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Re: [EnergyPlus_Support] How can I simulate a stuck open economizer?



Thanks Jim. This will simplify my model.

I did set up my controller as you suggested, with a value of 10 and E+ gave me a warning saying: Minimum outside air flow rate for OA Controller "VAV_5_OA_CONTROLLER" is greater than maximum supply flow rate for Air Loop "VAV_5"

Therefore, I need to know the max supply flow for the airloop, which I assume is the input "Design Supply Air Flow Rate" which currently is, and I think it should be "autosize".

So, I went to the rdd file and the i/o Reference manual but I could not find this variable.

Any idea how to find out the airloop design flow rate?

Thanks again.

Homero.

On Wed, Mar 21, 2012 at 9:01 AM, Jim Dirkes <jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
 

How about setting the Controller:OutdoorAir for a specific minimum flow, something like:

 

 

p.s., EnergyPlus expects flow rates in m3/s.

 

The Building Performance Team
James V. Dirkes II, P.E., BEMP , LEED AP
1631 Acacia Drive NW
Grand Rapids, MI 49504
616 450 8653

 

From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of hnoboam
Sent: Wednesday, March 21, 2012 9:53 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] How can I simulate a stuck open economizer?

 

 

I need to simulate a stuck open economizer damper. To do this I thought I could use an EMS program to override the outdoor air flow rate setpoint.

First I ran the simulation normally and found the maximum yearly outdoor air flow rate, which happens to be around 3 kg/s.

Next, in the EED file I found what I think it is the suitable actuator:

EnergyManagementSystem:Actuator Available,VAV_1_OA_CONTROLLER,Outdoor Air Controller,Air Mass Flow Rate,[kg/s]

Next, I did setup the EMS actuator and program, like this:

EnergyManagementSystem:Actuator,
AHU1_OA_Flow, !- Name
VAV_1_OA_CONTROLLER, !- Actuated Component Unique Name
Outdoor Air Controller, !- Actuated Component Type
Air Mass Flow Rate; !- Actuated Component Control Type

EnergyManagementSystem:Program,
set AHU1_OA_Flow=10.0, !- Program Line 2

When I run the simulation, the outdoor flow rate is, indeed 10 kg/s, but the problem is that E+ shows the "Actual Outdoor Air Fraction" greater than 1. How can this be? Should not this value be strictly between zero and one?
Furthermore, if I put a **very** large setpoint, e.g. 600 kg/s, E+ does not converge to the solution. Why?

Then, the larger questions are: Have you done something like this? Am I in the right track? Do you have any advise?

I posted my idf in the "Files" section at:
Files > _Problem_Submittals > EconomizerOpen.idf

Thanks.

Homero




--
Homero Noboa, Ph. D.



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