31
Line Voltage Wiring
It is recommended that the line voltage (115 VAC) to
the furnace be supplied from a dedicated branch circuit
containing the correct fuse or circuit breaker for the furnace
as listed in
.
IMPORTANT NOTES:
• An electrical disconnect must be installed readily
accessible from and located within sight of the
furnace. See
diagram label inside of the control door. Any other
wiring methods must be acceptable to authority
having jurisdiction.
• Proper line voltage polarity must be maintained in
order for the control system to operate correctly.
Verify the incoming neutral line is connected to the
white wire and the incoming “hot” line is connected
to the black wire. The furnace will not operate unless
the polarity and ground are properly connected as
shown in
Thermostat / Low Voltage Connections
• The furnace is designed to be controlled by a 24 VAC
thermostat. The thermostat’s wiring must comply with
the current provisions of the NEC (ANSI/NFPA 70) and
with applicable local codes having jurisdiction.
• The thermostat must be installed according to the
instructions supplied by the thermostat manufacturer.
Low voltage connections (24 VAC) from the thermostat
are wired to the terminal strip on the integrated control
in the furnace.
proper connections for heating only (two-wire) and
heating/cooling (four-wire) applications. Recommended
minimum wire gauge for thermostat wiring is shown in
• The thermostat should be mounted about 5 feet above
the floor on an inside wall. DO NOT install the thermostat
on an outside wall or any other location where its
operation may be adversely affected by radiant heat from
fireplaces, sunlight, or lighting fixtures, and convective
heat from warm air registers or electrical appliances.
Refer to the thermostat manufacturer’s instruction sheet
for detailed mounting information.
• The six pin terminal marked “Expansion Port” (
) is not used in the single stage furnace as
shipped from the factory. It is used for the furnace control
board to communicate to a fixed speed or variable speed
high efficiency motor that may be optionally installed.
Please contact your distributor for the proper upgrade
motor kit. Please
Set the heat anticipator according
to the instructions supplied by the thermostat
manufacturer.
To determine the heat anticipator setting:
1. Add the current draw of the system components; or
2. Measure the current flow on the thermostat
R-W
circuit
after the circulating blower motor has started.
The six pin terminal marked “Expansion Port” is not used
in the single stage furnace as shipped from the factory. It
is used for the furnace control board to communicate to a
fixed speed or variable speed high efficiency motor that
may be optionally installed. Please contact your distributor
for the proper upgrade motor kit.
Twinning
WARNING:
When servicing either twinned furnace, power
must be turned off on both furnaces. Failure to
comply may result in improper operation leading
to damage to the furnaces or personal injury!
Single stage M4 furnaces are not supplied with a built-
in twinning capability. Other valuable features and
enhancements were made to the new control that made it
necessary to remove the twinning capability. For twinning
of single stage furnaces with PSC motors, a twinning kit
(920919) is available for purchase.
Please follow the
instructions provided with the kit.
If both single stage furnaces are upgraded to the fixed
speed iSEER ™ blower, the twin terminal on the blower
control boards
may be used to
twin the single stage furnaces only if the following criteria
are met:
• Both furnaces and motors must be the same size.
• Both motors must be on the same speed for cooling
and heating.
• Both furnaces must have a common return duct and
common supply plenum.
• Both furnaces must be the same phase and on the
same leg of power.
• Furnaces equipped with variable speed iSEER
™ motors may not be twinned under any
circumstances.
For twinning of single stage furnaces equipped with fixed
speed iSEER ™ blowers, refer to
following instructions:
1. Turn off all power to both furnaces.
2. Attach a wire between the two twin terminals on the
twinning control boards. Use field supplied wire and
two 3/16” wire terminals. NOTE: One furnace can be
used for one stage of heating and the other furnace can
be used for the second stage of heating. The installer
also has the choice of running one furnace only or both
furnaces. In both cases the blowers will run at the same
time and at the same speeds:
•
Single stage heating: The W connection on each
furnace must be connected together and then connected
to the W connection of the thermostat. This will allow
both furnaces to ignite at the same time for one stage
heating.
•
Two stage heating: The W connection on one
furnace must be connected to the W1 connection
of the thermostat. The W connection of the second
furnace must be connected to the W2 connection of
the thermostat. This will allow one furnace to ignite for
Summary of Contents for M4RC-072D-35C
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