Heat Controller Water Source Heat Pump - Manual (Page 111)

WattMaster WHP Section 4
Start-Up and Troubleshooting 4-29
5.3.6 Checking the MiniLink Local Loop
Diagram
Meter Set To Read DC Volts
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 MiniLink is powered up
Overview
Proper loop voltages are essential for reliable communications. It is normal to see fluctua-
tions on an operating communications loop. The average value should be close to the ac-
ceptable range described below. Values will vary upon initial powerup for about 30-45 sec-
onds. 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.