Carrier 50DPE014 - Page 11

Table 4 — Air Quantity Limits
UNIT MODEL
MIN CFM
MAX CFM
50DPE014 3750
6250
50DP016
4500
7500*
50DP020 5400
9000
Mndoor Fan Max Watts = 3000
Indoor Air Fan — Fan belts and pulleys are factory
installed. Belts are secured to pulleys with tape.
Remove tape and, if required, adjust as described in
Service, Indoor Air Fan Adjustment.
50DP020 has 2 non-adjustable pulleys. Pulley A is
installed in unit. Pulley B is shipped in cardboard box
taped to vestibule below main control box.
Outdoor Air Fans and Motors are factory set. Refer
to Service, Outdoor Air Fan Adjustment as required.
Return Air Filters — Check that correct filters are
installed in filter tracks. See Table 1. Do not operate unit
without return air filters.
Outdoor Air Inlet Screens — Outdoor air inlet
screens must be in place before operating unit.
Economizer Section — Remove filter access
panel. Check that outdoor air damper is closed and return
air damper is open.
Economizer operation and adjustment is described in
Start-Up, Economizer Operation; and Service, Econo¬
mizer Adjustment, respectively.
Base Unit Operation
COOLING — Unit power on. System selector switch at
COOL; fan switch at AUTO.; thermostat at a setting
below room temperature.
50DPEQ14 and 50DP016 — Compressor starts unloaded
on closure of No. 1 contact in thermostat.
Additional rise in room temperature closes contact
No. 2 in thermostat which de-energizes the unloader coil.
Compressor is now fully loaded.
Check cooling effects at a setting below room tempera¬
ture. Check unit charge. Refer to Service, Refrigerant
Charge.
Reset thermostat at a temperature above room tem¬
perature. Compressor(s) will shut off.
50DP020 — Upon a rise in room temperature, cooling
contact No. 1 in the thermostat closes, energizing the
first-stage cooling contactor and the indoor fan con¬
tactor. The first-stage compressor, outdoor fan motor
and indoor fan motor start and run.
Upon a further rise in room temperature, cooling
contact No. 2 in the thermostat closes, energizing the
second-stage cooling contactor. The second-stage
compressor starts and runs.
To Shut Off Unit — Set system selector switch at OFF
position or reset thermostat above room temperature.
Units with Signal-LOC ™ protection device shut down on
any safety trip and thermostat light comes on. Determine
reason for safety trip. Restart compressor(s) by resetting
circuit breaker at unit.
HEATING — Turn on main power to unit. Set system
selector switch at HEAT, fan switch at AUTO.; and
thermostat at a setting above room temperature. First
stage of electric heater elements are energized on closing
of heating contact No. I in thermostat. On a further fall
of room temperature, heater contact No. 2 closes ener¬
gizing second-stage electric heater elements.
To Shut Off Unit — Set system selector switch at OFF.
VENTILATION AIR CIRCULATION (Continuous
Fan) — Unit power on. System selector switch at OFF,
HEAT or COOL; fan switch set at ON. Indoor fan con¬
tactor is energized through the switch on the thermostat,
and the indoor fan runs continuously.
AUTOMATIC CHANGEOVER (with Automatic
Changeover Thermostat) — System selector switch set
at AUTO. When temperature of conditioned space rises
to cooling selector lever setting, unit automatically
switches from heating mode to cooling mode. When tem¬
perature of the conditioned space falls to the heating
selector lever setting, unit automatically changes from
cooling mode to heating mode. The thermostat is inter¬
locked so that cooling and heating systems do not operate
at the same time.
HEAD PRESSURE CONTROL All units have fan
cycling thermostats which, at 55 F, shut off one outdoor
fan motor. This permits unit to operate down to 40 F
outdoor air temperature.
Economizer Operation — If unit is equipped with
modulating outdoor air control (economizer), it should
operate as follows:
COOLING MODE — Indoor and outdoor fans and com¬
pressor energize when there is a call for cooling and
enthalpy of outdoor air is above enthalpy control setting.
The economizer damper moves to VENT position.
Indoor fan starts and economizer damper opens fully
on a first-stage call for cooling when enthalpy of outdoor
air is below the enthalpy control setting. Compressor
remains off.
Compressor is energized and mechanical cooling
integrates with economizer cooling upon a second-
stage call for cooling. If outdoor air temperature falls
below 50 F, cooling lockout switch prevents compressor
from operating.
Economizer damper modulates when mixed air tem¬
perature is below mixed air thermostat setting.
A freeze protection thermostat (FPT) is located on the
indoor coil. It detects ice buildup and turns off the
compressor, thus allowing the coil to clear. Once ice
melts, the compressor can be re-energized.
HEATING MODE' — Outdoor air damper stays at
VENT position while indoor air fan runs.
NOTE: If fan switch is at ON position, and room thermo¬
stat is satisfied, damper goes to ventilation position.
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