JOHNSON CONTROLS
30
FORM 100.50-NOM12
ISSUE DATE: 04/02/2019
SECTION 2 – INSTALLATION
No external power source may be used
when field wiring any of the above inputs.
The 24 VAC source on terminal 3 of the
terminal block CTB1 must be used as
the power source when field wiring these
. Failure to do so will result in improper
unit operation and damage to the IPU
board.
VAV Heat Relay Output
This is a field wired OUTPUT that is used to com-
mand the VAV boxes to full open during morning
warm up operation. This 24 VAC signal should have
a maximum current draw not to exceed 20VA. If the
VA requirement of the VAV boxes approaches 20VA,
isolation relays should be field supplied and installed
to avoid overloading the unit power supply.
Note that this signal is used to drive the VAV boxes
open in morning warm up operations. Failure to drive
the VAV boxes open during this mode of operation can
cause unit shutdown and/or damage to the ductwork
due to over pressurization.
The VAV heat relay output cannot exceed
a current draw of 20VA. If the power re-
quirements of the VAV boxes exceed this
amount, isolation relays must be field sup
-
plied and installed to prevent overloading
the IPU board power supply.
RETURN AIR BYPASS DAMPER
Units built with the FlexSys option has an opening in
the base of the unit between the evaporator coil and the
supply air blower. A FlexSys unit requires a means to
bypass return air and mix it with the air off the evapo-
rator coil. Johnson Controls does have a special curb
with the return duct bypass built into the curb. The pur-
pose of the damper is to temper the supply air to the
under floor system by mixing return air with the air off
the evaporator coil. After the system is initialized, the
mixed air damper modulates based on the ratio of the
difference between the mixed air temperature minus
the supply air temperature compared to the return air
temperature minus the supply air temperature. As the
mixed air temperature decreases, the damper opens al-
lowing more air to bypass the evaporator coil resulting
in a higher mixed air temperature supply to the under
floor system.
The mixed air damper must be wired and installed into
the system in the field. The wires to connect the actua-
tor are located in the supply fan section, in the prox-
imity of the actuator in the supply fan section floor,
opposite the supply fan motor side. The plug assembly/
wires are attached with an elastic band and must be
wired to the actuator, and the “plugs” mated together.
Connect the wires to the motor as follows:
• Wire labeled “412” to terminal 1 in the actuator
• Wire labeled “303” to terminal 2 in the actuator
• Wire labeled “411” to terminal 5 in the actuator
BACNET COMMUNICATION
The packaged rooftop unit can communicate to any
building automation system using BACnet
MS/TP
communication protocol.
The field connections are made by connecting shielded
two-wire cable to Port 1 on the
IPU
board.
Refer to
Communication section on page 142
for ad-
ditional information.
DIRTY FILTER SWITCH
On units with a dirty filter switch option, an adjust-
able differential pressure switch is installed to monitor
the pressure drop across the filters. When the pressure
drop across the filters exceeds the setting of the switch
the switch closes sending a 24-volt signal to the IPU
board. The IPU board posts a trouble fault in the ser-
vice memory buffer; but will not shut down the unit.
ALARM CONTACTS
The IPU board has three sets dry alarm contacts that
are closed during a fault. When the unit experiences
a Supply Fan Fault, the IPU board closes a set of dry
contacts between terminals 28 and 29 of the low volt-
age terminal block (CTB1).
When the unit experiences a Cooling/Heating Fault,
the IPU board closes a set of dry contacts between
terminals 30 and 31 of the low voltage terminal block
(CTB1).
When the unit experiences a Sensor/Misc. Fault, the
IPU board closes a set of dry contacts between ter-
minals 32 and 33 of the low voltage terminal block
(CTB1).