9
IOM-T-482
2125
© 2021 Watts
The following tests are to be performed using standard
testing practices and procedures and should only be car-
ried out by properly trained and experienced persons.
A good quality electrical test meter, capable of reading
from at least 0-300 V (ac), 0-30 V (dc), 0-2,000,000
Ohms, and testing for continuity is essential to properly
test the wiring and sensors.
Test Meter
Control Terminals
Testing the Power
1. Remove the front and wiring covers from the control.
2. Use an electrical test meter to measure (ac) voltage
between the Power N and L terminals (1 and 2). The
reading should be 115 V (ac) + / – 10%. The Power
LED should be on.
3. If power is not present the Power LED will be off.
Check the circuit(s) that supply power to the Power
N and L terminals (1 and 2).
Testing the tN4 Buses
1. Remove the front and wiring covers from the control.
2. There are a total of five tN4 buses (tN4 and C).
The corresponding tN4 LED will be on if there is
communication on the tN4 bus.
3. If there is no communication on a tN4 bus that is
supposed to have communication, there may an
open or short circuit. An open or short circuit will be
indicated as a bus error on any tN4 thermostats, tN4
setpoint controls, and tN4 system controls.
4. To test for short circuits:
• Disconnect the tN4 bus wires on both ends.
• Install wire nuts on each wire on one end to ensure
the wire ends are not touching.
• Measure for continuity using an electrical meter.
• If continuity is present, there is a short circuit fault
along the wires. It is recommended to replace the
tN4 bus wires.
5. To test for open circuits:
• Disconnect the tN4 bus wires on one end and
connect them together.
• Disconnect the tN4 bus wires on the other end.
• Use an electrical meter to measure for continuity.
• If there is no continuity, there is an open circuit fault
along the wires. It is recommended to replace the
tN4 bus wires.
Testing the RS 232 Serial Port
A terminal shell called Termite can be used to test the RS
232 serial port hexadecimal data.
Step 1:
Download the Termite (complete setup) terminal
program for Windows.
http://www.compuphase.com/software_termite.htm
Step 2:
Settings
Baud rate = 9600, Data bits = 8, Stop bits = 1,
Parity = none, Flow control = none, Forward = none
Hex View = check marked
Step 3:
Enter commands
Hexadecimal values can be entered in the command line
at the bottom. The hexadecimal numbers must be entered
in the format 0x00 followed by a space.
The 482 includes a built-in test routine that transmits a
message via the RS232 port. The result of this is that the
Tx indicator will flash as the message is sent.
Start the test routine by pressing the Test button for
1 second. The Test LED turns red.
The RS232 message includes the following:
1. FirmwareRevision
0xca 0x07 0x06 0x02 0x87 0x01 0x00 0x00
0x91
0x00
0x28 0x35
This means that the 482 firmware version is 6c hexadecimal
or 145 in decimal.
2. ProtocolVersion
0xca 0x07 0x06 0x02 0x8f 0x01 0x00 0x00
0x02
0x00
0xa1 0x35
The means that the 482 protocol version is 02.
The 482 then exits the test routine and resumes normal
operation.
Troubleshooting the Wiring
General
Testing the Control
