[Equest-users] Systems /Zoning question.

[Nick Caton]

Pranita et al,

 

In this situation, you must either (A) define separate zones to define
the multiple systems as they exist, or (B) stick to your guns
(assumption of thermal equivalency), and further "lump together" the
individual PTAC's as large, "combined-equivalent" systems.

 

The first option would allow you to more easily specify the systems as
they exist - individually and independent in operation of each other,
will be more accurate if indeed the units have differing loads on an
hourly basis, as John is cautioning, and will render any concerns of
whether the assumption that the individual zones are thermally equal
moot.  

 

If you are concerned that the "multiple systems in one zone" is critical
for accuracy, you can always define the adjoining internal partitions as
air walls to thermally connect the adjacent spaces (indirectly the
corresponding zonal PTAC systems will work together to handle the
combined spaces' loads).  This seems to match the real-world  behavior
you're seeking to model.

 

The second option will actually be harder for you (the modeler) in the
long run, as you must average-together /sum the units' parameters to
come up with an equivalent collective system -
efficiency/capacity/scheduling/etc... if the validity of the "thermally
equivalent" assumption is questionable, so is the decision to have their
systems to act as one - it's your call.

 

Combining zones for thermal equivalency is a great technique when it
saves you work and time, but the approach sometimes can result in more
work than would otherwise be required in the long run.  If/when actual
system zoning is readily available at the wizard development stage of my
models, I personally tend to use that information when defining zones,
unless I'm certain the flexibility/accuracy benefits offered by a more
zonally-accurate model will be unnecessary.

 

~Nick

 

 

NICK CATON, E.I.T.

PROJECT ENGINEER

Smith & Boucher Engineers

25501 west valley parkway

olathe ks 66061

direct 913 344.0036

fax 913 345.0617

www.smithboucher.com 

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of John
Aulbach
Sent: Tuesday, December 07, 2010 3:27 PM
To: pranita kothuru; equest-users
Subject: Re: [Equest-users] Systems /Zoning question.

 

Pranita:

 

Careful about "all units have the same thermodynamic conditions". End
rooms have two exposures where those in the facing directions have one.

 

 

John R. Aulbach, PE, CEM

Senior Energy Engineer

________________________________

Partner Energy

1990 E. Grand Avenue, El Segundo, CA 90245
W: 888-826-1216, X254| D: 310-765-7295 | F: 310-817-2745

www.ptrenergy.com <http://www.ptrenergy.com/>  | jaulbach at ptrenergy.com
<mailto:%7C%20jaulbach at ptrenergy.com> 

 

 

 

________________________________

From: pranita kothuru <pranita.kothuru at gmail.com>
To: equest-users <equest-users at lists.onebuilding.org>
Sent: Tue, December 7, 2010 12:41:53 PM
Subject: [Equest-users] Systems /Zoning question.

Hello All -

 

I am modeling a multifamily 4 floors buildings in eQuest. I created
seperate zones for corridors and living spaces. My living spaces have
PTAC units and corridors have seperated HVAC system.

 

In DD wizard screen 1 what do I have to choose for 'System Per area'. 

 

All the living spaces were  zoned as one big zone (considering that all
units have same thermodynamic conditions).

 

If I choose system per zone, this can be wrong because I have more than
one PTAC units in that given zone(as several apats were clubbed to be in
one zone).

 

Please advice.

 



-- 

- Pranita 

 

 

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