Best temperature settings with a heat pump?
November 13, 2022 7:03 AM Subscribe
I recently moved into a place that has a heat pump; my previous experience has been with blown air, baseboard heat or wood burning stoves. Largely as an energy saver (and because I sleep better at lower temps), I’m used to setting the thermostat to 66F at night and then bumping it up to 70 in the morning. Last night we had our first “cold” night - low of 32 degrees - and it took almost an hour for the ambient temp to raise a single degree — and that might have been because I turned on the space heater in the main room.
Temps this week will drop into the teens — how do I set my thermostat so that it doesn’t take 4 hours to bring the place up to a comfortable temp but also don’t have the thing running constantly all night long?
Best answer: When we switched to a heat pump at our previous house, we also put in a programmable thermostat that could "learn" how long it took to change temperature. So if you set the thermostat to have the house at 70F at 6am, it would start the (slow) heating process enough time before that to get to the right temperature at 6am. At least with the heat pump we had, it wasn't like a gas furnace where it blows hot air so you can go directly from a cold room to warm -- it blew air that was slightly warmer and so would have slow temperature changes.
Heat pumps also have a temperature below which they don't work, or don't work as effectively. Ours had a supplemental gas furnace for when the temperature dropped too much, but not all will have that, so you may simply be running into an issue where the heat pump is not able to heat as effectively.
posted by Dip Flash at 7:42 AM on November 13, 2022 [1 favorite]
Heat pumps also have a temperature below which they don't work, or don't work as effectively. Ours had a supplemental gas furnace for when the temperature dropped too much, but not all will have that, so you may simply be running into an issue where the heat pump is not able to heat as effectively.
posted by Dip Flash at 7:42 AM on November 13, 2022 [1 favorite]
Best answer: I've got a heat pump, and it generally only takes 30 minutes or so to go from 68F, where I leave it at night, to 70F which is where I set it when I wake up and start my morning.
My suggestion: get a cheap-ish laser thermometer like this one: https://www.amazon.com/Etekcity-Lasergrip-774-Non-contact-Thermometer/dp/B00837ZGRY?th=1 and measure the air coming out of the registers. It should be around 100F or so.
Another thought is that your auxiliary heat isn't working. Heat pumps don't work well when the temperature is close to freezing, so my unit has what the HVAC folks call "auxiliary heat strips" which turn on and generate heat if the heat pump itself can't keep up. If those aren't working your heat pump may not be able to heat the house until the outside temperature starts to climb above 40F.
In either case I'd suggest calling a local HVAC company to see if they can send someone out, because your system isn't working correctly.
posted by ralan at 7:47 AM on November 13, 2022 [1 favorite]
My suggestion: get a cheap-ish laser thermometer like this one: https://www.amazon.com/Etekcity-Lasergrip-774-Non-contact-Thermometer/dp/B00837ZGRY?th=1 and measure the air coming out of the registers. It should be around 100F or so.
Another thought is that your auxiliary heat isn't working. Heat pumps don't work well when the temperature is close to freezing, so my unit has what the HVAC folks call "auxiliary heat strips" which turn on and generate heat if the heat pump itself can't keep up. If those aren't working your heat pump may not be able to heat the house until the outside temperature starts to climb above 40F.
In either case I'd suggest calling a local HVAC company to see if they can send someone out, because your system isn't working correctly.
posted by ralan at 7:47 AM on November 13, 2022 [1 favorite]
Response by poster: This is all helpful. I am renting, so I put in a ticket with the property management. Will look into getting a laser thermometer so I can track this. Thank y’all.
posted by Silvery Fish at 8:04 AM on November 13, 2022
posted by Silvery Fish at 8:04 AM on November 13, 2022
Is it an inverter heat pump? If it is, it's designed to run constantly rather than cycling on and off (or through two stages) like a gas or oil furnace. As a result, inverter heat pumps can be less effective and less efficient when asked to bring the temperature up rapidly, and it might actually be worth empirically verifying that you're saving enough energy to matter by letting the temperature drop at night and then running the heat pump flat out for a few hours vs. letting it "idle" all night (and switching to a lighter comforter).
Heat pumps don't work well when the temperature is close to freezing
This is entirely dependent on the model, and isn't true at all if it's a low-temp heat pump (like a Mitsubishi Hyper Heat or Gree Sapphire), which probably wouldn't need to fall back to supplemental gas or resistive heat until it's well below zero. It's not, like, a law of physics or an inherent feature of air-source heat pumps. That said it's definitely worth finding out what sort of heat pump you have and whether this is expected behavior or something worthy of a service call.
posted by pullayup at 8:05 AM on November 13, 2022 [1 favorite]
Heat pumps don't work well when the temperature is close to freezing
This is entirely dependent on the model, and isn't true at all if it's a low-temp heat pump (like a Mitsubishi Hyper Heat or Gree Sapphire), which probably wouldn't need to fall back to supplemental gas or resistive heat until it's well below zero. It's not, like, a law of physics or an inherent feature of air-source heat pumps. That said it's definitely worth finding out what sort of heat pump you have and whether this is expected behavior or something worthy of a service call.
posted by pullayup at 8:05 AM on November 13, 2022 [1 favorite]
Is it an inverter heat pump? If it is, it's designed to run constantly rather than cycling on and off (or through two stages) like a gas or oil furnace. As a result, inverter heat pumps can be less effective and less efficient when asked to bring the temperature up rapidly, and it might actually be worth empirically verifying that you're saving enough energy to matter by letting the temperature drop at night and then running the heat pump flat out for a few hours vs. letting it "idle" all night (and switching to a lighter comforter).
I think this is the type of heat pump we had at a recent apartment we lived in. It turned out to work much better to simply leave it at a single temperature setting 24/7, and (to my surprise from my lifetime conditioning for "you must turn down the heat at night!") was efficient/cheap when used that way.
posted by Dip Flash at 8:21 AM on November 13, 2022 [4 favorites]
I think this is the type of heat pump we had at a recent apartment we lived in. It turned out to work much better to simply leave it at a single temperature setting 24/7, and (to my surprise from my lifetime conditioning for "you must turn down the heat at night!") was efficient/cheap when used that way.
posted by Dip Flash at 8:21 AM on November 13, 2022 [4 favorites]
I have a heat pump and sometimes it runs but doesn't heat. The consensus around here is turn it off, flip the circuit breaker, leave it off for five minutes then turn the circuit breaker back on and turn it back on. This happens maybe once a year. Resetting it this ways always works for me. Note that the air coming out of the vents never feels particularly warm. I assume it's only slightly warmer than the ambient air (unlike a forced air gas furnace where it's much warmer).
posted by If only I had a penguin... at 8:24 AM on November 13, 2022 [1 favorite]
posted by If only I had a penguin... at 8:24 AM on November 13, 2022 [1 favorite]
The space heater wasn't near the thermostat, was it? We had a vent pointed straight at a thermostat and that changed its behavior.
posted by idb at 8:51 AM on November 13, 2022
posted by idb at 8:51 AM on November 13, 2022
Response by poster: The space heater wasn't near the thermostat, was it? We had a vent pointed straight at a thermostat and that changed its behavior.
Good question. No it wasn’t. The thermostat is in the hallway; the space heater was in the main room off of the hallway, pointing away from it.
posted by Silvery Fish at 11:41 AM on November 13, 2022
Good question. No it wasn’t. The thermostat is in the hallway; the space heater was in the main room off of the hallway, pointing away from it.
posted by Silvery Fish at 11:41 AM on November 13, 2022
I have a mini-split heat pump in my shop (in Santa Fe, NM). It was 50 in there when I arrived this morning, and it was up to 66 (the set temperature) within an hour or so. It’s only 288 square feet, but it’s also a small unit, sized for the shop.
It sounds like something is wrong with yours, either it’s low on refrigerant or the coils and gummed up with dust or something.
As for low temps, my Mitsubishi mini-split in my garage in Minneapolis worked fine down to about -10F. Depends on the unit, but that should be documented in the manual.
posted by DaveP at 1:56 PM on November 13, 2022 [1 favorite]
It sounds like something is wrong with yours, either it’s low on refrigerant or the coils and gummed up with dust or something.
As for low temps, my Mitsubishi mini-split in my garage in Minneapolis worked fine down to about -10F. Depends on the unit, but that should be documented in the manual.
posted by DaveP at 1:56 PM on November 13, 2022 [1 favorite]
Response by poster: Thanks for the sanity check, everyone. Hopefully it gets addressed tomorrow.
posted by Silvery Fish at 1:59 PM on November 13, 2022
posted by Silvery Fish at 1:59 PM on November 13, 2022
Heat pumps, especially if it's relatively new, are very efficient. So much so, that you really don't need to (and, probably shouldn't) set them on a cycle to lower the temperature in the evening to save money. They are efficient at what they do, but it's sort of "slow" heat. You won't get the instant gratification of a blast of hot air or chilly AC from your vent; it's a marathon not a sprint.
You may also find that the temperature setting on your heat pump is somewhat different than from a forced-air or baseboard system. Like, in a house with a forced-air furnace, you may have kept it set at 68F to feel comfortable, but this particular unit may require being set at 71, or perhaps 66, for the same "feel". Take some time to try it, a degree or two at a time, and see what feels best. But, for the most part, set it to a comfortable temperature and forget about it, let it do its thing in the background.
posted by xedrik at 2:55 PM on November 13, 2022
You may also find that the temperature setting on your heat pump is somewhat different than from a forced-air or baseboard system. Like, in a house with a forced-air furnace, you may have kept it set at 68F to feel comfortable, but this particular unit may require being set at 71, or perhaps 66, for the same "feel". Take some time to try it, a degree or two at a time, and see what feels best. But, for the most part, set it to a comfortable temperature and forget about it, let it do its thing in the background.
posted by xedrik at 2:55 PM on November 13, 2022
I'm not sure exactly what kind of heat pump you have, but I recommend checking to see if there are filters you can clean on the indoor unit. I've found the difference with clean vs dirty filters can be dramatic.
I'm sure you can find instructions online, but I just take the filters out of mine (after turning it off) and vacuum them every few months. It probably takes less than 10 minutes.
posted by imelcapitan at 5:26 PM on November 13, 2022
I'm sure you can find instructions online, but I just take the filters out of mine (after turning it off) and vacuum them every few months. It probably takes less than 10 minutes.
posted by imelcapitan at 5:26 PM on November 13, 2022
We have been in a home with a heat pump for the past six years. When it comes to heating season, it’s far better to set a temp and leave it, especially once it gets really cold. And, you definitely need to set the temp a tick higher than you would with a furnace.
Also, if this is your first experience with a heatpump, be aware that, once the temps reach freezing and below, the outside unit will go through a defrost cycle about once every hour or so. What happens is the unit reverses its functioning in order to defrost the coils, which can frost-up in cold weather. If you’re anywhere near the unit when it does this, it can seriously sound like it just imploded, so don’t freak-out. It’s all good.
The heatpump will not be heating your home while it’s defrosting. This is usually not an issue. If it’s really super cold, or the defrost cycle goes a long-ish time, though, your system might bring on the auxiliary/emergency heat for a short bit.
The timing of how often the heatpump defrosts is set with jumpers on the logic board of the outside unit. It can normally be set for every half-hour, every hour, or longer. Ours is set for every hour, and it seems appropriate. Every half-hour would be ridiculous.
...........
Is it an inverter heat pump? If it is, it's designed to run constantly rather than cycling on and off...
This isn’t strictly correct. A heat pump should only be running constantly (or semi-constantly) once the ambient temps are seriously low. Like, in the teens.
posted by Thorzdad at 6:04 PM on November 13, 2022
Also, if this is your first experience with a heatpump, be aware that, once the temps reach freezing and below, the outside unit will go through a defrost cycle about once every hour or so. What happens is the unit reverses its functioning in order to defrost the coils, which can frost-up in cold weather. If you’re anywhere near the unit when it does this, it can seriously sound like it just imploded, so don’t freak-out. It’s all good.
The heatpump will not be heating your home while it’s defrosting. This is usually not an issue. If it’s really super cold, or the defrost cycle goes a long-ish time, though, your system might bring on the auxiliary/emergency heat for a short bit.
The timing of how often the heatpump defrosts is set with jumpers on the logic board of the outside unit. It can normally be set for every half-hour, every hour, or longer. Ours is set for every hour, and it seems appropriate. Every half-hour would be ridiculous.
...........
Is it an inverter heat pump? If it is, it's designed to run constantly rather than cycling on and off...
This isn’t strictly correct. A heat pump should only be running constantly (or semi-constantly) once the ambient temps are seriously low. Like, in the teens.
posted by Thorzdad at 6:04 PM on November 13, 2022
There are typically filters that need regular cleaning in the inside unit. If they become clogged with lint and dust they can make the heat pump much less efficient. There is probably a latch to open it up, revealing the filters. How do they look?
posted by i_am_joe's_spleen at 6:49 PM on November 14, 2022
posted by i_am_joe's_spleen at 6:49 PM on November 14, 2022
My heat pump runs pretty constantly even in warm temperatures, because it changes power settings and will sometimes only need to provide a very small quantity of heat. It doesn't simply go off and on, it finds one of (many) levels to operate at. It also runs at a low level when the room is at the set point. (Also, the blowers are very low power compared to the old system, so what comes out of the vent is typically a very gentle breeze.)
Modern heat pumps are very different to the old aircon and furnace I had. They were off or on, and the air out of the vent was obviously very warm or very cold and always came out of the vents with force. That's not what I'm getting now.
posted by How much is that froggie in the window at 11:29 PM on November 18, 2022
Modern heat pumps are very different to the old aircon and furnace I had. They were off or on, and the air out of the vent was obviously very warm or very cold and always came out of the vents with force. That's not what I'm getting now.
posted by How much is that froggie in the window at 11:29 PM on November 18, 2022
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posted by obfuscation at 7:11 AM on November 13, 2022 [1 favorite]