Wired Zone Sensor Failure - Trane Symbio 210 Installation, Operation And Maintenance Manual

Wired Zone Sensor Failure

Hazardous Service Procedures!
Failure to follow all precautions in this manual and on the tags, stickers, and labels could result
in death or serious injury.
Technicians, in order to protect themselves from potential electrical, mechanical, and chemical
hazards, MUST follow precautions in this manual and on the tags, stickers, and labels, as well
as the following instructions: Unless specified otherwise, disconnect all electrical power
including remote disconnect and discharge all energy storing devices such as capacitors
before servicing. Follow proper lockout/tagout procedures to ensure the power can not be
inadvertently energized. When necessary to work with live electrical components, have a
qualified licensed electrician or other individual who has been trained in handling live electrical
components perform these tasks.
In the event that the Symbio 500 controller reports an incorrect zone temperature, check the following:
•
•
•
•
•
•
Table 19. Zone sensor
BAS-SVX091A-EN
voltage tests, refer to the BACnet MS-TP Wiring and Link Performance Best Practices and
Troubleshooting Guide (BAS-SVX51).
Verify that the actual room temperature is higher or lower than what the Symbio 500 controller
reads.
Check the location and installation of the zone sensor for heat sources or drafts. If necessary, a
calibration offset can be added with Tracer TU, in the Space Temperature Local configuration
screen.
Note: If the zone sensor is OFF more than ± 2 degrees, proceed to the next bullet item.
Verify that the zone sensor is wired correctly.
Verify that the zone sensor is working properly.
– Disconnect the zone sensor terminal plug from the Symbio 500 controller and using an
ohmmeter, measure the resistance across the terminals 1 and 2. Compare the resistance to the
temperature (refer to the table below). The resistance value should be within ± 2 degrees near
those measured with an accurate temperature measuring device. If not, replace the zone
sensor.
Verify that neither the wiring or the Symbio 500 controller are defective. With wires still connected to
the Symbio 500 controller, disconnect zone sensor wires that were connected to terminals 1 and 2 of
zone sensor. Measure for 2.6–3.0 Vdc and if it is not present, then verify whether the Symbio 500
controller is outputting 2.6–3.0 Vdc.
To do this, disconnect the wires on the Symbio 500 controller from terminals AI1 and
measure the Vdc– it should be 2.6–3.0 Vdc. If 2.6–3.0 Vdc is present at the Symbio 500
controller, the wires going to the zone are OPEN. If the correct voltage is not present, check the
incoming power to the Symbio 500 controller on XFMR 24 Vac input and
measure 24 Vac ± 15%. If the proper voltage is measured at the XFMR 24 Vac input and
and there is no voltage at AI1 and
Verify that the zone sensors are not shorted out. Check the resistance across the wires. Disconnect
wires from the Symbio 500 controller and zone sensor, ensuring that the ends are not touching each
other, and then measure resistance. It should be infinite or no conductivity. If lower resistance is
shown, then the wires are shorted together and need to be replaced.
Temperature (oF)
55
56
WARNING
, replace the Symbio 500 controller.
Thermostat Thumbwheel
Resistance (Ohms) (a)
792
772
Troubleshooting
, and
. It should
Sensor Resistance (k Ohms)
17.0
16.5
,
61