Heat pump
Yes, a Heat Pump, does not involve "creating" heat, as John and others have said but simply re-locating pre-existing heat from one area to another.
Heat is the flow of thermal energy from one body to another. Thermodynamics state that heat must flow from a warmer object to a cooler object. In the Winter, heat wants to flow OUT of your house to the colder outside air. A heat pump supplies just enough energy to move natural, pre-existing heat, contained in the outside air into your home.
When it is, say zero degrees F, it doesn't seem as if there is much heat out there. BUT...
Absolute zero, which is almost -460 F, is the coldest temperature that can exist in our Universe.
So when it is 0 degrees F outside, we still have 460 degrees of heat available in the air. More than enough to boil water! Your heat pump just uses enough energy to move some of this heat from the outdoors into your home.
From reading the postings here, and talking to others, it seems that people either hate or love Heat Pumps. Those who have never had one develop their opinions based on which of the two groups of people they have talked to, not from personal experience.
I have found that those who hate Heat Pumps, and have actually had one, are victims of improper installation, a low quality/less efficient unit, or improper operation due to ignorance. ("Ignorance" not meaning to be an insult, but meaning "not educated" or "not knowledgeable" of proper operation.)
Like the garbage disposal, the heat pump is laden with Old Wive's Tales of misinformation.
Many HVAC dealers do not take the time or money to properly install a central Heat Pump. Heat pumps are a different animal and operate by moving large quantities of air for longer times--since the temperature differential between air going into a heat pump and coming out is less than say from a fossil fuel furnace, such as a gas or oil-fired furnace.
Larger ducts must be used, and larger registers. Conventual heating systems often use the typical 4 by 10 floor registers, heat pumps must have a minimum of 4 by 12 inch registers or larger for most room sizes.
Builders are probably the number one source of Heat Pump irritation. They often use the lowest quality/efficiency unit they can find. They often do not properly size ducts, nor registers and rarely strategically place registers and cold air return intake vents. The result--an unhappy homeowner. don't blame the heat pump, blame the lazy and greedy builder.
I have read comments about a heat pump running "all the time." Actually, that is normal and that is the way they are designed. Near the balance point a heat pump should be running continuously or near continuously....moving large amounts of air with low temperature differentials. The air is not supposed to necessarily be hot such as from a gas furnace. However, in mild weather, yes, heat pump air can be hot enough to nearly burn your hand on a register if you leave it on there.
As outside temperature goes down, so does the the temperature of the air exiting from your Heat Pump air handler. To compensate, the heat pump runs longer. When in perfect balance, heat loss from your home equals heat gain from your Heat Pump, your heat pump will be running continuously. It is supposed to. When continuous running cannot balance the temperature, then the auxiliary heating will come on sporadically to add heat energy to the air. (This auxiliary hear is often electric, but doesn't have to be. It could be gas, etc.)
For simplicity, I am talking about an "air source" heat pump. Not geothermal. Air-source meaning it is pulling heat out of the Winter air.
A house with leaking windows, or under-insulated can change the balance point to occurring at a higher outdoor temperature. A super-insulated house or very well constructed house can lower the balance point tremendously. The more efficient the heat pump, the lower the outdoor air temperature is at which the balance point is reached.
Heat pumps are now most often listed with SEER (Seasonal Energy Efficiency Rating). Such as 11, 14, etc.
Less often seen is the COP, Coefficient of Performance. This is the ratio of energy put into to the system compared to the heat energy put out by your Heat Pump. For example, a COP of 3.0 for your heat pump, means that at a given outdoor temperature, for every unit of energy you put into your heat pump, you get three units of heat energy out.
I don't recall the COP, exactly, of straight electric resistance heat but it is quite high around 99.7 or something in that vicinity. So, for every unit of energy you put in, you get almost one unit of heat energy out. Little is lost due to efficiency.
With a heat pump, manufacture's rate at two typical outdoor temperatures, one of them is 17 degrees F. So a COP for a residential heat pump might be, for example, 2.3 at 17 degrees F. Meaning at this outdoor temperature, for every unit of energy you put in you will get 2.3 units of heat energy out. Many residential heat pumps retain COP's greater than one into the single digits or even below zero.
That is why Heat Pumps are ecologically such sound ways to heat your home.
Often, I find people do not understand that most heat pump thermostats are programed to kick in the auxiliary heat if you turn them up 2 degrees or more at a given time. If you have an "Aux Heat" indicator light you will see it come on. The thermostat thinks you are cold and want heat fast, so the aux heat will speed up your getting the house warm.
Of course, you just dumped money down the drain when you utilize you auxiliary heat because you may be creating heat with a COP of nearly one, when you could have been using the heat pump to move heat with a COP of, let's say 3 or 3.5 or more.
Unless you are shivering in your boots, it is best to never turn a heat pump up more than one degree at a time. If you are still wanting a higher room temperature, wait until the room comes up to temp, then turn up the thermostat another degree.
If you turn your thermostat down at night, most modern programmable heat pump thermostats will compute at what time in the morning to start heating the house, using the auxiliary heat as little as possible, to get it up to temperature at your waking time.
Oddly, many of the newer thermostats do not have the Axillary Heat indicator light. Some have none, and some show a small icon or word that one may easily overlooked.
Thinking back, and adding up, I have had five homes/apartments with Heat Pumps. My current home is my fifth house equipped with an air source heat pump. I love them. If you understand them, know what to expect, and how to use them, they can save you a lot of money.
You are not burning any fossil fuel (it's much more efficient, and cleaner for your electrical utility to burn fossils fuels, centrally, that it is for each separate house to do so). There is no danger of gas leakage, carbon monoxide, or explosions.
A Heat Pump, as mentioned, is a different kind of animal. You can't expect a cougar to act like a wolf. They are different creatures but each has its own beauties.
A Heat Pump is not a gas fired furnace, nor is it a coal unit, nor an oil fired unit. So quit thinking it should act like one.
A heat pump will run near continuously or continuously in very cold weather, it is not going to give toasty feeling air out of the register at very cold temps, and you have to have the knowledge to know how to operate the thermostat so as to not kick in the auxiliary heat.
The continuous air is a good thing, it means continuously filtered and circulated air. The lower register air temps (in very cold weather) means the moving air is not as drying to the skin and you get greater temperature uniformity around the house as you do not have zones of blasting hot heat near the registers.
Heat pumps aren't for everyone, but if you want greater efficiency using natures heat, you like greater temperature uniformity in your house and cleaner air then you probably will become best friends with your Heat Pump should you decide to get one.
[this post was last edited: 3/13/2021-11:46]
