10
SYSTEM OPERATION
The integrated control module electronic air cleaner ter
-
minals (EAC) are energized with 115 volts whenever the
circulator blower is energized.
24 VOLT THERMOSTAT WIRING
NOTE:
Low voltage connections can be made through
either the right or left side panel. Wire routing must not
interfere with circulator blower operation, filter removal, or
routine maintenance.
A 40 V.A. transformer and an integrated electronic control
are built into the furnace to allow use with most cooling
equipment. Consult the wiring diagram located in this
manual, the installation manual, or on the blower door for
further details of 115 Volt and 24 Volt wiring.
THERMOSTAT WIRING
The *MEC80 furnace has W1 & W2 terminals for connection
of a two stage heating thermostat. If desired, a thermostat
with only one stage of heat may be used. As shipped, the
furnace S1-1 switch is OFF; S1-2 switch is ON. This is the
correct position to use a single stage heating thermostat
with auto timing transition to high fire.
R
Y
C
Furnace
Integrated
Control
Module
Remote Condensing Unit
(Single-Stage Cooling)
R
Thermostat - Single -Stage Heating with Single-Stage Cooling
NOTE:
To apply a single-stage Heating Thermostat, the
thermostat selector switch on the Integrated Control Module
must
be set on single-stage.
R
Y
C
Furnace
Integrated
Control
Module
Remote Condensing Unit
(Single-Stage Cooling)
R
Thermostat - Two-Stage Heating with Single-Stage Cooling
W1 W2
Y
Furnace
Integrated
Control
Module
Remote Condensing Unit
(Two-Stage Cooling)
Y2
W1 W2
Y2
Thermostat - Two-Stage Heating with Two-Stage Cooling
Thermostat Wiring Diagrams
Single-Stage Heating Thermostat Application
A single-stage thermostat with only one heating stage
may be used to control this furnace. The application of a
single-stage thermostat offers a
timed
transition from low
to high fire. The furnace will run on low stage for a fixed
period of time before 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 a fixed 10 or 20 minute time delay
or a load based variable 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.
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
Off*
ON*
90
OFF
OFF
120
OFF
ON
150
ON*
OFF*
180
ON
ON
*Factory Setting
Staging and Blower Off Delay Dip Switches PCBBF139
Heating Fan Off
Delay
S3
Dip Switch
Purpose
Switch Group
Function
Thermostat
setup
S3
Twinning
Using the “TWIN” terminals and proper wiring enables
two *MEC80 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 fur
-
nace to operate synchronously into a common duct system.
Using the twinning function will require only field installed
wiring with no external 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
ZERO
.
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
