Carrier 58MTA Installation, Start-Up, And Operating Instructions Manual page 47

ON/OFF SWITCH
INLET
PRESSURE TAP
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Fig. 53—Redundant Automatic Gas Control Valve
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 to obtain pressure
in this range.
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FIRE HAZARD
Failure to follow this caution may result in reduced furnace
life, property damage, personal injury, and death.
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-1 to OFF position after completing
low-heat adjustment.
g. Jumper R and W1 and W2 thermostat connections on
control. (See Fig. 32.) This keeps furnace locked in
high-heat operation.
h. Turn high-heat adjusting screw (3/32 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 to obtain pressure
in this range.
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. 54.)
j. Remove jumper R-to-W1 and W2.
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UNIT DAMAGE HAZARD
Failure to follow this caution may result in component
damage due to flame impingement of burners and heat
exchangers.
DO NOT redrill orifices. Improper drilling (burrs, out-of-
round holes, etc.) can cause excessive burner noise and
misdirection of burner flames.
3. Verify Natural Gas Input Rate By Clocking Gas Meter.
REGULATOR COVER SCREW
PLASTIC ADJUST SCREW
REGULATOR SPRING
HIGH STAGE GAS
PRESSURE REGULATOR
ADJUSTMENT
(
PROPANE–WHITE, 13.5 TURNS
)
NATURAL–SILVER,12 TURNS
LOW STAGE
GAS PRESSURE
REGULATOR ADJUSTMENT
( PROPANE–WHITE, 9.5 TURNS
NATURAL–SILVER,9.5 TURNS)
MANIFOLD
PRESSURE TAP
A04048
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.
Furnace Input Rate
NOTE: Clocking gas input rate MUST always be performed with
the burner box cover INSTALLED.
47
BURNER FLAME
MANIFOLD
Fig. 54—Burner Flame
Fig. 55—Burner Orifice
a. Calculate high-altitude adjustment (if required).
UNITED STATES
At altitudes above 2000 ft, this furnace has been approved
for 2 percent derate for each 1000 ft above sea level. See
Example and Table 11 for derate multiplier factor.
EXAMPLE:
100,000 Btuh input furnace installed at 4300 ft.
Derate
X Multiplier
at Sea Level Factor
100,000 X 0.91
CANADA
At installation altitudes from 2001 to 4500 ft, this furnace
must be derated 5 percent by an authorized Gas Conversion
Station or Dealer. To determine correct input rate for
altitude, see example above and use 0.95 as derate multi-
plier factor.
b. Reinstall burner box cover.
BURNER
A89020
BURNER
ORIFICE
A93059
Furnace Input Rate
= at Installation
Altitude
= 91,000