How does Pelican control a parallel fan powered box during a ventilation 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 Series 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 Series Fan Powered Box:
When a Pelican thermostat is configured as the following:
- Damper Type: Open/Close or Floating
- Reheat Type: Fan Powered
- Fan Control: Series (technical support configuration)
The thermostat controls the zone damper, local reheat, and series 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 – Series Fan Enable
- (W2): Unused
Sequence of Operation for a Series Fan Powered Box during a Ventilation Cycle:
A zone is requesting ventilation: A zone thermostat will send a ventilation request to the zone controller at the central HVAC equipment anytime Fan mode and Outside Ventilation is set to On*. If the zone controller has central cooling or heating active, it will place the zone with the ventilation request into a “waiting” state until the heat/cool change-over sequence allows for a ventilation cycle to become active. Once a ventilation cycle is available: the zone controller will release all zone thermostats with ventilation requests to open their dampers. All zones that do not have ventilation requests will close their dampers. Once zones with ventilation requests have their dampers open, the zone controller will enable the central unit’s supply fan, maintain the Target Circulation Static pressure, and open the outside damper to the Minimum Damper Position + the increased position based on the difference between the Target Circulation Static pressure and the Target Operating Static pressure**. This will remain true until one of the following occur:
- A central cooling or heating cycle becomes active: The thermostat will receive a “change-over” notification from the zone controller and shut its damper.
- The Fan mode is set to AUTO: The thermostat will shut its damper.
A zone is requesting a Demand Ventilation cycle: A zone thermostat will send a demand ventilation request to the zone controller and its carbon dioxide (CO2) reading to the zone controller at the central HVAC equipment. If the zone controller has central cooling or heating active, it will place the zone with the demand ventilation request into a “waiting” state until the heat/cool change-over sequence allows for a ventilation cycle to become active, but it will still immediately increase the outside damper position to provide additional ventilation into the entire building. Once a ventilation cycle is available: the zone controller will release all zone thermostats with demand ventilation and standard ventilation requests to open their dampers. All zones that do not have ventilation requests will close their dampers. Once zones with ventilation requests have their dampers open, the zone controller will enable the supply fan, maintain the Target Circulation Static pressure, and open the outside damper to the Minimum Damper Position + the increased position based on the difference between the Target Circulation Static pressure and the Target Operating Static pressure**. This will remain true until a central cooling or heating cycle becomes active: The thermostat will receive a “change-over” notification from the zone controller and shut its damper.
*When Outside Ventilation is set to On, the thermostat includes in its requests for Heat/Cool/Fan to the zone controller a request for Outside Ventilation. If Outside Ventilation is set to Off, then the thermostat will still request Heat/Cool/Fan, but will not request Outside Ventilation.
**The zone controller uses its Minimum Damper Position when it is maintaining the Target Operating Static pressure. Because the Target Circulation Static pressure is usually set to a lower pressure than the Target Operating Static, the zone controller will automatically calculation an increased Minimum Damper Position to maintain a proper ventilation CFM.
Does Pelican run the Series Fan during a ventilation cycle?
Yes. During a cooling, heating, and ventilation cycle, the series fan is enable. If the fan powered box needs its fan to to run only during a heating cycles, this would be considered a “parallel” fan powered box. Contact Pelican Technical Support for further assistance.