What is a Heat Pump and How Does it work?
There are a lot of questions and confusion surrounding Heat Pumps in the Kansas City, MO. area. The basic concept for heat pumps has been around since 1856. Heat Pumps became popular in the 1970s due to rising fuel prices from the oil shortage. The popularity of heat pumps surged again in the early to mid-2000s due to tax credits and rebate programs. If this sounds familiar, you may have read our January article on the state of the IRA and heat pumps. Though the technology has been around for a while, the heat pump hasn’t had much-staying power in colder climates. As technology continues to improve and come up with advancements, heat pumps are on the rise all across the country once again. In this article, we will be discussing how a heat pump works, the benefits and drawbacks, and some of the advancements in heat pump technology that make heat pumps attractive in all markets.
Whether you have an Air Conditioner or Heat Pump, the industry term for your undefined outdoor unit is the condenser. There are several different styles of condensers, but when we are describing the refrigerant system it’s easier to discuss them through the lens of an air conditioner. If we start with the basics, an air conditioner is just a heat rejection machine. That simple. Now how it does it is a little more complicated, but all it’s doing is rejecting heat. I’m going to simplify this a bit. Air is pulled from your return, through your filter, into the furnace or air handler, where the heat from the air is absorbed through the metal coil, into the refrigerant. The refrigerant is pulled through the copper lines by the compressor to a condenser outside, when the heated refrigerant gets outside a fan on the condenser moves air past the coil, putting the heat back into the air, and the fan rejects that warm air as far away from the condenser as it can. See, simple. Heat rejection machine.
Our technicians have been trained on all the complexities of Heat Pumps, but a lot of homeowners don’t understand how the heat pump works. A heat pump does the exact same thing that an air conditioner does, it’s a heat rejection machine. We say that an air conditioner only has one direction it can run, forward. A heat pump has a forward and reverse. If an air conditioner is a heat rejection machine, then a heat pump is a bi-polar air conditioner. It does not pull any air from outside; it’s just moving the heat from outside to inside. There is a component that is called a reversing valve that is told by the thermostat which way to reject the heat. And yes, we can get enough heat from outside to provide relatively comfortable heat in a home down to -20 degrees Fahrenheit. Not all units can do this, it takes specific cold-climate heat pumps to do this, but the technology is now there to do it. Think about how much colder -20 is than 0. Within that difference, there is heat, as we lose heat the sensible temperature decreases, but there is heat even when it feels extremely cold to us. These machines just grab that heat and reject it into the home.
There are 3 main system types that we use residentially with heat pumps. They are all electric, dual fuel, and mini split. All electric applications should have a heat pump outside and an electric air handler inside. An air handler is basically a furnace without gas. It has 3 main components built into the unit. The blower, the electric heat kit, and the evaporator (inside) coil. The blower, or fan, works the exact same way as the blower on a furnace. An air handler heats with an electric coil, similar to the heating element in a toaster. It’s a mildly effective way to heat but has a high demand for electrical consumption. Electric heat is best utilized as supplemental heating, used in conjunction with a heat pump, to offset the difference between the capacity of the heat pump and the load demand being put on the house. You want to use it as little as possible since it rapidly increases your electric bill. The evaporator coil is the indoor coil that absorbs the heat in AC mode and expels the heat in heat pump mode. The idea is that the heat pump does the majority of the work, at a certain set temperature the electric heat comes on to give supplemental heat to hit capacity. As the outdoor temperature decreases and demand increases, electric heat is needed more. The key point here is that the 2 methods of heating work together most of the time. A Dual fuel system is one with a heat pump for the condenser and a gas furnace inside. With these systems, the heat pump is the primary heating down to a set temperature between 35 and 40 degrees. At this point the furnace takes over and provides the heat to the home. So, they are not very good teammates. Mini Split Systems have a side discharge heat pump condenser outside and individual head units for each room that they are responsible for conditioning. A mini split is solely responsible for heating the space. When temperatures drop below the capacity of the systems, the space has no heat. This is only in extreme conditions, generally -13 or below, but it does happen on occasion.
Newer technology advancements have given Heat Pumps the ability to be utilized in more applications and in more climates. For heat pumps, the advent of the cold climate heat pump dramatically lowers the minimum temperature required for use. Some of these systems can go as low as 20 or even 40 below zero. This has opened up the market for heat pumps in northern regions. Variable capacity is another technology that allows HVAC contractors to utilize heat pumps. When we describe variable capacity systems, we compare them to the temperature dial in your car. It doesn’t have to be full blast all the time. We can reach the desired temperature, then lower the setting to maintain the preferred temperature. A variable capacity system does exactly that, only with capacity. Capacity is just the volume of heat that the unit can, or is, rejecting. For years one problem contractors have struggled with heat pumps is sizing. Generally, a home’s heat load, how much heat you have to add to hit a desired temperature, is larger than a home’s cooling load, how much heat you have to remove to hit a desired temperature. If you size a heat pump to what it needs to be for heating, then when it goes into cooling mode it will have too much capacity and short cycle. This would lead to higher humidity in the home, thus decreased comfort. With variable capacity, we can oversize a system by a little bit. This will give us more capacity for heating, but allow us to reduce the size for cooling, dramatically increasing dehumidification and indoor comfort.
There are many benefits of using a heat pump. Some of them are comfort reasons such as heat pumps don’t have a gas flame that dries out the air. Moist air is more comfortable, so it’s easier for a humidifier to hit desired humidity levels. Many heat pump systems are quieter than gas furnaces. Heat pumps are considered a safer appliance as well. They don’t burn gas so there aren’t combustion concerns where CO could get into the living space. These systems are considered more environmentally friendly because they are using electricity instead of fossil fuels to create heat in the home.
While there are several benefits to heat pumps, there are drawbacks to owning a heat pump. Gas/Air Conditioner systems typically last 14 to 17 years, heat pump systems generally last 10-15 years with consistent maintenance. This is because the condenser is operating 3 to 4 times more than an air conditioner. Due to higher moisture content in these systems, air handlers have a higher potential for mold growth. We generally recommend installing a UV light above the evaporator coil in the air handler. This will emit UV rays across the coil and the air that flows past it. This kills the food sources required for growth and mitigates the problem. An iWave ionizer emits ions throughout the home which also neutralizes growth in the air handler, but also improves the entire home’s air quality. Both are great options. Another knock on heat pumps is that ice develops on the condenser, especially in extreme cold. To mitigate damage to the unit, systems are designed to go into a defrost cycle to melt the ice. Essentially, the system is turning the cooling on to utilize the rejected heat to melt the ice. This can lead to cool air production for a short time and less comfort. Last, and likely most important, is the upfront cost. Heat pumps are noticeably more expensive than traditional air conditioners. Prices vary among manufacturer and tiering, but you should expect to pay $1,500 to $6,000 more than an air conditioner. No matter your decision our comfort experts are trained and prepared to give you all your options, answer your questions, and solve the problems that you have with your heat pump system.
Maintenance is always a good idea to maximize the efficiency, maintain the reliability, and preserve the longevity of your HVAC system. This is even more true with heat pumps. Heat pumps are in operation way more than an air conditioner because its being utilized for cooling and heating. It is extremely important to keep the condenser coil clean and free of debris. In the summertime, cottonwood can wreak havoc on a condenser, covering the coil, and limiting the ability of the condenser to reject the heat. In the fall and winter leaves can do the same thing. This limits the absorption of heat, lowering capacity and efficiency. Having a dirty coil makes for a hard life for your compressor, which is responsible for moving the heat through the system. Compressor repairs are extremely expensive. When performing maintenance, we take a look at refrigerant levels and electrical components, which gives us the full picture of what is going on with your system, and allows us to inform you of needed and coming repairs. Ask any Summit Family member or check out our website to learn about our different maintenance programs. We have traditional plans called the Peak Performance Membership (PPM), a Wash Program, PPM+ that includes the wash program and maintenance program, or the PPM Platinum which is designed to keep your system running as reliably, as long, and as factory fresh as possible. You can pay for these programs upfront or sign up for our Perpetual Payment Program and get discounts along with your monthly subscription to our annual plans.
All this being said, our technicians are extensively trained in all areas of heat pump Installation, Service, and Maintenance. You can trust us with your in-home comfort needs with your heat pump system or any HVAC system you have. Remember if you are looking for the top, Reach for the Summit. Summit Heating and Cooling, 816.832.7770 or summithckc.com.