace, the heat pump might only bump it up to 85-100F but much much longer runs (continuous) with lower air flow.

wlee

Not hours - the worst case measurement for that floor console was about 36 minutes from power on to providing warm air. This unit has upper (outlet) and lower (inlet) air doors. At power-on, the upper door opened, with no other visible activity; at power on plus 5 minutes 30 seconds, the lower door opened; at +21 minutes, the fan cage (visible through the upper door) began blowing cool to lukewarm air. At this point I could begin to hear the clicking of the coils as they started to expand as the heated refrigerant flowed through them. At +36 minutes the air coming out was noticeably warmer and the upper door began to oscillate per the setting from the remote control. As I said, this was the longest measurement. IIRC the outdoor temperature when I took these timings was about 22F. If one or more of the other split heads were operating, the console unit heated faster.

I have not measured the temp of the air flow from the ceiling registers.

GGross

It really depends on how a heat pump system is designed whether they can recover or not from a setback. its all a matter of BTU capacity. I find it important to have these conversations with owners before installation, get ahead of the game. With enough money spent on equipment you can get heat pump systems that would recover at below zero temperatures, it is not practical (economically speaking) with current gen equipment though.

Many heat pump systems, like furnace and AC installs, are sized based on a WAG. Basically they look at your condenser and if the new heat pump is an inverter they go up one size and away she goes. works great for cooling, and for heating when Tstats are left alone, not always so much for setbacks!

a few things to note. Heat pumps are harvesting the latent energy from the outdoor air, therefore when its colder outside the heat pump will have lower heating capacity than at higher outdoor temps. This is part of the reason a typical heat pump tends to struggle with recovery after a temperature setback on the thermostat.

Your mini split system is an inverter, and will strive to run for long periods delivering as close to correct temperature air to maintain the temperature in the space as it can. So you will not have the blasts of hot air like you are used to with a gas forced air system, and even with those the modulating systems are similarly disorienting for folks used to single stage gas.

Multi split systems have a few quirks, some is brand specific some not. Typically the large (48k+) multi split systems can be a bit finnicky when a single smallest sized head is calling. Personally I would run the whole system to maintain a temperature and see if you notice any issues with the one in question

wlee

"Your mini split system is an inverter, and will strive to run for long periods delivering as close to correct temperature air to maintain the temperature in the space as it can. So you will not have the blasts of hot air like you are used to with a gas forced air system"

"Heat pumps are harvesting the latent energy from the outdoor air, therefore when its colder outside the heat pump will have lower heating capacity than at higher outdoor temps. This is part of the reason a typical heat pump tends to struggle with recovery after a temperature setback on the thermostat."

Thanks, this sounds exactly like what I'm experiencing. During the initial sales call, the installer did tell me not to use setbacks, or at best only set back two or three degrees at most - his advice was to set a comfortable temperature and keep it steady throughout the day and overnight. Looking back on it, he also advised that the system would take "some getting used to", especially coming from baseboard heat. I thought my prior experience with forced hot-air would better prepare me for the HP, but no. As far as recovery, my understanding is there is a setting in the smart thermostat (it's an Ecobee Lite) that, in addition to switching over to the boiler when outdoor temps are below 35F, will run the boiler if there is a specific difference between the room temperature and thermostat setting. I guess this is to allow the boiler to do the "heavy lifting" of bringing the room back to the set point, and then letting the HP maintain it.

"Typically the large (48k+) multi split systems can be a bit finnicky when a single smallest sized head is calling"

One of service techs who came out to sort the installation issues told me exactly this. You could design the system for better responsiveness at the cost of additional outdoor units to split the load, but in my case, in addition to the cost for the another outdoor unit, there were zoning and electrical issues that would have increased the final figure to way outside what I had budgeted.

So what I'm taking from all this is the unit is basically working the way it should. I will consider myself educated 😁 Thanks again.