46
ON/OFF
SWITCH
INLET
PRESSURE
TAP
ON
O
F
F
BURNER
ENCLOSURE
REFERENCE
PRESSURE TAP
MANIFOLD
PRESSURE
TAP
LOW-FIRE
ADJUSTMENT
ALLEN SCREW
(UNDER CAP)
HIGH-FIRE
ADJUSTMENT
ALLEN SCREW
(UNDER CAP)
A097386
Fig. 51
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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
completing 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 (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. 53.)
j. Remove jumpers R to W/W1 and R to W2
BURNER
ORIFICE
A93059
Fig. 52
---
Burner Orifice
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, this furnace has been
approved for a 2 percent derate for each 1000 ft above
sea level. See Table 12 for derate multiplier factor and
example.
CANADA
At installation altitudes from 2000 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 and use
0.95 as derate multiplier factor.
EXAMPLE: 100,000 BTUH HIGH--HEAT INPUT
FURNACE INSTALLED AT 4,300 FT
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.
58U
VB
