9
Final System Checks
16. 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.
17. Check for air leaks in the ductwork.
18. See Sections on
Air Flow Measurement and
Adjustment
and
Checking Charge
.
19. 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.
20. Set the thermostat at the appropriate setting for
cooling and heating or automatic changeover for
normal use.
21. 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 EEM Motors
- 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.
