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Center Zones Too Warm

asked 2015-12-21 19:34:06 -0500

Dustin gravatar image

updated 2015-12-22 07:32:47 -0500

Hey all,

Working with OpenStudio and when looking at the zone temperatures, the center zones are getting significantly warmer than my exterior zones. It may also be important to note that while this is the case year round, in the summer months the affects are much more noticeable. I am asking for some troubleshooting techniques around this kind of occurrence.

The one thing that may be strongly affecting this is that the center zones aren't serve by any of the AHUs, they only have exhaust fans in the rooms because they are washrooms, copy rooms, etc. But the exterior zones stay within the setpoints that I have set pretty well. It may have to do with air changes per hour and air flow between zones. Just wondering if anyone can offer any advice on this matter.

Thanks in advance for the tips guys.

Edit: This may help in determining the problem. Below is a screenshot of a center and exterior zone's air temperature. image description

My building loads and occupancy begin at 7:00 which is where I expected a jump in temperature to be. That being said the 2C zone temperature jumping from 22.15 to 41.83 is a bit unreasonable. I do think David's suggestion of zone mixing may help fix this but I am unsure of how to do that.

I may also be using the space infiltration design flow rates and schedules for those incorrectly. I say this because the AHUs run from 07:00 to 21:00. But much of the occupancy and loads in the building are complete at 16:00. The next screenshot shows around the times I am concerned with. image description Basically I see the drop in 2C air temperature at 16:15 which is expected but the temperature stays fairly constant until the AHU unit shuts off at 21:00. For the space infiltration I just used one of the predefined wholeBuilding md office loads based on the flow/exterior area for the exterior zones and used ACH for the center zones. The schedule applied to these loads was a medium office infiltration quarter on but adjusted to being "on" from 07:00 to 21:00.

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Have you used the API to add zone mixing from the perimeter zones to the core zones?

David Goldwasser gravatar image David Goldwasser  ( 2015-12-21 23:36:19 -0500 )edit

I have not @David. I am pretty unfamiliar with the API and how to go about using it.

Dustin gravatar image Dustin  ( 2015-12-22 06:21:35 -0500 )edit

I am looking through some previous posts on zone mixing.

https://unmethours.com/question/1853/...

Would I just be able to put that code into my ruby console through SketchUp when I have my .osm file opened in there? I think that was my problem before when I was playing around with manually inputting something through the ruby console.

Dustin gravatar image Dustin  ( 2015-12-22 06:25:16 -0500 )edit

That code is for an EnergyPlus measure prior to when we added Zone Mixing to the OpenStudio API.

David Goldwasser gravatar image David Goldwasser  ( 2015-12-24 10:29:07 -0500 )edit

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answered 2015-12-24 10:31:36 -0500

updated 2015-12-24 10:32:02 -0500

If you aren't comfortable working with zone mixing objects, is there any reason you just don't include the core zone on the air loop? Exhaust air will be deducted from return air from the core zone.

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The core zones aren't directly supplied by the AHUs. They take air out of the zones but don't supply cooling or heating air to the core zones. This is why I didn't include them in the AHUs.

Dustin gravatar image Dustin  ( 2015-12-26 05:23:49 -0500 )edit

The short answer for now is that we don't have a measure that does what you want, so you would have to write a measure. You could borrow code from the link in your earlier comment and write an EnergyPlus measure, or you could use the new ZoneMixing object in the OpenStudio API to write an OpenStudio measure.

We have a few measures that add zone mixing, but they are very use case specific.

David Goldwasser gravatar image David Goldwasser  ( 2015-12-28 10:12:27 -0500 )edit

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Asked: 2015-12-21 19:34:06 -0500

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Last updated: Dec 24 '15