Ductless Heat Pumps

All About Heat Pumps

A heat pump doesn’t create heat. Rather, it transfers heat from one place to another by using a compressor to compress and expand a gas, called a refrigerant, through a network of sealed copper pipes. The refrigerant stays inside the pipes, and is expanded in the place where you want it to be cold (absorbing heat) and compressed where you want it to be warm (releasing heat).

A refrigerator is one of the oldest, and most common examples of a heat pump. The refrigerant is expanded in tubes inside the fridge and absorbs heat, then is pumped under or behind the fridge and compressed, where it releases heat. If you put your hand under or behind a fridge when it is running, you will feel some of this heat.

A ductless heat pump, also known as a minisplit, uses the same principle as a refrigerator to heat or cool your home. The outdoor unit is about the size of a large piece of luggage, and contains a compressor, a lot of copper pipes, a large fan, and a small computer. It is connected to the indoor unit by two pipes and an electric cable.

The indoor unit is about the size of a large child, and contains a bunch of pipes, a small fan, an air filter, and a small computer which connects to a wireless controller. The indoor unit also has a plastic pipe to the outside that drains water out of the unit when needed.

When you want to heat your home with a ductless heat pump, you use the wireless controller to turn the unit on, select the heat setting, and select a temperature. The outdoor unit begins expanding the gas in the outdoor unit, and once it has absorbed enough heat, compresses it and pushes it through the pipes to the indoor unit. A louver on the indoor unit opens, and a small fan blows over the warm pipes, sending the heat into the room.

To cool your home, you select the cooling setting on the wireless controller, and select a temperature. The compressor begins compressing the gas in the outdoor unit, and once it has released enough heat, expands it and runs it through the pipes to the indoor unit.

You can do several other things with a ductless heat pump, including using it as a dehumidifier and as an air filter (fan only, no heat). You can use the wireless controller to adjust how much power it uses, and set it to automatically switch between heating and cooling. Ductless heat pumps do not transfer air between the inside and outside of a home, making them ideal for use when the outside air quality is poor.

Because ductless heat pumps transfer heat, instead of creating it, they can be incredibly energy efficient. The electricity that is used to run the compressor and the fans is significantly less than the heat that is generated by that process. In fact, many ductless heat pumps produce 3 to 4 times the energy that they use. To put this in perspective, the most efficient natural gas furnace is about 98 percent efficient, which means that for every dollar you spend on fuel, 98 cents is converted to heat for your home, and 2 cents goes up the flue as waste heat. With a heat pump, for every dollar you spend on fuel, you generate 3 to 4 dollars of heat that is delivered into your home.

Heat pumps can be installed in many different situations. They can be mounted on walls, ceilings, and floors; can be ducted from the attic or crawlspace; and can replace an existing

furnace. One outdoor unit can connect with as many as 8 indoor units, and for larger applications you can switch to a commercial unit that can heat and cool apartment buildings, offices, and warehouses.

The most common installation in an existing home is of a single head unit. This is a set up where one outdoor unit is connected to one indoor unit, and that indoor unit heats a large main room, with the other rooms in the house heated by other means (often electric radiant heaters). The heat pump is sized to displace, not replace, the heating load of the house. This setup balances the cost of installing a heat pump, with the energy savings and comfort that come with it. Other set ups involve heat pumps in every room, or a balance of heat pumps and other heating sources. Be cautious about installing a ductless heat pump in the same house as an existing furnace. The thermostats on the different units often confuse each other.

Heats pumps are sized in British Thermal Units, or Btu. A 7000Btu unit will heat a small room, and a 48,000Btu will heat a whole house. When you are sizing a heat pump, bear in mind that a well insulated and air tight home will need a significantly smaller system than an uninsulated, drafty house. Insulating your house will save you money, as smaller systems cost less to install and run.

You can also heat the water in your house with a heat pump. These units look like a traditional electric water heater, but have a compressor and fan on top of the unit. The refrigerant is expanded in pipes on top of the unit, then compressed inside the tank. This removes heat from the air in the house, and puts it into the water. These units also have electric resistance heaters in the tank, just like a regular electric water heater, so if the heat pump can’t create enough hot water, the electric resistance takes over.

Heat pumps need a dedicated breaker on your electrical panel, ranging in size from 20 to 60 amps, depending on the size of the heat pump. You will need to run appropriately sized wire from the panel to the outdoor unit, or water heater.

Ductless heat pumps can range in cost from $4000 to $7000 for a single head unit, with additional indoor heads adding $1000 to $4000 each. Costs increase when the refrigerant pipes, condensate lines, or electric wires have long runs through areas that are difficult to access, when the electrical panel has to be upgraded, or when there are many indoor units to install. Prices decrease when the run between the indoor and outdoor unit is short and simple, there is space in the panel for a breaker, and there is enough room to work on the jobsite. For the indoor unit, a model that looks like a box on the wall is the least expensive, and a model that is a box mounted inline with your furnace, or that includes ducting, is more expensive.

Heat pump water heaters range in price from $3000 to $6000, depending on the number of gallons in the tank, and how difficult it is to install. The least expensive installation is in a large garage, where you are replacing an existing electric water heater, with plenty of space to move the unit in. The most expensive install is in an indoor closet, where there is not an existing water heater, and where the unit would need to be vented to another room. In this scenario you would need to run new hot and cold water lines to the closet, new electric lines, a new breaker on the panel, a condensate line to the exterior, and cut vents into the door or run ducting so the heat pump can pull heat from a different room in the house.

Most electric utilities provide rebates to switch from electric resistance heating to a heat pump. In areas where heat pumps are required by code, these rebates are often not available. For the most up-to-date rebates, please contact the utilities directly.

PSE has rebates of up to $1500 to replace a furnace with a heat pump, and $500 for a heat pump water heater.

The Community Energy Challenge in Bellingham has rebates of up to 45% of the project cost.

The Inflation Reduction Act, passed in 2022, is projected to be in place for rebates and tax credits starting in 2023. These rebates could be up to $10,000, and depend on a number of factors including income. Consumer Reports has a good overview.

Heat pumps are an efficient way to heat or cool your home. If you have any questions about heat pumps, or would like a bid to install one, please contact CAZ Construction at 360-389-1056 or info@cazconstruction.com