Design Specification ZoneHVAC Sizing Object Name in ZoneHVAC:IdealLoadAirSystem

asked 2016-03-12 06:06:02 -0600

updated 2016-03-12 08:01:41 -0600

10147 ●1 ●19 ●26 https://www.nrel.gov/b...

In EP-launch I have investigated the "ZoneHVAC:IdealLoadAirSystem" and the last field is the "Design Specification ZoneHVAC Sizing Object Name".

What does it mean for the "ZoneHVAC:IdealLoadAirSystem"'s way of working, if I activate the last field by writing a name (and of course also have specified/defined this name in a "Design Specification ZoneHVAC Sizing")??

Is it okay to not fill out this last field?

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@EnnaEnitsriK I retagged your question using existing ones. There are many previous questions for ideal-loads-air-system, which can be viewed by clicking on that tag.

MatthewSteen ( 2016-03-12 08:04:06 -0600 )edit

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answered 2016-03-15 09:35:11 -0600

Aaron Boranian

14250 ●86 ●24 http://bigladdersoftware.com/

According to Input/Output Reference documentation for the Ideal Loads Air System object, the input field for "Design Specification Zone HVAC Sizing Object Name" is OPTIONAL, so it is OK to leave this field blank. If you did want to use this input field, it will reference the name of a DesignSpecification:ZoneHVAC:Sizing object that provides more sizing options to modelers.

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Oh great! But how does that fit with the IdealAirLoadSystem-object being a "not-sizing"-object?

EnnaEnitsriK ( 2016-03-15 10:17:07 -0600 )edit

Yes, Ideal Air Loads is meant to be a "Loads Calculation" object more than a "Sizing" object. However, there are still some sizing calculations done based upon space loads and Ideal Air Loads input fields. For example, you can set the max air flow in heating and cooling for Ideal Air Loads, which then is used with space loads and supply air temperature to calculate capacity required. If you wanted to alter those max air flow values, you could use the Design Specification Zone HVAC Sizing object to do that. You should witness changes in calculated capacity requirements as a result.

Aaron Boranian ( 2016-03-15 10:42:23 -0600 )edit

Thanks for elaborating! Just to be sure; When you write "...you could use the Design Specification Zone HVAC Sizing object...", are you then referring to the other option for defining max flow rate for cooling and heating via the fields within the actual IdealLoadAirSystem-object?

EnnaEnitsriK ( 2016-03-15 13:05:24 -0600 )edit

If you use the Ideal Air Loads object, you should always enter values for max heating and cooling air flow, since they don't have default values according to the IDD file. The Design Specification Zone HVAC Sizing object will modify those max flow rate values you enter in the Ideal Air Loads object.

Aaron Boranian ( 2016-03-15 13:27:06 -0600 )edit

Great, I think I've got it now - thanks so much!

EnnaEnitsriK ( 2016-03-15 15:04:03 -0600 )edit

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