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New Tech: Heat Pump Water Heaters


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Heat Pump Water Heaters

Most homeowners who have heat pumps use them to heat and cool their homes. But a heat pump also can be used to heat water—either as stand-alone water heating system, or as combination water heating and space conditioning system.

How They Work

Heat pump water heaters use electricity to move heat from one place to another instead of generating heat directly. Therefore, they can be two to three times more energy efficient than conventional electric resistance water heaters. To move the heat, heat pumps work like a refrigerator in reverse.

While a refrigerator pulls heat from inside a box and dumps it into the surrounding room, a stand-alone air-source heat pump water heater pulls heat from the surrounding air and dumps it—at a higher temperature—into a tank to heat water. You can purchase a stand-alone heat pump water heating system as an integrated unit with a built-in water storage tank and back-up resistance heating elements. You can also retrofit a heat pump to work with an existing conventional storage water heater.

Heat pump water heaters require installation in locations that remain in the 40ºÃ¢â‚¬â€œ90ºF (4.4ºÃ¢â‚¬â€œ32.2ºC) range year-round and provide at least 1,000 cubic feet (28.3 cubic meters) of air space around the water heater. Cool exhaust air can be exhausted to the room or outdoors. Install them in a space with excess heat, such as a furnace room. Heat pump water heaters will not operate efficiently in a cold space. They tend to cool the spaces they are in. You can also install an air-source heat pump system that combines heating, cooling, and water heating. These combination systems pull their heat indoors from the outdoor air in the winter and from the indoor air in the summer. Because they remove heat from the air, any type of air-source heat pump system works more efficiently in a warm climate.

Homeowners primarily install geothermal heat pumps—which draw heat from the ground during the winter and from the indoor air during the summer—for heating and cooling their homes. For water heating, you can add a desuperheater to a geothermal heat pump system. A desuperheater is a small, auxiliary heat exchanger that uses superheated gases from the heat pump's compressor to heat water. This hot water then circulates through a pipe to the home's storage water heater tank.

Desuperheaters are also available for demand (tankless or instantaneous) water heaters. In the summer, the desuperheater uses the excess heat that would otherwise be expelled to the ground. Therefore, when the geothermal heat pump runs frequently during the summer, it can heat all of your water. During the fall, winter, and spring—when the desuperheater isn't producing as much excess heat—you'll need to rely more on your storage or demand water heater to heat the water. Some manufacturers also offer triple-function geothermal heat pump systems, which provide heating, cooling, and hot water. They use a separate heat exchanger to meet all of a household's hot water needs.

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Selecting a Heat Pump Water Heater

Heat pump water heater systems typically have higher initial costs than conventional storage water heaters. However, they have lower operating costs, which can offset their higher purchase and installation prices.

Before buying a heat pump water heating system, you also need to consider the following:

If you're considering installing an integrated water heating, space heating, and cooling heat pump system in your home, also see our information about air-source heat pumps and geothermal heat pumps.

Installation and Maintenance

Proper installation and maintenance of your heat pump water heating system can optimize its energy efficiency.

Proper installation depends on many factors. These factors include fuel type, climate, local building code requirements, and safety issues. Therefore, it's best to have a qualified plumbing and heating contractor (or geothermal heat pump system installer/designer) install your heat pump.

Do the following when selecting a qualified professional:

  • Request cost estimates in writing
  • Ask for references
  • Check the company with your local Better Business Bureau
  • See if the company will obtain a local permit if necessary and understands local building codes, etc.
Periodic water heater maintenance can significantly extend your water heater's life and minimize loss of efficiency. Read your owner's manual for specific maintenance recommendations.

Improving Energy Efficiency

After your water heater is properly installed and maintained, try some additional energy-saving strategies to help lower your water heating bills. Some energy-saving devices and systems are more cost-effective to install with the water heater.

Other Water Heater Options

Printable Version

Source: U.S. Dept. of Energy - Energy Efficiency & Renewable Energy

Additional Links:

Home Energy Magazine article about heat pump water heaters

Ruud Heat Pump Water Heaters

Rheem Heat Pump Water Heaters

GE Heat Pump Water Heaters

E-Tech Heat Pump Water Heaters

NOrth Road Technologies Geyser Heat Pump Water Heater

Wattersaver Heat Pump Water Heater

Air-Generate Heat Pump Water Heater

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I just caught wind of these heat pump water heaters a few weeks ago, while doing an exhaustive search on the efficiency of electric on demand water heaters. It was a pleasant surprise, and I'll definitely be considering one when mine needs replacement.

If anyone has real life experience with them, please clue us in. I'd love to learn more.

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Slight thread drift ... but relates to the new high efficiency "tank" water heaters. I just had an A.O. Smith product installed replacing my old unit. State owns/makes A.O. Smith so they have a rebranded version under the State name as well.

Nice system. I had posted about this several weeks ago if I recall correctly.

A.O. Smith Vertex "high efficiency"

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Slight thread drift ... but relates to the new high efficiency "tank" water heaters.

These new, natural gas powered, high efficiency water heaters achieve an efficiency of up to 96%. But even if they were to hit 100%, they would still not approximate the performance of a heat pump which renders heat energy in the vicinity of 300% of the electrical energy that is invested in it.

The only problem is that the operating temperature range of the evaporator (outside) half of the heat pump has a lower limit of about 40 degrees.

Doesn't bode well for applications in the northern USA unless it's ground sourced.

Marc

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Hi All,

My apologies; I just realized that I'd forgotten to attach the list of links to various HPWH products that I'd put together. It's now at the bottom of the OP.

Marc, these work best in climes where there are long warm seasons and the unit must be indoors in a room large enough that won't be over-cooled by the unit.

OT - OF!!!

M.

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  • 3 months later...
  • 4 months later...

wow,fantastic post,I think When comparing the performance of heat pumps, it is best to avoid the word "efficiency" which has a very specific thermodynamic definition. The term coefficient of performance (COP) is used to describe the ratio of useful heat movement to work input. Most vapor-compression heat pumps utilize electrically powered motors for their work input. However, in most vehicle applications, shaft work

DDTS..

http://www.gadgetshack.com

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Hi All,

My apologies; I just realized that I'd forgotten to attach the list of links to various HPWH products that I'd put together. It's now at the bottom of the OP.

Marc, these work best in climes where there are long warm seasons and the unit must be indoors in a room large enough that won't be over-cooled by the unit.

OT - OF!!!

M.

Aw.. I was mulling over the possibility of having one in the attic, where it could capitalize on endless on all the passive heat in the summer time and maybe recover a bit of lost heat in the Winter? Bad idea? Any thoughts or experience?

M.

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  • 2 weeks later...
  • 3 months later...

Greetings;

I am a distributor for the Geyser heat pump water heater in south florida. I would be happy to answer any questions I can about how well it works in a residential application.

I have always felt that there was a specific market for the Geyser in south florida. Some of the characterisitics of homes make the Geyser a pretty good solution. Basically, most water heaters are electric, in the garage, and next to the air handler unit (you can use the installed air handler drain to drain the condensate from the Geyser without having to run a separate drain line.)

Some of the other advantages have to do with the climate. It is unusual for the temperature to drop below 32F, and for at least 6 months of the year I would estimate that most garage temperatures are greater than 85F.

If anyone has any questions specific to the Geyser , I will certainly do my best to answer them.

Regards,

Ron Palinkas

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Greetings;

I am a distributor for the Geyser heat pump water heater in south florida. I would be happy to answer any questions I can about how well it works in a residential application.

I have always felt that there was a specific market for the Geyser in south florida. Some of the characterisitics of homes make the Geyser a pretty good solution. Basically, most water heaters are electric, in the garage, and next to the air handler unit (you can use the installed air handler drain to drain the condensate from the Geyser without having to run a separate drain line.)

Some of the other advantages have to do with the climate. It is unusual for the temperature to drop below 32F, and for at least 6 months of the year I would estimate that most garage temperatures are greater than 85F.

If anyone has any questions specific to the Geyser , I will certainly do my best to answer them.

Regards,

Ron Palinkas

Hello Ron,

Has the technology changed in the last 10 years? New refrigerant or anything else major?

Marc

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I'm going to install one of the GE Geospring units in my house just to experiment with. I'm going to leave the gas fired (propane) unit in place and install the heat pump unit next to it and valve it so I can use either or. I have a dedicated hot water circulation loop in my house as well. I just want to compare the performance and cost of the heat pump unit verses the gas fired unit.

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  • 3 years later...

Hello Ron,

Has the technology changed in the last 10 years? New refrigerant or anything else major?

Marc

Most things are R-410A now as R-22 was sent out the door a few years ago and R-134 will be replace by YF-1234 soon.

R-410A has a better co-efficient for heat pumps, Some are reporting it does not due to good in desert temps when used for comfort cooling.

Also scroll compressors are the norm now due to EER ratings.

Other than that it is still a cooling medium going through its life cycle.

The next big change we will see is Hydrocarbon and CO2 refrigerants, They are using R-600, R-600A and R-290 "N-Butane, Iso-Butane, and Propane" along with R-744 "CO2" in Europe. They have just approved R-290 for use in the states in systems that contain under 1lbs of refrigerant. We had the first run of soda machines come out last year that operate on propane!

Looks like we are heading back to the basics!

Sam

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