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521271-UIM-D-1211
Single-Wire Twinning Instructions
Connect the control wiring as shown in Figure 21.
1.
Connect the low voltage wiring from the wall thermostat to the ter-
minal strip on the control board of Furnace #1.
2.
Connect a wire from the TWIN terminal of Furnace #1 to the TWIN
terminal of Furnace #2.
3.
Install a separate 24V relay as shown in the diagram below. Use of
this relay is required, as it ensures that the transformers of the two
furnaces are isolated, thus preventing the possibility of any safety
devices being bypassed.
4.
Connect the common wires of furnace #1 to the common terminal
of furnace #2.
Single-Wire Twinning Operation
Heating - On a call for heat (W signal) from the wall thermostat, both
furnaces will start the ignition sequence and the burners on both fur-
naces will light. About thirty seconds after the burners light, the blowers
on both furnaces will come on in heating speed. When the thermostat is
satisfied, the burners will all shut off and, after the selected blower off
delay time, both blowers will shut off at the same time. The twinning
control ensures that both blowers come on and shut off at the same
time.
Cooling - On a call for cooling (Y signal) from the wall thermostat, both
furnace blowers will come on at the same time in cooling speed. When
the thermostat is satisfied, both blowers will stay on for 60 seconds,
then will shut off at the same time.
Continuous Fan - On a thermostat call for continuous fan (G signal),
both furnace blowers will come on at the same time in cooling speed
and will stay on until the G signal is removed.
FURNACE 1
CONTROL BOARD
W
G
C
R
TWIN
Y
W G
TO A/C
WALL THERMOSTAT
FIGURE 20: Single Wire Twinning Wiring Diagram
SECTION VII: VENT SYSTEM
VENT CONNECTIONS
All models are provided with a flue transition that is sized for 4" diame-
ter vent connections. If a larger size vent connector is required, that
connection must be installed external to the furnace. Figure 21 shows
the furnace as it is shipped from the factory. To convert to a horizontal
or downflow position, remove the four screws that secure the inducer
assembly and rotate 90° being careful not to damage the gasket. Rein-
stall screws. Remove cap from appropriate vent outlet location on the
cabinet, cut insulation in cabinet to same size as the hole provided and
reinstall cap in the hole in the top panel.
In downflow applications, do not block the combustion air inlet. The
furnace must be installed on a coil cabinet or subbase to allow com-
bustion air to enter the burner compartment.
16
FURNACE 2
CONTROL BOARD
W
G
C
R
TWIN
Y
ISOLATION
RELAY
R
Y
COMBUSTION AIR INDUCER
90°
Pressure Switch
Tube Routing
Pressure
Switch
FIGURE 21: Combustion Air Inducer
CATEGORY 1 - 450 F. MAX. VENT TEMP.
The venting system must be installed in accordance with Section 5.3,
Air for Combustion and Ventilation, of the National Fuel Gas Code
Z223.1/NFPA 54 (latest edition), or Sections 7.2, 7.3 or 7.4 of CSA
B149.1, National Gas and Propane Codes (latest edition) or applicable
provisions of the local building code and these instructions.
The furnace shall be connected to any type of B, BW or L vent connec-
tor, and shall be connected to a factory-built or masonry chimney. The
furnace shall not be connected to a chimney flue serving a sepa-
rate appliance designed to burn solid fuel.
It is recommended that the appliance is installed in a location where the
space temperature is 32 °F (0°C) or higher. If the appliance is installed
in a location where the ambient temperature is below 32 °F (0°C), the
combustion byproducts could condense causing damage to the appli-
ance heat exchanger.
This appliance may be common vented with another gas appliance for
residential installations as allowed by the codes and standards listed in
these instructions.
Non-HUD approved Modular Homes must be vented with an approved
roof jack and may not be common vented with other appliances.
VENTING
Category I venting consists of vertically venting one or more appliances
in B-vent or masonry chimney (as allowed), using single wall metal pipe
or B-vent connectors. Type B-vent system extends in a general vertical
direction and does not contain offsets exceeding 45°. A vent system
having not more than one 60° offset is permitted.
VENTING INTO AN EXISTING CHIMNEY
For Category I installations, the furnace shall be connected to a factory
built chimney or vent complying with a recognized standard, or a
masonry or concrete chimney lined with a material acceptable to the
authority having jurisdiction. Venting into an unlined masonry chimney
or concrete chimney is prohibited.
Where use of an existing chimney is unavoidable, the following rules
must be followed:
1.
The masonry chimney must be built and installed in accordance
with nationally recognized building codes or standards and must
be lined with approved fire clay tile flue liners or other approved
liner material that will resist corrosion, softening, or cracking from
flue gases. THIS FURNACE IS NOT TO BE VENTED INTO AN
UNLINED MASONRY CHIMNEY.
2.
This furnace must be vented into a fire clay tile lined masonry
chimney only if a source of dilution air is provided, such as by com-
mon venting with a draft hood equipped water heater. If no source
of dilution air is available, Type B vent must be used, or masonry
chimney vent kit 1CK0603 or 1CK0604 must be used. Refer to the
instructions with the kit to properly apply these masonry chimney
kits.
90°
Mounting Screw
(Remove)
Flue Transition
(Do Not Remove)
Mounting Screw
(Remove)
Johnson Controls Unitary Products
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