Maxsys PC4020 - 2.3.3 How to Determine Line Loss; 2.3.4 Step by Step Procedure for Calculating Line Loss

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PC4020 Design Notes
If line loss is determined to be the problem with a job AFTER it is installed you will normally be
left with one option, the addition of a PC4204 power supply module. The additional cost of the
module and the time required to troubleshoot the system can be avoided by doing the
calculations ahead of time.
2.3.3 How to Determine Line Loss
You may find that the system does not require a PC4204 module for additional current if your
system is not too large. However your system may still require a PC4204 power supply module if
the line loss on the COMBUS is excessive.
Line loss is one of the most common cause of problems we have found. The following is a simple
and quick method for determining if the line loss on the COMBUS will require the additional of one
or more PC4204 modules.
2.3.4 Step by Step Procedure for Calculating Line Loss
Step 1 - Draw a block diagram of the system including all modules and the COMBUS wire runs
to these modules.
Step 2 - Find out how many Power Units are available for the gauge of wire used (See - POWER
UNITS CHART- Section 2.3.8). If different gauge wires are used throughout the system
these calculations will not work. If this is the case use the second method. (See -LINE
LOSS CALCULATION - SECOND METHOD - Section 2.3.10.)
Step 3 - Find out the distance of wire of each run of the COMBUS. Round up to the nearest 50'.
THIS IS THE MOST IMPORTANT STEP! IF THE DISTANCES ARE INCORRECT THE
CALCULATIONS WILL BE WRONG!
Step 4 - Indicate if any devices that require power (PIR, glassbreak, LED’s, relays etc...) other
than those connected to the AUX of a PC4204, the module they will be drawing power
from and the current required for these devices.
Step 5 - Write down for each module the base number indicated (See - BASE NUMBER CHART -
Section 2.3.7). Don’t forget to add to the Base number if additional devices requiring
power are connected.
Step 6 - Calculate how many Power Units will be required for each module of each branch of the
COMBUS. (See - POWER UNIT CALCULATION CHART - Section 2.3.9.)
Step 7 - Starting with the Power Units number determined in Step 2 for each branch, subtract the
Power Units required by each module.
Step 8 - If any branch of the system falls below 0 Power Units a PC4204 module will be required.
Depending on the size of the system, it shouldn’t take too long to calculate if line loss is excessive
on the system and could help save hours of troubleshooting time.