Step 3—Cleaning or Replacing Refrigerant Flow-Control
Device
Refer to Fig. 30 and instructions given in Piston Body Cleaning or
Replacement section above.
Step 4—Liquid Tube Strainer
The refrigerant flow-control device is protected by a wire mesh
strainer. It is located inside the 3/8-in. liquid tube at field braze
joint next to flow-control device. Access to strainer is through field
braze joint.
Step 5—Sequence of Operation
Refer to Fig. 33.
CONDENSING UNIT
Cooling
When thermostat calls for cooling, the circuit between R and G is
complete and single-pole single-throw relay FR is energized. The
normally-open contacts close causing blower to operate. The
circuit between R and Y is also complete. This completed circuit
causes contactor in outdoor unit to close which starts compressor
and outdoor fan.
Heating
When thermostat calls for heating and FAN switch is set on
AUTO, the circuit between R and W is complete. The heater
sequence SEQ is energized which closes contacts of relay. There
will be a time delay. This completed circuit energizes all heating
elements HTR and blower motor.
HEAT PUMP
Cooling
On a call for cooling, the thermostat makes circuits R-O, R-Y, and
R-G. Circuit R-O energizes reversing valve, switching it to cooling
position. Circuit R-Y energizes contactor starting outdoor fan
motor and compressor. Circuit R-G energizes indoor unit blower
relay starting indoor blower motor. When thermostat is satisfied,
its contacts open de-energizing contactor reversing valve and
blower relay. This stops compressor and fan motors.
Heating
On a call for heating, the thermostat makes circuits R-Y and R-G.
Circuit R-Y energizes contactor starting outdoor fan motor and
compressor. Circuit R-G energizes indoor blower relay starting
blower motor. Should temperature continue to fall, R-W circuit is
made through second-stage room thermostat bulb. Circuit R-W
energizes a sequencer bringing on supplemental electric heat.
When thermostat is satisfied, its contacts open de-energizing
contactor and sequencer. All heaters and motors should stop.
Step 6—Care and Maintenance
The minimum maintenance requirements for this equipment are as
follows:
1. Inspect and clean or replace air filter each month or as
required.
2. Inspect cooling coil, drain pan, and condensate drain each
cooling season for cleanliness. Clean as necessary.
3. Inspect blower motor and wheel for cleanliness each heating
and cooling season. Clean as necessary.
4. Inspect electrical connections for tightness and controls for
proper operation each heating and cooling season. Service as
necessary.
As with any mechanical equipment, personal injury can result
from sharp metal edges. Be careful when removing parts.
AIR FILTER
To clean or replace air filter, grasp it at bottom and lift it out of
unit. Clean filter using cold water. Rinse clean and let dry. Oiling
or coating of filter is not required. To replace, stand filter in rack
with binding facing coil. Press top edge under access panel.
NOTE:
Steel rods in filter prevent it from being pulled into coil.
Retain these rods and reinstall after cleaning or before replacement
if new filter is used.
Never operate unit without a filter.
COOLING COIL, DRAIN PAN, AND CONDENSATE DRAIN
The cooling coil is easily cleaned when it is dry. Inspect coil and
clean (if necessary) before each cooling season. To check or clean
cooling coil, remove blower/heater access panel to gain full access
to cooling coil. If coil is coated with dirt or lint, vacuum with a soft
brush attachment.
Be careful not to bend coil fins. If coil is coated with oil or grease,
clean it with a mild detergent-and-water solution. Rinse coil with
clear water. Be careful not to splash water onto insulation.
Inspect drain pan and condensate drain at same time cooling coil
is checked. Clean drain pan and condensate drain by removing any
foreign matter from pan. Flush pan and drain tube with clear water.
If drain tube is restricted, it can generally be cleared by high-
pressure water. Cut plastic line and work outside condensate pan
and away from coil to clear drain tube.
NOTE:
There MUST be a trap in condensate line. Trap must be
at least 3-in. deep, not higher than the bottom of unit condensate
drain opening, and pitched downward to an open drain or sump.
Do not use caustic household drain cleaners in condensate
pan or near coil. Drain cleaners can quickly destroy coils.
BLOWER MOTOR AND WHEEL
Clean blower motor and wheel when cooling coil is cleaned.
To clean or service wheel or motor, proceed as follows:
1. Pull unit disconnect (when used) and remove blower access
panel.
2. Disconnect motor electrical leads from control box and
capacitor. Mark location of wires for reassembly.
3. Remove 3 bolts holding motor mount to blower housing while
supporting motor shell with hand.
4. Pull motor inlet ring and blower wheel assembly out of blower
housing.
5. With blower wheel, inlet ring, and motor mount still attached
to motor, place motor on flat, horizontal surface, shaft up.
Mark position of wheel on motor shaft for reassembly.
6. Loosen blower wheel setscrew and remove blower wheel from
motor shaft.
NOTE:
Further disassembly of motor and mount is not necessary
as adequate clearance is available to clean motor.
7. Clean blower motor and wheel using a vacuum with a soft
brush attachment. Remove grease with a mild solvent such as
hot water and detergent. Be careful not to disturb balance
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