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[EnergyPlus_Support] Re: Heating problem in AirflowNetwork

***see comments***

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "mehry1205" <m_yazdanian@...> wrote:
> I have a one zone Packaged Single Zone model. I have added Airflow Network to control the 2 windows on the facade. 

***I can only assume the current operational controls based on dTs inside outside, etc. were not satisfactory. I must point out that there exists a hybridventilation manager object which can be used to turn off mech ventilation when windows open.***

I wrote an EMS to control the opening/closing of the windows. I then noticed that the fan is on even when the windows are open. I therefore added the second EMS to turn off the fan when the windows are open. I placed the EMS  'AfterPredictorBeforeHVACManagers" so the system availability manager can overwrite it, when needed. I created the detailed output and noticed that the heating energy comes on for one or two cycles (detailed report cycle) and then turns off. This happens throughout the annual run and causes some annual heating energy. I see no indication that heating is needed. 

***Which variables did you report to check this? Zone heating and cooling loads? With nightmanager the fan will turn on (availibilitymanagers overwrite normal schedules) even when the fan is scheduled to off if there exists a load in the space. "nightmanager" also effects the simulation during day hours. The time when it may indeed effect the simulation may in fact be scheduled in the object. ***

So here are my questions:
> 1) is 'AfterPredictorBeforeHVACManagers' the right place for EMS to control the fan?
***your nightmanager will overwrite the schedule value that the EMS had just overwritten, if it is scheduled to be effective at this time and if there is a load. ***
> 2) What temperature does heating control use as its control sensor to determine the Supply Air Temperature, in other words, what temp causes the heating to come on? I don't see any obvious reason for heating to come on.
***If there exists a heating load, the system will try and heat. The delivery air temp when the system is in heating mode is setup by an array of coil controllers and setpoint managers which assign target temperature setpoints on different nodes. This is highly customizable. ***
> 3) What temperatures causes the 'Availability Manager Night Cycle Control Status' to be set to 2?
***check the object input fields***
> These questions came about because of the amount of annual heating produced by these runs and I'd like to be able to explain it. I have an idf file that demonstrates this problem (NV.idf) which I will upload.
> Thanks for your help,
> --Mehry


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