Re: [EnergyPlus_Support] Multiple HVAC systems serving one zone

[Jean Marais <jeannieboef@xxxxxxxxx>]

I believe the fan:zoneexhaust object is a sort of zone equipment, i.e. not connected to the airloop per say. But e+ will warn you that the supply and exhaust of the AHU does not balance. But x2 airloops per zone is currently not possible (unless you're an advanced user and start looking into the userdefined ventilation objects and how they can do amazing things linked with ems as hinted at by Brent). Actually, you should use the fan:zoneexhaust object and write a small ems to override the on schedule of the fan by monitoring the ODA conditions. ems is not a black art...it is just a scary name. a small piece is usually quite easy.

On 26 November 2012 21:34, thevinyldropper <thevinyldropper@xxxxxxxxx> wrote:

 

I am having some difficulty setting up multiple HVAC systems serving one zone. The situation is that I am modeling a building with packaged rooftop units as well as exhaust fans. However, I can't model the exhaust fans using the exhaust fan object because the exhaust fans are controlled based on enthalpy differential with outdoor air (as I understand it, exhaust fan availability managers only allow temperature differential).

So I thought I would set up another HVAC system in addition to the RTUs that would function like the exhaust fans (with a supply fan, rather than exhaust, no heating or cooling coils). I could then use an outside air controller to specify the enthapy differential control. The issue I am having is setting up both systems to serve one zone. Do I connect the second system (exhaust system)to the zone inlet node, or upstream of the zone splitter associated with the RTUs? Where do I connect downstream of the zone?

Any help would be much appreciated. Of course, if anyone has a way of getting the exhaust fan object to run on differential enthalpy, I would take suggestions there too!!

Andrew

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