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Modeling a Standard Split AC with economizer

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

Yannis gravatar image

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: http://www.inventorairconditioner.com...

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

Diffuser

  • 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

Thanks!

EDIT-------------------------------------------------------------------

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?

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

NickC gravatar image

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

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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 ...

Thanks!

Yannis gravatar image Yannis  ( 2016-03-25 18:31:19 -0600 )edit

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

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Last updated: May 03 '16