JohnCU, if you have a heat pump, then it won't cool well OR heat well. You house would only heat if your thermostat thinks there is a need for the supplemental or emergency heat. In which case a second functional furnace kicks in.
Originally posted by: runzwithsizorz
Sorry I'm late to this thread, but John, I also, now,(5yrs) have a heat pump. Thank God it's only in my basement! Moving from Ca. I had no idea what they were, so heres what I've found out so far, THEY SUCK! Unless they are used for a small area, that is double insulated, and you leave them on nearly 24/7, they neither, cool, or heat. I also have a switch similar to your, "supplt.", but mine is more aptly named, emerg. John, you DO NOT want to use this too often, if at all. I believe there are a few HVAC people here at ATOT that could explain in more detail.
Heat pumps do one thing and they do it very well: they keep a room (or house) at a constant temperature cheaply. In many cases, heat pumps can do that at a fraction of the cost of running an air conditioner or furnace (think roughly 1/5th of the cost). This is great if you have your thermostat set for one temperature all day every day. If the outside temperature is hotter than your set-point, then the heat pump will provide air that is slightly colder than your normal house temperature to keep it cool. If the outside temperature is colder than your set-point, then the heat pump will provide air that is slightly hotter than your house temperature to keep it warm.
Heat pumps are efficient since they give you free energy. Suppose you input 2000W of energy into an electric furnace to heat your house. Then 2000W of energy goes into your house to heat it up. But suppose you instead put 2000W of energy into a heat pump, that 2000W of energy goes into the house plus you PUMP 8000W of energy from outside back into your house for free (even if it is cold outside). The net effect is you spend money for 2000W of energy but you get 10,000W. Even natural gas or other forms of heating are generally far more expensive than heating via a heat pump with electricity.
Heat pumps, however, have limitations.
1) If you expect to feel really frigid or really hot air coming through your ducts, it won't happen. Heat pumps don't operate with short bursts of extreme temperatures, instead they heat or cool slightly and nearly continuously. You still save hundreds or thousands of dollars a year in energy costs.
2) If you rapidly change temperatures in the house, heat pumps can't keep up. Remember, they only give slightly hotter or cooler air. If you need to suddenly change your house temperature from 60°F to 75°F, a heat pump can't do it. This is where the "supplimental" or "emergency" switch comes in. An additional standard furnace will turn on and rapidly heat your house with really hot air. Of course, compared to the heat pump, this will cost you about 5x more. This is why you want to use that feature sparingly.
3) Having no rapid temperature swings mean programable thermostats aren't usually good fits with heat pumps. Programable thermostats are intended to give your house rapid temperature swings several times a day to save energy when you aren't home or aren't awake.
4) If the outside temperature is really extreme, then heat pumps can't keep up. Suppose it is -10°F outside, then you need that secondary furnace to keep up. It'll cost a lot though to run it since it isn't nearly as efficient as a heat pump.
5) Heat pumps are expensive to buy or fix.
Heat pumps are great as long as those limitations aren't problematic. For example, if you live in a place that is regularly in temperature extremes (say well below freezing or well over 100°F), you'll rarely use your heat pump feature and buying that expensive heat pump is a waste.
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