9
7. If checking the unit in the wintertime, when the
outdoor coil is cold enough to actuate the defrost
control, observe at least one defrost cycle to make
sure the unit defrosts completely.
Final System Checks
Check to see if all supply and return air grilles are adjusted
and the air distribution system is balanced for the best
compromise between heating and cooling.
Check for air leaks in the ductwork.
See Sections on
Air Flow Measurement and Adjustment
and Checking Charge.
Make sure the unit is free of “rattles”, and the tubing in the
unit is free from excessive vibration. Also make sure tubes
or lines are not rubbing against each other or sheet metal
surfaces or edges. If so, correct the trouble.
Set the thermostat at the appropriate setting for cooling
and heating or automatic changeover for normal use.
Be sure the Owner is instructed on the unit operation, filter,
servicing, correct thermostat operation, etc.
The foregoing “Start-up Procedure and Check List” is
recommended to serve as an indication that the unit will
operate normally.
COMPONENTS
1. Contactor
- This control is activated (closed) by the
room thermostat for both heating and cooling. The
contactor has a 24V coil and supplies power to the
compressor and outdoor fan motor.
2. Crankcase Heater
- This item is “ON” whenever
power is supplied to the unit and the crankcase
heater thermostat is closed. Crankcase heater
thermostat closes at 67° and opens at 85°. It warms
the compressor crankcase thereby preventing liquid
migration and subsequent compressor damage. The
insert type heater is self regulating. It is connected
electrically to the contactor L1 and L2 terminals.
3. Condenser Motor
- This item is activated by the
contactor during heating and cooling, except during
defrost and emergency heat operation.
4. Compressor
- This item is activated by the contactor
for heating and cooling, except during emergency
heat. It is protected by an internal overload.
5. Contactor Relay
- This control is activated by the
thermostat (24V coil) and supplies power to the
contactor.
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 ECM Motors. The
ECM 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 ECM motors.
ECM 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
