Carrier 50HCQA05 Service And Maintenance Instructions page 40

Additional Installation/Inspection
Inspect the field installed accessories for proper
installation, making note of which ones do or do not
require configuration changes. Inspect the RTU-OPEN's
Alarms for initial insight to any potential issues. See
troubleshooting section for alarms.
sensor for relocation as intended during installation.
Inspect special wiring as directed below.
Unit Preparation
Ensure the unit has been installed in accordance with
installation instructions and applicable codes.
Return- -Air Filters
Ensure the correct filters are installed in the unit (see
Appendix II - - Physical Data). Do not operate unit without
return- - air filters in place.
Outdoor- -Air Inlet Screens
Outdoor- - air inlet screen must be in place before operating
unit.
Compressor Mounting
Compressors are internally spring mounted. Do not loosen
or remove compressor hold down bolts.
Internal Wiring
Check all electrical connections in unit control boxes.
Tighten as required.
Compressor Rotation
CAUTION
!
EQUIPMENT DAMAGE
Failure to follow this caution can result in equipment
damage.
Scroll compressors can only compress refrigerant if
rotating in the right direction. Reverse rotation for
extended times can result in internal damage to the
compressor. Scroll compressors are sealed units and
cannot be repaired on site location.
On 3- - phase units with scroll compressors, it is important
to be certain compressor is rotating in the proper
direction. To determine whether or not compressor is
rotating in the proper direction:
1. Connect service gauges to suction and discharge
pressure fittings.
2. Energize the compressor.
3. The suction pressure should drop and the discharge
pressure should rise, as is normal on any start- - up.
If the suction pressure does not drop and the discharge
pressure does not rise to normal levels:
1. Note that the evaporator fan is probably also rotating
in the wrong direction.
2. Turn off power to the unit and apply lockout/tagout
3. Reverse any two of the unit power leads.
4. Re- - energize to the compressor. Check pressures.
The suction and discharge pressure levels should now
Inspect the SAT
move to their normal start- - up levels.
NOTE: When the compressor is rotating in the wrong
direction, the unit will make an elevated level of noise
and will not provide cooling.
Refrigerant Service Ports
Each unit system has two
valves) service ports: one on the suction line, and one on
the compressor discharge line. Be sure that caps on the
ports are tight.
Cooling
Set space thermostat to OFF position. To start unit, turn on
main power supply. Set system selector switch at COOL
position and fan switch to AUTO. position. Adjust
thermostat to a setting below room temperature.
Compressor starts on closure of contactor. (D08–12:
Second stage of thermostat will energize Circuit 2
contactor, start Compressor 2.)
Check unit charge. Refer to Refrigerant Charge section.
Reset thermostat at a position above room temperature.
Compressor will shut off. Evaporator fan will shut off
after a 60- - second delay if the dip switch for the indoor fan
off delay on the Defrost Control Board (DFB) is set to on.
To shut off unit - - set system selector switch to the OFF
position. Resetting thermostat at a position above room
temperature shuts the unit off temporarily until space
temperature exceeds thermostat setting.
Heating
To start unit, turn on main power supply.
Set system selector switch to the HEAT position and set
thermostat at a setting above room temperature. Set fan to
AUTO position.
First stage of thermostat energizes compressor heating
(D08–12: both compressors will start). Second stage of
thermostat energizes electric heaters (if installed). Check
heating effects at air supply grille(s).
If electric heaters do not energize, reset limit switch
(located on supply- - fan scroll) by pressing button located
between terminals on the switch.
Shut unit off - - set system selector switch to the OFF
position. Resetting thermostat at a position below room
temperature temporarily shuts unit off until space
temperature falls below thermostat setting.
Ventilation (Continuous Fan)
Set fan and system selector switches at ON and OFF
positions, respectively. Supply fan operates continuously
to provide constant air circulation.
40
procedures.
1
/ " SAE flare (with check
4