Orion System VAV/Zone Controller - Manual (Page 23)

VAV/Zone Controller
Technical Guide
23
a known good Space Temperature Sensor. If that sensor works when
connected to the VAV/Zone controller board, you can assume you have
a defective or damaged sensor.
Supply Air Temperature Sensor
If you suspect the Supply Air Temperature Sensor is not reading cor-
rectly, make sure the wiring terminal connections are tight and that any
wiring splices are properly connected. You can check the operation of
the Supply Air Temperature Sensor by measuring the resistance or volt-
age using a digital multimeter. Set the meter to DC Volts. Place the
positive probe on the AIN terminal and the negative probe on the GND
terminal. Read the DC Volts and find that voltage in Table 6 on the
following page. Read the temperature corresponding with that voltage
and determine if this is close to the actual temperature the sensor is
exposed to. If the temperature from the chart is different by more than a
few degrees you probably have a defective or damaged sensor. You can
also check the sensor resistance to determine correct operation. To read
the resistance set the meter to Ohms. Unplug the sensor connector from
the board and measure the resistance across the disconnected wires.
This resistance should match the corresponding temperature from Table
6 on the following page.
Airflow Sensor
If the Airflow Sensor seems to be reading incorrectly, first check the
Airflow Sensor’s modular cable connector and be sure it is firmly con-
nected to its mating connector on the VAV/Zone controller board. Also
make sure that jumper JP2 on the VAV/Zone controller board is set
properly for the type of system you are using. See Figure 3 for the
jumper location. If this is a Zoning system, the jumper must be removed.
If it is a true VAV system, the jumper needs to be in place. You will have
problems setting and measuring proper airflows if this jumper is not set
according to your system type.
Caution:
If the JP2 Jumper on the VAV/Zone controller is
not set correctly your CFM readings will not be
accurate.
Check the Airflow Sensor tubing connections at the airflow pickup tubes.
The high pressure port of the sensor needs to be connected to the up-
stream pickup tube. The low pressure port of the sensor needs to be
connected to the downstream pickup tube.
If none of the above procedures solves the problem, remove power from
the VAV/Zone controller. Shut down the HVAC unit supplying the duct
that the VAV/Zone damper is located on. Be sure that no airflow is
present in the duct. Reapply power to the board and wait for the VAV/
Zone controller to run through its calibration sequence. Restart the HVAC
unit and check the VAV/Zone controller CFM readings. If the CFM
reading still seems to be in error, you probably have a defective Airflow
Sensor and will need to replace it.
Actuator
Check the Modular cable between the controller and the actuator. Be
sure both ends of the cable are firmly connected to the mating connec-
tors on the actuator and the VAV/Zone controller board. Be sure the
damper moves freely and is not bound. Do this by pressing the actuator
clutch button and rotating the damper shaft in both directions to verify
smooth operation. If binding is present fix the problem as required.
Remove power from the VAV/Zone controller. Reapply power and ob-
serve the damper rotation. If the actuator does not drive the damper in
both directions, the actuator is probably defective or damaged. Another
test that can be performed, is to swap cables with another known oper-
ating actuator to determine if the cable could be bad. If the problem
goes away you have a defective cable that must be replaced. You can
also try swapping a functioning actuator with the suspected defective
actuator. If this solves the problem then the defective actuator will need
to be replaced.
Expansion Board
If the Expansion Board does not seem to operate correctly, first make
sure the modular cable between the Expansion Board and the VAV/
Zone controller is firmly connected at both ends. Be sure that the Ex-
pansion Board has been configured correctly. The expansion board must
be configured using the Modular Service Tool, Modular System Man-
ager or Prism computer front end software, for your application, before
it will operate. You must configure it for the number of heat stages and
if this is a fan terminal, whether it is a Series or Parallel Flow fan termi-
nal. On a non fan terminal unit, when a call for heat is initiated the
LED labeled RLY2 should light up. If the expansion board is config-
ured as a fan terminal, on a call for the fan, the LED labeled RLY1
should light up. If the LEDs do not light up the Expansion Board is
probably defective and must be replaced.