Many homes are equipped with heat pumps as their heating and cooling system. Heat pumps work well at most temperatures; however, in extreme temperatures they may not provide the comfort level you expect. The following are some operating and maintenance tips to help you set realistic expectations about heat pumps and to maintain the system at peak energy efficiency and operating effectiveness.
Heat pumps absorb heat from one place and transfer it to another. In air conditioning mode, they absorb heat from inside the home and transfer it outside. In heating mode, they absorb heat from outside and transfer it inside. This process works when the outside temperature is between about 40 and 95 degrees F. It is more difficult for the system to maintain comfortable interior temperatures when the outside temperature is beyond this range. Older systems and systems that are poorly maintained may have a narrower outside temperature range within which they can maintain comfortable interior temperatures.
Heat pumps, like any heating and cooling system, should be correctly sized for the home. A common misconception about heat pumps is that a larger system is always better; in fact too large is bad. A heat pump that is too large may not run long enough in air conditioning mode to effectively remove humidity from the air. This can create moisture control problems that can contribute to mold growth. A heat pump is less energy efficient when it begins operating and does not reach full energy efficiency for several minutes. A heat pump that runs for short periods costs more to run and may have a shorter useful life.
Heat pumps are less effective in cold weather. This is why they are less common in northern areas. When the outside temperature falls below about 40 degrees F., a heat pump may not be able to raise the internal temperature to a comfortable level. Heat pumps in cooler climates are equipped with auxiliary heating elements. These elements look and act much like the wires that glow red in a toaster. Like their cousins in a toaster, these elements provide additional heat to help bring the inside temperature to a normal level. Because it is difficult to know if these elements are operating properly, you should have them tested as part of normal system maintenance.
A heat pump should maintain a comfortable indoor temperature. The International Residential Code (IRC) heating performance standard requires that the system maintain a temperature in the home of at least 68 degrees F. The IRC has no performance standard for cooling. The National Association of Home Builders (NAHB) heating performance standard is 70 degrees F. and the cooling standard is 78 degrees F. or 15 degrees C. below an outside air temperature of 95 degrees F. States and cities may have different standards. The performance standard temperature is often measured near the center of the room and about five feet above the floor.
The IRC and NAHB standards are not clear about temperature variances between areas in the home, but it is reasonable to expect that the temperature in each area be near the temperature at the thermostat. Some temperature variation between areas is normal and unavoidable. It is reasonable to allow one or two degrees temperature variance between areas.
Operating a heat pump is similar to operating any forced air HVAC system. In most cases, the recommended thermostat settings for heat pumps are 68 degrees F. in winter and 78 in summer. These settings provide energy efficient operation at reasonable comfort levels.
Use of setback thermostats is generally not recommended with heat pumps, particularly in heat mode. Heat pumps are often designed so that in heating mode, if there is a difference of about 3 or more degrees between the thermostat setting and inside air temperature, the auxiliary heating elements will be activated. The heating elements are far more expensive to run than the heat pump itself, so use of the heat strips should be avoided.
Heat pump maintenance starts with regular filter replacement. If you choose disposable filters, use the inexpensive blue or white fiberglass mesh type. The more expensive pleated paper filters can restrict the air flow in the system making it work longer. Change these filter every month.
If you have an access tube in the condensate drain line at the air handler, pour about ½ cup of bleach into the line when you change the filter. This will help keep the line clean and reduce the chance that it will clog and force water into your home. If you do not have an access tube, consider having one installed at the next service call.
Use a garden hose to wash the fins on the condenser (the outside unit) about once per month. Keep walls and plants at least 1 foot from the sides and 10 feet from the top of the condenser. Keep the condenser shaded from direct sunlight to the extent practical.
Finally, have preventative maintenance service performed on the system at least once per year.
Like all mechanical components, heat pumps wear out. Condensers typically last between about 5 and 15 years. Air handlers typically last between 15 and 20 years.
Heat pumps are a good choice for heating and cooling in warm climates where gas service is not available. A gas furnace is usually a more cost-effective choice where gas service is available. Heat pumps can provide energy efficient service for many years when properly installed, operated, and maintained.
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