HP water heaters: where the rubber meets the road

Aug. 9, 2010
Dave Yates talks about the guidelines for installing heat pump water heaters

"I haven't offered heat pump (HP) water heaters because I don't have an EPA refrigerant handling license."

The good news, no make that great news, for my friend and competitor who said that: he doesn't need the license to sell and install HP water heaters. The refrigerant circuit is self-contained. The potentially bad news is that failure to follow a few basic guidelines will increase operating costs for his customers and potential for service issues he'll be forced to correct.

Location, location, location
While ideal operating conditions will grant reasonably good gallon per hour recovery rates, adverse conditions will increase operating costs while reducing the GPH recovery rate.

  • A minimum 10' x 10' x 8' room is needed to allow for air conditioning of the space. As the room cools down, the operating efficiency falls-off because there's less heat available to extract from the room's air. The colder the room, the longer it takes to recover storage target temperature. At 45°F ambient air, most heat pump water heaters shut down the compressor in a self-protect mode. A few models grant the ability to directly pipe intake and discharge air to another larger space or outdoors. This permits installing a HP water heater in a more confined space.
  • Auxiliary air conditioning: In the scope of whole-house A/C systems, the cooling output from a HP water heater is relatively tiny. However, be aware of where you're placing this benefit, so that it doesn't become an issue during the heating season. Cooling indoors in winter may need to be offset by the home's heating system – or at least perceived by the owners as an added load. Some HP water heater models have optional vent kits allowing you to direct the cooled air to another room or to the great outdoors with the ability to divert the cooled air-flow indoors/outdoors as desired.
  • Bear in mind that you’re installing an air conditioner! Adequate air-space around the heat pump section is necessary to ensure proper air-flow across its coil. Generally, the correctly orientated tank needs to be 6-in. away from the back wall; 3-ft. clearance on its air-inlet side; and 5-ft. on the air-discharge side. Cramped quarters will cause the cooled conditioned air to short-circuit back through the inlet, reducing operating efficiency.
  • Air filters must be kept clean and that may require the owners perform this routine maintenance task four or more times a year, depending on conditions. Here again, internal sensors will disable the heat pump if air-flow becomes too restricted by operating with clogged air-filters. Just one more reason for you to sell homeowners value-added service contracts.
  • Dehumidification of the surrounding space can be a side-benefit, but requires the addition of a condensate drain, just like any standard air conditioning system. Drilling a hole in the floor is a half-fast way to deal with condensate. If a gravity drain isn’t available, add a condensate pump and don't pipe the discharge to the outdoors if you live in an area where the drain will be exposed to freezing weather conditions. Small-diameter flexible vinyl tubing can normally be routed to the laundry drain from the pump, which allows you to terminate using the washing machine's sewer drain trap as a safe-waste. Gravity condensate drains need to be cleaned annually (service contract item).
  • Attics and garages subject to cold outdoor weather conditions will require operating in a hybrid mode that incorporates the use of the immersed electric elements. Cost savings will be lower. Condensate drains subject to freezing conditions may need to be insulated and incorporate a heat-trace rated for being overlapped and covered with insulation.
  • Height needs to be accommodated! Eighty gallon models can be 6.5-ft. to 7-ft. tall and may require another 6-in. of free air-space above the top.
  • When assigning jobs, consider the weight of the model. Figure out which ones are suitable for a one-person installation. For example, a 250- to 400-lb. model probably needs more than one person working on the installation.
  • At least one model indicates water pressure cannot exceed 80 psi. Although your incoming pressure may be within guidelines, don't forget to compensate for the increase in pressure resulting from thermal expansion by incorporating a properly sized thermal expansion tank.
  • If you are going to install a 115-volt add-on model, bear in mind that a thorough clean and flush may be required and become an issue requiring annual cleaning if mineral deposits from hard water are an issue. At least one model suggests the owner(s) perform a 5-gal. flush each month to get rid of scale and sediment accumulations.

HP water heaters are a smart choice for direct-replacements or new installations if properly installed and programmed. Operating in the full heat-pump mode (rather than hybrid or in electric-heat modes) offers your customers the ability to purchase a water heater that will more than pay for itself over the course of its life-span. Up-selling to a larger model can be easily justified and grants a nice cushion for those times of heavier-than-normal use of hot water. With or without the tax credit, heat pump water heaters make perfect sense.

Dave Yates owns F.W. Behler, a contracting company in York, Pa. He can be reached by phone at 717/843-4920 or by e-mail at [email protected].

All Dave Yates material in print and on Contractor's Web site is protected by Copyright 2010. Any reuse of this material (print or electronic) must first have the expressed written permission of Dave Yates and Contractor magazine. Please contact via email at: [email protected].

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