NOTE: To find the Btuh input, multiply the number of
cubic feet of gas consumed per hour by the BTU
content of the gas in your particular locality. Contract
your gas company for this information, as it varies
widely from city to city.
EXAMPLE: It is found by measurement that it takes 26 seconds
for the hand to turn on the 1 cubic foot dial to make a revolution
with only a 120,000 Btuh furnace running. Using this informa-
tion, locate 26 seconds in the first column of Table 3.
Read across to the column headed "1 Cubic Foot" where you
will see that 138 cubic feet of gas per hour are consumed by
the furnace at that rate. Multiply 138 by 850 (the BTU rating of
the gas obtained from the local gas company). The result is
117,300 Btuh, which is close to the 120,000 Btuh rating of the
furnace.
If the actual input is not within
±
2% of the furnace rating, with
allowance being made for the permissible range of the regula-
tor setting (0.3 inches W.C.), replace the orifice spuds with
spuds of the proper size.
CAUTION: Be sure to relight any gas appliances that
were turned off at the start of this input check.
ADJUSTMENT OF MANIFOLD GAS PRESSURE
1. Turn gas off at main gas valve. Remove 1/8" plug in the main
gas valve body and install proper manometer tube adapter
fitting. Connect line from gas valve tap to manometer.
2. Refer to Figure 7 for location of pressure regulator adjust-
ment cap and screw on main gas valve.
NOTE: The screw-off cap for the pressure regulator
must be removed entirely to gain access to the ad-
justment screw.
WARNING: The cap must be replaced in order for the
furnace to operate properly.
3. Turn gas and electrical supplies ON. Start furnace and
observe manifold pressure on manifold.
4. Adjust manifold pressure by adjusting gas valve regulator
screw.
If gas valve regulator is turned in, or clockwise, manifold
pressure is increased. If screw is turned out, or counterwise,
manifold pressure will decrease.
WARNING: The manifold pressure must be checked
with the screw-off cap in place on the pressure regu-
lator.
WARNING: If manifold pressure is too high, an over-
fire condition exists which could cause heat ex-
changer failure. If the manifold pressure is too low,
sooting and eventual clogging of the heat exchanger
could occur.
5. Once the correct gas pressure to the burners has been
established, turn the gas valve knob to OFF and turn the
electrical supply switch OFF; then, remove the pressure
tap at the gas valve and re-install the plug using a com-
pound (on the threads) resistant to the action of LP gases.
6. Turn the electrical and gas supplies back on, and, with the
burners in operation, check for gas leakage around the
plug with a soap and water solution.
WARNING: Be sure that the gas valve pressure regu-
lator cap is replaced.
ADJUSTMENT OF PRIMARY AIR
The main burners should be in operation for 15 minutes before
making the primary air adjustment. The burner flame should
not contain any yellow color. With the furnace operating at full
input, adjust the primary air of the burners as follows:
Natural Gas - All models are shipped with the air shutters
partially open.
Local variations in the gas supply may require changes in the
settings described above. To change the air shutter settings,
use the following procedure:
1. Remove the front access door.
2. Loosen shutter locking screw.
3. Adjust the air shutters with power to the unit "off", and
retighten the locking screws.
4. Observe through the observation port to see if all flames are
now blue in color. See Figure 8 for proper flame pattern. If
yellow flames are still visible, repeat steps 2 thru 4.
5. Cycle the burners on and off a few times to verify the
burners are lighting promptly and properly.
6. Replace the front access door.
ADJUSTMENT OF TEMPERATURE RISE
The temperature rise, or temperature difference between the
return air and the heated air from the furnace, must be within
the range shown on the furnace rating plate and within the
application limitations shown in Table 1. After the temperature
rise has been determined, the cfm can be calculated.
After about 20 minutes of operation, determine the furnace
temperature rise. Take readings of both the return air and the
heated air in the ducts, about six feet from the furnace where
they will not be affected by radiant heat.
Increase the blower speed to decrease the temperature rise;
decrease the blower speed to increase the rise.
To adjust blower speed, perform the following steps:
FIGURE 7 - GAS VALVE - WHITE-RODGERS 36E97
LIGHT BLUE
OUTER CONE
CROSSOVER
FLAME
INTERGAL
CROSSOVER TUBE
MANIFOLD
BURNER
BLUE
INNER
CONES
FIGURE 8 - PROPER FLAME APPEARANCE
650.64-N4
Unitary Products Group
9
