[Bldg-sim] Appendix G - Exhaust Air Energy Recovery - G3.1.2.10

[Ulrik Welle-Strand Horn]

Dear all,

I have trouble interpreting this section of Appendix G, ASHRAE 90.1-2004 for
my application.

My application is 4 million square feet and uses district cooling. The
cooling load is met by fan coils which are placed in nearly every room
throughout the building. There is also a small fan coil near each air
intake. There are many (more than 50) separate air intakes, some of which
draw less than 5000 cfm. There is no mixing of return air. All the air
provided to the spaces is 100% outdoor air, and the air removed from the
spaces is exhausted directly to the outside.

Here are my questions:

1 - Does the term "Individual fan systems" in the text of this section refer
to the fan system in the proposed or baseline building?

2 - In my case, where there are many small fans serving a very large
building, does the limit of 5000 cfm refer to the capacity of each of these
individual fans, or the sum total of the capacities in the entire building?

3 - It seems the limit of 70% or greater of outdoor air in supply air is
meant for a system like VAV. In my system it is impractical to mix air,
since the cooling happens locally at each fan coil, and the supply air is
equal to the outdoor air provided. Even though I don't draw more air than an
equivalent VAV system with less than 70% of outdoor air in the supply air,
must I still model a recovery wheel?

4 - Is the 70% limit discussed above referring to the system in the proposed
or baseline building?

Thank you for your time.

Sincerely yours,


*Ulrik Welle-Strand Horn *
Sustainability Engineer

*Silpa Inc.*
*s* i m p l e  .  *s* c i e n t i f i c  .  *s* u s t a i n a b l e
AMERICAS | MIDDLE EAST | ASIA
www.silpainc.com

India: +91.90080.96083
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