If you’ve just moved into a home with a heat pump, or never really understood how a heat pump works, or just want a solid base of knowledge about your heat pump before you discuss it with a service person or sales person, then this is for you. 

A heat pump - air conditioner heats your home during the winter, it also cools it during the summer. It does not burn fuel to produce heat nor does the electricity it consumes go through an electric element except during defrost. The compressor does the work of heating and air conditioning.

The heat pump functions on the same principle as an  air conditioner. It simply air conditions the outside air colder than it is and rejects that heat indoors. 

The increased use of heat pumps in Raleigh then explains why Raleigh winters are getting colder, we are moving all the heat indoors for our personal comfort, even more so in the Knightdale and Garner area where there are more heat pumps, (air conditioning humor ?, well I thought so ). Cary of course has it’s weather controlled by Town of Cary weather regulations and  so is unaffected.

Anyway a liquid (freon) absorbs heat as it turns into a gas and releases heat as it condenses to a liquid state. The amount of heat that can be gathered from the outside air is limited by humidity in the air which freezes on the coil outside and requires energy to defrost. Your heat pump turns into an air conditioner for 10 minutes or so in defrost, using your homes heat to defrost the outdoor coil, $$$$. It also turns on an electric heater built into the air handler / furnace to temper the indoor air, so you won’t feel cold air blowing on you. Again $$$. Proper heat pump charging , clean coils, clean filters, and the right defrost control setting keeps this cost as low as it can be.

At Rainbow we don’t get a lot of  “I think I need freon“ service calls in heating weather, and the reason is that the electric furnace part of the heat pump will blow warm air even if the heatpump is not operating efficiently. You may notice that the fan runs a lot, and the electric bill is high, but unless the condenser (H.P.. outdoor section actually) freezes up you may not have a comfort problem, except in your budget (not humorous at all). Take a look outside once in awhile, see if the heat pump is running. A light coat of frost is okay, a heavy block of ice is a problem.

One more heating thing, if the fan stops, the heat pump “shoooooshes!” and you see steam coming from the H.P.. , it is not on fire. It is defrosting and will begin normal operation in less than 10 minutes.

During the summer, the heat pump operates as a standard central air conditioner: It removes heat from the house (evaporator coil) and rejects heat ( condenser coil )to the outside. A liquid refrigerant, usually R-22 or R-410a ( the new freon), (Freon is a brand name) is pumped through an evaporator coil. The liquid expands as it moves through the coil, changing to its gaseous state as it absorbs heat from the warm air surrounding the coil.

A blower then pushes air around the cooled coil through ducts and into the house. The gas, now carrying considerable heat, moves through a compressor and begins the liquefying process. It moves to a condenser coil outside the house, where the compressed gas releases its heat and returns to a liquid state. The air conditioner does does not use up the freon, it just goes from liquid freon to gaseous freon and back again. If you need freon it’s because you have a leak.

During the winter, the heat pump reverses this process, extracting heat from the cold air outside and releasing it inside the house. The heat pump is very efficient when the outside temperature is around 47 degrees ( a common rating temperature), but it does not become horribly less efficient as the temperature drops (17 degrees is the low end rating temperature) it just goes down in capacity ( BTUH).  Your heat pump is still pretty efficient at below freezing temperatures it just gets effectively smaller, and can no longer keep up with your homes heat loss. When the outside air temperature is very low, an  electric heater must be used to supplement the heat pump's output. 

The heat pump should be allowed to run and contribute as much heat as it can at even the lowest outdoor temperatures. It will always give back almost twice the energy it uses in heat. As it gets colder outside the amp. draw or amount of electricity is uses drops with the outdoor temperature. The efficiency does not suffer greatly, only the heat pump’s heating capacity. This is a fact too often misunderstood by the proponents of “dual fuel” systems that are forced to shut off the heat pump prematurely in most cases. Call Ed (me ) at Rainbow we’ll discuss it.

As long as we’re talking efficiency, keep in mind as you shop for a new heat pump that the SEER, Seasonal Energy Efficiency Rating, ever how high, is not the same as the HSPF, Heating Seasonal Performance Factor which does not get talked about nearly as much. SEER is about Air Conditioning your home, HSPF is about heating your home and the numbers don’t vary so wildly. Ask about HSPF, you’ll usually find a little less bragging.  A good question is : How much more efficient will my new heat pump be in heating service weather?

One last thing. Your thermostat. In cooling weather if the air conditioner is large enough you can save some money by setting it to a higher temperature when you are not at home for long periods. Just keep in mind it will take awhile to catch up when you get home. However in heating weather, set it and forget it is the general rule. We service Raleigh, Durham, Cary, Knightdale and Garner heat pumps, and very seldom find outdoor thermostats installed to prevent electric heaters from coming on with thermostat adjustments. When you move the thermostat up more than 2 degrees at one time the electric heaters will come on and use up the money you may save during set back. Going on vacation, by all means set it low, going to work? It may be little or no savings at all.

E-mail me with questions or comments Ed Cline http://www.RainbowServicesRaleighNC.com/get-in-touch.php or just call 919-630-1776