Carrier 50DQ - Manual (Page 4)

Refrigerant Shutoff Valves — Open (backseat)
compressor service valves fully. Replace and
tighten valve caps to prevent leaks. Open liquid line
valve in a similar manner.
Indoor Air Fans — Install fan belt. Belt is taped to
fan pulley. Adjust as described in Indoor Air Fan
Adjustment section.
Outdoor Air Fans — Fans are factory set. Refer to
Outdoor Air Fan Adjustment section as required.
Cooling — To start unit, turn on main power
supply. Refer to Crankcase Heater (page 3). Set
thermostat at “Cool,” “Auto” and desired temper­
ature. Wait about 5 minutes for compressor to
start. Check cooling effect at air supply grilles, fan
speeds, refrigerant sight glass level(s) and operation
of all controls and safety devices as described in
the Service section of this book.
IF UNIT FAILS TO START ON COOL
1. Check thermostat to make sure it is set at the
proper temperature and that system selector
switch is at “Cool.”
2. Make sure main disconnect switch is turned on.
3. Make sure air filters are not dirt clogged.
4. Wait at least 5 minutes before attempting to
restart unit.
Heating — To start unit, turn on main power
supply. Refer to Crankcase Heaters. Set thermostat
at “Heat,” “Auto” and desired temperature. Wait
about 5 minutes for compressor to start.
Stage 2 of heating thermostat will energize the
electric heater elements if installed.
IF UNIT FAILS TO START ON HEAT
1. Check thermostat setting.
2. Make sure power is on.
3. Make sure air filters are not dirt clogged.
Defrost Cycle — As frost builds up on the outdoor
coil, the air pressure switch closes and if the
defrost thermostat is closed, the unit will operate
in a defrost cycle (controlled by the defrost timer).
During this cycle the two outdoor air fans shut off
as the unit operates on cooling cycle for a
maximum of 10 minutes. The accessory electric
heaters are energized to maintain a warm air supply
to the conditioned spaces.
Ventilating (Continuous Fan) — Set fan and system
selector switches at “On” and “Off” respectively.
Indoor air fan will operate continuously to provide
constant air circulation.
Refrigerant Charging — 50DQ016 contains correct
operating charge as dehvered from the factory. If
complete refrigerant charge is lost, evacuate unit
and weigh charge in accurately. Refer to Table 1
for system refrigerant charge. If only a partial
charge is required, use coohng or heating cycle
charging chart. Fig. 4 or 5 to recharge system.