Bryant Bruant 4 Way Gas 355AAV - Manual (Page 55)

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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 regulator seal caps that conceal adjustment
screws for low-- and high--heat gas valve regulators.
(See Fig. 59.)
c. Move setup switch SW1--2 on control center to ON
position. (See Fig. 37.) This keeps furnace locked in
low--heat operation.
d. Jumper R and W/W1 thermostat connections on control
to start furnace.
e. Turn low--heat adjusting screw (3/32) 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 to obtain manifold
pressure in this range.
UNIT DAMAGE HAZARD
Failure to follow this caution may result in reduced furnace
life or property damage.
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.
CAUTION
!
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 SW1--2 to OFF position after
completing low--heat adjustment.
g. Jumper R and W/W1 and W2 thermostat connections
on furnace control. (See Fig. 37) 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
manifold pressures 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. 61.)
j. Remove jumpers R to W/W1 and R to W2.
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.
REGULATOR COVER SCREW
PLASTIC ADJUST SCREW
LOW STAGE
GAS PRESSURE
REGULATOR ADJUSTMENT
MANIFOLD
PRESSURE TAP
INLET
PRESSURE TAP
ON/OFF SWITCH
REGULATOR SPRING
HIGH STAGE GAS
PRESSURE REGULATOR
ADJUSTMENT
1/2˝ NPT OUTLET
1/2˝ NPT INLET
A04167
Fig. 59 -- Redundant Automatic Gas Valve
BURNER
ORIFICE
A93059
Fig. 60 -- Burner Orifice
a. Calculate high--altitude adjustment (if required).
UNITED STATES
At altitudes above 2000 ft. (610 M), this furnace has
been approved for a 2 percent derate for each 1000 ft.
(305 M) above sea level. See Table 15 for derate
multiplier factor and example.
355A