Johnson Controls System 450 Series Technical Bulletin page 21

Important:
• Use copper conductors only. Make sure that all wiring connections are in accordance with
local, national, and regional regulations.
• Do not exceed the System 450 module electrical ratings. Exceeding module electrical ratings
can result in permanent damage to the modules and void any warranty.
• Run all low-voltage wiring and cables separately from all high-voltage wiring. It is
best practice to use shielded cable for input sensor cables that are exposed to high
electromagnetic or radio frequency noise.
• Make sure that the wire length between the sensors and control module is as short as
possible and practical, and that the wire size is correct.
• Electrostatic discharge (ESD) can damage System 450 modules. Use proper ESD precautions
when you install and service the modules to avoid damaging System 450 modules.
• Do not apply power to a C450YNN power module or the 24 VAC/VDC power source for the
System 450 modules before you finish wiring and checking all wiring connections. Short
circuits or improperly connected wires can result in damage to the modules and void any
warranty.
• You can connect a System 450 control module and module assembly to an internal power
source, such as a System 450 power module, or an external power source, such as 24 VAC/
VDC power that connects to the 24 V and COM terminals on the control module. Do not
connect a control module to both power sources simultaneously. If you connect a control
module to both internal and external power sources, you can damage the modules and
void any warranty.
• When you connect System 450 compatible sensors with shielded cable to a System 450
control module, connect the cable shield drain lead to one of the C terminals on the input
sensor terminal block. Do not connect the shield at any other point along the cable. Isolate
and insulate the shield drain at the sensor end of the cable. If you connect a cable shield
at more than one point, this can cause transient currents to flow through the sensor cable
shield, which can cause erratic control operation.
Figure 5 shows the locations of and designations for the wiring terminals for System 450 standard
control modules.
Figure 5: Control and expansion modules with relay output
System 450 Series C450CCU Condensing Unit Control System Technical Bulletin 21