Defrost Control; Outdoor Thermostat; Reversing Valve Coil; Indoor Blower Motor - Maytag Amana APC15 H Series Installation Instructions Manual

6. Defrost Control - The Defrost control provides time/temperature initiation and termination of the defrost cycle. When a Defrost
cycle is initiated, the defrost control shifts the reversing valve to "cooling" mode, stops the outdoor fan and brings on supplemental
heat. Normally, a Defrost cycle will take only 2-3 minutes unless system is low on charge or outdoor conditions are severe. (Windy
and cold.) The defrost control also provides for a 3 minute off cycle compressor delay.
7. Outdoor Thermostat - These optional controls are used to prevent full electric heater operation at varying outdoor ambient (0° F-to
45° F). They are normally open above their set points and closed below to permit staging of indoor supplement heater operation. If
the outdoor ambient temperature is below 0° F (-18° C) with 50% or higher RH, an outdoor thermostat (OT) must be installed and set
at (0°) on the dial. Failure to comply with this requirement may result in damage to the product which may not be covered by the
manufacturer's warranty.
8. Reversing Valve Coil - This coil is activated by the thermostat, in the cooling mode and during defrost. It positions the reversing valve
pilot valve for cooling operation.
9.

Indoor Blower Motor

Units with EEM Motors Only The EEM model indoor blower motor is activated by the room thermostat by COOLING/HEATING or
FAN ON position. The motor is energized by a 24 volt control signal (from thermostat Y, G or W) for EEM motors. EEM motors are
constant torque motors with very low power consumption.
(See Air Flow Measurement and Adjustment for speed adjustment instructions).
10. Blower Interlock Relay - This relay is used to energize the blower during the electric heat operation. Some room thermostats do not
energize the motor during electric heat. This relay insures blower operation when the room thermostat energizes heat. This relay has
a 240 volt coil and an 8 amp contact relay. This relay is energized by the electric heat kit sequencer.

EXPLANATION AND GUIDANCE (HEAT PUMP)

The heat pump is a relatively simple device. It operates exactly as a Summer Air Conditioner unit when it is on the cooling cycle.
Therefore, all the charts and data for service that apply to summer air conditioning apply to the heat pump when it is on the cooling
cycle, and most apply on the heating cycle except that "condenser" becomes "evaporator", "evaporator" becomes "condenser",
"cooling" becomes "heating".
When the heat pump is on the heating cycle, it is necessary to redirect the refrigerant flow through the refrigerant circuit external
to the compressor. This is accomplished with a reversing valve. Thus, the hot discharge vapor from the compressor is directed to
the indoor coil (evaporator on the cooling cycle) where the heat is removed, and the vapor condenses to liquid. It then goes through
the expansion device to the outdoor coil (condenser on the cooling cycle) where the liquid is evaporated, and the vapor goes to the
compressor.
When the solenoid valve coil is operated either from heating to cooling or vice versa, the piston in the reversing valve to the low
pressure (high pressure) reverse positions in the reversing valve.
Figure 7 shows a schematic of a heat pump on the cooling cycle and the heating cycle. In addition to a reversing valve, a heat pump
is equipped with an expansion device and check valve for the indoor coil, and similar equipment for the outdoor coil. It is also
provided with a defrost control system.
The expansion devices are flowrator distributors and perform the same function on the heating cycle as on the cooling cycle. The
flowrator distributors also act as check valves to allow for the reverse of refrigerant flow.
When the heat pump is on the heating cycle, the outdoor coil is functioning as an evaporator. The temperature of the refrigerant
in the outdoor coil must be below the temperature of the outdoor air in order to extract heat from the air. Thus, the greater the
difference in the outdoor temperature and the outdoor coil temperature, the greater the heating capacity of the heat pump. This
phenomenon is a characteristic of a heat pump. It is a good practice to provide supplementary heat for all heat pump installations
in areas where the temperature drops below 45° F. It is also a good practice to provide sufficient supplementary heat to handle the
entire heating requirement should there be a component failure of the heat pump, such as a compressor, or refrigerant leak, etc.
Since the temperature of the liquid refrigerant in the outdoor coil on the heating cycle is generally below freezing point, frost forms
on the surfaces of the outdoor coil under certain weather conditions of temperature and relative humidity. Therefore, it is
necessary to reverse the flow of the refrigerant to provide hot gas in the outdoor coil to melt the frost accumulation. This is
accomplished by reversing the heat pump to the cooling cycle. At the same time, the outdoor fan stops to hasten the temperature
rise of the outdoor coil and lessen the time required for defrosting. The indoor blower continues to run and the supplementary
heaters are energized.

DEFROST CONTROL

During operation the power to the circuit board is controlled by a temperature sensor, which is clamped to a feeder tube entering
the outdoor coil. Defrost timing periods of 30, 60 and 90 minutes may be selected by setting the circuit board jumper to 30, 60 and
90 respectively. Accumulation of time for the timing period selected starts when the sensor closes (approximately 34 + 5° F), and
when the wall thermostat calls for heat. At the end of the timing period, the unit's defrost cycle will be initiated provided the sensor
remains closed. When the sensor opens (approximately 60° F), the defrost cycle is terminated and the timing period is reset. If the
defrost cycle is not terminated due to the sensor temperature, a twelve minute override interrupts the unit's defrost period.
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