In this podcast, John Maher and Jesse Corso from N.E.T.R., Inc. discuss how ductless heat pumps perform in cold climates. They cover the efficiency of cold-climate models, inverter technology, and specific installation and maintenance practices to ensure optimal operation during New England winters. Jesse explains how these heat pumps can serve as the sole heating source for a home and provides tips for proper care in snowy conditions.
John Maher: Hi, I am John Maher and I’m here today with Jesse Corso, comfort consultant with N.E.T.R., Inc., a heating and cooling company in Massachusetts with a focus on ductless heating and cooling products. Today our topic is ductless heat pump performance in cold climates. Welcome Jesse.
Jesse Corso: Hi John. Thanks for having me.
How Do Ductless Heat Pumps Perform in Extreme Cold?
John: Sure. So Jesse, how do ductless heat pumps perform in extreme cold?
Jesse: I would say if you go with a cold climate version of a ductless heat pump system, they perform quite well. Most models today, if they’re cold climate, they’re maintaining 100% of their heating capacity down to a five degree outside air temperature. One model in particular I can think of maintains 100% of its capacity, even down to negative five, and then 75% of their capacity even at a negative 13 degree outside air temperature. So these are rated for well beyond how cold it gets really in the Boston area.
Importance of Cold Climate Systems
John: Right. So you made a good point though that you have to make sure that you have one of these cold climate heat pumps because they come in two different styles. There’s the cold climate ones and then, I don’t know, what do they call the other ones? Just a standard, you know what I mean?
Jesse: Yeah, I would say two categories. One is that we call them standard heat pumps or standard systems, and one would be cold climate. The standards are great for air conditioning and they work well even for supplemental heating solutions, say down to about freezing temperatures. Anything below that outside, they start to lose some capacity, some heating capacity, but the cold climate systems are designed to produce heat well at much colder outside air temperatures. So those are really the two categories.
Do You Need Any Supplemental Heat in Cold Weather?
John: So, people might be thinking of those old style then when they think that they maybe need to add some sort of supplemental heat for the winter or keep their fossil fuel system in their house for those cold days in the winter. With these cold climate heat pumps, do you still need any kind of supplemental heat at all?
Jesse: We have a lot of customers, many situations where we have specifically designed the heat pump system, the mini split system, to be the sole source of heat for the building or the house. You have to make sure at that point you’re really diving deep into an accurate load calculation for the house, how much heat does it need, and then you really have to pay attention to your equipment sizing. If you can size it according to your load and do it accurately, then they can be the sole source of heat for the home. Obviously you want to make sure the home is as weather tight as it can be, as well insulated as it can be just to help you achieve the total heating load with a heat pump system.
Does Boston Get Too Cold For Ductless Heat Pumps?
John: And you mentioned that we’re here in the Boston area and we really rarely get down into those negative degree days or even overnight in the winter. Certainly it would very unusual to be down at that negative 10, negative 13 kind of area. So there’s very few days or nights or even hours in the winter in the Boston area when we’re getting down into that low temperature.
Jesse: Yeah, exactly. Even probably just hours, not even days. I do a lot of load calculations in this area, in the Boston area and the predetermined outside condition that we should be designing at, a lot of times I see 10 degrees, 11 degrees, 12 degrees, 13 degrees, which is 99% of the time it’s warmer than that.
How Does Inverter Technology Improve Ductless Heat Pump Performance?
John: Right. Right. How does the inverter technology improve ductless heat pump performance in cold climates?
Jesse: Yeah, so the inverter compressors on the cold climate systems. They are able to ramp up in speed faster and when they do that, they are able to produce heat from the speed of the compressor operating and make up the difference or make up the loss, the amount of capacity that the system would be losing due to extreme outside cold weather, they’re able to make up the difference of that capacity loss and dump that heat back into the system and maintain that full heating capacity. So I guess what I’m trying to say is the compressor can speed up, create heat itself, become a little heater itself based on how fast it’s running, dump that heat back into the system and maintain 100% of its heating capacity, and they’re able to do that by inverter technology and inverter compressors.
Do You Lose Efficiency At Extremely Cold Temperatures?
John: And then that’s why you lose a little bit of that efficiency. Like you said, it goes down to 75% efficiency when you’re down below five degrees, it’s because that inverter is speeding up the outside compressor and so you’re using a little bit more electricity in order to maintain the heat in those really low temperatures.
Jesse: Yeah, I mean at that point the system’s probably running close to full speed, if not full speed and beyond. At negative 13 where it’s got that 75% rating, there’s just such a little amount of heat left in the air to grab, to absorb that it works hard, draws that higher nameplate amperage, but does still produce heat for the home.
Installation Considerations for Ductless Heat Pumps in Cold Climates
John: Right. Are there any specific installation considerations for ductless heat pumps in cold climates, or is installing a cold climate heat pump kind of just the same as a standard heat pump?
Jesse: The biggest thing is snow right? So if we know we’re going to be using this thing all winter long, snow is a factor here in Boston, in New England, so we want to make sure we’re mounting that thing on a stand at least 12 inches up off the ground, 18 inches maybe, or wall mounting the unit to the side of a house, even taller, even higher than that off the ground to get it up out of the snow. We also want to, if we can avoid putting the condenser maybe under a roof line where snow’s going to fall off the roof and crash down and create a big pile of snow where the condenser is. So maybe on a gable end might be better than on the end of a house where the snow’s going to travel and fall right off the roof line. So I would say the biggest factor is snow considerations for those cold climate pumps.
Ductless Heat Pumps and Snow
John: Right. You don’t want it to get buried by a snow drift or something like that and then not be able to spin around anymore.
Jesse: Exactly. I mean, I would even recommend if we have a heavy snowfall, a large amount of snow coming down in one snowstorm, that the customer would at least just go out there and maybe take a peek at their unit, just check on it, make sure it’s not buried.
What Maintenance is Needed for a Ductless Heat Pump in Cold Climates?
John: That brings up a good point. What types of maintenance practices are recommended for ductless heat pumps in cold climates?
Jesse: Yeah. So yeah, that does… it segues nicely. I would say if we have a heavy snowfall, just check on that thing, make sure it’s not covered, clear it out if you need to. Again, it should be up off the ground a little bit though. Other than that, obviously air filters on the indoor units need to be periodically checked and cleaned. They’re washable. If they’re ductless units, they’re washable filters, so checking the filters. And then annual maintenance is important if you’re using it year round, maybe even maintenance twice a year if you’re using it for one season and not the other. If you’re using it for AC only, maybe one maintenance a year. If you’re using it for heat, only one maintenance a year. But if you’re using it for both, if it’s your only source of heating and cooling, two maintenances would be nice.
John: That makes sense. All right, well that’s really great information, Jesse. Thanks again for speaking with me today.
Jesse: Thanks, John.
Information About N.E.T.R.
John: And for more information, you can visit the N.E.T.R website at netrinc.com or call (781) 933-NETR. That’s (781) 933-6387.
