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SENSOR'S POWER LED IS OFF
1.
Check the controller's Power LED. If it is off, determine
why the controller does not have power and make the nec-
essary repairs.
2.
Check the wiring between the sensor and the controller. If
wiring is loose or missing, repair or replace as required.
CONTROLLER'S POWER LED IS OFF
1.
Make sure the circuit supplying power to the controller is
operational. If not, make sure JP2 and JP3 are set correctly
on the controller before applying power.
2.
Verify that power is applied to the controller's supply
input terminals. If power is not present, replace or repair
wiring as required.
REMOTE TEST/RESET STATION'S TROUBLE LED DOES
NOT FLASH WHEN PERFORMING A DIRTY TEST, BUT
THE CONTROLLER'S TROUBLE LED DOES
1.
Verify that the remote test/station is wired as shown in
Fig. 43. Repair or replace loose or missing wiring.
2.
Configure the sensor dirty test to activate the controller's
supervision relay. See "Dirty Sensor Test" on page 24.
SENSOR'S
TROUBLE
CONTROLLER'S TROUBLE LED IS OFF
Remove JP1 on the controller.
PROTECTIVE DEVICES
Compressor Protection
OVERCURRENT
The compressor has internal line-break motor protection.
OVERTEMPERATURE
The compressor has an internal protector to protect it against ex-
cessively high discharge gas temperatures.
HIGH PRESSURE SWITCH
The system is provided with a high pressure switch mounted on
the discharge line. The switch is stem-mounted and brazed into the
discharge tube. Trip setting is 630 psig ± 10 psig (4344 ± 69 kPa)
when hot. Reset is automatic at 505 psig (3482 kPa).
LOW PRESSURE SWITCH
The system is protected against a loss of charge and low evapora-
tor coil loading condition by a low pressure switch located on the
suction line near the compressor. The switch is stem-mounted.
Trip setting is 54 psig ± 5 psig (372 ± 34 kPa). Reset is automatic
at 117 ± 5 psig (807 ± 34 kPa).
EVAPORATOR FREEZE PROTECTION
The system is protected against evaporator coil frosting and low
temperature conditions by a temperature switch mounted on the
evaporator coil hairpin. Trip setting is 30°F ± 5°F (–1°C ± 3°C).
Reset is automatic at 45°F (7°C).
SUPPLY (INDOOR) FAN MOTOR PROTECTION
Disconnect and lockout power when servicing fan motor.
The standard supply fan motor is equipped with internal overcur-
rent and over-temperature protection. Protection devices reset au-
tomatically.
The high static option supply fan motor is equipped with a pilot-
circuit Thermix combination over-temperature/over-current pro-
tection device. This device resets automatically. Do not bypass
this switch to correct trouble. Determine the cause and correct it.
LED
IS
ON,
BUT
CONDENSER FAN MOTOR PROTECTION
The condenser fan motor is internally protected against over-
temperature.
Relief Device
A soft solder joint at the suction service access port provides pres-
sure relief under abnormal temperature and pressure conditions
(i.e., fire in building). Protect this joint during brazing operations
near this joint.
Control Circuit, 24-V
The control circuit is protected against overcurrent conditions by a
circuit breaker mounted on control transformer TRAN. Reset is
manual.
GAS HEATING SYSTEM
General
The heat exchanger system consists of a gas valve feeding multi-
ple in-shot burners off a manifold. The burners fire into matching
primary tubes. The primary tubes discharge into combustion ple-
num where gas flow converges into secondary tubes. The second-
ary tubes exit into the induced draft fan wheel inlet. The induced
fan wheel discharges into a flue passage and flue gases exit out a
THE
flue hood on the side of the unit. The induced draft fan motor in-
cludes a flue gas pressure switch circuit that confirms adequate
wheel speed through the Integrated Gas Control (IGC) board.
Safety switches include a Rollout Switch (at the top of the burner
compartment; see Fig. 46) and a limit switch (mounted through
the heat exchanger cover panel, over the tubes). (See Fig. 47.)
Induced-
Draft
Motor
Mounting
Plate
Burner
Section
Induced-
Draft Motor
Manifold
Pressure
Tap
Fig. 46 — Burner Section Details
Fig. 47 — Limit Switch Location
27
Rollout
Switch
Flue
Exhaust
Vestibule
Plate
Blower
Housing
Gas
Valve
Gas Limit
Switch
Heat Exchanger
Cover Panel
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Table of Contents
Troubleshooting
