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2-Heat Exchanger (Figure 19)
Units use aluminized steel inshot burners with matching
tubular aluminized (stainless steel is an option) steel heat
exchangers and two-stage redundant gas valves.
LGH156/300 uses two eleven-tube/burners for high heat,
two six-tube/burners for standard or low heat and two
ninetube/ burners for medium heat. Burners in all units
use a burner venturi to mix gas and air for proper com-
bustion. Combustion takes place at each tube entrance.
As hot combustion gases are drawn upward through each
tube by
the combustion air blower, exhaust gases are drawn out
the top and fresh air/gas mixture is drawn in at the bottom.
Heat is transferred to the air stream from all surfaces of
the heat exchanger tubes. The supply air blowers, con-
trolled by the Unit Controller A55, force air across all sur-
faces of the tubes to extract the heat of combustion. The
shape of the tubes ensures maximum heat exchange.
The gas valves accomplish staging by allowing more or
less gas to the burners as called for by heating demand.
(one heat section shown)
COMBUSTION
AIR INDUCER
VENT
CONNECTOR
GAS VALVE
HEAT
EXCHANGER
TUBE
(one heat section shown)
COMBUSTION
AIR INDUCER
VENT
CONNECTOR
GAS VALVE
HEAT
EXCHANGER
TUBE
FIGURE 19
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