[BLDG-SIM] Night Cycling Fans and Loads Not Met

Jon Evans jevans at sustaineng.com
Wed Nov 28 14:02:35 PST 2007


Michael,

I don't have a lot of experience with unmet load hours in Equest, but do in
Trane Trace. An unmet load hour is any hour in which the building is
occupied (above a certain percentage- in Trace its 5%) and the space
temperature is more than 1.5 degrees colder (in heating) or warmer (in
cooling).

I would first try removing your thermostat setback and see if that solves
your problem.  If it does, your building is not getting back up to the
occupied thermostat temperature quick enough before it becomes occupied
causing unmet load hours.  How aggressive is your setback?

You can also try operating your fans at least 1 hour before occupancy.

Your system may also be undersized (if it's heating unmet load hours) and
the lack of internal gains during the night hours trigger unmet load hours
because the system can't keep up.

Use the output to give you a clue to which space(s) are causing the
problems.  Good luck!

-Jon
-----Original Message-----
From: BLDG-SIM at gard.com [mailto:BLDG-SIM at gard.com] On Behalf Of Michael
Rosenberg
Sent: Wednesday, November 28, 2007 3:20 PM
To: BLDG-SIM at gard.com
Subject: [BLDG-SIM] Night Cycling Fans and Loads Not Met

Using eQuest, I am working on a building model with a VAV system with fans
cycling on at night to meet setback temperatures. The SS-C report indicates
about 1,500 annual  hours of night cycling. If I change the
Night-Cycle-Control from Cycle-On-Any to Stay-Off,  the 1,500 hours of night
cycling disappears as expected. However, there is no difference in the
number of hours of loads not met either in the BEPS report or the SS-R
report. Anyone have an explanation?

Mike


Michael Rosenberg
Oregon Department of Energy
625 Marion St. N.E.
Salem, OR 97301-3742
Phone : (503) 373-7809
Fax: (503) 373-7806


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