Installation manual

55Pumped Refrigerant System Operation and Maintenance
Troubleshooting
Problem
Possible Cause Corrective Action
Display interface not
operational, but
equipment operates
• Display interface
not connected
properly
• Verify that the display interface cable is connected properly.
Alarms do not show up
on monitoring equipment
(Customer Output
Contact)
• External
monitoring
equipment is not
receiving power or
is not functioning
properly
• Confirm that power, if required, is being supplied to the external
equipment.
• If the RDU is providing power to the external equipment, verify that the
external equipment is <
50 mA.
• Test the external equipment by bypassing the customer output contact.
Equipment does not shut
down on command
• Drive voltage • Verify that there is a drive voltage entering the input of the RDU. You
may use the +12 V or +24 V. You must also use the ground.
No communication with
building management
system (BMS) port
• Improper
connection
• Confirm that the RDU is connected to the BMS port and not to the
Control port.
• Make sure that the wire polarity is correct. Using a DC voltmeter, test the
signal with no transmissions in progress. Expect the voltage at pin 2 to
be greater than at pin 1 by at least 200 mV. Measure the RDU with the
cable disconnected, and then measure it again with the cable connected.
If the signal is less than 200 mV, the RDU may be reverse-wired.
• Make sure every CM has either two sets of wires on the connector or one
set of wires and a terminating resistor of 100 to 120 ohms.
Cooling modules are not
communicating with the
RDU
• A-Link failure • Verify that the first and last cooling modules have one cable and a
terminator.
• Verify that every other cooling module has two cables.
• Confirm that the A-Link cables are connected to the A-Link ports and
that a network cable is connected to the network port.
• Verify that the number of cooling modules in the cooling group matches
the group number setting.
Equipment does not shut
down on command
• Drive voltage • Verify that there is a drive voltage entering the input of the cooling unit.
You may use the available +12 V or +24 V. You must also use the
ground.
No communication with
building management
system (BMS) port
• Improper
connection
• Confirm that the RDU is connected to the BMS port and not to the
Control port.
• Make sure that the wire polarity is correct. Using a DC voltmeter, test the
signal with no transmissions in progress. Expect the voltage at pin 2 to
be greater than at pin 1 by at least 200 mV. Measure the RDU with the
cable disconnected, and then measure it again with the cable connected.
If the signal is less than 200 mV, the RDU may be reverse-wired.
• Make sure that every CM has either two sets of wires on the connector or
one set of wires and a terminating resistor of 100 to 120 ohms.
CMs are not
communicating with
each other
• A-Link failure • Verify that the first and last CMs have one cable and a terminator.
• Verify that every other cooling module has two cables.
• Confirm that the A-Link cables are connected to the A-Link ports and
that a network cable is connected to the network port.
• Verify that the number of CMs in the cooling group matches the group
number setting.
Output air is 17° C
(62° F) and CM fans are
running at a very high
rate of speed.
•Upper or lower
supply air sensor
• Either the upper or lower supply air temperature sensor has a fault.
Verify that both supply air temperature sensors are installed and working
properly.