[Bldg-sim] Modeling PTAC system with economizer (E+)

Joe Huang yjhuang at whiteboxtechnologies.com
Fri Jun 7 12:39:00 PDT 2013


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Joe Huang
White Box Technologies, Inc.
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yjhuang at whiteboxtechnologies.com
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On 6/6/2013 1:26 PM, Qinpeng Wang wrote:
> Hi, all,
> I'm trying to model a PTAC system with economizer within E+ environment.
> The specification of the system is:
> The OA economizer here is to provide "free" cooling during times of cool ambient 
> conditions. The amount of outside air taken into the building will vary between the 
> design percentage and the maximum percentage. And the design percentage of OA of the 
> system is not defined as related to occupancy or floor area but 25% of total supply air.
> I read the I/O reference about Controller:OutdoorAir, but it seems:
> "If all the limits are satisfied, the outdoor air controller does the following for 
> cycling fan systems: the outdoor air flow rate is set to the maximum when the fan cycles 
> on. If the limits are not satisfied, the outdoor air flow rate is at the minimum when 
> the fan cycles on."
> The problem is it's either minimum or maximum instead of modulating according to outdoor 
> and return air condition?
> Does anyone have suggestions on this? Help greatly appreciated.
> Do I have to go to EMS for this control scheme?
> Best,
> Qinpeng
> -- 
> Qinpeng Wang, PhD Student
> College of Architecture
> Georgia Institute of Technology
> Atlanta, GA 30332-0155
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