[Bldg-sim] PSZ-AC

[Paul Riemer]

I would be leery about combining zones as the baseline cooling efficiency, fan power, and economizer should be set by each unit's tonnage, cfm, and sf respectively.  Further it is not your design cfm & tonnage but rather the baseline autosized cfm & tonnage.

Also be sure you know your software because some programs will allow you to but more than one zone on a "single zone system" and then model no control or reheat on the secondary zones, either of which be outside the intent of Appendix G's system 3.


________________________________
From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Kendra Tupper
Sent: Friday, September 05, 2008 9:34 AM
To: Dan Russell; Eric Youngson; bldg-sim at lists.onebuilding.org
Cc: bldg-rate at lists.onebuilding.org
Subject: Re: [Bldg-sim] PSZ-AC

I agree with Dan.  The 90.1 User's Manual is a bit more clear on this subject, and references that a PSZ unit is created for each thermal zone.

________________________________
From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Dan Russell
Sent: Thursday, September 04, 2008 4:12 PM
To: Eric Youngson; bldg-sim at lists.onebuilding.org
Cc: bldg-rate at lists.onebuilding.org
Subject: Re: [Bldg-sim] PSZ-AC

Eric,

I understand System 3 (PSZ-AC) to be a standard packaged rooftop that may serve multiple "spaces", but only serves a single "thermal zone".  In other words, there is only one thermostat that controls the entire unit.

Your baseline should have a separate PSZ-AC for each thermal zone depicted by your HVAC drawings.  Note that adjacent thermal zones with similar load characteristics (light/equip gain, people count, exterior exposure, etc.) may be lumped into a single thermal zone for modeling purposes (i.e. less zones = simpler model).

Hope that helps.

 Dan Russell, EIT

[cid:907414614 at 05092008-34AE]

From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Eric Youngson
Sent: Thursday, September 04, 2008 3:33 PM
To: bldg-sim at lists.onebuilding.org
Cc: bldg-rate at lists.onebuilding.org
Subject: [Bldg-sim] PSZ-AC

Sim List,
                ASHRAE system 3 is, Packaged Single Zone Air Conditioner (PSZ-AC). The description of PSZ-AC says, "Packaged rooftop air conditioner". I assume that this means a single unit serving multiple zones. This doesn't seem to make sense since the name contains the phrase 'single zone'.
                I have a building with baseline system 3, PSZ-AC and I'm not sure how to apply this system. The proposed building has a variety of systems. Should I have a system per zone or a single unit for the building?

Thanks

[cid:907414614 at 05092008-34B5]<http://console.mxlogic.com/redir/?bbBT6rTpdFLLLnuusdw0BJYLY2cEvYqsLxKVKVIwuwhbQAGn8lrxrW0E-l9QWIf8dOfgB0zM04SOqen6mjqaqtT4TSnDPqq9I5-Aq83iScDE4iZ9aCBQQg1oo0AK82hKvxYY1NJ4SyrjvvuKYYYrkV-8>

Eric Youngson



PAE Consulting Engineers, Inc.



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