L.B. White AW250(building controller) - Manual (Page 18)

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The following explains a typical procedure to be followed
in checking gas pressures.
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Consult the dataplate on the heater or page 4 in this
manual for specific pressures to be used in conjunction
with this procedure.
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Gas pressure entering the gas valve is Inlet Pressure.
Gas pressure flowing out of the gas valve is Burner
Manifold pressure.
A. Preparation
1. Obtain two pressure gauges capable of reading up to
35 in. W.C.
2. Disconnect the heater from the electrical supply and
close the fuel supply valve to the heater inlet.
3. Open the burner access panel.
4. Brush or blow off any dust and dirt on or in the vicinity
of the gas control valve.
B. Gauge Installation
1. Locate the inlet and outlet pressure taps, see Fig. 16.
Using a screwdriver, open the pressure taps by turning
both screws one full turn counterclockwise.
FIG. 16
2. Securely connect a pressure gauge to each pressure
tap. See Fig.17.
FIG. 17
3. Open the fuel supply valves to the heater and
reconnect the heater electrical supply.
4. Start the heater
C. Reading Pressures
1. Set the building controller to call for maximum
temperature. With the heater operating, the pressure
gauges should read the pressures specified on the
dataplate.
2. Do the readings at the inlet and outlet pressure
gauges agree with that specified on the dataplate?
If so, then no fur ther checking or adjustment is
required. Proceed to section D.
3. If the inlet pressure does not agree with that specified
on the dataplate, then the regulator controlling gas
pressure to the heater requires adjustment.
4. If the inlet pressures are correct but the burner
manifold pressure does not agree with that specifed
on the dataplate, check the heater’s burner orifice for
blockage. if the orifice is unblocked, the gas control is
defective and should be replaced.
D. Completion
1. Once the proper inlet and burner manifold pressures
have been confirmed and/or properly set, close the
fuel supply valve to the heater and allow the heater to
burn off any gas remaining in the gas supply line.
2. Disconnect the heater from its electrical supply.
3. Remove the gauges and connecting hoses.
4. Close both pressure tap screws by turning clockwise,
snugging in securely. Check for gas leaks.
WARNING
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Do not disassemble the gas control valve.
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Do not attempt to replace any components of the gas
control valve.
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The gas control valve must be replaced if any physical
damage occurs to the control valve assembly.
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Failure to follow this warning will result in fire or
explosions, leading to injury or death to humans, and
property damage.
18
Gas Pressure Checks
INLET PRESSURE TAP
OUTLET PRESSURE TAP