Question-and-Answer Resource for the Building Energy Modeling Community
Get started with the Help page
Ask Your Question

Modeling a Standard Split AC with economizer

asked 2016-03-23 17:54:19 -0600

Yannis's avatar

updated 2016-05-03 05:36:20 -0600

I followed the steps in the question "hvac template for standard split ac"to build up a standard split system according to the technical data:

The only changes I made from the default are:

Unitary - Single Speed DX cooling - Cycling - Elec reheat

  • OS:AirLoopHVAC:UnitarySystem

Controlling Zone or thermostat location: Τhe relevant zone

  • OS:Coil:Cooling:DX:SingleSpeed

Rated Total Cooling Capacity: 6156 W

Rated COP: 3.24

  • OS:Coil:Heating:Electric

Nominal Capacity: 6498 W


  • OS:AirTerminal:SingleDuct:Uncontrolled

Maximum Air Flow Rate: 0.236 m3/s (Air Circulation 850 CMH Max)

My first question is if my settings are correct according to the technical data?

The second Question is according to openstudio results summary. Using a Unitary - Single Speed DX cooling - Cycling - Elec reheat system the total calculated power consumption for cooling or heating is cooling/heating+fans consumption?

The third question is if I can model an economizer, since the relevant zone is a IT room/Data center space and what are the appropriate settings for an economizer for such a space so as to estimate possible changes in energy consumption



The following error occurs:

"Error: Sizing: Coil:Cooling:DX:SingleSpeed "1SPD DX CLG COIL 7": Rated air volume flow rate per watt of rated total cooling capacity is out of range. Min Rated Vol Flow Per Watt=[4.027E-005], Rated Vol Flow Per Watt=[8.196E-005], Max Rated Vol Flow Per Watt=[6.041E-005]. See Input Output Reference Manual for valid range."

When all set to default (autosize), no error occured. Acording to the technical data, is it posible to be overrided this error?

edit retag flag offensive close merge delete

1 Answer

Sort by » oldest newest most voted

answered 2016-03-25 14:21:49 -0600

NickC's avatar

updated 2016-03-25 14:50:10 -0600

Re: question#1 - I did not check your conversions but it looks like you've entered the information available in the system hardware link. This is a start; if you need a more realistic model of this equipment, I'd suggest emailing the vendor and asking for additional information (max supply temp, approximate fan pressure rise, etc.)

Re: question#2 - if you haven't already checked, a place to look for the explanation of output parameters is the E+ input/output reference; this link is for the unitary system you are using; check under "outputs"

Re: question#3 - yes, you can model economizer since you have an OutdoorAirSystem element in your airloop; click on the air loop's dotted line to access it's settings; economizer will be there; a good place to start would be "FixedDryBulb"; technical groups (like ASHRAE) publish guidelines on suggested economizer settings for different areas

GL! -N

edit flag offensive delete link more


Q#1 The answer from the vendor was not helpful ....

Q#2 I was not sure if the HVAC fan consumption is separated from the total cooling/heating consumption. Besides there is no HVAC system other than that in my model, and is rather reasonable. So I figured that is separated.

Q#3 I'm searching ...


Yannis's avatar Yannis  ( 2016-03-25 18:31:19 -0600 )edit

Your Answer

Please start posting anonymously - your entry will be published after you log in or create a new account.

Add Answer

Training Workshops


Question Tools

1 follower


Asked: 2016-03-23 17:54:19 -0600

Seen: 1,062 times

Last updated: May 03 '16