34
Table 8 – Detector Indicators
CONTROL OR INDICATOR DESCRIPTION
Magnetic test/reset switch
Resets the sensor when it is in the alarm or trouble state. Activates or tests the sensor when it is in
the normal state.
Alarm LED Indicates the sensor is in the alarm state.
Trouble LED Indicates the sensor is in the trouble state.
Dirty LED
Indicates the amount of environmental compensation used by the sensor
(flashing continuously = 100%)
Power LED Indicates the sensor is energized.
Condenser Fan Motor Protection
The condenser fan motor is internally protected against
over--te mperature.
Relief Device
A soft solder joint at the suction service access port
provides pressure 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 ci rcuit is protected against overcurrent
conditions by a circuit bre aker mounted on control
transformer TRAN. Reset is manual.
GAS HEATING SYSTEM
General
The heat exchanger system consists of a gas valve feeding
multiple in --shot burners off a manifold. The burners fire
into matching primary tubes. The primary tubes discharge
into com bustion plenum where gas flow converges into
secondary tubes. The secondary tubes exit into the
induced draft fan wheel inlet. The induced fan wheel
discharges into a flue passage and flue gases exit out a
flue hood on the side of the unit. The induced draft fan
motor includes a Hall Effect sensor circuit tha t confirms
adequa te wheel speed through the Integrated Gas Cont rol
(IGC) board. Safety switches include a Rollout Switch (at
the top of the burner compartment) and a limit switch
(mounted through the fan deck, over the tubes). (See Fig.
45 and Fig. 46.)
INDUCED-
DRAFT
MOTOR
MOUNTING
PLATE
INDUCED-
DRAFT
MOTOR
MANIFOLD
PRESSURE
TAP
VESTIBULE
PLATE
FLUE
EXHAUST
ROLLOUT
SWITCH
BLOWER
HOUSING
GAS
VALVE
BURNER
SECTION
C06152
Fig. 45 -- Burner Section Details
Limit Switch
for Sideshot
Limit Switch
for Downshot
C10336
Fig. 46 -- Limit Switch Location
Fuel Types and Pressures
Natural Gas
The 48HC unit is factory --equipped for use with Natural
Gas fue l at elevation under 2000 ft (610 m). See section
Orifice Replacement for information in modifying this
unit for installation at elevations above 2000 ft (610 m).
Gas line pressure entering the unit’s main gas valve must
be within specified ranges. Adjust unit gas regulator valve
as required or consult local gas utility.
Table 9 – Natural Gas Supply Line Pressure Ranges
UNIT MODEL UNIT SIZE MIN MAX
48HC All
4.0 in. wg
(996 Pa)
13.0 in. wg
(3240 Pa)
Manifold pressure is factory--adjusted for NG fuel use.
Adjust as required to obtain best flame characteristic.
Table 10 – Natural Gas Manifold Pressure Ranges
UNIT
MODEL
UNIT
SIZE
HIGH
FIRE
LOW
FIRE
RANGE
48HC All
3.5 in. wg
(872 Pa)
1.7 in. wg
(423 Pa){
2.0--- 5.0 in. wg (Hi)
(498--- 1245 Pa)
48HC
Low NOx
All
3.5 in. wg
(872 Pa)
NA
2.0--- 5.0 in. wg (Hi)
(498--- 1245 Pa)
NA: Not Available
{ 3 Phase models only
Liquid Propane
Accessory packages are available for field--installation
that will convert the 48HC unit ( except low NOx model)
48HC
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