[Trace-users] Split System with DOAS for LEED (UNCLASSIFIED)

[Eurek, John S NWO]

Classification: UNCLASSIFIED
Caveats: NONE

Good timing Robert, I am modeling almost the exact same system.

I called Trane, but I still don't like how the system is working.

Under create system, select the dedicated outside air unit and fill in the
information.  This is equivelant to modeling two separate pieces of
equipment.

I modeled it the way Trane instructed, but I had my doubts.

I also modeled one system like normal but used 0 ventilation and another
system with 1sqft and nothing else but 100% ventilation (7400 cfm in my case)

The thing I didn't like about the method with 2 separate systems was that it
showed the return air of the second system to be 14800 cfm, I can't figure
out why it doubles the return air cfm.


-----Original Message-----
From: trace-users-bounces at lists.onebuilding.org
[mailto:trace-users-bounces at lists.onebuilding.org] On Behalf Of Robert Arnott
Sent: Thursday, February 03, 2011 3:46 AM
To: trace-users at lists.onebuilding.org
Subject: [Trace-users] Split System with DOAS for LEED

Hi all,

I am a new Trace 700 user and I'm busy modelling a building for LEED. I'm
struggling with two fundamental aspects of how the HVAC system modelling
works in Trace.


1. The building uses a split unit heating/cooling system, with a completely
separate dedicated outdoor air system for fresh air. The fresh air supply is
constant and does not vary with the heating and cooling load. The split unit
draws air directly from each zone (recirculating indoor air only) and is not
at all connected to the supply ducting of the fresh air. Since there are two
completely independent systems serving the same zones, how should this be
modelled for LEED? Would it be acceptable to assume that a single system is
being used, and that the heating/cooling is done directly on the supply air?

2. All zones receive fresh air, with only the bathrooms exhausting air,
creating a definite airflow network between the zones. If I set every zone's
"Adjacent air transfer from room" to the passageway connecting all the zones,
will Trace determine the correct airflow rate and direction between each
zone? Or is the adjacent air transfer directional, so that the bathroom would
need to be set to have an airflow transfer from the passage, then the passage
would need an airflow transfer from multiple zones (but trace only allows a
single zone to be set)?


I'd appreciate any feedback. Thanks in advance!

Regards,
Robert


Classification: UNCLASSIFIED
Caveats: NONE