Article and photos by Gregory Havel
A package air-source heat pump is a refrigeration unit that is usually installed below a window to heat and air-condition a single room. On the inside of the room, it appears as a low cabinet against the wall with controls for heating and cooling cycles, room temperature, fan speed, and even fresh air intake and exhaust air. On the outside of the building, it can appear as a shallow box with louvers, similar to an air-conditioning unit installed through an opening in the wall, or as a louver below the window (Photo 1). An internal fan circulates the room air across the interior coil.
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In cooling mode, it operates like an air-conditioner, using refrigerant circulating through a coil in the room air, a coil in the outdoor air, a compressor, and valves. The refrigerant absorbs heat from the room air, evaporates, is compressed, releases the heat into the outdoor air, condenses as it cools, and recirculates to the coil in the room air. Humidity is also removed from the room air and drained away outside the building.
In heating mode, a control valve at the compressor reverses the flow of refrigerant so that the refrigerant absorbs heat from the outdoor air, evaporates, is compressed, releases the heat into the room air, condenses as it cools, and recirculates to the coil in the outdoor air. Today’s heat pumps are more efficient than in the past and are capable of producing heat from outdoor air with as little as one-half to one-third of the electrical energy required in the past.
In climates with winter temperatures near or below freezing for extended periods, the heat pump unit is usually supplemented with an electric heating coil built into the heat pump package.
Package heat pumps are usually installed in place of conventional heating and air-conditioning systems. These units are installed from inside the room in an opening below the window. Since each is supported by the exterior wall and the floor, it is unlikely that they will be dislodged and fall outside the building during interior firefighting operations.
Small package heat pump units are frequently used in spaces where individual room temperature control is essential, as in hotel rooms, college dormitories, and elderly care facilities. Larger package units are used in conference rooms and small apartments.
These heat pump units usually require a 240-volt single-phase electrical circuit for operation, with increased circuit breaker ampere capacity if an electric heating coil is included. Units for larger spaces may require a larger electrical circuit.
A concern to firefighters is the additional high-voltage electrical circuit present in each room or apartment, in addition to the pressure within the sealed refrigerant system. In some buildings, the circuits that supply power to these heat pumps are in a different circuit panel from the circuits that supply power to lights and convenience outlets.
This type of heating/air-conditioning system in a building is worth a note on the building’s preincident plan, including the locations of the circuit breakers for these units.
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Gregory Havel is a member of the Town of Burlington (WI) Fire Department; retired deputy chief and training officer; and a 30-year veteran of the fire service. He is a Wisconsin-certified fire instructor II, fire officer II, and fire inspector; an adjunct instructor in fire service programs at Gateway Technical College; and safety director for Scherrer Construction Co., Inc. Havel has a bachelor’s degree from St. Norbert College; has more than 30 years of experience in facilities management and building construction; and has presented classes at FDIC.
