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EnergyPlus™ is a whole building energy simulation program that engineers, architects, and researchers use to model both energy consumption and water use in buildings.
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PTAC Supply Air Fan Operating Mode Schedule #5441

Open MatthewSteen opened 8 years ago

MatthewSteen commented 8 years ago

This optional field defaults to 0 (cycling) but does not display a value or mention this in the IO reference. A value of 0 is inconsistent with other similar, ~although required~, fields such as Availability Schedules. Suggest updating the documentation and/or displaying the default value. Fan Electric Power output below.

Supply Air Fan Operating Mode Schedule = blank

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Supply Air Fan Operating Mode Schedule = Always On Discrete

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mjwitte commented 8 years ago

This same field appears 24 times under two different names "Supply Fan Operating Mode Schedule Name" (HVACTemplate:*) and "Supply Air Fan Operating Mode Schedule Name" (all others). From a quick scan of the IDD and the I/O Reference, many instances include a note stating that the default is cycling fan when this field is left blank, but not all. The description of this schedule name varies a bit, especially what values denote continuous, e.g.:

"Schedule values other than 0 denote that the supply fan runs continuously" "A schedule value greater than 0 (usually 1 is used) indicates constant fan operation (fan runs continually regardless of the coils operation)" "Non-zero schedule values mean that the supply air fan will operate continuously"

It is not possible to display a default value, because there are no built-in schedule names.

Suggested changes:

@MatthewSteen You mention "other similar, although required, fields such as Availability Schedules." All of the Availability Schedules should have been made optional by now. If you have found any that are not, please note them here. I understand the point about "blank availability schedule" = Always1 vs. "blank fan operating mode schedule" = Always0. It would be difficult to change that now without introducing some built-in schedules or some reserved keyword to indicate the default schedule.

rraustad commented 8 years ago

Starting a list of verified objects.

Defaults to cycling fan if fan operating mode schedule blank (Tests for CycFan = 0 if schedule exists):

Defaults to constant fan if fan operating mode schedule is blank:

rraustad commented 8 years ago

@Myoldmopar @EnergyArchmage @mjwitte should allow comments before someone moves this forward. All fan op mode schedules check for ==0 for cycling fan, all other schedule values force constant fan with a few exceptions based on fan type. Any other equipment types missing in list above?

EnergyArchmage commented 8 years ago

This is the same list of equipment types that I have been working with over on the fan project and I don't notice any omissions.

It may make sense to add a built in zero-value schedule, and handle this the same way we handle the blank availability schedule fields with the ScheduleAlwaysOn index.

Makes sense to me that some of the AirloopHVAC unitarys would default to constant fans and those should not necessarily be changed.

Seems like documentation is the only issue.

mjwitte commented 8 years ago

It's confusing that some of the systems default to constant fan or cycling fan dependent upon a different field (or fan type). This will impact transitions when the day comes that we drop the old fan types and the old unitary system types - transition may need to insert a schedule to match the old default. Adding warnings to say what will happen for all of these is annoying. Perhaps we should add a table for these systems in the Equipment Summary that could have a column for fan operating mode and list the schedule name or say or .

EnergyArchmage commented 8 years ago

As an example of the confusion, noticed today that the ZoneHVAC:UnitVentilator example files, UnitVent5Zone, UnitVent5ZoneAuto, and UnitVent5ZoneFixedOANoCoilOpt, are confusing because they leave the fan operation schedule blank but then use constant volume fans. The blank schedule should be for cycling fan, but the fan type used really makes it operate as a constant fan so the input is not consistent. This was a big waste of time for me when trying to get the new Fan:SystemModel to match the Fan:ConstantVolume. I had to add these schedules (always 1) to get the unit ventilator to work as expected and this might be difficult to deal with during transition.

mjwitte commented 8 years ago

Then I would suggest that it's time to make them all consistent and add a transition rule that inserts a schedule in places where it's needed to match the standard rule. Since the majority of systems go to cycling fan when the schedule is left blank, I would suggest that be the rule and we have transition insert an "always-1" or "always-0" schedule for the few combinations that depend on the fan type - it can check what the fan input is and insert the appropriate schedule.

mjwitte commented 8 years ago

@rraustad @EnergyArchmage @Myoldmopar Do we want to try to tackle this before IDD freeze?

rraustad commented 8 years ago

Not sure what the end result would look like. There are 5 cases where constant fan is the default. Cycling fan doesn't work with SP based control so default was chosen accordingly (I could force a constant fan schedule here). I could change VRF and changeover bypass to default to cycling fan. That leaves Unit* with Fan:ConstantVolume to figure out. Worst case is adding fan operating mode schedules to these 5 cases. And docs.

mjwitte commented 8 years ago

@rraustad Sounds like this needs to wait for v8.7.

rraustad commented 7 years ago

Ran into this again with VRF TUs requiring a fan operating mode schedule. It's been a year and I haven't even thought of this since then. With the recent discussion of deprecating old style fan objects this is more important now and should be elevated to a high priority status.

rraustad commented 7 years ago

It seems like a good place to start is with the 5 objects that default to constant fan operating mode.

Defaults to constant fan if fan operating mode schedule is blank:

AirloopHVAC:UnitarySystem (SetpointBased) (CycFan = 0)
ZoneHVAC:UnitHeater - Fan:ConstantVolume (don't care, constant fan operation)
ZoneHVAC:UnitVentilator - Fan:ConstantVolume (don't care, constant fan operation)
ZoneHVAC:TerminalUnit:VariableRefrigerantFlow (blank or sch doesn't exist [warn issued]) (CycFan = 0)
AirLoopHVAC:UnitaryHeatCool:VAVChangeoverBypass (CycFan = 0)

Easy one:

A little harder:

Harder one:

Once these are done we can move on to others.

Comments?

MatthewSteen commented 5 years ago

This issue also affects the No Load Supply Air Flow Rate and No Load Outdoor Air Flow Rate When No Cooling or Heating is Needed fields in several objects (e.g. PackagedTerminalAirConditioner and WaterToAirHeatPump).

...This field is only used when the heat pump’s supply air fan operating mode schedule specifies continuous fan operation.