[Trace-users] Unmet Load Hours and Baseline Outside Air (Jason Boehning)

Bob Vogt BVogt at luckett-farley.com
Tue Dec 7 08:20:37 PST 2010


I have done several Trace runs with VRV and have seen a lot of unmet
load hours. Following are some suggestions:
1. Download the latest update from CDS. I believe they have corrected
some issues regarding unmet load hours.
2. Check your T'stat location, it should be "Room".
3. Tighten up your set back temperatures on the thermostat template. I
don't know if you are but I never use a T'stat schedule. Use the set
back temperatures and Cycle with Occupancy on the fans screen.
4. Check for very low airflows in janitors closets, storage rooms etc.
These spaces with low cooling loads may not have enough air flow to
heat. I sometimes add a minimum airflow using AC/H for these spaces.
5. IT rooms, try "No Fan Cycling" and/or no set back for these spaces.
6. Have you tried a morning warm-up schedule.
7. Make sure you use a ventilation schedule to close OA at night.
8. Last resort, increase capacity on the System's Coil's tab.

Outdoor Air,

Fans available is OK as long as you select cycle with occupancy. I would
use a fan schedule for room exhaust and optional vent fans. Schedule OA
off at night. Schedules need to be the same for baseline and proposed.

Hope this helps

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Today's Topics:

   1. Unmet Load Hours and Baseline Outside Air (Jason Boehning)
   2. Roof Top (Leandro Lopes)


Message: 1
Date: Tue, 7 Dec 2010 08:49:11 -0600
From: Jason Boehning <Jason.Boehning at ricegardner.com>
To: "trace-users at lists.onebuilding.org"
	<trace-users at lists.onebuilding.org>
Subject: [Trace-users] Unmet Load Hours and Baseline Outside Air
	<457DDD1943557042B717A5F43B84C5F00FB954B5F1 at ems08.ems-1.net>
Content-Type: text/plain; charset="us-ascii"


I am having problems with unmet load hours while modeling a school in
Trace. I have checked all my error messages and gone through the
reducing unmet load hours paper from Trace. I am modeling a VRV system,
so each classroom has its own fan coil unit in the room and there are
dedicated outside air units. There are also small server rooms with
their own fan coil units. Those 2 types of rooms, classrooms and server
rooms, seem to have the highest unmet load hours. Does anyone have any
suggestions on reducing these unmet load hours?

Also, our dedicated outside air units for the school will be controlled
more with a timer than CO2 sensors. So the ventilation is scheduled from
8-3 for classroom occupancy and offices from 7-5. I have all fans at
available 100% though. For the baseline, I have just put all outside air
on from 7-5. I am uncertain if this is the correct way to do the outside
air for the baseline. Does anyone have suggestions or can anyone point
me to the section in 90.1? Thanks for any help you can give me!


Jason Boehning
Engineer in Training/Designer
[cid:image001.gif at 01CB95E9.2045B930]
6161 Savoy, Suite 1212
Houston, Texas  77036

 v.  713.482.2322
 f.   713.482.2314
Jason.Boehning at ricegardner.com<mailto:Jason.Boehning at ricegardner.com>

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Message: 2
Date: Tue, 7 Dec 2010 15:08:47 +0000
From: Leandro Lopes <o.leandro.lopes at gmail.com>
To: trace-users at lists.onebuilding.org
Subject: [Trace-users] Roof Top
	<AANLkTimPKPZXay+cUZ5uR8JaymW2BvR0v=_FHYL6vKuV at mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"


I  created a roof top sistem and linked it to a plant, but  in the
heating mode this sistem doesn't work, instead the heating is being done
from the heating plant,my goal is to have this "Cooling Equipment"
working  in Cooling Mode and Heating Mode.

Can some one help me...

Leandro Lopes
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