[Bldg-rate] [Bldg-sim] PSZ-AC

[Eric Youngson]

Paul,

                Thanks for the heads-up. This is good insight! In fact
this is exactly why I am questioning my interpretation of Appx G. I have
only combined common spaces such as corridors & restrooms, however I
believe I should take a closer look to make sure that these zones have
similar exposure on their exterior surfaces.

 

Thanks again!

 

Eric

 

From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Paul Riemer
Sent: Friday, September 05, 2008 8:15 AM
To: bldg-sim at lists.onebuilding.org
Cc: bldg-rate at lists.onebuilding.org
Subject: Re: [Bldg-sim] PSZ-AC

 

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 

	 

	 

	 

	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

	 

 
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Eric Youngson 

 

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