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VRF system - Error

asked 2015-02-19 10:44:36 -0600

Stephanie12's avatar

updated 2015-02-19 17:06:51 -0600


I used the openstudio to modeling an office building. At this building I have 5 thermal zone. I want to set a VRF system. My question is "Must I set one VRF system for each thermal zone?" Because I want different thermostat to each zone... At my first effort, I set one VRF system and 5 terminals, but I had this error ...

For autosizing of ZoneHVAC:TerminalUnit:VariableRefrigerantFlow ZONE HVAC TERMINAL UNIT VARIABLE REFRIGERANT FLOW, a zone sizing run must be done. * ~~~ * No "Sizing:Zone" objects were entered. * Fatal * Program terminates due to previously shown condition(s). ...Summary of Errors that led to program termination: ..... Reference severe error count=1 ..... Last severe error=For autosizing of ZoneHVAC:TerminalUnit:VariableRefrigerantFlow ZONE HVAC TERMINAL UNIT VARIABLE REFRIGERANT FLOW, a zone sizing run must be done. *** Warning: Node connection errors not checked - most system input has not been read (see previous warning).

I don't know If I have to change some data at "EDIT"....

I would appreciate any help. Thanks in advance

image description

I try it and with different VRF system for each thermal zone , without any change

image description

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3 Answers

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answered 2015-02-24 03:26:11 -0600

dannyllim's avatar

I did a quick 5-zone model (1 core and 4 perimeters) with 189.1 office wholebuilding spaces, schedule set, and construction set. I assigned a VRF system and one terminal for each zone, and assigned different thermostat cooling setpoint for each zone following the description of your model as I understand it. The rest of the default values were not changed. The model ran to completion with 0 error and 23 warnings. I am using OS 1.6.1.

The error message "No Sizing:Zone objects were entered" suggests the source of the problem since the succeeding calculations use the zone sizing calculation results. Perhaps checking the sizing parameters in the thermal zone tab could show where the problem is. Another suggestion is to build and run your model using the default values of OS similar to what I did. If successful, then replace the specific parameters with that of the building being modeled. Hope this helps.

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answered 2015-02-20 09:59:25 -0600

Xiaolin's avatar

I have never used OS. But I have worked with original energyplus. I think, in your case, you can set several sizing:Zone objects if you want to account for different indoor conditions. The sizing:system is a global sizing factor that would be applied to all the rooms. However, you still need to have individual sizing of the zones. As to to the thermostats, you can also set individual thermostats for each zone if you want to have different set points in different rooms.

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answered 2015-02-19 11:16:52 -0600

updated 2015-02-19 12:43:56 -0600

image description

Make sure you have set the program to Do System Sizing Calculation as shown in the image above. This setting should be on if you are autosizing VRF. You should also turn on the Zone Sizing & Plant Sizing if you are autosizing everything.

The file is using version 1.4.0, if anyone has that on their computers - I am not able to open this file using version 1.6.0

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I set it already... I don't know where is the problem

Stephanie12's avatar Stephanie12  ( 2015-02-19 11:27:30 -0600 )edit

Stephanie, if you want to send your .osm file to me at I can have a look at it, but I make no promises. There are better OS experts on this site than I :)

Benjamin's avatar Benjamin  ( 2015-02-19 12:08:29 -0600 )edit

@Stephanie12 can you send the .osm to so we can take a look?

aparker's avatar aparker  ( 2015-02-24 09:25:47 -0600 )edit

I am having the exact same problem. Was there a solution to this?

jnbattle5's avatar jnbattle5  ( 2015-03-06 14:22:37 -0600 )edit

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Asked: 2015-02-19 10:44:36 -0600

Seen: 679 times

Last updated: Feb 24 '15