How Ductless Heating and Cooling Systems Work

Choosing to install a ductless heating and cooling system in your home is a great way to save money and energy. Mike Cappuccio, owner of N.E.T.R., Inc., discusses how these systems work to ensure proper cooling and heating of your home.

John Maher: Hi. I am John Maher. I’m here today with Mike Cappuccio, owner of N.E.T.R. Inc., a heating and cooling company in Massachusetts with the focus on Mitsubishi Ductless Heating and Cooling products. Today we’re talking about how ductless heating and cooling systems work. Welcome, Mike.

Mike Cappuccio: Good morning, John. How are you?

John: Good thanks. Mike, what is a ductless heating and cooling system?

Mike: Well, a ductless heating and cooling system, John, is devised of basically three components. What we have on the ductless heating and cooling system, so we have one outdoor unit, which you’ve probably seen on the central air conditioning system, it’s a box that it’s outside the home.

John: One of those air conditioner unit things that sits on the ground, outside the house?

Mike: Yes. It’s outside the home and has a fan in it, makes very little noise, I see a little bit differently than the way that you would see a traditional air conditioning system. Those fans basically blow up in the air, where our fans blow straight out. They don’t blow up; they blow sideways so a little bit different, a lot quieter than one of those systems. Then inside the home, we have what’s called an air handling unit and that usually mounts on the wall inside the home, and we do have different types of indoor units, we have ceiling recessed units that go into the ceiling.

Then, we have small ducted units too that we can actually put ductwork on with those but the third part of it is this … a two pipe system and an electrical wire in the drain that goes between the indoor and outdoor unit and what’s happening there is, we have electricity flowing from the outdoor unit to the indoor unit and refrigerant is being pumped by a compressor from the outdoor unit to the indoor unit of the home.

Differences Between a Ductless Heating and Cooling System vs. Traditional

John: Okay. Tell me a little bit about how that’s different from a traditional heating and cooling system with a furnace and that sort of thing?

Mike: Okay, well a traditional heating and cooling system, those systems usually run on the heating side, will either run on natural gas or oil. On the cooling side of the central heating and cooling system, you would have ductwork in the home that would run to all of the different rooms in the home and typically you have one thermostat in the home or maybe on the first floor or the second floor that control that basic zone of the home. That zone is being made up of multiple rooms and one thermostat.

Our systems are a little bit different. We basically put one zone in each room so the temperature in that space can be controlled to how you want that space to operate. Example, you have a home office and you want to be 68 degrees in that office, you have basically your own heating and air conditioning system in that office. You’re not running outside into the hallway and turning the thermostat up and down, because you’re hot or cold and vice versa when you leave the office, you can turn that unit off to save energy to go to a different part of the home and turn on that unit. We have multiple units in different areas in the home — we zone out the home. That’s the biggest difference between the two systems.

Then the other thing is that .. that does operate on electricity and we have an inverter-driven compressor on that unit outside that basically speeds up and slows down. Your typical systems turn on and turn off. Our system doesn’t turn on and off; it speeds up and slows down as needed for the temperature in the space.

Ductless Heating System

John: Tell me about ductless systems in terms of heating, because I’ve heard of them for air conditioning and it’s a good way to do air conditioning but how does it work with heating? Is it electric heat?

Mike: It is electric heat, but it’s not a typical toaster oven type electrical heat as I would call it. When you look at a typical electric-based board heater or any type of electric heat like your old heat pump you used to talk about that people associate the word with heat pump and they go, “Oh, that’s an expensive electric heat we’re going to be using.” Well, we don’t use back-up electric heat with us. We basically have a reverse cycle in the winter time.

Our unit from the outside becomes the indoor unit, so that’s where the cold air gets distributed outside. It takes the heat from the outdoor unit and puts it into the space on the inside. So it basically … the compressor speeds up and slows down in the space to give you what you need for heating in there. There’s nothing red that’s going to glow in the ductwork, this is just strictly refrigerant that’s flowing through a coil.

Single-Split Ductless System

John: Interesting. What is a single-split ductless system?

Mike: A single-split ductless system, we called that a one-on-one system is what we call that in our trade, but basically what that is you have one outdoor unit, one indoor unit. Example of where you would use a single-split ductless system would be — let’s say, you’re adding on a room into your home, you’re doing a three-season room or maybe you’re adding a master bedroom in a home and you just want to get heating and air conditioning in the one space, so you would put one indoor unit, one outdoor unit and that would be that zone of that home, so it’s basically one indoor, one outdoor, that’s what it’s comprised of.

Multi-Split Ductless System

John: Then there is this multi-split ductless system, what is that?

Mike: Yes. The multi-splits, that’s basically we call a multi-zone so we’re adding more indoor units to one outdoor unit. Now, we have systems that you can put, two indoor units on one outdoor condensing unit and then we have systems you can put up to eight indoor units on one outdoor unit. So what you’d be doing is, you’d be zoning off the home. Example, putting one unit in each bedroom, making that bedroom its own zone, one unit in the living room, one unit in the master bedroom … however you would want to do that. We do a lot of that, we do multiple units inside of a home when we go in there.

John: How does that work in terms of having that one unit and yet you were able to control where the heat or the air conditioning goes in the home. How does that work?

Mike: Basically there’s a set of pipes just like what we explained on the single-zone system. There’s one set of two pipes, electrical and drain, that go to the outdoor unit. Then that outdoor unit knows, [for] example, if we have, let’s say, we have eight indoor units on that one outdoor unit. If four of those indoor units are not running, the outdoor unit says, “Whoa, wait a minute, I only have four units hooked on to me.” It doesn’t run at full speed, it basically runs at half-speed, very similar to an accelerator in your car.

If you’re driving on the highway, you speed up to get out onto the highway. Basically our systems speeds up real fast to bring the temperature down then as it brings the temperature down on the room it goes into a cruise control type mode. So, if the other units aren’t on, it senses that it can only run at 50% of the speed and then as it gets down to temperature on the room, it can run at like an eighth of the speed of what that compressor can run at. That’s how we gain our efficiency on the multi-zone systems.

John: Right. Okay, and that’s good news too for homeowners are installing one of these systems. You have units like you said that are outdoor units but can control up to– you said eight –?

Mike: — Eight zones.

John: — zones indoor units. You don’t have to worry about in your backyard, if you’ve got eight different compressors out there.

Mike: No, no. There’s only one compressor out there working at that time.

John: Right.

Mike: Exactly.

Choosing a Ductless Heating and Cooling System

John: How do you determine what kind of system somebody needs in their — in their home?

Mike: Well, at that point, if we go out to the home or when we go out to the home we do a low calculation, see how many BTUs each room needs, then from there we pick what indoor unit, what size BTU unit could go in there we have anywhere from 6,000 BTUs up to 30,000 BTUs that we could put on one zone. So, we calculate what they need and then we determine from there how many, what size units we going to put in that space.

John: Alright. That’s really a great information. Thanks again for speaking with me today, Mike.

Mike: Great John. Thank you.

John: For more information, this is the N.E.T.R., Inc. website at or call 781-933-NETR, that’s 781-933-6387.

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