Carrier 48TC 04 Series, Service And Maintenance Instructions

Page: 88 / 152

88
Gas Piping
Check gas piping for leaks.
FIRE, EXPLOSION HAZARD
Failure to follow this warning could result in death,
serious personal injury and/or property damage .
Disconnect gas piping from unit when pressure testing
at pressure greater than 0.5 psig. Pressures greater
than 0.5 psig will cause gas valve damage resulting in
hazardous condition. If gas valve is subjected to
pressure greater than 0.5 psig, it must be replaced
before use. When pressure testing field-supplied gas
piping at pressures of 0.5 psig or less, a unit connected
to such piping must be isolated by closing the manual
gas valve(s).
!
WARNING
FIRE, EXPLOSION HAZARD
Failure to follow this warning could result in death,
serious personal injury and/or property damage .
Refer to the User’s Information Manual provided with
this unit for more details.
Do not store or use gasoline or other flammable
vapors and liquids in the vicinity of this or any other
appliance.
WHAT TO DO IF YOU SMELL GAS:
DO NOT
try to light any appliance.
DO NOT touch any electrical switch, or use any
phone in your building.
IMMEDIATELY call your gas supplier. Follow the
gas supplier’s instructions. If you cannot reach
your gas supplier, call the fire department.
!
WARNING
Return--Air Filters
Ensure correct filters are installed in unit (see Appendix I
-- Physical Data). Do not operate unit without return--air
filters.
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.
Refrigerant Service Ports
Each unit system has two 1/4” SAE flare (with check
valves) service ports: one on the suction line, and one on
the compressor discharge line. Be sure that caps on the
ports are tight.
Compressor Rotation
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:
4. Note that the evaporator fan is probably also rotating
in the wrong direction.
5. Turn off power to the unit and install lockout tag.
6. Reverse any two of the unit power leads.
7. Re--energize to the compressor. Check pressures.
The suction and discharge pressure levels should now
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.
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 at AUTO. position. Adjust
thermostat to a setting below room temperature.
Compressor starts on closure of contactor.
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 30--second delay.
To shut off unit, set system selector switch at OFF
position. Resetting thermostat at a position above room
temperature shuts unit off temporarily until space
temperature exceeds thermostat setting.
Main Burners
Main burners are factory set and should require no
adjustment.
To check ignition of main burners and heating controls,
move thermostat setpoint above room temperature and
verify that the burners light and evaporator fan is
energized. Check heating effect, then lower the thermostat
setting below the room temperature and verify that the
burners and evaporator fan turn off.
48TC