Heat Pumps and Energy Savings
•GE Zoneline Heat Pumps are designed to provide cost efficient heat pump operation while monitoring room conditions to maintain comfort.
The units employ a logic system monitoring both outdoor and indoor temperatures to determine the heat source, thus increasing energy savings by operating longer in the heat pump mode.
Heat pumps save energy and cost less to operate than units with electric resistance heaters as the only heat source. Just as the EER of an air conditioner is an indication of the efficiency of the unit, COP (Coefficient of Performance) is the indication of the efficiency of the heat pump. This relative efficiency of a heat pump compares the unit to electric resistance heat. If a unit has a COP of 3.0, it means the unit will produce three times as much heat at rating conditions for the same electrical input wattage used for electric resistance heat.
The compressor is used in heat pump operation just as in air conditioning operation. In heat pump operation, the hot refrigerant gas is directed to the indoor coil rather than to the outdoor coil. Room air that circulates over the indoor coil gains heat from the coil rather than losing heat to the coil as during cooling operation.
As the outdoor temperature falls, the heat pump is able to extract less heat from the outdoor air to raise the temperature of the indoor air. For this reason, all packaged terminal heat pumps also have electric resistance heaters as backup to heat pump operation. At some point, the heat pump is unable to provide sufficient heat to adequately warm the room. Many Packaged Terminal Heat Pumps cease heat pump operation and change to more expensive resistance heat at some
Balance Point
An important consideration of the selection of a heat pump unit is the “balance point” of the installation. Virtually every room is unique - with different insulation - different sizes and types of windows - different types of construction - different directional exposures. All of these variables, as well as geographical location, must be considered in order to determine the balance point, the point at which the heat pump is unable to produce enough heat to compensate for the heat loss of the room or area being heated. For these reasons a consulting engineer should be engaged to calculate the heat loss and specify the heat pump unit required.
GE offers two series of Zoneline Heat Pump units - the 3500 Series with Standard Microprocessor controls and the 5500 Series with Highly Featured Microprocessor controls - and both series react to the indoor temperature as well as the outdoor temperature in determining the heat source to provide comfortable room conditions and energy savings. This determination of the heat source based on the indoor temperature helps provide a more comfortable room.
•Heat Pump Operation - Zoneline 3500 Series
Switchover to resistance heat is determined by indoor temperature differential and outdoor coil temperature
The Zoneline 3500 Series heat pumps are Standard Microprocessor controlled units. A solid state thermostat control is used to measure the room temperature and compare it to the temperature selected with the “TEMP” control knob. A temperature sensor is in contact with the outdoor coil to monitor the outdoor coil temperature during heat pump operation.
The switchover point of the 3500 Series heat pump is determined by the outdoor coil temperature or the indoor air temperature. When the outdoor coil temperature is above 9°F. (which corresponds to approximately 25°F. outdoor air temperature), the unit attempts to provide sufficient heat through heat pump operation to satisfy the selected temperature setting.
The microprocessor monitors the indoor room temperature and determines if the heat pump output is adequate to maintain comfort conditions. As long as the heat pump output maintains the room temperature within 2.7°F of the set point, the unit will operate in the heat pump mode. If the room temperature continues to decline with the heat pump operating, heat pump operation will terminate and the unit will switch over to electric resistance heat to warm the room. This heat source logic allows the heat pump to operate to lower outdoor temperatures, increasing the savings from heat pump operation, while providing the ability to use resistance heat only when necessary. The heat pump and the electric resistance heaters never operate simultaneously on the Zoneline 3500 Series Units.
A heat pump override switch is provided in the auxiliary controls to allow the unit to operate only in resistance heat. The use of this option significantly increases the cost for heating.
Heat pump defrost - Zoneline 3500 Series
If the outdoor coil drops below 9°F. (which corresponds to approximately 25°F. outdoor air temperature), the unit employs a passive defrost system. A “passive defrost system” prevents heat pump operation until outdoor temperatures rise sufficiently to enable economical heat pump operation to resume. During the defrost mode, the indoor temperature is maintained by the electric resistance heater. The defrost cycle terminates when the outdoor coil temperature rises above 36°F., at which point the microprocessor will allow the unit to return to economical heat pump operation.
Heat pump condensate
See page 34 for information on heat pump condensate. The Zoneline 3500 Series heat pumps may be ordered with a factory installed Internal Condensate Removal (ICR) system to minimize the amount of condensate water draining from the unit during heat pump operation. The ICR system has proven to be an effective means of minimizing the amount of heat pump condensate dripping from the unit. However, if the requirements of a particular installation will allow no dripping of condensate water from the wall case, the installation of an internal or external drain system is recommended.
Units with ICR may not be installed in seacoast or corrosive environment applications.
19
