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3.
Measure the time (in seconds) required for
the gas meter to complete one revolution.
4.
Convert the time per revolution to cubic
feet of gas per hour using Table 10.
5.
Multiply the gas flow rate in cubic feet per
hour by the heating value of the gas in Btu
per cubic foot to obtain the firing rate in Btu
per hour. Example:
• Time for 1 revolution of a gas meter with
a 1 cubic foot dial = 40 seconds.
• From Table 10 read 90 cubic feet per
hour of gas.
• Heating value of the gas (obtained from
gas supplier) = 1040 Btu per cubic foot.
• Firing rate = 1040 x 90 = 93,600 Btuh.
6.
Adjustments to the firing rate can be made
by adjusting the gas manifold pressure.
See the High Altitude Application section
for additional information of firing rate at
elevations above 2000 ft.
The manifold pressure must be set to the
appropriate value for your installation. Refer to
either Table 5 for natural gas or Table 6 for LP/
propane gas to verify the manifold pressure
setting required for your particular installation.
To adjust the manifold pressure, remove the
regulator cap and turn the adjusting screw
clockwise to increase pressure or counter-
clockwise to reduce pressure. Replace the
regulator cap after adjustments are complete.
Verifying and Adjusting Temperature Rise
Verify the temperature rise through the furnace
is within the range specified on the furnace rating
plate. Temperature rises outside the specified
range could result in premature heat exchanger
failure and/or cycling on limit switch.
Place thermometers in the return and supply air
stream as close to the furnace as possible. The
thermometer on the supply air side must be
shielded from direct radiation from the heat
exchanger to avoid false readings. Adjust all
registers and duct dampers to the desired
position and run the furnace for ten to fifteen
minutes before taking any temperature readings.
The temperature rise is the difference between
the supply and return air temperatures.
For typical duct systems, the temperature rise
will fall within the range specified on the rating
plate with the blower speed at the factory
recommended setting. If the temperature rise
measured is outside the range specified, it may
be necessary to change the blower speed.
Lower blower speeds will increase the
temperature rise and higher blower speeds will
decrease the temperature rise.
The furnace is equipped with a multi-speed
motor. Heating and cooling speed selection is
made by moving the leads on the integrated
control located in the furnace. The wiring diagram
on the furnace and Figures 12, 13 and 14 show
the speed taps for adjusting motor speed.
If it is desired that the blower operate at the same
unused speed for heating and cooling, move
blower leads to M1, M2, and/or M3 and install the
jumper wire found in the plastic instruction bag.
Remove the desired blower tap, and install the
jumper wire piggyback to the heating speed tap,
and straight quick connect to the cooling speed
tap. Reconnect the desired blower tap to
piggyback quick connect.
The integrated control is factory set to start the
circulating air blower 30 seconds after the gas
valve is opened. The integrated control is
factory wired to turn the blower motor off 120
seconds after the gas valve is closed. If
necessary for comfort, the “off” time may be
changed by adjusting the Blower Off jumper on
the integrated control. See Figure 12 or 13 for
blower on and off time adjustments.
!
WARNING:
To avoid electric shock, personal injury,
or death, disconnect the electric power
before performing any maintenance.
Verifying Burner Operation
To verify operation of the burners, make sure
that the furnace door is in place and that there
is power to the furnace. Set the thermostat to a
temperature above room temperature and
observe the ignition sequence. The burner flame
should carry over immediately between all
burners. The flames should be blue, without
yellow tips. Flames should extend from each
burner without lifting off, curling, or floating.
After verifying satisfactory flame characteristics,
set the thermostat to a temperature below room
temperature and verify that the burner flame
extinguishes completely.
