25
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.
Figure 34
R
Y
C
Furnace
Integrated
Control
Module
Remote Condensing Unit
(Single-Stage Cooling)
R
Thermostat - Two-Stage Heating with Single-Stage Cooling
Figure 35
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
Figure 36
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.
PCBBF139 CONTROL BOARD
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
DIP SWITCH
SWITCH
GROUP
FUNCTION
S3
S3
Heating
Fan Off
Delay
PURPOSE
Thermostat
Setup
Fossil Fuel Applications
This furnace can be used in conjunction with a heat pump
in a fossil fuel application. A fossil fuel application refers to
a combined gas furnace and heat pump installation which
uses an outdoor temperature sensor to determine the most
cost efficient means of heating (heat pump or gas furnace).
A heat pump thermostat with
three stages of heat
is required
to properly use a two-stage furnace in conjunction with a heat
pump. Refer to the fossil fuel kit installation instructions for
additional thermostat requirements.
Strictly follow the wiring guidelines in the fossil fuel kit instal
-
lation instructions. All furnace connections must be made
to the furnace two-stage integrated control module and the
“FURNACE” terminal strip on the fossil fuel control board.
Twinning
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 twin
-
ning 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 it’s own
115 VAC power supply. The L1 connection to each
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.