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Heat Pumps


kurt
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I've never inspected one. Never seen one. Understand the fundamentals, but after that, I'm clueless.

So, I have a customer here @ the 42nd parallel that wants to install one in his 17 year old home & is asking my opinion. I've got all the usual outdated misconceptions about them; I have no opinion that's meaningful.

Anyone using one in a similar climate to Chicago? Opinions?

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It's the most economic way to go, since you're transferring heat, rather than creating it whole from natural gas or something else. Around here, the auxiliary heat is almost always electrical, but you'll want to recommend natural gas, 'cause it's less expensive and will used more due to the cooler temperatures.

Below is the heat pump description from the glossary I include with my inspection reports. Pretty basic, but it may help your customer.

HEAT PUMP—To understand heat pumps and how they work, it’s first necessary to have a basic grasp of air-conditioning systems. It’s actually a misnomer to say that an air-conditioning system cools a house. It actually removes heat from within the home. How? The refrigerant, which travels through a loop of copper tubing between the indoor evaporator-coil and the outdoor condenser-coil, enters the heat pump—located within the home—in a liquid state. Once inside the evaporator coil, however, the refrigerant expands into a gas. And when gas expands, it absorbs heat. Press the button of an aerosol spray-can for more than a few seconds. The can noticeably cools because expanding gas is absorbing heat from both the can and the air around it. This same process occurs when refrigerant enters the evaporator coil. The refrigerant expands into a gas, and absorbs heat from air in the coil’s cabinet before the blower circulates the air back into a home.

How does this relate to heat pumps? A heat pump, when set to cooling mode, works exactly like an air-conditioning system. When set to heating mode, however, the heat pump utilizes a mechanical device called a reversing valve, which isn’t found in standard air-conditioning systems. The reversing valve, as you may have guessed, reverses the air-conditioning process described above. Instead of refrigerant expanding within the evaporator coil located inside the home, it expands within the outdoor condenser and absorbs heat from atmospheric air surrounding the compressor cabinet. The warmed refrigerant is then transported back into the home through copper tubing to heat air circulating within the heat pump.

When outdoor temperatures reach thirty degrees or lower, a heat pump can have difficulty maintaining a comfortable temperature inside a home. Because of this, nearly all heat pumps—geothermal units are common exceptions—contain auxiliary-heat systems that either assist or take over when the heat pump is incapable of adequately warming a home’s interior. Most heat pumps in Lexington have electrical resistance back-up heating systems. These heat pumps contain two, three, or four five-kilowatt elements that glow red like coils in a toaster, and which elevate the temperature of air passing through them. When outdoor temperatures fall below a point where the heat pump can no longer effectively warm a house, the auxiliary heating system is energized, one five-kilowatt element at a time, to supplement heat that’s being extracted from outdoors. Inside the home, a light—normally blue or green in color, but sometimes orange—housed within the thermostat glows to notify occupants that the auxiliary heating system is in use. Next to the auxiliary-heat indicator light is the emergency-heat indicator light, which is almost always red. This light illuminates when a lever on the thermostat is set to emergency heat, which is seldom necessary unless one of the heat-pump components needs servicing.

Heat pumps—when auxiliary heat systems are not in use—are less expensive to operate than electric- or natural-gas furnaces which create heat rather than transfer it. A standard electric furnace, for instance, only produces 3,400 BTUs per kilowatt of electricity consumption. A heat pump, however, consuming the same kilowatt of electricity, will produce nearly 10,000 BTUs.

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We bought this dump a few years ago and the only heat that was ever added was electric bsbd in half the rooms. Being waaaay out in the boonies, we'd have to bring in a LP or oil tank and pay extra to have fuel delivered.

After spending my career telling folks how horrible they are N. of the M/D line, I chose to install an air source h/p with electric back-up. I gotst no complaints. Other folks around here moaned about the huge jump in fuel costs last winter while we saw no increase. (Thank you nuke plants)

When choosing a h/p for a colder climate, the proper size is important. Choose one with a heating season performance factor (HSPF) of 9 or 10. It's also important for correct air flow and precise refrigerant charge. Install the condensing unit out of the Chicago wind and a demand-defrost control system uses less energy.

We are 40 degrees, 38' N. of the Equator. If your guy can get gas back-up, I don't think it would be a dumb choice, but the fact that you've never seen one may be an indication that I'm wrong.

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Hi,

We had them in Colorado Springs when I was stationed at Ft. Carson, so they do work in colder climates - just realize that once the temperature drops to below about 45°F you're heatin the house with the auxiliary heat source (Ours was gas but some folks I knew had electric).

I only see them occasionally here. Not sure why. The climate here is so temperate that you'd expect them to work well year-round.

OT - OF!!!

M.

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I see a few heat pumps now and then but only in municipalities that have protected electric rates. A couple communities made deals w/ the electric co. about a hundred years ago and they have fixed rates for their citizens around 3-4 cents for a kilowatt hour. At that rate, in our climate, they work OK, but even then are not a lot more economical than NG. My electric is 14 cents a Kwh so for me it'd be out of the question. 43.24 degrees

If your customer has enough land to put in a ground loop w/o digging wells, ground source will work nicely.

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We have a good deal of heat pumps in middle Tennessee. We also have cheap electricity! 6.8 cents a KW hour, thank you TVA! Most of the ones I have seen have electric resistance coils for their back-up or supplemental heat. In my home I have an HP for my bonus room that is a dual fuel system. Small 1.5 ton unit that works like a champ. Right now it is 45f and raining outside and I have 83f degree heat coming out of the register. It will switch over to the supplemental heat when it hits around 40f outside. Then it operates like a normal fan forced gas furnace.

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Originally posted by kurt

I've never inspected one. Never seen one. Understand the fundamentals, but after that, I'm clueless.

So, I have a customer here @ the 42nd parallel that wants to install one in his 17 year old home & is asking my opinion. I've got all the usual outdated misconceptions about them; I have no opinion that's meaningful.

Anyone using one in a similar climate to Chicago? Opinions?

http://www.energyright.com/cgi-bin/dtc?tvaparms

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