Heat Pump in Northern Climates?

[sxg6]

I’ll take a temperature tomorrow morning when mine comes on when the outside temp hits 40 F.

When you guys are talking about the air temperature coming out of them, what exactly is that indicative of? And what heat pumps are you using? The older ones which do stink in colder temps, or the Mitsubishi one like I have in Maine, and linked to above with hyper heating technology?

attached picture from this pdf.
https://www.mitsubishicomfort.com/sites/default/files/manual/m-series_hyper-heat_brochure_3.pdf

 

[Snagglefoot]

When you guys are talking about the air temperature coming out of them, what exactly is that indicative of? And what heat pumps are you using? The older ones which do stink in colder temps, or the Mitsubishi one like I have in Maine, and linked to above with hyper heating technology?

attached picture from this pdf.
https://www.mitsubishicomfort.com/sites/default/files/manual/m-series_hyper-heat_brochure_3.pdf

The one you have is really advanced. Mine is 10 years old and needs air temps of about 40 degrees F to run.

The temps coming out of the hot air duct are indicative of the plenum temperature where the heat exchange occurs and the blower fan forces return air across the heat exchanger inside the plenum. On mine, when in the auxiliary mode, my blower heats the heat exchanger with 148 F hot water. The air picks up the heat and it comes out at 92 F at the hot air duct in the floor. My return air is 70 F.

I”m going to measure my air temp later this morning when the heat pump will be running by noon and will see what the heat pump exchanger can heat the air to. It’s usually 20 to 30 F more than than the return air according to most sources but I’ll see.

 

[Snagglefoot]

So here we go.

With heat pump on with outdoor temp temp at 60 F.

Temp gong into heat exchanger 120 F
Return air going into plenum 70 F
Temp at hot air vent 84 F

On aux heat ( hot water from boiler)
Temp into exchanger 148 F
Return air going into plenum 70F
Temp at hot air vent 92 F

For sure the air temp out is hotter when fueled by propane but when on the electric heat pump is still 84 F.

I’d like try it tomorrow at an outdoor temp of 40 F .

 

[Snagglefoot]

Ran the heat pump this morning with an outdoor temp of 40 F. The temp at the hot air vent was 80 F, down from 84 F when the outdoor temp was 60 F.

 

[PandaBear]

So here we go.

With heat pump on with outdoor temp temp at 60 F.

Temp gong into heat exchanger 120 F
Return air going into plenum 70 F
Temp at hot air vent 84 F

On aux heat ( hot water from boiler)
Temp into exchanger 148 F
Return air going into plenum 70F
Temp at hot air vent 92 F

For sure the air temp out is hotter when fueled by propane but when on the electric heat pump is still 84 F.

I’d like try it tomorrow at an outdoor temp of 40 F .

84F vent is more comfortable than 92F vent in humidity control, IMO.

 

[Ws6]

Hi All,

Just replaced my NG furnace with a 2-stage variable speed 96% AFUE unit. Now it's time to replace the outside AC coil, and I'm curious if I should also consider a heat pump for a dual-fuel set-up. My gas rate is $0.35/therm and my electric rate is $0.10/KWh, but I believe I could get better on an off-peak rate. I live in ND where temps routinely can stay below 0 for weeks in the winter, and we can hit low 90s at times in the summer. Would the extra cost for a heat pump over an A/C unit be warranted in my case for the swing seasons, or just stick with my highly efficient furnace/cheap gas rate for all my heating needs?

For what it's worth: house is 2400sq. feet and pretty well sealed and insulated. Gas bill last month with an average temp of 9F was $80, which includes keeping my 600sq. ft garage heated at 50 degrees as well.

Oof.

I would only consider a heat pump if it were on of the new high tech Mitsubishi's or similar. Otherwise, I'd get a large propane tank, and place it below ground level in a properly drained pit, or build a berm that met pertinent industrial standard for withstanding blast.

 

[dlundblad]

Its certainly good for 32*F and above. I imagine ND has plenty of those days.

With ours, we saw no real difference in the power bill by running the gas furnace and heat pump vs. just running the furnace.

 

[PandaBear]

Its certainly good for 32*F and above. I imagine ND has plenty of those days.

With ours, we saw no real difference in the power bill by running the gas furnace and heat pump vs. just running the furnace.

I ran some calculation and while heat pump is more efficient, electricity is more expensive. So in my calculation example, let's say gas is 5x cheaper and heat pump is 5x efficiency of gas, the energy cost would break even and you will be paying for the installation.

The higher tier usage or peak pricing would likely end up costing you more than the break even electricity, and replacing a working furnace and AC with HVAC will likely never recoup your cost. For new building or necessary replacement I can see it make sense however.

 

[brianl703]

I have a heatpump in my house. House is located in Northern Virginia. Is 3300sq feet not including basement. Natural gas is not available. Propane is expensive.

So, when the house was being built, before the drywall went in, whatever the builder didn't seal up with caulk or great stuff, I did so myself. I used Sikaflex or Loctite polyurethane caulk. In several cases I removed the caulk the builder used at the toe plate because it was some 99-cent-per-tube junk that seemed like it would eventually shrink.

After the drywall went in, I went into the attic before the insulation went in and sealed the top plate to the drywall on either side with great stuff. I figure I probably sealed several hundred linear feet of drywall/top plate seam. I got a great stuff pro dispenser and great stuff pro cans to make job much easier and less messier. I also sealed every single cable penetration into the top plate and every electrical junction box.

After the house was complete, I added a switch so I could disable aux heat. It really isn't needed, even down to 20F, because of how tight this house is, but the thermostats I have (it's a zoned system) are really dumb about turning on aux heat unnecessarily.

My highest electric bill (keeping the house at 68F during the day and 62F during the night) has been $200 and that includes charging a 2013 Chevy Volt. That also includes running the pumps for an advanced treatment septic system and a well pump.

I do have propane but it is only used for a gas fireplace and a gas cooktop. I have not had the 100 gallon tank refilled since the initial fill almost 4 years ago.

 

[PWMDMD]

Heat pumps can work well in northern climates.

I'm in central MA and it gets plenty cold here. I had a high efficiency Bosch IDS 2.0 heat pump installed Spring of 2021. The house also has an oil powered boiler with 5-zones as a dual-fuel setup. I had never owned a heat pump before but because of the rebates it made it significantly cheaper than putting in a standard AC. Now oil prices are high and my electric prices are significantly lower and I'm glad I did it. This unit is rated down to -5F but I have it set to run above 20F. We've had a few mornings get down to 23F and the highs have been in the 30's and low 40's for a few weeks and it has no problem generating heat. It takes about 10 mins at an outside temp of 23F from the time the heat call goes out until the thermostat is satisfied. The first 2-3 mins is cool air but no big deal. I'm using a fraction of the oil I normally would right now.

 

[atikovi]

Remember living in a townhouse many years ago with a heat pump. It seemed to be running constantly in the winter and always feeling like a draft with the cool air coming from the vents. Not sure how it saved energy if it was always on.

 

[alarmguy]

It would make no sense at all to install a heat pump in a home with gas.
It would also make a heat pump incredibility inefficient and expensive to operate in your temperatures compared to gas.

Heck, we live in South Carolina and lucky enough to have gas heat on the main level, keeping in mind heat rises, our second floor heat pump will only kick on in the most extreme of circumstances on the coldest of days 20+ degrees which is maybe a handful of times a winter. That would be only to speed up warming the house faster after nighttime setback.

I would suspect your auxiliary coils would be turning on almost all the time in those cold temperatures equaling the cost of electric baseboard heat.

(just my thoughts)

 

[LowMilesLesabre]

I would say in ND it won't make sense. Now a ground source heat pump may make sense.

There are additional costs with ground source systems due to the initial digging that comes with installation. On the plus side, the ground source versions save quite a bit on utility bills due to their efficiency. How long the return on investment for that would be something you would need to calculate based on location and utility rates. One other benefit to a ground source system is that they are projected to have a longer lifespan. They simply don’t have to work as hard as a heat pump that pulls heat from the air.

 

[henni]

We run Mitsubishi HyperHeat systems in homes above Arctic Circle and in Keys, Florida
Works fine in any temperature

An added bonus is that a Honda EU7000isnan generator easily powers all systems as backup

 

[Snagglefoot]

I have an update on my system, the HVAC technician lowered my set point from 40 F to 27 F in order to have it run for more of the cold shoulder season. The COP ( Coefficient of Performance ) gets lower with decreased outdoor temperature. Mine is right on the limit. It has to run 100% of the time with an outdoor temp of 27F and also goes into a defrost cycle once it awhile where it essentially runs as a air conditioner but with the furnace circulation fan off, which defrosts the coils. Mine is a 42,000 BTU/hr unit. She’s giving all she’s got Captain.

 

[Snagglefoot]

We run Mitsubishi HyperHeat systems in homes above Arctic Circle and in Keys, Florida
Works fine in any temperature

An added bonus is that a Honda EU7000isnan generator easily powers all systems as backup

May I ask what setpoint you use before it goes to the back up electrical resistance mode for the one up north? Mine is 27 F. Good info on that generator. It’s a 220 V unit, correct?

 

[Snagglefoot]

Incidentally, if anyone is wondering how a heat pump can pull energy from 27 F air, I measured the temp of my outdoor coil after the refrigerant went through the expansion orifice. It was minus 26 F.

 

[Astro14]

Incidentally, if anyone is wondering how a heat pump can pull energy from 27 F air, I measured the temp of my outdoor coil after the refrigerant went through the expansion orifice. It was minus 26 F.

I don’t think anyone was questioning the physics.

I think most were questioning the cost.

It’s a matter of efficiency more than possibility.

 

[Snagglefoot]

I don’t think anyone was questioning the physics.

I think most were questioning the cost.

It’s a matter of efficiency more than possibility.

I have a few suggestions on the topic. If someone was planning on having a full house air conditioner, might as well make it a heat pump for the small increment. If you have natural gas, don’t bother running the heat pump at freezing temps. However, a heat pump run at freezing temps is still cheaper than propane.

 

[Astro14]

Propane and NG are very different commodities, though. I was talking NG, you are talking propane.

Our NG comes via pipeline under the street.

My winter heating and hot water bill is about $50 a month.