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See unit nameplate for manufacturer
and address.
505,111M
10/2008
Supersedes 4/2006
Do not store or use gasoline or other
flammable vapors and liquids in the
vicinity of this or any other appliance.
Installation and service must be per-
formed by a qualified installer, ser-
vice agency or the gas supplier.
10/08
*2P1008*
READ ALL INSTRUCTIONS IN THIS MANUAL
AND RETAIN FOR FUTURE REFERENCE
WARNING
FIRE OR EXPLOSION HAZARD
Failure to follow safety warnings ex-
actly could result in serious injury
death or property damage.
D Do not try to light any appliance.
D Extinguish any open flames.
D Do not touch any electrical switch; do not
D Leave the building immediately.
D Immediately call your gas supplier from a
D If you cannot reach your gas supplier, call
SGA420, 480, 540, 600
(35, 40, 45 and 50 TONS)
WHAT TO DO IF YOU SMELL GAS:
use any phone in your building.
neighbor's phone. Follow the gas suppli-
er's instructions.
the fire department.
ROOFTOP
UNITS
Litho U.S.A.
©2006
505,111M
*P505111M*
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Summary of Contents for Lennox SGA420
- Page 1 See unit nameplate for manufacturer and address. 505,111M 10/2008 Supersedes 4/2006 SGA420, 480, 540, 600 (35, 40, 45 and 50 TONS) ROOFTOP UNITS READ ALL INSTRUCTIONS IN THIS MANUAL Litho U.S.A. AND RETAIN FOR FUTURE REFERENCE ©2006 WARNING FIRE OR EXPLOSION HAZARD...
- Page 2 Page 1...
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Page 3: For Your Safety Read Before Lighting
Safety CAUTION Label all wires prior to disconnection when servic- 1− Keep unit area clear and free of combustible ing controls. Wiring errors can cause improper and materials, gasoline and other flammable vapors and dangerous operation. Verify proper operation after liquids. - Page 4 1− Set thermostat to lowest setting. TYPICAL ELECTROMECHANICAL THERMOSTAT 2− Turn off all electrical power to furnace. 3− This furnace is equipped with an ignition device which automatically lights the burner. Do not try to light the burner by hand. 4−...
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Page 5: Heat Exchanger Assembly
Burner Flame Service To maintain efficiency and longevity, your equipment must be serviced yearly by a qualified service technician. WARNING Failure to provide proof of service can void warranty. Danger of explosion and fire. Can cause CAUTION injury or product or property damage. Periodically inspect burner flame to en- sure proper unit operation. - Page 6 REMOVE FILTERS WARNING Danger of explosion. Can cause injury or death. Do not overtighten main burner mounting screws. Snug tighten only. BURNER BOX ASSEMBLY BURNER SUPPORT FLAME SENSOR FIGURE 4 BURNERS Lubrication All motors are lubricated at the factory. No further lubrication is required.
- Page 7 Combustion Air Inducer is recommended that the combustion air inducer gasket be replaced during reassembly. A combustion air inducer proving switch checks 6− Use a small brush to clean the combustion air inlet combustion air inducer operation before allowing power louvers on the heat access panel.
- Page 8 MODULATING GAS VALVE (MGV) TO RIGHT HEAT SECTION RIGHT HEAT SECTION MODULATING TO LEFT HEAT GAS VALVE SECTION MANIFOLD PRESSURE PORT LEFT HEAT SECTION MODULATING RIGHT HEAT GAS VALVE SECTION GAS VALVE LEFT HEAT SECTION GAS VALVE MANIFOLD PRESSURE PORT INLET FIGURE 7 Optional Modulating Gas Valve (MGV)