Carrier 50HJQ004-007 Installation, Start-Up And Service Instructions Manual page 35

HEATING, UNITS WITH ECONOMIZER — When the room
temperature calls for heat through terminal W1, the indoor fan
contactor and heater contactor no. 1 are energized. On units
equipped for 2 stages of heat, when additional heat is needed,
heater contactor no. 2 is energized through W2. The economiz-
er damper moves to the minimum position. When the thermo-
stat is satisfied, the damper moves to the fully closed position.
Defrost —
As frost builds up on the outdoor coil, the coil
temperature drops below 28 F. When this outdoor-coil temper-
ature drop is sensed by the defrost thermostat (DFT) and the de-
frost timer is at the end of a timed period (adjustable at 30, 50,
90 minutes), the unit operates in a defrost cycle controlled by
the defrost timer and thermostat. During this cycle, the revers-
ing valve solenoid (RVS) is energized and the outdoor fan
shuts off. The electric heaters (if installed) will be energized.
The unit continues to defrost until the coil temperature as
measured by DFT reaches 65 F, or the duration of defrost cycle
completes a 10-minute period.
At the end of the defrost cycle, the electric heaters (if in-
stalled) and the reversing valve will be deenergized, and the
outdoor-fan motor will be energized. The unit will now operate
in the heating mode.
If the thermostat is satisfied during a defrost cycle, the unit
will continue in the defrost mode until the time or temperature
constraints are satisfied.
SERVICE
When servicing unit, shut off all electrical power to unit
and tag disconnect to avoid shock hazard or injury from
rotating parts.
Cleaning —
Inspect unit interior at the beginning of each
heating and cooling season and as operating conditions require.
INDOOR COIL
1. Turn unit power off and install lockout tag. Remove filter
access panel and indoor coil access panel.
2. If accessory economizer is installed, remove economizer
by disconnecting Molex plug and removing economizer
mounting screws.
3. Slide filters out of unit.
4. Clean coil using a commercial coil cleaner or dishwasher
detergent in a pressurized spray canister. Wash both sides
of coil and flush with clean water. For best results, back-
flush toward return-air section to remove foreign materi-
al. Flush condensate pan after completion.
5. Reinstall economizer and filters.
6. Reconnect wiring.
7. Replace access panels.
OUTDOOR COIL — Inspect coil monthly. Clean outdoor
coil annually, and as required by location or outdoor-air
conditions.
One-Row Coils — Wash coil with commercial coil cleaner. It
is not necessary to remove top panel.
2-Row Coils — Clean coil as follows:
1. Turn off unit power and tag disconnect.
2. Remove top panel screws on outdoor end of unit.
3. Remove outdoor coil corner post. See Fig. 35. To hold
top panel open, place coil corner post between top panel
and center post. See Fig. 36.
4. Remove device holding coil sections together at return
end of outdoor coil. Carefully separate the outer coil sec-
tion 3 to 4 in. from the inner coil section. See Fig. 37.
5. Use a water hose or other suitable equipment to flush
down between the 2 coil sections to remove dirt and de-
bris. Clean the outer surfaces with a stiff brush in the nor-
mal manner.
6. Secure the sections together. Reposition the outer coil
section, and remove the coil corner post from between the
top panel and center post. Install the coil corner and cen-
ter posts, and replace all screws.
Fig. 35 — Cleaning Outdoor Coil
Fig. 36 — Propping Up Top Panel
Fig. 37 — Separating Coil Sections
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