How does Pelican control a parallel fan powered box during a cooling cycle?
Note:
For a Pelican thermostat to be configured as a zone damper thermostat and provide the following sequence of operation (SOO), a Pelican Z8 or Z24 must be installed, powered On, and connected to the Pelican wireless network. For the following SOO to operate, the Z8 or Z24 must also control the central HVAC equipment.
Configuring a Pelican Thermostat for Parallel Fan Powered Box:
When a Pelican thermostat’s Reheat Type is configuration to Fan Powered, Pelican Technical Support must set for you if the Fan Control is Series or Parallel. Please email or call Pelican Technical Support for the following Parallel Fan Powered Box SOO.
Control Outputs to a Parallel Fan Powered Box:
When a Pelican thermostat is configured as the following:
- Damper Type: Open/Close or Floating
- Reheat Type: Fan Powered
- Fan Control: Parallel (technical support configuration)
The thermostat controls the zone damper, local reheat, and parallel fan with the following outputs:
- (Y): 24VAC Output – Damper Open
- (Y2): 24VAC Output – Damper Close (if an open/closed or floating damper actuator is installed)
- (W): 24 VAC Output – Reheat Enable
- (G): 24 VAC Output – Parallel Fan Enable
- (W2): Unused
Sequence of Operation for a Parallel Fan Powered Box with Cooling Demand:
A zone has “Low” cooling demand: The zone thermostat will send a “low” cooling demand request to the zone controller at the central HVAC equipment. If the zone controller has central heating active, it will place the zone with cooling demand into a “waiting” state until the heat/cool change-over sequence allows for a cooling cycle. Once a cooling cycle is available: the zone controller will release the zone thermostat(s) with cooling demand to open their dampers. All zones that do not have cooling demand will close their dampers*. The zone controller will enable the central unit’s supply fan, maintain the Target Operating Static pressure, follow any of its ventilation or economizer sequences, and, if needed, enable mechanical cooling to condition the zones. The zone controller will target a “moderate” cooling discharge air temperature during a “low” cooling demand sequence. This will remain true until one of the following occur:
- The zone thermostat reaches its cool set point: The thermostat will send a “satisfied” signal to the zone controller, keep its damper open for a purge cycle, and then reverse out of the cooling cycle and shut its damper.
- The heat/cool change-over occurs and the zone controller has calculated that a central heating or reheat cycle needs to begin: The thermostat will receive a “change-over” notification from the zone controller, it will keep its damper open for a purge cycle, and then reverse out of the cooling cycle and shut its damper.
- The zone thermostat goes into “high” cooling demand: the below “High” cooling demand sequence will occur.
A zone has “High” cooling demand: The zone thermostat will send a “high” cooling demand request to the zone controller at the central HVAC equipment. If the zone controller has central heating active, it will place the zone with cooling demand into a “waiting” state until the heat/cool change-over sequence allows for a cooling cycle. Once a cooling cycle is available: the zone controller will release the zone thermostat(s) with cooling demand to open their dampers. All zones that do not have cooling demand will close their dampers*. The zone controller will enable the central unit’s supply fan, maintain the Target Operating Static pressure, follow any of its ventilation or economizer sequences, and, if needed, enable mechanical cooling to condition the zones. The zone controller will target an “aggressive” cooling discharge air temperature during a “high” cooling demand sequence. This will remain true until one of the following occur:
- The zone thermostat reaches its cool set point: The thermostat will send a “satisfied” signal to the zone controller, keep its damper open for a purge cycle, and then reverse out of the cooling cycle and shut its damper.
- The heat/cool change-over occurs and the zone controller has calculated that a central heating or reheat cycle needs to begin: The thermostat will receive a “change-over” notification from the zone controller, it will keep its damper open for a purge cycle, and then reverse out of the cooling cycle and shut its damper.
- The zone thermostat goes into “low” cooling demand: the above “Low” cooling demand sequence will occur.
Does Pelican engage the Parallel Fan during a cooling cycle?
No. During a cooling cycle, the parallel fan is left disabled. If the fan powered box needs its fan to run during both cooling and heating cycles, this would be considered a “series” fan powered box. Contact Pelican Technical Support for further assistance.