[Equest-users] eQUEST fan energy question re: autosizing

[Cox, Christopher]

Hello All,

I'm wondering about fan autosizing in eQuest.  When we select "variable speed" fan control, the fan energy plummets by 80-90%.  Report SS-L (attached below) shows the first fan only running about 60% for 4 hours per year, and never running above 70%.  This is typical across all 10 systems in the building - with the exception of 1 zone that runs above 60% for 36 hours per year and above 90% for 4 hours per year.

The result of this is that when "variable speed" is chosen, ~90% of the fan energy goes away.  Any idea why the 'autosized' fan is so much bigger than is needed?  We're finding this situation on a lot of models that we review, and it's making savings from VFDs seem much bigger than what is measured in the field.  How should we be modeling this?

Thanks in advance,


Christopher Cox  ■  Engineer  ■  Demand Management(DM)
Nexant, Inc. ■ 4021 S 700 E #250 ■ SLC, UT 84107 ■ O| 801.639.5632 ■ F| 801.266.4786 ■ E| ccox at nexant.com<mailto:ccox at nexant.com>


I've attached the .inp and .pd2 files for your reference, but want to point out these 2 inputs:
Sizing ratio:  = 1.00
Sizing option:  = Coincident (but irrelevant because only one zone on this system).





            FAN ELEC    FAN ELEC   FAN ELEC    FAN ELEC      --------  Number of hours within each PART LOAD range  --------- TOTAL

            DURING       DURING     DURING      DURING         00    10    20    30    40    50    60    70    80    90   100   RUN

            HEATING     COOLING   HEAT & COOL  FLOATING        10    20    30    40    50    60    70    80    90   100    +  HOURS

MONTH      (KWH)       (KWH)       (KWH)       (KWH)

-----    ----------- ----------- ----------- -----------    ----  ----  ----  ----  ----  ----  ----  ----  ----  ----  ----  ----







  JAN           1.344       0.109       0.000       0.184     466     2     1     0     0     0     0     0     0     0     0   469



  FEB           0.741       1.575       0.000       0.302     326    13     9     7     1     0     0     0     0     0     0   356



  MAR           0.355       6.352       0.000       0.478     273    52    18    11    14     5     0     0     0     0     0   373



  APR           0.158       8.066       0.000       0.376     203    48    27    20    20     2     0     0     0     0     0   320



  MAY           0.042      12.987       0.000       0.267     131    99    63    49    19     0     0     0     0     0     0   361



  JUN           0.003      15.799       0.000       0.062      64   115   123    58    11     0     0     0     0     0     0   371



  JUL           0.000      22.947       0.000       0.000      17   108   108    68    47     8     0     0     0     0     0   356



  AUG           0.000      32.307       0.000       0.007      18    98   112    95    48    35     0     0     0     0     0   406



  SEP           0.000      25.667       0.000       0.057      51   133    72    39    34    39     4     0     0     0     0   372



  OCT           0.113      17.743       0.000       0.343     170    51    31    24    25    28     8     0     0     0     0   337



  NOV           0.445       2.875       0.000       0.493     294    12     9    12     5     1     0     0     0     0     0   333



  DEC           1.179       0.010       0.000       0.287     448     0     0     0     0     0     0     0     0     0     0   448

          ----------- ----------- ----------- -----------    ----  ----  ----  ----  ----  ----  ----  ----  ----  ----  ----  ----





  ANNUAL        4.381     146.437       0.000       2.857    2461   731   573   383   224   118    12     0     0     0     0  4502






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