Bryant 355CAV - Manual (Page 55)

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d. Jumper R and W/W1 thermostat connections on control
to start furnace.
e. Turn medium--heat adjusting screw counterclockwise
(out) to decrease manifold pressure or clockwise (in) to
increase manifold pressure.
NOTE: DO NOT set medium--heat manifold pressure less than
1.3-- in. wc or more than 1.7--in. wc for natural gas.
UNIT DAMAGE HAZARD
Failure to follow this caution may result in reduced furnace
life.
DO NOT bottom out gas valve regulator adjusting screws.
This can result in unregulated manifold pressure and result
in excess over--fire 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.
(See Fig. 61.)
f. Move setup switch SW4--2 to OFF position after
completing medium--heat adjustment.
g. Jumper R and W/W1 and W2 thermostat connections
on furnace control. (See Fig. 33.) This keeps furnace
locked in high--heat operation.
h. Turn high--heat adjusting screw counterclockwise (out)
to decrease manifold pressure or clockwise (in) to
increase manifold pressure.
NOTE: DO NOT set high--heat manifold pressure less than
3.2--in. wc or more than 3.8--in. wc for natural gas.
i. Remove jumpers R to W/W1 and R to W2.
j. Wait for blower off--delay to finish then reset 115--v
power to furnace.
k. Jumper R and W/W1 thermostat connections on control
to start furnace.
l. Wait for the blower to turn ON then check low--heat
manifold pressure. It should be between .5 to .6--in. wc.
This setting should not require adjustment but if it does
remove the low--heat adjustment cap (See Fig. 60) and
turn the low--heat adjusting screw clockwise (in) to
decrease manifold pressure or counterclockwise (out) to
increase manifold pressure. You will only have 15
minutes to make an adjustment if needed. If you need
more time then move setup switch SW1--2 on control
center to ON position (See Fig. 33).
NOTE: DO NOT set low--heat manifold pressure before setting
medium--heat manifold pressure. DO NOT set low--heat manifold
pressure less than .5--in. wc or more than .6--in. wc for natural gas.
m. When correct manifold pressures are obtained, replace
caps that conceal gas valve adjustment screws. Main
burner flame should be clear blue, almost transparent.
(See Fig. 62.)
n. Remove jumper across R and W/W1. If necessary move
setup switch SW1--2 to the OFF position.
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).
UNITED STATES
At altitudes above 2000 ft. (609.6M), this furnace has
been approved for 2 percent derate for each 1000 ft.
(304.8M) above sea level. See Table 11 for derate
multiplier factor and example.
CANADA
At installation altitudes from 2000 to 4500 ft. (609.6 to
1371.6M), this furnace must be derated 5 percent by an
authorized Gas Conversion Station or Dealer. To
determine correct input rate for altitude, see example
and use 0.95 as derate multiplier factor.
EXAMPLE: 80,000 BTUH HIGH--HEAT INPUT
FURNACE INSTALLED AT 4,300 ft. (1310.6M).
Furnace Input Rate at Sea Level X Derate Multiplier
Factor = Furnace Input Rate at Installation Altitude
80,000 X 0.91 = 72,800
b. Reinstall burner box cover.
NOTE: Clocking gas input rate MUST always be performed with
the burner box cover INSTALLED.
c. Check that gas valve adjustment caps are in place for
proper input to be clocked.
d. Obtain average heat value (at altitude) from local gas
supplier.
NOTE: Be sure heating value of gas used for calculations is
correct for your altitude. Consult local gas utility for altitude
adjustment of gas heating value.
e. Check and verify orifice size in furnace. NEVER
ASSUME THE ORIFICE SIZE. ALWAYS CHECK
AND VERIFY.
f. Turn off all other gas appliances and pilots.
g. Move setup switch SW4--2 to ON position. (See Fig.
33.) This keeps furnace locked in medium--heat
operation.
BURNER
ORIFICE
A93059
Fig. 61 -- Burner Orifice
355C
A
V
355C
A
V