SYSTEM OPERATION
24
A single-stage thermostat with only one heating stage may be
used to control this furnace. The application of a single-stage
timed
stepping up to high stage to satisfy the thermostat’s call for
heat. The delay period prior to stepping up can be set at either
time between 1 and 12 minutes (AUTO mode). If the AUTO
mode is selected, the control averages the cycle times of the
previous three cycles and uses the average to determine the
time to transition from low stage to high stage.
Purpose
Auto 1 OFF* 2 ON*
10 Minutes 1 ON 2 OFF
20 Minutes 1 ON 2 ON
2 Stage 1 OFF 2 OFF
90 Seconds 3 OFF 4 OFF
120 Seconds 3 OFF 4 ON
150 Seconds 3 ON* 4 OFF*
180 Seconds 3 ON* 4 ON
Staging and Blower Off Delay DIP Switches PCBBF137
1 2 3 4
2 Stage Stat OFF OFF
1 Stg Stat 10 min delay ON OFF
1 Stg Stat 20 min delay ON ON
Auto
180 ON ON
*Factory Setting
Staging and Blower Off Delay Dip Switches PCBBF139
Using the “TWIN” terminals and proper wiring enables two
*MEC96 furnaces of the same model and size to be twinned.
Twinning allows simultaneous operation of two furnaces and
forces the indoor blower motors of each furnace to operate
synchronously into a common duct system. Using the twinning
kits or parts.
• The staging DIP switches and speed tap DIP switches
must be set the same on both furnaces.
NOTE: Each furnace must be connected to its own 115 VAC
power supply. The L1 connection toeach furnace must be
in phase (connected to circuit breakers on the same 115
VAC service panel phase leg). To verify that the furnaces
are in phase, check from L1 to L1 on each furnace with a
voltmeter. If the furnaces are in phase, the voltage between
both furnaces will be .
Room
Thermostat
Y2
Y
W
W2
R
G
C
Ylo
Y
W
W2
R
G
C
Ylo
Y
W
W2
R
G
C
Furnace 1
Furnace 2
G
TG
T
R BR GG T
T R R B RT
R T
R
RT G R JR R T
This furnace is equipped with a multi-speed ECM motor. Two
wiring harnesses connect the motor to the integrated control
board and furnace power supply. 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 24 VDC
tables for heating and cooling speeds show the relationship
size furnace.
T
O
AVOID
PERSONAL
INJURY
OR
DEATH
DUE
TO
ELECTRICAL
SHOCK
,
TURN
OFF
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.
requirement. Filters can also be installed elsewhere
in the duct system such as a central return.
T
O
AVOID
PERSONAL
INJURY
OR
DEATH
DUE
TO
ELECTRICAL
SHOCK
,
TURN
OFF
POWER
TO
THE
FURNACE
BEFORE
CHANGING
SPEED
TAPS
.
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