Installation Instructions

26
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.
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
115 VOLT LINE CONNECTION OF ACCESSORIES (HUMIDIFIER AND
ELECTRONIC AIR CLEANER)
The furnace integrated control module is equipped with line volt-
age accessory terminals for controlling power to an optional field-
supplied humidifier and/or electronic air cleaner.
The accessory load specifications are noted in the chart below:
Humidifier 1.0 Amp maximum at 120 VAC
Electronic Air Cleaner 1.0 Amp maximum at 120 VAC
Turn OFF power to the furnace before installing any accessories.
Follow the humidifier or air cleaner manufacturers’ instructions
for locating, mounting, grounding, and controlling these acces-
sories. Accessory wiring connections are to be made through the
1/4" quick connect terminals provided on the furnace integrated
control module. The humidifier and electronic air cleaner hot
terminals are identified as HUM and EAC. The humidifier and
electronic air cleaner neutral terminals are identified as NEU-
TRAL. All field wiring must conform to applicable codes. Connec-
tions should be made as shown.
If it is necessary for the installer to supply additional line voltage
wiring to the inside of the furnace, the wiring must conform to
all local codes, and have a minimum temperature rating of 105°C.
All line voltage wire splices must be made inside the furnace
junction box.
The integrated control module humidifier terminal (HUM) is en-
ergized with 115 volts whenever the induced draft blower is en-
ergized. The integrated control module electronic air cleaner
terminal (EAC) is energized with 115 volts whenever the circula-
tor blower is energized. This terminal can also be used to
provide 115 volt power to a humidifier transformer. The re-
maining primary transformer wire would be connected to the
Line N on the control board.
HIGH VOLTAGE !
T O AVOID PERSONAL INJURY OR DEATH DUE TO
ELECTRICAL SHOCK , DISCONNECT ELECTRICAL POWER
BEFORE SERVICING OR CHANGING ANY ELECTRICAL
WIRING .
WARNING
Accessories - Accessories Wiring
Figure 33
G AS S UPPLY AND P IPING
T O AVOID POSSIBLE UNSATISFACTORY OPERATION OF EQUIPMENT
DAMAGE DUE TO UNDERFIRING OR EQUIPMENT , USE THE PROPER SIZE
OF NATURAL / PROPANE GAS PIPING NEEDED WHEN RUNNING PIPE FROM
THE METER / TANK TO THE FURNACE .
WARNING
Natural Gas Minimum: 4.5" w.c. Maximum: 10.0" w.c.
Propane Gas Minimum: 11.0" w.c. Maximum: 13.0" w.c.
INLET GAS SUPPLY PRESSURE
The furnace rating plate includes the approved furnace gas input
rating and gas types. The furnace must be equipped to operate
on the type of gas applied. This includes any conversion kits
required for alternate fuels and/or high altitude.