GF - D 21
Gas Valves
Step 13
When the correct operating gas valve pressures are
obtained, turn the furnace off. Remove the field supplied
manometer tubing and the tee installed at the beginning
steps and TIGHTEN DOWN THE MANIFOLD DUST
CAPS and the GAS PRESSURE PORT SCREW.
Using a leak detection solution or soap suds, check
for leaks at plug or outlet pressure tap screw. Turn on
the 115V power to the furnace.
Step 11
Replace and tighten the dust cap for the third stage
adjustment screw and then read the manifold pressure
again. This procedure may need to be repeated until
the manifold gas pressure is 3.5" of Water Column
(Figure 48).
Table 48
Step 12
If the firing rate cannot be obtained with the manifold
pressures specified in Table 9, check inlet gas piping
for proper sizing and pressure. If insufficient, correct
and/or contact gas company to adjust input pressure.
Table 46
Step 9
Let the furnace go through the third stage learning
routine and have its temperature rise stabilize. This
temperature rise and learning routine will take three
minutes.
Step 10
Remove the dust cap and adjust the gas valve third
stage of heat pressure adjustment screw slightly to
obtain the correct rate (Figure 47).
THIRD STAGE ADJUSTMENT:
COUNTERCLOCKWISE TO DECREASE OR
CLOCKWISE TO INCREASE PRESSURE.
NOTE: The dust cap screw covering the third stage
pressure adjustment screw must be in place during
manifold gas pressure readings.
Table 47
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