Issue:
Space Pressure Sensor Failure
Resolution:
The space static pressure sensor is used on units with the Statitrac option. This diagnostic occurs when the voltage output from the transducer is outside the range for normal building pressures. Normal pressures range from -.67 IWC to .67 IWC. During normal operation if the voltage dips below 0.04 VDC or rises above 0.75 VDC the diagnostic will be generated.
Note: The sensor is capable of responding to pressures from -.75IWC to 9 IWC, but the controls can only read values in the range of -.67 IWC to .67 IWC as valid for space pressure.
This diagnostic can also be generated if the calibration solenoid is not functioning properly. For one second every minute, the calibration solenoid is energized to zero out the transducer. It connects the high port and the low port to outside air static reference. The controls expect to see 0.53 VDC @ 0.00 IWC during this time. Any difference from this value is used as an error amount and used to adjust the sensor reading for the next minute. If the calibration solenoid is not functioning, the controls will not receive the correct error signal and will interpret the sensor reading as zero pressure. In these cases, if power is cycled to the unit, the sensor will read correctly for one minute and then read decline to 0.00 IWC before giving the diagnostic.
Items to check include:
- wiring
- sensor
- calibration solenoid
- control module 1U52
- pneumatic tubing connections
Step #1 Wiring Errors
The space pressure transducer connects to the Reliatel Ventilation Module (RTVM) at pins J4-3 (+5 VDC), J4-5 (signal from transducer), J4-4 (common). Verify that the wiring is correct, all the plugs are connected, and the voltages are present at the transducer. Refer to the unit schematics for wire numbers.
Step #2 Pneumatic Tubing
Refer to above diagram for proper tubing connections for the transducer. Verify that factory installed tubing is correct and there are no air leaks. Also verify that outside air static pressure reference is properly installed. If the outside air static pressure reference is not properly installed, rainwater can enter the tubing. If this is the case, correct the installation and dry out the pneumatic tubing. The customer installed tubing should be connected as shown in the above diagram. If not installed, the sensor will see a large negative pressure when the supply fan is energized and report an error. The customer installed tubing should also be checked for kinks and obstructions. If all appears to be correct, continue to the next step.
Step #3 Sensor Checkout
-.75 to 9 IWC Transducer
Tee a manometer/magnehelic into both the high and low ports on the transducer. Verify that the voltage read at J4-5 and J4-4 on the RTVM module corresponds to the pressure indicated on the manometer using the chart above. If it does not and Steps 1 and 2 have been performed, replace the transducer. If the voltage corresponds to the pressure, proceed to the next step.
Step #4 Calibration Solenoid Checkout
The calibration solenoid is energized for one second every minute. During calibration, the RTVM should see 00.53 IWC @ 0.00 IWC at pins J4-5 and J4-4. The coil voltage is approximately 26VDC and is supplied from the RTVM module at pins JJ11-1 and J11-2. If a squeeze bulb is connected the Normally Closed (NC) port and pressurized, it should be relieved for one second every minute. If not, verify that the RTVM is supplying the 26 VDC every minute. If not, replace the RTVM. If the RTVM is supplying the correct voltage but the solenoid does not function, replace the calibration solenoid. If the solenoid checks out, proceed to the next step.
Step #5 Control Module
If all the previous steps have been performed, the diagnostic remains, and no errors are found, replace the RTVM module.