Operating instructions

EXAMPLE: (0—2000 ft altitude)
Heating value = 1075 Btu/cu ft
Specific gravity = 0.62
Therefore: Orifice No. 45
Manifold pressure: 3.7-in. wc for high heat
1.5-in. wc for low heat
* Furnace is shipped with No. 45 orifices. In this example,
all main burner orifices are the correct size and do not need
to be changed to obtain proper input rate.
(7.) Check and verify burner orifice size in furnace.
NEVER ASSUME ORIFICE SIZE; ALWAYS
CHECK AND VERIFY.
b. Adjust manifold pressure to obtain input rate.
(1.) Remove caps that conceal adjustment screws for
low- and high-heat gas valve regulators. (See Fig.
19.)
(2.) Move setup switch SW-2 on control center to ON
position. (See Fig. 17.) This keeps furnace locked in
low-heat operation.
(3.) Jumper R and W/W1 thermostat connections on
control center to start furnace.
(4.) Turn low-heat adjusting screw (5/64 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.
CAUTION: 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.
(5.) Move setup switch SW-2 to OFF position after
completing low-heat adjustment.
(6.) Jumper R and W2 thermostat connections on con-
trol center. (See Fig. 14.) This keeps furnace locked
in high-heat operation.
(7.) Turn high-heat adjusting screw (5/64 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.
(8.) 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. 20.)
(9.) Remove jumper R to W2.
c. Verify natural gas input rate by clocking gas meter.
UNITED STATES
At altitudes above 2000 ft, this furnace has been ap-
proved for a 4 percent derate for each 1000 ft above sea
level. See Table 9 for derate multiplier factor and
example.
EXAMPLE:
85,000 Btuh input furnace installed at 4300 ft.
Furnace Input
Rate at
Sea Level
X
Derate
Multiplier
Factor
=
Furnace Input Rate
at Installation
Altitude
85,000 X 0.82 = 69,700
CANADA
At installation altitudes from 2000 to 4500 ft, this
furnace must be derated 10 percent by an authorized Gas
Conversion Station or Dealer. To determine correct input
rate for altitude, see example above and use 0.82 as
derate multiplier factor.
a. Check that gas valve adjustment caps are in place for
proper input to be clocked.
b. Obtain yearly heat value average for local gas supply.
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.
c. Check and verify orifice size in furnace. NEVER AS-
SUME THE ORIFICE SIZE. ALWAYS CHECK AND
VERIFY.
d. Turn off all other gas appliances and pilots.
e. Move setup switch SW-2 to ON position. (See Fig. 17.)
This keeps furnace locked in low-heat operation.
f. Jumper R to W/W1.
CAUTION: DO NOT redrill orifices. Improper drilling
(burrs, out-of-round can cause holes, etc.) excessive
burner noise and misdirection of burner flames. This can
result in flame impingement of burners and heat exchang-
ers, causing failures.
A93059
BURNER
ORIFICE
TABLE 9—ALTITUDE DERATE MULTIPLIER FOR U.S.A.
ALTITUDE
(FT)
%OF
DERATE
DERATE MULTIPLIER
FACTOR FOR U.S.A.*
0—2000 0 1.00
2001—3000 8—12 0.90
3001—4000 12—16 0.86
4001—5000 16—20 0.82
5001—6000 20—24 0.78
6001—7000 24—28 0.74
7001—8000 18—32 0.70
8001—9000 32—36 0.66
9001—10,000 36—40 0.62
* Derate multiplier factor is based on midpoint altitude for altitude range.
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