15
PC4020 Design Notes
2.3.10 Line Loss Calculations - Second Method
If you unsure of the wiring of the system, the distances of the COMBUS wire runs or where devices are
getting power from it will not be possible to do the line loss calculations. If this is the case, after all the
wiring is completed, measure the voltage across the Red and Black of the COMBUS at EACH module.
If the voltage measured at a module is less than 12.5 V
DC there is too much line loss to guarantee the
operation of the module if an extended loss of AC power was to occur. A PC4204 module should be
used to power the module to prevent operation failure in the event of an extended AC power loss
If the voltage applied to the module is less than 11.5 V
DC it is quite likely the module will indicate a
‘Low Power’ trouble until the problem is resolved. In addition, even a short loss of AC could result
in module failure.
If the voltage applied to the module is less than 10.5 V
DC the module will most likely cause the system
to do several ‘Power Up Warms’, cause ‘COMBUS Trouble’ conditions or could cause the module to
‘runaway’ communicate, preventing other modules from communicating properly on the COMBUS.
2.3.11 Final Line Loss Test
There is one final test which can be performed which will guarantee your calculations are correct
and that excessive line loss is not a factor in you installation.
The following is a step-by-step procedure to check this:
1. Connect the system and wait 24 hours for all batteries on the main panel and any PC4204
modules to fully charge.
2. Disconnect the AC power from the main panel and all PC4204 modules.
3. Wait 10 minutes.
4. Go into ‘Diagnostics’. If no module shows a ‘Low Power’ trouble condition you can eliminate
line loss or insufficient power as a potential problem.
2.3.12 When to Perform Line Loss Calculations
Line loss calculations should be performed (either calculated or manually tested) whenever the
following occurs:
• before wiring the job - hours of troubleshooting and testing can be saved by identifying and
correcting line loss problems in the design stage
• if any module indicates a ‘Low Power’ or ‘Mod Comm Fault’ trouble
• if the system performs several ‘Power Up Warms’
2.4 COMBUS Power
The PC4000 main board can provide up to 500 mA to power modules and devices connected to
the system. A PC4204 module is required when additional current is needed for powering mod-
ules, devices or siren outputs.
The PC4204 module requires a transformer (16-18 volt, 40 VA) and a battery and will provide up
to 1.5 Amps of additional current at 12 V
DC. Four relays on the module provide Form C switched
outputs with contact ratings of 10 Amps @ 120 V
DC for any of the programmable output options. In
addition, the PC4204 monitors the AC power input, low battery condition and the AUX voltage
output and can report any or all of these trouble conditions in the event of a failure.
A PC4204 MODULE MUST BE USED TO POWER ADDITIONAL MODULES ON THE SYS-
TEM AND MUST BE WIRED IN ACCORDANCE WITH THE INSTRUCTIONS SUPPLIED
WITH THE UNIT.
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