Purge Gas Lines; Adjustments; Set Gas Input Rate - Carrier 58SMA Operating Instructions Manual

Fig. 38—Inducer Housing Drain Tube
2. Connect field-supplied 1/2-in. ID tube to upper inducer
housing drain connection.
3. Insert field-supplied funnel into tube.
4. Pour 1 quart of water into funnel/tube. Water should run
through inducer housing, overfill condensate trap, and flow
into open field drain. (See Fig. 39.)
5. Remove funnel and tube from inducer housing and replace
drain connection cap and clamp.
Step 3—Purge Gas Lines
If not previously done, purge lines after all connections have been
made and check for leaks.
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 soap-and-water solution
to check for leakage. Failure to follow this warning could
result in fire, explosion, personal injury, or death.
Step 4—Adjustments

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.
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Fig. 39—Filling Condensate Trap
b. Obtain average yearly specific gravity from local gas
supplier.
c. Verify furnace model. Table 7 can only be used for model
58MSA furnaces.
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: (0—2000 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.
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