Carrier 58MVP080 Installation, Start-Up, And Operating Instructions Manual page 39

Fig. 48—Inducer Housing Drain Tube
Fig. 49—Filling Condensate Trap
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
high-heat gas valve regulators. (See Fig. 50.)
c. Move setup switch SW-2 on control center to ON position.
(See Fig. 25.) This keeps furnace locked in low-heat
operation.
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d. Jumper R and W/W1 thermostat connections on control
center to start furnace.
e. Turn low-heat adjusting screw (5/64 hex Allen wrench)
counterclockwise (out) to decrease input rate or clockwise
(in) to increase input rate.
NOTE: DO NOT set low-heat manifold pressure less than 1.3-in.
wc or more than 1.7-in. wc for natural gas. If manifold pressure is
outside this range, change main burner orifices.
DO NOT bottom out gas valve regulator adjusting screw.
This can result in unregulated manifold pressure and result in
excess overfire and heat exchanger failures.
NOTE: If orifice hole appears damaged or it is suspected to have
been redrilled, check orifice hole with a numbered drill bit of
correct size. Never redrill an orifice. A burr-free and squarely
aligned orifice hole is essential for proper flame characteristics.
f. Move setup switch SW-2 to OFF position after completing
low-heat adjustment.
g. Jumper R and W2 thermostat connections on control
center. (See Fig. 25.) This keeps furnace locked in high-
heat operation.
h. Turn high-heat adjusting screw (5/64 hex Allen wrench)
counterclockwise (out) to decrease input rate or clockwise
(in) to increase rate.
NOTE: DO NOT set high-heat manifold pressure less than 3.2-in.
wc or more than 3.8-in. wc for natural gas. If manifold pressure is
outside this range, change main burner orifices.
i. When correct input is obtained, replace caps that conceal
gas valve regulator adjustment screws. Main burner flame
should be clear blue, almost transparent. (See Fig. 51.)
j. Remove jumpers R to W/W1 and R to W2
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3. Verify natural gas input rate by clocking gas meter.
NOTE: Be sure all pressure tubing, combustion-air and vent
pipes, and burner enclosure front are in place when checking input
by clocking gas meter.
a. Calculate high-altitude adjustment (if required).
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Manifold pressure: 3.6-in. wc for high heat
1.5-in. wc for low heat