Bryant DURAPAC 579F Installation, Start-Up And Service Instructions Manual page 33

4. Set main gas valve to ON position.
5. Set thermostat at setting to call for heat.
6. Remove screw cap covering regulator adjustment
screw (See Fig. 44).
7. Turn adjustment screw clockwise to increase pres-
sure or counterclockwise to decrease pressure.
8. Once desired pressure is established, set thermostat
setting for no call for heat, turn off main gas valve,
remove pressure-measuring device, and replace
1 / -in. pipe plug and screw cap.
8
X. MAIN BURNERS
For all applications, main burners are factory set and should
require no adjustment.
A. Main Burner Removal
1. Shut off (field-supplied) manual main gas valve.
2. Shut off power to unit.
3. Remove unit control box access panel, burner section
access panel, and center post (Fig. 4 and 5).
4. Disconnect gas piping from gas valve inlet.
5. Remove wires from gas valve.
6. Remove wires from rollout switch.
7. Remove sensor wire and ignitor cable from IGC
board.
8. Remove 2 screws securing manifold bracket to
basepan.
9. Remove 2 screws that hold the burner support plate
flange to the vestibule plate.
10. Lift burner assembly out of unit.
B. Cleaning and Adjustment
1. Remove burner rack from unit as described in Main
Burner Removal section above.
2. Inspect burners, and if dirty, remove burners from
rack.
3. Using a soft brush, clean burners and crossover port
as required.
4. Adjust spark gap. See Fig. 45.
5. Reinstall burners on rack.
6. Reinstall burner rack as described above.
XI. FILTER DRIER
Replace whenever refrigerant system is exposed
atmosphere.
XII. PROTECTIVE DEVICES
A. Compressor Protection
Phase Protection
On 579F180 and 216 units, the phase monitor relay (PMR)
will monitor the sequence of the 3-phase electrical system to
provide phase reversal protection. The PMR will also moni-
tor the 3-phase voltage inputs to provide phase loss protec-
tion for the 3-phase device.
Overcurrent
Each compressor has internal line break motor protection,
except the circuit no. 1 on the 579F300 units. Compressor
no. 1 on the 579F300 unit uses an electronic module, located
with the compressor junction box, to provide motor protec-
tion. This electronic module monitors winding and discharge
temperatures. If these temperatures reach the trip values,
the module interrupts the control line and causes the com-
pressor to switch off.
Crankcase Heater
Only the 579F300 unit and units with optional Perfect
Humidity dehumidification system are equipped with a
70-watt crankcase heater to prevent absorption of liquid
refrigerant by oil in the crankcase when the compressor is
idle. The crankcase heater is energized whenever there is a
main power to the unit and the compressor is not energized.
IMPORTANT: After a prolonged shutdown or servicing, ener-
gize the crankcase heaters for 24 hours before starting the
compressors.
Compressor Lockout
If any of the safeties (high-pressure, low-pressure, freeze
protection thermostat, compressor internal thermostat) trip,
or if there is loss of power to the compressors, the cooling
lockout (CLO) will lock the compressors off. To reset, manu-
ally move the thermostat setting.
B. Evaporator-Fan Motor Protection
A manual reset, calibrated trip, magnetic circuit breaker
protects against overcurrent. Do not bypass connections or
increase the size of the breaker to correct trouble. Determine
the cause and correct it before resetting the breaker.
C. Condenser-Fan Motor Protection
Each condenser-fan motor is internally protected against
overtemperature.
D. High-Pressure and Low-Pressure Switches
If either switch trips, or if the compressor overtemperature
switch activates, that refrigerant circuit will be automati-
cally locked out by the CLO. To reset, manually move the
thermostat setting.
E. Freeze Protection Thermostat (FPT)
An FPT is located on the top and bottom of the evaporator
coil. They detect frost build-up and turn off the compressor,
allowing the coil to clear. Once the frost has melted, the
compressor can be reenergized by resetting the compressor
lockout.
XIII. RELIEF DEVICES
All units have relief devices to protect against damage from
excessive pressures (i.e., fire). These devices protect the high
and low side.
XIV. CONTROL CIRCUIT, 24-V
This control circuit is protected against overcurrent by a
3.2 amp circuit breaker. Breaker can be reset. If it trips,
to
determine cause of trouble before resetting. See Fig. 46 and
47 for typical wiring diagrams.
XV. REPLACEMENT PARTS
A complete list of replacement parts may be obtained from
any Bryant distributor upon request.
XVI. DIAGNOSTIC IGC LEDs
The IGC board has LEDs for diagnostic purposes. Refer to
Troubleshooting section on page 38.
— 33 —
Fig. 44 — Gas Valve