GMEC96 Installation Manual

48
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.
SUPPLY
AIR
RETURN
AIR
Temperature Rise Measurement
Figure 40

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


and external static pressure for each size furnace.
T
O
AVOID
PERSONAL
INJURY
OR
DEATH
DUE
TO
ELECTRICAL
SHOCK
,
TURN
OFF
POWER
TO
THE
FURNACE
BEFORE
CHANGING
SPEED
TAPS
.
WARNING

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

size furnace.

other thermostat input.
5. Cooling input (YLo/ Y) has priority over continuous
fan input.
6. Continuous fan input (G) has lowest priority.

The actual gas input rate to the furnace must never be greater

gas input using the gas meter, use the following procedure.
1. Turn OFF the gas supply to all other gas-burning
appliances except the furnace.
 
and record one complete revolution of the gas meter
dial measuring the smallest quantity, usually the dial
that indicates 1/2 cu. ft. per revolution. You will use
this number to calculate the quantity of gas in cubic
ft. if the furnace would consume if it ran steadily for
one hour (3600 seconds).
3. If the 1/2 cu. ft. dial was used, multiply your number
x 2.
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.

more than ± 0.3” w.c. for Natural and + 0.5” for

gas supplier if additional input rate adjustment is
required.

in step 1. Be certain that all appliances are functioning
properly and that all pilot burners are operating.

   
unit rating plate. An incorrect temperature rise may result in


applicable to your model. Determine and adjust temperature
rise as follows:
 
ten minutes. Ensure all registers are open and all

position.
2. Place thermometers in the return and supply ducts as
close to the furnace as possible. Thermometers must

the heat exchanger.