Auto-Zone Control Systems Auto-Zone Plus Systems Installation & Operation (Version 03A) - Manual (Page 165)

Auto-Zone Plus Section 4
Start-Up and Troubleshooting 4-15
1.3.6 Checking the Zone Manager Local Loop
Diagram
Meter Set To Read DC Volts
TO
OTHER
ZONE
MANAGERS
TO
ZONE CONTROLLERS
and
CONSTANT VOLUME
UNITS IF USED
NETWORK LOOP
FROM THE COMMLINK OR
PREVIOUS ZONE MANAGER
T
R
SHLD
+ - +
-
+2.9 VDC
to
+3.1 VDC
T - to - G
T
R
SHLD
+ -
+
-
+1.9 VDC
to
+2.1 VDC
R - to - G
The indicated readings are typical of a normally operating system. Actual readings may vary
slightly due to the number of units installed and other factors. Any significant deviation
from these values generally indicates a problem.
Note: These tests assume the Zone Manager is powered up.
Overview
Proper loop voltages are essential for reliable communications. It is normal to see
fluctuations on an operating communications loop. The average value should be close to the
acceptable range described below. Values will vary upon initial powerup for about 30-45
seconds. Voltages fluctuate as normal communications occur.
Measurements
Local Loop Acceptable Range
T – SHLD 2.9 - 3.1 Volts DC
R – SHLD 1.9 - 2.1 Volts DC
Action
Condition Action
Readings near zero volts Check for shorted wiring.
If voltages are too high or too low on either
side 1. One or more devices connected to this
loop may have damaged Comm Driver
chips.
2. Wiring errors. Check for multiple loops
inadvertently “cross connected”, short
circuits, etc.