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28
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
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) and a limit switch (mounted through the fan deck,
over the tubes). (See Fig. 46 and 47.)
Fig. 46 — Burner Section Details
Fig. 47 — Limit Switch Location
Fuel Types and Pressures
NATURAL GAS
The 48HC unit is factory-equipped for use with natural gas (NG)
fuel at elevation under 2000 ft (610 m). See section “Orifice Re-
placement” 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 (see Table 8). Adjust unit gas regulator valve as
required or consult local gas utility.
Manifold pressure is factory-adjusted for NG fuel use. Adjust as
required to obtain best flame characteristic. See Table 9.
NA: Not Available
†3 Phase models only
LIQUID PROPANE
See Tables 10 and 11.
Accessory packages are available for field-installation that will
convert the 48HC unit (except low NOx model) to operate with
liquid propane (LP) fuels. These kits include new orifice spuds,
new springs for gas valves and a supply line low pressure switch.
See section on Orifice Replacement for details on orifice size se-
lections.
Low NOx models include specially-sized orifices and use of dif-
ferent flue flow limits and tube baffles. Because of these extra
features, conversion of these models to LP is not recommended.
Fuel line pressure entering unit gas valve must remain within
specified range.
Manifold pressure for LP fuel use must be adjusted to specified
range. Follow instructions in the accessory kit to make initial read-
justment.
NA: Not Available
SUPPLY PRESSURE SWITCH
The LP conversion kit includes a supply low pressure switch. The
switch contacts (from terminal C to terminal NO) will open the
gas valve power whenever the supply line pressure drops below
the set point. See Fig. 48 and 49. If the low pressure remains open
for 15 minutes during a call for heat, the IGC circuit will initiate a
Ignition Fault (5 flashes) lockout. Reset of the low pressure switch
is automatic on rise in supply line pressure. Reset of the IGC re-
quires a recycle of unit power after the low pressure switch has
closed.
INDUCED-
DRAFT
MOTOR
MOUNTING
PLATE
INDUCED-
DRAFT
MOTOR
MANIFOLD
PRE
SS
URE
TAP
VE
S
TIBULE
PLATE
FLUE
EXHAU
S
T
ROLLOUT
S
WITCH
BLOWER
HOU
S
ING
GA
S
VALVE
BURNER
S
ECTION
Limit
S
witch
for
S
ide
s
hot
Limit
S
witch
for Down
s
hot
Table 8 — 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)
Table 9 — 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)
Table 10 — Liquid Propane Supply Line Pressure
Ranges
UNIT MODEL
UNIT SIZE
MIN
MAX
48HC
All
11.0 in. wg
(2740 Pa)
13.0 in. wg
(3240 Pa)
48HC Low NOx
All
NA
NA
Table 11 — Liquid Propane Manifold Pressure
Ranges
UNIT MODEL
UNIT SIZE
MIN
MAX
48HC
All
11.0 in. wg
(2740 Pa)
13.0 in. wg
(3240 Pa)
48HC Low NOx
All
NA
NA
Summary of Contents for WeatherMaster 48HC04 Series
Page 37: ...37 Fig 60 Integrated Gas Control IGC Board RED LED STATUS ...
Page 45: ...45 Fig 65 RTU Open Overlay for Economizer Wiring ...
Page 46: ...46 Fig 66 VFD Overlay for W2770 Controller Wiring ...
Page 98: ...98 Fig E 48HC A07 YAC Control Diagram 208 230 3 60 460 575 3 60 APPENDIX D WIRING DIAGRAMS ...
Page 100: ...100 Fig G 48HC D11YAC Control Diagram 208 230 3 60 460 575 3 60 APPENDIX D WIRING DIAGRAMS ...
Page 101: ...101 Fig H 48HC D12 YAC Control Diagram 208 230 3 60 460 575 3 60 APPENDIX D WIRING DIAGRAMS ...
Page 102: ...102 Fig I 48HC A04 A06 YAC Power Diagram 208 230 1 60 APPENDIX D WIRING DIAGRAMS ...
Page 103: ...103 Fig J 48HC A04 A06 YAC Power Diagram 208 230 3 60 460 3 60 APPENDIX D WIRING DIAGRAMS ...
Page 104: ...104 Fig K 48HC A04 A06 YAC Power Diagram 575 3 60 APPENDIX D WIRING DIAGRAMS ...
Page 107: ...107 Fig N 48HC A07 A12 YAC Power Diagram 208 230 3 60 460 3 60 APPENDIX D WIRING DIAGRAMS ...
Page 108: ...108 Fig O 48HC A07 A12 YAC Power Diagram 575 3 60 APPENDIX D WIRING DIAGRAMS ...
Page 109: ...109 Fig P 48HC D08 D09 YAC Power Diagram 230 460 3 60 APPENDIX D WIRING DIAGRAMS ...
Page 110: ...110 Fig Q 48HC D08 D09 YAC Power Diagram 575 3 60 APPENDIX D WIRING DIAGRAMS ...
Page 111: ...111 Fig R 48HC D11 YAC Power Diagram 208 230 3 60 APPENDIX D WIRING DIAGRAMS ...
Page 112: ...112 Fig S 48HC D11 YAC Power Diagram 460 3 60 APPENDIX D WIRING DIAGRAMS ...
Page 113: ...113 Fig T 48HC D11 YAC Power Diagram 575 3 60 APPENDIX D WIRING DIAGRAMS ...
Page 114: ...114 Fig U 48HC D12 YAC Power Diagram 230 460 3 60 APPENDIX D WIRING DIAGRAMS ...
Page 115: ...115 Fig V 48HC D12 YAC Power Diagram 575 3 60 APPENDIX D WIRING DIAGRAMS ...
Page 116: ...116 Fig W 48HC D14 YAC Control Diagram 208 230 3 60 460 575 3 60 APPENDIX D WIRING DIAGRAMS ...
Page 117: ...117 Fig X 48HC D14 YAC Power Diagram 208 230 3 60 APPENDIX D WIRING DIAGRAMS ...
Page 118: ...118 Fig Y 48HC D14 YAC Power Diagram 460 3 60 APPENDIX D WIRING DIAGRAMS ...
Page 119: ...119 Fig Z 48HC D14 YAC Power Diagram 575 3 60 APPENDIX D WIRING DIAGRAMS ...
Page 142: ...142 Fig AW PremierLink System Control Wiring Diagram System APPENDIX D WIRING DIAGRAMS ...
Page 144: ...144 Fig AY RTU Open Wiring Diagram APPENDIX D WIRING DIAGRAMS ...