Setpoints and related data
The setpoints and related data include the following items:
- Operating purge command (OprPurgeCmd)
- Purge command source (PurgeCmdSrc)
- Exhaust type (ExFType)
Inputs
The inputs include the following items:
- Network override purge command (NetPurge) sent through the UI display menu or communicated on the FC Bus
- Local purge command input (Purge) - 24 VAC to the PURGE terminal
Operation
The purge function is effective only if an economizer board has been connected to the UCB to trigger the economizer presence indicator. The operating purge command, purge command source, local purge command input, and network override purge command parameters are then shown in the UCB display menu.
Purge command source describes the related input in current use for the purge command. The inputs include the following items:
- BAS Override
- Indicates network override purge command (NetPurge)
- Local Input
- Indicates local purge command input (Purge)
The operating purge command indicates True in either of the following cases:
- The network override purge command is set to True and has not reached or exceeded the 15-minute timeout for communicated values
- The local purge command input indicates True - 24 VAC input is applied to Economizer board PURGE terminal
When the operating purge command indicates heating and cooling staging outputs are de-energized regardless of stage Min On Time timers. Heating and cooling staging outputs remain de-energized as long as the operating purge command indicates True.
- UCB FAN output is energized regardless of anti-short cycle delay timers
- UCB VFD output is 100% (10 VDC)
- Economizer board ECON output increases at a rate of 1% every 2 seconds until it reaches 100% (10 VDC)
In addition to the above, when operating purge command indicates True and the exhaust type is set to None:
- Economizer board EX-FAN output is off
- Economizer board EX VFD output is 0% (2 VDC)
In addition to the above, when operating purge command indicates True and the exhaust type is set to Non-Modulating, Modulating Damper, or Variable Frequency Fan:
- Economizer board EX-FAN output is energized regardless of anti-short cycle delay timers
- Economizer board EX VxFD output is 100% (10 VDC)
Operating purge command indicates False if both:
- Network override purge command is set to False or a true setting has reached or exceeded the 15-minute timeout for communicated values
- Local purge command input indicates False - 24 VAC input is not applied to Economizer board PURGE terminal.