47
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. 51 -- Redundant Automatic Gas Valve
UNIT DAMAGE 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.
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 com-
pleting low--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 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 con-
ceal gas valve regulator adjustment screws. Main burner
flame should be clear blue, almost transparent. (See Fig.
53.)
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.
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 12 for derate multi-
plier factor and example.
CANADA
At installation altitudes from 2000 to 4500 ft. (610 to
1372 M), this furnace must be derated 5 percent by an
authorized Gas Conversion Station or Dealer. To de-
termine correct input rate for altitude, see example and
use 0.95 as derate multiplier factor.
BURNER
ORIFICE
A93059
Fig. 52 -- Burner Orifice
EXAMPLE:
100,000 BTUH HIGH--HEAT INPUT
FURNACE INSTALLED AT 4,300 FT (1310 M)
Furnace Input Rate at Sea Level
X Derate Multiplier
Factor = Furnace Input Rate at Installation Altitude
100,000
X 0.91 = 91,000
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 SW1--2 to ON position. (See Fig.
33.) This keeps furnace locked in low--heat operation.
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BURNER FLAME
BURNER
MANIFOLD
A89020
Fig. 53 -- Burner Flame
355B
A
V
