eQuest outdoor air shows 0 CFM in Hourly Reports, but it's not 0 in model

asked 2020-08-06 15:21:46 -0600

John1
131 ●3

updated 2020-08-06 18:21:52 -0600

shorowit

11851 ●200 ●9 https://www.nrel.gov/b...

For #1 (see image below, blue #1), it shows 0 hot air flow. and #4 shows 0 outdoor air. But, it must be receiving hot air flow because the space is at the right temperature (even with 0 baseboard, space temp was good). And, I'm pretty sure it is getting outdoor air, because when I increase outdoor air, my total building energy use goes up. Any idea why it is showing "0" for these items? Did I set something up wrong in Hourly Reports? FYI the date I'm showing below is January 7th when it is about 20F outside (-5 C), so it is heating season.

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What type of system is being used? Is there a schedule for outdoor air being applied to the system? Also, what question are you trying to answer by printing these hourly reports? And can you please share the results of the SV-A report for this system from the .SIM file?

Daniel ( 2020-08-07 05:40:21 -0600 )edit

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answered 2020-08-08 10:43:39 -0600

John1
131 ●3

Hi Daniel, thanks for your response. I was going to reply yesterday but when I tried to go to the unmethours webpage, it said there was a security issue and I shouldn't go to the site. I had the same issue with energy-models.com.

So the system that is being used is an air handling unit (AHU) with a chiller for chilled water loops and boiler for hot water loops. Yes there is a schedule for outdoor air applied to the system, I have it set to be off during unoccupied hours, and on during occupied. What question am I trying to answer via hourly reports: I'm just checking to make sure my model is behaving as it should, I wanted to see how much outdoor air is entering the building via the AHU, to make sure it matches what I want. I've attached a screenshot of the SV-A report. C:\fakepath\cccccc.JPG

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an issue with Hourly Reports for OA in eQuest is that the reports are looking for OA for ERV or OA for DCV. If you have neither ERV or DCV, the reports aren't much good and will show 0 for all hours. This is a HUGE weakness of eQuest that I would love a solution to, if one exists.

A workaround I have use is to enable ERV with limited effectiveness and 0.0001 pressure drop (both to minimize the impact on the rest of the simulation) - but allow me to look at the OA hourly report.

Now, looking at the SV-A you shared. you have 188025cfm supply. OA Ratio 0.226. This is 42,493 CFM OA.

dradair ( 2020-08-10 08:47:47 -0600 )edit

note-enable the ERV to check OA behavior....disable the ERV for 'normal' simulations where the results matter. While the lower pressure drop and limited effectiveness means it should have limited impact....thats "should". When ERV is removed then, there results shouldn't change greatly.

dradair ( 2020-08-10 08:57:06 -0600 )edit

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