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

[Jim Dirkes]

Qinpeng,
Normal PTAC equipment does not ever have an economizer, so the E+ object does not allow it.
If you really need to model a DX cooling system with economizer, construct an E+ air loop with equivalent components for the fan, DX coil, supplemental heat, etc.

James V Dirkes II, PE, BEMP, LEED AP
www.buildingperformanceteam.com<http://www.buildingperformanceteam.com/>
Energy Analysis, Commissioning & Training Services
1631 Acacia Drive, Grand Rapids, MI 49504 USA
616 450 8653

From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Joe Huang
Sent: Friday, June 07, 2013 3:39 PM
To: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Modeling PTAC system with economizer (E+)

Qinpeng,

You might get responses to your question on the EnergyPlus_Support bulletin board than on BLDG-SIM.

Joe


Joe Huang

White Box Technologies, Inc.

346 Rheem Blvd., Suite 108D

Moraga CA 94556

yjhuang at whiteboxtechnologies.com<mailto:yjhuang at whiteboxtechnologies.com>

www.whiteboxtechnologies.com<http://www.whiteboxtechnologies.com>

(o) (925)388-0265

(c) (510)928-2683

"building energy simulations at your fingertips"

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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