Heat Controller Water Source Heat Pump - Manual (Page 110)

WattMaster WHP Section 4
4-28 Start-Up and Troubleshooting
5.3.5 Checking the MiniLink Network Driver
Diagram
Meter Set To Read DC Volts
Note: These tests assume that the MiniLink being checked is powered up
Overview
This check is intended to determine if the Network Comm Driver chip on a MiniLink is
damaged.
Tip: Before unplugging the Network loop from the MiniLink, observe the Network Loop
LED (located near the connector). It should periodically “flicker” as the CommLink II
requests data from the MiniLink. The LED will also flicker when power to the
CommLink II is cycled. If the LED is not flickering, the unit is not communicating
with the CommLink II.
Damage typically occurs when the communications loop is exposed to excessive voltage, as
may occur during installation due to wiring errors. The driver chips are socketed on all
boards to facilitate servicing. It is unusual for driver chips to fail during normal operation.
Almost all failures occur as a result of wiring related problems.
Measurements
Network Loop Acceptable Range
T – SHLD 2.4 - 2.5 Volts DC
R – SHLD 2.4 - 2.5 Volts DC
Note: Minor variances may not indicate a problem if both tests indicate similar values
Action
Condition Action
If voltages are too high or too low on either
side The MiniLink has a damaged Network
Comm Driver chip. Replace the driver
chip. See "1.3.11Comm Driver Chip Re-
placement”.