joseph-robertson · Oct 23, 2026 · Oct 23, 2026 · Oct 23, 2026 · Oct 23, 2026 · Oct 23, 2026
diff --git a/doc/input-output-reference/src/overview/group-fans.tex b/doc/input-output-reference/src/overview/group-fans.tex
@@ -812,18 +812,17 @@ \subsubsection{Outputs}\label{outputs-3-007}
 
 \subsection{FanPerformance:NightVentilation}\label{fanperformancenightventilation}
 
-This object is used for specifying an alternate set of performance parameters for a fan (i.e., the performance of the fan during night venting may be very different than during normal operation).
-These alternate parameters are used when a system manager (such as \hyperref[availabilitymanagernightventilation]{AvailabilityManager:NightVentilation}) sets a specified flow rate for a central forced air system.
-At this time, it can be used with \hyperref[fanconstantvolume]{Fan:ConstantVolume}, \hyperref[fanvariablevolume]{Fan:VariableVolume}, \hyperref[fanzoneexhaust]{Fan:ZoneExhaust}, and \hyperref[fanonoff]{Fan:OnOff} fans, but not with \hyperref[fansystemmodel]{Fan:SystemModel} or \hyperref[fancomponentmodel]{Fan:ComponentModel} fans.
-\hyperref[fansystemmodel]{Fan:SystemModel} fans have replaced \hyperref[fanperformancenightventilation]{FanPerformance:NightVentilation} (i.e., provides built-in night ventilation settings so \hyperref[fanperformancenightventilation]{FanPerformance:NightVentilation} is not applicable/needed for that fan type).
+This object specifies alternate performance parameters for a fan when night ventilation is active. It can be used with \hyperref[fanconstantvolume]{Fan:ConstantVolume}, \hyperref[fanvariablevolume]{Fan:VariableVolume}, \hyperref[fanzoneexhaust]{Fan:ZoneExhaust}, and \hyperref[fanonoff]{Fan:OnOff} fans, but not with \hyperref[fansystemmodel]{Fan:SystemModel} or \hyperref[fancomponentmodel]{Fan:ComponentModel} fans. Fan:SystemModel has separate night-ventilation inputs, but its Night Ventilation Mode Flow Fraction field currently has no effect.
 
-The fan model checks whether a fixed flow rate has been set; if it has the fan model will use these alternate performance parameters. Note that it is assumed that the fan will run at a fixed speed in the alternate mode. The inputs needed by this object are the fan name, fan total efficiency, pressure rise, flow rate, motor efficiency, and motor in airstream fraction.
+For zone equipment other than air distribution units, night-ventilation mode is determined by that component's own AvailabilityManager:NightVentilation status. An air distribution unit follows the status of its connected air loop. A coupled \hyperref[fanzoneexhaust]{Fan:ZoneExhaust} follows an air loop serving its zone; a decoupled exhaust fan does not enter night-ventilation mode.
+
+The fan uses these alternate performance parameters during night ventilation and is assumed to run at a fixed speed. This does not fix airflow or power at design values; power is calculated from actual operating airflow using the entered pressure rise and fan total efficiency. The inputs are the fan name, fan total efficiency, pressure rise, motor efficiency, and motor in airstream fraction.
 
 \subsubsection{Inputs}\label{inputs-4-013}
 
 \paragraph{Field: Fan Name}\label{field-fan-name-001}
 
-This is the name of a fan defined elsewhere in the input file. The night vent performance parameters will be applied to the named fan when a system manager (such as \hyperref[availabilitymanagernightventilation]{AvailabilityManager:NightVentilation}) has set the air system flow rate.
+This is the name of a fan defined elsewhere in the input file. The night vent performance parameters are applied when the named fan is operating in night-ventilation mode.
 
 \paragraph{Field: Fan Total Efficiency}\label{field-fan-total-efficiency-4}
 
@@ -833,13 +832,9 @@ \subsubsection{Inputs}\label{inputs-4-013}
 
 The pressure rise in Pascals at full flow and standard (sea level) conditions (\SI{20}{\celsius} and 101325 Pa). This is a required field with no default.
 
-\paragraph{Field: Maximum Flow Rate}\label{field-maximum-flow-rate-4}
-
-The design volumetric flow rate of the fan (m\(^{3}\)/sec) at standard conditions. This input is not currently used by the night ventilation manager. The flow rate during night ventilation is specified using the \hyperref[availabilitymanagernightventilation]{AvailabilityManager:NightVentilation} ``Night Venting Flow Fraction'' field. This fraction is multiplied by the fan object's design flow rate.
-
 \paragraph{Field: Motor Efficiency}\label{field-motor-efficiency-3}
 
-The shaft power divided by the electrical power consumed. Must be between 0 and 1. This is a required field with no default.
+The shaft power divided by the electrical power consumed. Must be between 0 and 1. This is a required field with no default. This input is not used by \hyperref[fanzoneexhaust]{Fan:ZoneExhaust}, which calculates electrical power from the air power and Fan Total Efficiency.
 
 \paragraph{Field: Motor in Airstream Fraction}\label{field-motor-in-airstream-fraction-3}
 
@@ -871,7 +866,6 @@ \subsubsection{Inputs}\label{inputs-4-013}
   Supply Fan 1,               !- Fan Name
   0.7,                        !- Fan Total Efficiency
   67.0,                       !- Pressure Rise {Pa}
-  autosize,                   !- Maximum Flow Rate {m3/s}
   0.9,                        !- Motor Efficiency
   1.0;                        !- Motor in Airstream Fraction
 \end{lstlisting}

diff --git a/doc/input-output-reference/src/overview/group-system-availability-managers.tex b/doc/input-output-reference/src/overview/group-system-availability-managers.tex
@@ -448,7 +448,7 @@ \subsection{AvailabilityManager:NightVentilation}\label{availabilitymanagernight
 
 This manager allows the user to implement a strategy for precooling a building at night using outdoor air. This strategy can consist of running the system fans with the outdoor air dampers open when outdoor conditions are favorable for a precooling strategy. The zone terminal unit air dampers may also be held at their fully open position to minimize fan energy consumption while precooling. Fan energy consumption is the critical parameter in deciding whether a precooling strategy will save energy.
 
-The inputs for the night ventilation manager consist of an applicability schedule name (determining when the manager is active), a fan schedule name (for the fan(s) that the manager can switch on), a ventilation temperature schedule name (one zone must be above this temperature for night venting to be active), a ventilation temperature difference (indoor / outdoor temperature difference for night venting), a low limit temperature (no conditioned zone may fall below this temperature during night venting), a night venting flow fraction (fraction of the design flow rate at which the fans run during night venting), and the zone name of a control zone.
+The inputs for the night ventilation manager consist of an applicability schedule name (determining when the manager is active), a fan schedule name (for the fan(s) that the manager can switch on), a ventilation temperature schedule name (one zone must be above this temperature for night venting to be active), a ventilation temperature difference (indoor / outdoor temperature difference for night venting), a low limit temperature (no conditioned zone may fall below this temperature during night venting), a night venting flow fraction (for primary air loops, the fraction of design flow requested during night venting; for zone equipment, the manager controls availability without scaling flow), and the zone name of a control zone.
 
 The night ventilation manager is used in conjunction with another object: \hyperref[fanperformancenightventilation]{FanPerformance:NightVentilation}. The performance of the fan during night venting may be very different than during normal operation (a different fan might even be used). The \hyperref[fanperformancenightventilation]{FanPerformance:NightVentilation} object allows the user to specify alternate fan performance parameters for use during night ventilation.
 
@@ -480,7 +480,7 @@ \subsubsection{Inputs}\label{inputs-9-023}
 
 \paragraph{Field: Night Venting Flow Fraction}\label{field-night-venting-flow-fraction}
 
-The fraction (could be greater than 1) of the design flow rate at which the night ventilation will be done. The default is 1.
+For a primary air loop, this is the fraction of design flow requested for night ventilation. The default is 1. Values greater than 1 may request flow above design, but actual flow remains subject to fan and system flow limits. For zone equipment, the manager controls availability only; the fraction does not scale the equipment's flow.
 
 \paragraph{Field: Control Zone Name}\label{field-control-zone-name-000}
 

diff --git a/idd/Energy+.idd.in b/idd/Energy+.idd.in
@@ -53073,16 +53073,12 @@ FanPerformance:NightVentilation,
        \units Pa
        \ip-units inH2O
        \required-field
-  N3 , \field Maximum Flow Rate
-       \units m3/s
-       \minimum 0.0
-       \autosizable
-  N4 , \field Motor Efficiency
+  N3 , \field Motor Efficiency
        \type real
        \required-field
        \minimum> 0
        \maximum 1.0
-  N5 ; \field Motor in Airstream Fraction
+  N4 ; \field Motor in Airstream Fraction
        \type real
        \default 1.0
        \minimum 0.0
@@ -89006,6 +89002,8 @@ AvailabilityManager:NightVentilation,
        \default 1.
        \note the fraction (could be > 1) of the design system Flow Rate at which
        \note night ventilation will be done
+       \note This fraction is applied to primary air loop flow requests. For zone equipment,
+       \note the availability manager controls availability but does not scale component flow.
   A5 ; \field Control Zone Name
        \type object-list
        \object-list ZoneNames