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2-Heat Exchanger (Figures 14 and 15)
The LGT units use aluminized steel inshot burners with
matching tubular aluminized (stainless steel is an option)
steel heat exchangers and two‐stage redundant gas
valves. Units are equipped with one eleven tube/burner for
high heat and one nine tube/burner for medium heat. Burn
ers 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 sur
faces of the heat exchanger tubes. The supply air blowers,
controlled by the A55 Unit Controller, force air across all
surfaces 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.
3-Gas Heat Exchanger Inserts
Inserts are installed on standard (130,000Btuh) heat ex
changers in tubes one and three. Medium and high heat ex
changers do not require inserts. See figure 16. Inserts are
used to maintain even temperature distribution through the
heat exchanger. Temperature distribution can vary de
pending on supply air flow, number of heat exchanger
tubes and the blower deck opening.
HEAT EXCHANGER ASSEMBLY
FIGURE 14
BURNER
COMBUSTION
AIR INDUCER
VENT
CONNECTOR
GAS VALVE
HEAT
EXCHANGER
TUBE
BURNER BOX ASSEMBLY
FIGURE 15
Gas Valve
Burners
Gas Manifold
Rollout Switch
4-Burner Assembly (Figure 17)
The burners are controlled by the spark electrode, flame
sensing electrode, gas valve and combustion air blower.
The spark electrode, flame sensing electrode and gas
valve are directly controlled by ignition control. Ignition con
trol and combustion air blower is controlled by A55 Unit
Controller.
Burners
All units use inshot burners (see figure 17). Burners are
factory set and do not require adjustment. A peep hole
with cover is furnished in the heating access panel for
flame viewing. Always operate the unit with the access
panel in place.
Burners can be removed for service. Burner mainte
nance and service is detailed in the SERVICE CHECKS
section of this manual.
STANDARD HEAT (130,000BTUH)
INSERTS (2)
INSERT LOCATION
FIGURE 16
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