[Equest-users] 2007 90.1 Appendix G3.1.2.4

[Paul Diglio]

Brad:

Sorry, I have not submitted a project with PTAC units to LEED yet.  I am 
modeling two buildings right now that use a VRV system with a DOAS that supplies 
ventilation air directly to the space.  One is a commercial property in 
Middletown, CT and the other is a high rise residential in Waterbury, CT.

I am preparing an requested for an official interpretation of this section to 
ASHRAE right now.

I think it takes several months to receive an answer.  I will post the answer on 
the forum once I receive it.

Paul Diglio




________________________________
From: Brad L. Huff <BradH at BVHis.com>
To: Paul Diglio <paul.diglio at sbcglobal.net>
Cc: "equest-users at lists.onebuilding.org" <equest-users at lists.onebuilding.org>
Sent: Fri, June 10, 2011 11:50:27 AM
Subject: RE: [Equest-users] 2007 90.1 Appendix G3.1.2.4


Paul:
 
The message I wanted to post originally is pasted below. I should go on to 
further state that the PTAC units are naturally ventilated spaces. In your 
experience with these systems did you model them as operating 24/7 and if you 
did, did problems arise from a LEED review?
 
 
 
 
 
 
 
Modelers,
 
I apologize for the blank email I previously sent, I meant to hit save, not send 
(Paul was quick to respond, thank you). I am modeling a dormitory of System Type 
1. Appendix G Section G3.1.2.4 states, “Supply and return fans shall operate 
continuously whenever spaces are occupied and shall be cycled to meet heating 
and cooling loads during unoccupied hours.” If the building occupancy schedule 
is fractionally loaded 24/7, am I over exaggerating fan energy consumption of 
the PTAC units by operating the fans continuously 24/7? Has anyone received 
review comments from LEED on the issue? 

 
Thank you,
Brad
 
 
Brad Huff, E.I.T., LEED Green Associate, Mechanical EngineerI BVH Integrated 
Services I860.286.9171 tel I860.242.0236 fax I50 Griffin Road South, Bloomfield 
CT 06002 I .bvhis.com Itwitter.com/bvhis I Hartford  Boston 

 
 
From:Paul Diglio [mailto:paul.diglio at sbcglobal.net] 
Sent: Friday, June 10, 2011 11:06 AM
To: Brad L. Huff; equest-users at lists.onebuilding.org
Cc: Jason Glazer
Subject: Re: [Equest-users] 2007 90.1 Appendix G3.1.2.4
 
Brad:

Did you intended to post a message?

G3.1.2.4 is unclear.  First it states that the supply fan shall run continuously 
during the occupied hours and shall be cycled to meet heating and cooling loads 
during unoccupied hours.  Ok , I get that.

Then it states that if the supply fan is modeled as cycling and the fan energy 
is included in the EER, then the fan energy shall not be modeled explicitly.   
That is confusing.  When is it permissible to model the supply fan as cycling.  
Is AHSRAE talking a supply fan serving a space that is never occupied?  
Obviously, there is no such thing, someone will sometime do something in the 
room.

Then G3.1.2.4 goes on to state that the supply, return or exhaust fans will 
remain on during occupied and unoccupied hours in spaces that have heath and 
safety mandated minimum ventilation requirements during unoccupied hours.

This requirement does not cover many of the scenarios that I model.  For 
example, natural ventilation provided by operable windows.  It does not make 
sense to keep the fan running if it not supplying ventilation air.  I am 
presently modeling a residential high-rise.  No one keeps their apartment supply 
fan running 24X7.  Especially if there are operable windows.

Another example is a commercial property that has a DOAS supplying minimum air 
directly to the zone HVAC system or supplying minimum directly to the zone 
without isolation dampers.  If I supply the 62.1 minimum air required by the 
DOAS, then why run the supply fan?

I would be interested to hear other interpretations.  Perhaps Jason Glazer can 
give us his unofficial opinion.

Paul Diglio
 
 

________________________________

From:Brad L. Huff <BradH at BVHis.com>
To: "equest-users at lists.onebuilding.org" <equest-users at lists.onebuilding.org>
Sent: Fri, June 10, 2011 10:10:50 AM
Subject: [Equest-users] 2007 90.1 Appendix G3.1.2.4
Modelers,
 
Brad Huff, E.I.T., LEED Green Associate, Mechanical EngineerI BVH Integrated 
Services I860.286.9171 tel I860.242.0236 fax I50 Griffin Road South, Bloomfield 
CT 06002 I .bvhis.com Itwitter.com/bvhis I Hartford  Boston 
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