WHEELER ON HVACR: The New Cold Climate Heat Pump
Yes, this is an article about some manufacturer’s product. I hate writing about things like this, because each such article brings a flood of requests from other manufacturers who want me to write about their products, and some can be very persistent. I believe that articles like this need to be written, because how else will you learn about new ideas and new technology? But too many of them give the appearance of unethical promotion.
However, I was contacted by a manufacturer that truly has some new and interesting ideas. They have developed an air-to-air residential heat pump that may not need much in the way of the energy-hogging electric-resistance backup heaters. And what’s more, at very low outdoor temperatures, the heat output isn’t as cold and drafty as standard heat pumps.
You know, despite the terrible reputation that they may have developed in some areas, heat pumps are a great idea. Since they use stronger compressors, they make very reliable air conditioners. And in most climates, they can provide heat for about the same cost, or at a lower cost, than high-efficiency gas furnaces - as long as the outdoor winter temperature is average. But when the temperature drops well below freezing at night, the electric-resistance backup heat kicks in and the electric bill rises rapidly. This is why I have found the new low-ambient heat pump product from Enerkon Corp. so interesting.
How do heat pumps work? Like air conditioners, they don’t create heat or cooling, they simply take the heat from one place and move it to another place by lowering and raising the pressure of the refrigerant (the heat-conducting medium). The compressor recirculates and changes the refrigerant pressures - picking up heat at low pressure in one place and squeezing it out under high pressure in the other location. It’s like a sponge that you use to pick up moisture in one place and then squeeze it out in another. But when there isn’t much heat to pick up (as when it’s zero degrees outside), there isn’t much heat to be moved.
What have the folks at Enerkon (www.enerkoncorp.com) done to create more heat from their heat pumps when it’s very cold outside? They’ve added a second compressor that works ahead of, and in series with, the first compressor whenever it is very cold outside. So they are squeezing harder and sucking up more. And then they’ve added another feature - a special heat exchanger that transfers waste heat from the liquid line to the discharge of the booster compressor whenever extra heating is needed. When this device kicks in, the manufacturer tells me there is a significant rise in the temperature output.
There are several more interesting features of this heat pump that I could talk about, such as the two-speed primary compressor and a commercial-style control system, which add comfort and efficiency, but let’s look at some of the operating figures from their engineering data. This is what interests me. One of their claims is that at an outdoor temperature of 17°F, they achieve more than twice the efficiency of a standard heat pump and more than three times the efficiency of furnaces (but that’s a matter of apples vs. oranges).
Of course, this is a pricey system, but I think there is a huge potential market for it in northern climates, and they are looking for distributors. By the way, it also uses the environmentally friendly R-410A refrigerant, which will likely always be readily available.