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How does Pelican control a zone 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:

The configuration of a Pelican zone thermostat for cooling operation:

Control Outputs to a Zone Box with No Reheat:

When a Pelican thermostat is configured as the following:

  • Damper Type: Open/Close or Floating
  • Reheat Type: None

The thermostat controls the zone damper 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): Unused
  • (W2): Unused
  • (G): Unused

Control Outputs to a Zone Box with Reheat:

When a Pelican thermostat is configured as the following:

  • Damper Type: Open/Close or Floating
  • Reheat Type: Open/Close, Floating, or Electric

The thermostat controls the zone damper and local reheat 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 or Hot Water Valve Open
  • (W2): 24VAC Output – Hot Water Valve Close (if an open/closed or floating valve actuator is installed)
  • (G): Unused

Sequence of Operation for a Zone 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 or a reheat cycle active, it will place the zone with cooling demand into a “waiting” state until the heat/cool change-over sequence allows for a central cooling cycle to become active. Once a central cooling cycle is available: the zone controller will release zone thermostats 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:

  1. 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.
  2. 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.
  3. 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:

  1. 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.
  2. 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.
  3. The zone thermostat goes into “low” cooling demand: the above “Low” cooling demand sequence will occur.
*During a cooling cycle, if a zone keeps its damper open, but does not have cooling demand: This zone has been setup as a “Dump” zone using Pelican’s Capacity Management Algorithm.