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Sizing error of Coil:Cooling:DX:SingleSpeed unit in DOAS ystem

asked 2016-03-09 11:12:44 -0500

updated 2016-03-09 13:46:49 -0500

I am simulating DOAS system with an air-cooled DX unit using OpenStudio, and there is an error when sizing the "Coil:Cooling:DX:SingleSpeed".

Based on the "input output reference" of E+, the rated volumetric air flow to total cooling capacity of "Coil:Cooling:DX:SingleSpeed" should be 300 to 450 cfm/ton; for DOAS application, it should be 125 to 250 cfm/ton. My DOAS system is 168 cfm/ton, which locates in the range of DOAS application. However, E+ seems to use the range of 300 to 450 cfm/ton, and it comes out the error:

* Severe * Sizing: Coil:Cooling:DX:SingleSpeed "1 SPD DX CLG COIL": Rated air volume flow rate per watt of rated total cooling capacity is out of range. * ~~~ * ...Air Volume Flow Rate used in calculation = 1.179869 m3/s * ~~~ * ...Air Volume Flow Rate per Watt of Rated Cooling Capacity is also out of bounds at = 2.2566585E-005 m3/s/W * ~~~ * During Warmup, Environment=NEWARK INTERNATIONAL ARPT ANN CLG .4% CONDNS DB=>MWB, at Simulation time=07/21 00:00 - 00:10

How should I let the program know that it is DOAS application?

Here is my setup:

The "Type of Load to Size On" was set as "VentilationRequirement", and both "100% Outdoor Air in Cooling" and "100% Outdoor Air in Heating" as "Yes". As for the "Coil:Cooling:DX:SingleSpeed", cooling capacity is 178400 BTU/h and air flow rate is 2500 cfm

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answered 2016-03-09 11:56:57 -0500

Depending on the system type and where and how this coil is configured and used in the simulation, you can tell the program that the coil is a 100% outdoor air coil. This is typically accomplished in a parent wrapper around the coil object.

 A11,  \field Use Outdoor Air DX Cooling Coil
    \type choice
    \key Yes
    \key No

 A16, \field Use DOAS DX Cooling Coil
   \type choice
   \key Yes
   \key No
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I didn't find the field of "Use DOAS DX Cooling Coil" in OpenStudio, but I do set both "100% Outdoor Air in Cooling" and "100% Outdoor Air in Heating" to "Yes". I didn't use "AirLoopHVAC:UnitarySystem", instead, I created an empty air loop and add coils, fans. In this case, is there any place I could setup DOAS?

Yan's avatar Yan  ( 2016-03-09 13:14:13 -0500 )edit

Place your DX coil inside the CoilSystem:Cooling:DX object and select Yes in the "Use Outdoor Air DX Cooling Coil" field.

rraustad's avatar rraustad  ( 2016-03-09 14:37:44 -0500 )edit

@rraustad, does OpenStudio include "CoilSystem:Cooling:DX" object?

Yan's avatar Yan  ( 2016-03-09 14:59:47 -0500 )edit

@macumber could answer that question.

rraustad's avatar rraustad  ( 2016-03-09 15:20:08 -0500 )edit

I believe that the answer is yes but @Kyle Benne and @aparker are the best to field OpenStudio questions about HVAC

macumber's avatar macumber  ( 2016-03-09 15:39:43 -0500 )edit

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Asked: 2016-03-09 11:12:44 -0500

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Last updated: Mar 09 '16