Purge Gas Lines; Adjustments; Set Gas Input Rate - Carrier 58MVP Installation, Start-Up, And Operating Instructions Manual

→ Fig. 49—Inducer Housing Drain Tube
→ Fig. 50—Filling Condensate Trap
Step 4—Purge Gas Lines
If not previously done, purge the 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 the
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 5—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 rating for altitudes above 2000 ft must be
reduced by 2 percent for each 1000 ft above sea level.
In Canada, the input rating must be derated by 5 percent for
altitudes of 2000 ft to 4500 ft above sea level.
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 yearly heat value average (at installed altitude) from
A94208
local gas supplier.
b. Obtain yearly specific gravity average from local gas
supplier.
c. Verify furnace model. Table 12 can only be used for model
58MVP Furnaces.
d. Find installation altitude in Table 12.
NOTE: For Canada altitudes of 2000 to 4500 ft, use U.S.A.
altitudes of 2001 to 3000 ft in Table 12.
e. Find closest natural gas heat value and specific gravity in
Table 12.
f. Follow heat value and specific gravity lines to point of
intersection to find orifice size and low- and high-heat
manifold pressure settings for proper operation.
EXAMPLE: (0—2000 ft altitude)
Heating value = 1050 Btu/cu ft
Specific gravity = 0.62
Therefore: Orifice No. 45
* 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 proper input rate.
g. Check and verify burner orifice size in furnace. NEVER
ASSUME ORIFICE SIZE; ALWAYS CHECK AND
VERIFY.
2. Adjust manifold pressure to obtain input rate.
a. Remove burner enclosure front.
NOTE: Manifold pressure MUST always be measured with the
burner box cover REMOVED.
→
b. Remove caps that conceal adjustment screws for low- and
A94209
high-heat gas valve regulators. (See Fig. 51.)
c. Move setup switch SW-2 on control center to ON position.
(See Fig. 25.) This keeps furnace locked in low-heat
operation.
38
Manifold pressure: 3.6-in. wc for high heat
1.5-in. wc for low heat