Goodman MEC96 Series Instruction Manual page 48

EXAMPLE: If it took 23 seconds to complete one
revolution of the 1/2 ft. dial (23 x 2 = 46).
This tells us that at this rate, it would take 46 seconds to
consume one cu. ft. of gas. 3600 / 46 = 78.
This tells us that in one hour, the furnace would consume
78 cu. ft. of gas.
The typical value range for 1 cu. ft. of natural gas is around
1000 BTU. Check with your gas utility, if possible. In this
example, the furnace is consuming 78,000 BTUH.
NOTE: The final manifold pressure cannot vary
by more than ± 0.3" w.c. for Natural and + 0.5" for
LP from the specified setting. Consult your local
gas supplier if additional input rate adjustment is
required.
4. Turn ON gas to and relight all other appliances
turned off in step 1. Be certain that all appliances
are functioning properly and that all pilot burners are
operating.
Temperature Rise
Temperature rise must be within the range specified on the
unit rating plate. An incorrect temperature rise may result
in condensing in or overheating of the heat exchanger. An
airflow and temperature rise table is provided in the Specifi-
cation Sheet applicable to your model. Determine and adjust
temperature rise as follows:
1. Operate furnace with burners firing for approximately
ten minutes. Ensure all registers are open and all
duct dampers are in their final (fully or partially open)
position.
2. Place thermometers in the return and supply ducts
as close to the furnace as possible. Thermometers
must not be influenced by radiant heat by being able
to "see" the heat exchanger.
3. Subtract the return air temperature from the supply
air temperature to determine the air temperature rise.
Allow adequate time for thermometer readings to
stabilize.
4. Adjust temperature rise by adjusting the circulator
blower speed. Increase blower speed to reduce
temperature rise. Decrease blower speed to increase
temperature rise. Refer to Startup Procedure and
Adjustment - Circulator Blower Speeds for speed
changing details.
Temperature Rise Measurement
Circulator Blower Speeds
This furnace is equipped with a multi-speed ECM motor. The
line voltage (115 VAC) power supply to the motor is constant
and not switched by the control board. Motor operation is
also dependent on a pulsing D.C. signal on one of the four
speed taps on the motor. The airflow tables for heating and
cooling speeds show the relationship between airflow (CFM)
and external static pressure for each size furnace.
T
O AVOID PERSONAL INJURY OR DEATH DUE TO ELECTRICAL SHOCK
OFF
TURN POWER TO THE FURNACE BEFORE CHANGING SPEED TAPS
Circulator Blower Speed Facts
1. Motor speed Tap wiring must remain in factory position
on the control board and motor.
2. There are 4 speed Tap wires to the motor T1, T2, T3,
T4.
3. There are 5 speeds available, depending on DIP
switch settings and found in air flow table for each
size furnace.
4. Heating input (W1/ W2) always has priority over all
other thermostat input.
5. Cooling input (YLo/ Y) has priority over continuous fan
input.
6. Continuous fan input (G) has lowest priority.
a. Refer to the air flow table for your specific model
furnace
b. If a cooling or heat pump condensing unit is being
used in conjunction with this furnace, DIP switches
S1-1, S1-2, S1-3 are used to select the proper
cooling speeds to match the outdoor unit size.
Typical CFM requirements are 400 CFM / Ton.
48
SUPPLY
AIR
RETURN
AIR
Figure 45
WARNING
,
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