Problem:
IntelliPak units with Symbio 800 controls can read duct pressure down to 0.05 iwc. Operating at this low of a pressure requires the need of a calibration solenoid so that transducer readings can be calibrated accordingly to temperature changes. On earlier versions of the Firmware (pre 1.20.0031), the problem experienced is that if the calibration solenoid fails, the low pressure is subtracted from the supply air pressure reading.
Example,
unit is reading 1.5 iwc supply air pressure. If the calibration solenoid is working, low pressure measured is .02 iwc. The .02 is subtracted from 1.5 and the unit will use 1.48 as its supply air pressure. If the solenoid were to fail, 1.5 is measured during the calibration step. 1.5 subtracted from 1.5 gives the unit a 0 iwc for a supply air pressure. The unit will increase the speed of the supply fan to achieve the supply air pressure setpoint. The calibration sequence happens every sixty seconds. This cycle continues until the VFD is operating at 100%.
The inaccurate supply air pressure will not send the unit into a supply air pressure sensor failure diagnostic.
Since the High Limit command is based on the supply air pressure reading, the unit also will not generate a High Duct Static Limit alarm. This can cause serious over-pressurization of the supply duct
Solution:
The current fix is available with the latest Symbio Firmware update, 1.30.0008. The firmware has been updated to prevent the supply fan from over-pressurizing the duct with a feature that tracks the low pressure reading.
If the unit senses the low pressure value is too high it will now generate an alarm or diagnostic. The user can now also specify how their system will operate. If the supply air pressure setpoint does not need to be lower than 0.5 iwc then it is recommended to select the High Pressure option in Duct Pressure Range selection in the Configuration option with TU.
Link to IntelliPak Symbio 800 Latest Firmware Version
Trane Controls Software & Firmware Downloads
Initial Screen Shown when TU is connected to Symbio 800 controller after firmware update.
Firmware can be updated utilizing TU (File Transfer Utility) or from the Symbio UI (198.80.18.1).