Maxsys PC4020 - 2.4.1 How to Wire a PC4204 for COMBUS Power

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PC4020 Design Notes
When a PC4204 is required because of excessive line loss due to long wire runs it is
suggested the module be located as close as possible to the device(s) requiring power. This
will help reduce the total wire length and decrease the voltage lost due to line loss.
No other power supply other than a PC4204 module may be used for the following reason:
The main panel supervises the modules on the system. If communications is lost with a module,
within a maximum of 10 seconds the system will power down the COMBUS for 5 seconds in an
attempt to reset the module. Five seconds later when power is applied the panel will again
attempt to communicate with the module. If the panel is still unsuccessful communicating with the
module it will display and report a COMBUS communication fault. In most instances the module
will be reset and will operate normally.
When the panel performs this power reset, Relay #1 of all PC4204 modules connected will open,
disconnecting power to all modules connected.
IF A POWER SUPPLY OTHER THAN A PC4204 MODULE IS USED THE MODULE WILL
NOT POWER DOWN, WILL NOT RESET AND WILL STAY OFF LINE REQUIRING THE
ATTENTION OF SERVICE PERSONNEL.
Relay #1 of any PC4204 module connected to the system CANNOT be used for any other
purpose other than COMBUS RESET as it will activate every time the main panel resets the
COMBUS.
2.4.1 How to Wire a PC4204 for COMBUS Power
A PC4204 used to provide additional power for modules on the system MUST be wired
according to the following diagram.
The diagram is also included on the sheet that comes with the module.
AC IN
RED RED
BLK BLK
YEL YEL
GRN GRN
PC4020
MODULES
PC4204
The RED wire of the COMBUS from the main panel is terminated at the PC4204. The black, yellow
and green wires continue on to any additional modules. The AUX output of the PC4204 is con-
nected to Relay #1 normally open (NO). The common (COM) of Relay #1 becomes the RED wire
for any additional modules connected the system.
Modules connected further down the line will receive power from the AUX output of the PC4204,
not the panel. This will accomplish two objectives. Firstly, it will lessen the load on the panel
(which can only supply 500 mA of current). Secondly, since the PC4204 connects to the
COMBUS, it can be located close to the modules requiring power, lessening the distance and the
line loss.