Table 12: Troubleshooting
Problem
Possible cause and correction
Verification
Controller is OFF.
•
Transformer has tripped: power is
at primary of transformer, 0 V at
secondary.
•
Breaker or fuse has tripped: power
is at primary of transformer, 24 V at
secondary, 0 V at breaker or fuse.
Cause:
1. Transformer is shorted.
2. 24 VAC powered sensor is not
wired with the same polarity as the
controller.
3. SA Bus device is not wired with the
same polarity as the controller.
Correction:
1. Ensure that the polarity of ~24 V COM,
ICOM, +15 V COM, and SA BUS COM
on the controller, auxiliary devices,
and input and output devices is the
same.
2. Ensure that the OUT1 to OUT3
terminals of binary outputs are not
connected to ~24 VAC COM, and
verify that OCOM1 to OCOM3 are not
connected to ~24 VAC HOT, because
these terminals are internally sourced.
3. Verify that the short circuit has been
resolved with an ohm-meter.
4. Reset the breaker or fuse, or replace
the transformer.
Note:
When replacing the
transformer, it is best practice to
replace with a model that uses a
resettable circuit breaker. A circuit
breaker makes it easier to solve wiring
problems.
1. Disconnect the secondary of the 24
VAC transformer.
2. Use an ohm-meter to measure
between ~24 V HOT and COM. Ensure
that no short circuit occurs.
Note:
Some installations require
the secondary of the transformer
to be earth grounded. If this is
the case, verify that the earth
ground connection is valid and not
shared between multiple pieces of
equipment.
Configurable output - analog mode is
invalid
:
0 V to 10 V output is set to 10% to 100%, but
0 V is at output terminals.
Output is in protection mode
, a state the
analog portion of the configurable output
goes into when it detects a wiring problem.
The analog output is set to 0% regardless
of the command whenever a wiring fault is
detected.
Cause:
There is a power polarity mismatch between
the connected device and the configurable
output.
Correction:
Ensure that the polarities of ~24 V COM and
OCOM match and that the connected end
device uses the same polarity.
1. Measure the output and verify that it
matches the command.
2. Disconnect the connected device
and verify the commanded value is
present.
Configurable output - analog mode is
invalid
:
0 V to 10 V output has an undesirable offset
of up to 1 V.
The Common Reference is incorrect.
Cause:
The OCOM terminal is not connected.
Correction:
Connect the OCOM terminal of the
configurable output to the common of the
connected end device.
1. Measure the output and verify that it
matches the command.
2. Disconnect the connected device
and verify the commanded value is
present.
VAV1717 and VAV1732 VAV Controllers Installation Guide
19
