.Buildings.Templates.Plants.Controls.Pumps.Primary.EnableLeadHeadered .Buildings.Templates.Plants.Controls.Pumps.Primary.EnableLeadHeaderedThe lead primary pump is enabled when any equipment isolation valve is commanded open.
The lead primary pump is disabled when all equipment isolation valves are commanded closed.
For modulating valves, the "valve commanded open" condition is evaluated based on a command signal > 0 %. The "valve commanded closed" condition is evaluated as the negation of the previous condition.
The lead primary pump is enabled when any equipment isolation valve is commanded closed.
The lead primary pump is disabled when all equipment isolation valves are commanded open.
For modulating valves, the "valve commanded closed" condition is evaluated based on a command signal < 100 %. The "valve commanded open" condition is evaluated as the negation of the previous condition.
This logic is prescribed in ASHRAE, 2021 for:
The valve command is used in contrast to the feedback of the valve position or the end switch status, as prescribed by Guideline 36. This is for the sake of simplicity, as there is no harm in deadheading the pump for a couple seconds and it simplifies the programming.
For modulating valves, the "valve commanded open/closed" condition is evaluated without hysteresis because the valve command signal is generated by the enabling or staging logic and both use minimum runtime conditions. Therefore, the valve command signal is not subject to any oscillatory behavior.