[Equest-users] FW: DOE Ref Bldgs to eQUEST

Nessle, Willis wnessle at nexant.com
Wed Mar 7 15:34:43 PST 2012

Dear Everybody,

Couple long-winded *but easy* questions here!   Any help is much appreciated.

-- I'm modeling a DOE Commercial Reference Bldg (the Small Office) in eQUEST, location is DFW in Dallas, TX

-- I'm not actually designing a building.  I just want to make a model and extract the hourly cooling load that the coil sees.  My understanding, thanks to some on this list, is I should pull SYSTEM load (variable list item #6), which is "...total cooling coil output".    I figure since I'm looking at an "output" variable to represent the cooling load demand, the coil must be sized correctly.   For example, if there is a 4 ton load but only a "2 ton coil", I don't suspect the coil output variable will ever show more than 2 tons.  Is that correct?

-- My Min OA Schedule is Fraction type and all hourly values are either 0 or 1, generally following occupied hours.  I want eQUEST to size the system appropriately.  From the Help file I understand that if I want to define a schedule I must also define the Min OA Ratio.  But I'm not sure how or where to enter this value.   My SV-A report chose OA Ratio = 0.048, which is about 16 cfm/person.  I want the model to reflect 20 cfm/person.   According to the SV-A, my Fan capacity = 1384 cfm, so 20cfm per person would equal 5.7%.   Do I enter "0.057" into the Min OA ratio txt box on the System Props>Outside Air>Outside Air and Economizer tab?   Note: When I tried this the SV-A report values did not change - the OA ratio was still 0.048.

-- When I define the Min OA ratio (and schedule) the cooling load grows.  I  expect this since I increased the OA ratio, but since the SV-A doesn't reflect my change I don't know how to judge or validate the result.

-- A perhaps larger problem is the very high percentage Unmet Hours.  A couple questions and comments here:

---- Is it correct to assume that "Unmet Hours" does NOT count unmet loads occurring when my Sys Fans = Off (schedule = 0), like Sundays?

---- Again, I was thinking eQUEST could size the system correctly.  But judging from the "unmet hours" and comparing my results to the Reference Bldg results, it doesn't appear that eQUEST sized the system correctly.  Further, when I changed the system capacity directly in Detailed Edit that just made matters worse - the load actually increased somehow, seemingly as result of increasing the capacity...which is weird.   What am I missing?  If eQUEST doesn't choose correct size, how do I go in and define the correct size?

---- Oddly, *before* I defined Min OA Ratio and Min OA Schedule my SS-F report showed two "humps" in the "Hours Under Cooled" column during the shoulder seasons.   That is, April and May and Oct were quite a bit higher than other months.   I'm totally perplexed why the system would have more trouble meeting the load during the time of year with lowest delta T.   *After* I defined the Min OA ratio and schedule, the humps were gone; unmet hours increased from Jan to Aug, then decreased again to Dec, as might be expected.   Also confusing: my SS-E report showed no  coincident heating and cooling for either case.

---- I attached the files in case any of you have time to skim through the model.

I know this was a lot to read through. I really appreciate any feedback.

Many thanks,

Willis Nessle
Sr. Project Engineer
Nexant, Inc.
1331 Lamar St. Ste 1575
Houston, TX 77010
c: 713-758-8718

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