A99118
→Fig. 38ÐInducer Housing Drain Tube
5.Remove funnel and tube from inducer housing and replace drain connection cap and clamp.
III.PURGE GAS LINES
If not previously done, purge lines after all connections have been made and check for leaks.
WARNING: Never purge a gas line into a combustion chamber. Never use matches, candles, flame, or other sources of ignition for purpose of checking leakage. Use a
IV. ADJUSTMENTS
A.Set Gas Input Rate
Furnace gas input rate on rating plate is for installations at altitudes up to 2000 ft. Furnace input rate must be within ±2 percent of input on furnace rating plate.
1.Determine natural gas orifice size and manifold pressure for correct input.
a.Obtain average yearly heat value (at installed altitude) from local gas supplier.
b.Obtain average yearly specific gravity from local gas supplier.
c.Verify furnace model. Table 7 can only be used for model 345MAV furnaces.
A99119
→ Fig. 39ÐFilling Condensate Trap
d.Find installation altitude in Table 7.
NOTE: For Canada altitudes of 2000 to 4500 ft, use U.S.A. altitudes of 5001 to 6000 ft in Table 7.
e.Find closest natural gas heat value and specific gravity on Table 7.
f.Follow heat value and specific gravity lines to point of intersection to find orifice size and manifold pressure settings for proper operation.
EXAMPLE: (0Ð2000 altitude)
Heating value = 1050 Btu/cu ft
Specific gravity = 0.62
Therefore: Orifice No. 45
Manifold pressure 3.6-in. wc
*Furnace is shipped with No. 45 orifices. In this example all main burner orifices are the correct size and do not need to be changed to obtain the proper input rate.
Check and verify burner orifice size in furnace. NEVER ASSUME ORIFICE SIZE; ALWAYS CHECK AND VERIFY.
2. Adjust manifold pressure to obtain input rate.
NOTE: Manifold pressure must always be measured with burner enclosure front REMOVED. Gas meter must always be clocked with burner enclosure front INSTALLED.
a. Remove burner enclosure front.
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