blockEventSequencingSingle

Information

If a heat pump is commanded on in a desired heating or cooling mode:

• The isolation valves for desired heating or cooling mode are commanded open.
• Plants with dedicated primary pumps: The dedicated primary pumps are commanded on when the associated isolation valves are commanded open.
• Plants with headered primary pumps: The headered primary pumps are commanded on as described in Buildings.Templates.Plants.Controls.Pumps.Generic.StagingHeadered.
• Once the isolation valves are fully open (based on nominal valve timing dtVal) and the lead pumps are proven on, the heat pump is enabled in heating or cooling mode.

If a heat pump is commanded off:

• The heat pump is disabled.
• After the time required for the internal shutdown cycle to time out (dtOff to be determined empirically, defaulting to 3 min), all isolation valves are commanded closed.
• Plants with dedicated primary pumps: The dedicated primary pumps are commanded off when the associated isolation valves are commanded closed.
• Plants with headered primary pumps: The headered primary pumps are commanded off as described in Buildings.Templates.Plants.Controls.Pumps.Generic.StagingHeadered.

Polyvalent heat pumps

Note: For polyvalent heat pumps with dedicated primary pumps, no isolation valves are required. This is in contrast with two-pipe reversible heat pumps, which require changeover valves regardless of the primary pump arrangement.

If a polyvalent heat pump is commanded on in either heating-only or cooling-only mode:

• Plants with dedicated primary pumps: The associated primary pumps are commanded on. Once the associated primary pumps are proven on, the polyvalent heat pump command for the desired mode is switched on.
• Plants with headered primary pumps: The isolation valves for the desired mode are commanded open. The headered primary pumps are commanded on as described in Buildings.Templates.Plants.Controls.Pumps.Generic.StagingHeadered. Once the isolation valves are fully open (based on nominal valve timing dtVal) and the lead pumps are proven on, the polyvalent heat pump command for the desired mode is switched on.

If a polyvalent heat pump is commanded on in simultaneous heating and cooling mode, the enable interlocking logic described above applies to both the CHW and HW sides. Once both the CHW and HW isolation valves, if any, are fully open (based on nominal valve timing dtVal) and the associated CHW and HW primary pumps are proven on, the polyvalent heat pump commands for both modes are switched on.

If a polyvalent heat pump switches from heating-only or cooling-only mode to simultaneous heating and cooling mode, the enable interlocking logic described above applies to the side being enabled: the polyvalent heat pump command for the newly enabled mode is switched on once the isolation valves of that side, if any, are fully open (based on nominal valve timing dtVal) and the associated primary pumps are proven on.

If a polyvalent heat pump switches from simultaneous heating and cooling mode to heating-only or cooling-only mode:

• The polyvalent heat pump command for the disabled mode is switched off.
• Plants with dedicated primary pumps: The associated primary pumps of the disabled side are commanded off without delay.
• Plants with headered primary pumps: The isolation valves of the disabled side are commanded closed without delay. The headered primary pumps of the disabled side are commanded off as described in Buildings.Templates.Plants.Controls.Pumps.Generic.StagingHeadered.

If a polyvalent heat pump is commanded off:

• The polyvalent heat pump commands for both modes are switched off.
• Plants with dedicated primary pumps: After the time required for the internal shutdown cycle to time out (dtOff to be determined empirically, defaulting to 3 min), the dedicated primary pumps are commanded off.
• Plants with headered primary pumps: After the time required for the internal shutdown cycle to time out (dtOff to be determined empirically, defaulting to 3 min), all isolation valves are commanded closed. The headered primary pumps are commanded off as described in Buildings.Templates.Plants.Controls.Pumps.Generic.StagingHeadered.

Implementation details

The timer tracking the heat pump shutdown cycle is reset if the heat pump is enabled in any mode. This implies that the isolation valves remain open unless the heat pump stays disabled for at least dtOff. The heat pump enable sequence must therefore guarantee that the heat pump remains off for at least dtOff before being enabled in the opposite mode. For polyvalent heat pumps, this requirement is not needed for valve and pump control: when one mode is disabled while the other remains enabled, the isolation valves and pumps of the disabled side are commanded off without delay. However, any minimum off time required by the heat pump between opposite operating modes must still be enforced by the enable sequence.

To facilitate integration into plant controllers serving both reversible and polyvalent heat pumps, the output connectors for the isolation valve commands and the primary pump enable commands are always instantiated, and set to false when the corresponding equipment is not present.

Parameters

Connectors

Components

Revisions

• July 10, 2026, by Antoine Gautier:
  Refactored to support polyvalent heat pumps.
• March 29, 2024, by Antoine Gautier:
  First implementation.