Carrier 58MXA Installation, Start-Up, And Operating Instructions Manual page 39

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. 56.)
Fig. 56—Filling Condensate Trap
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 test
for gas leaks with an open flame. Use a commercially
available soap solution made specifically for the detection of
leaks to check all connections, as specified in "Adjustments"
section. 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.
In the U.S.A., the input ratings for altitudes above 2000 ft must be
reduced by 2 percent for each 1000 ft above sea level.
In Canada, the input ratings must be derated by 5 percent for
altitudes of 2001 ft to 4500 ft above sea level.
Furnace input rate must be within ± 2 percent of input on furnace
rating plate adjusted for altitude.
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 and size. Table 9 can only be used for
model 58MXA furnaces with heating sizes of 040 through
120. Table 10 can only be used for model 58MXA furnaces
with a 140,000 Btuh input.
d. Find installation altitude in Table 9 or 10.
NOTE: For Canada altitudes of 2001 to 4500 ft, use U.S.A.
altitudes of 2001 to 3000 ft in Table 9 or 10.
e. Find closest natural gas heat value and specific gravity on
Table 9 or 10.
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 ft altitude using Table 9)
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
A99119
with burner enclosure front INSTALLED.
a. Remove burner enclosure front.
b. Remove cap that conceals adjustment screw for gas valve
regulator. (See Fig. 57.)
→
c. Jumper R and W thermostat connections on control to start
furnace.
Fig. 57—Redundant Automatic Gas Valve
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