[Equest-users] Systems /Zoning question.
Nick Caton
ncaton at smithboucher.com
Wed Dec 8 09:07:34 PST 2010
My responses/thoughts are below in red.
Hope that helps!
~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: pranita kothuru [mailto:pranita.kothuru at gmail.com]
Sent: Wednesday, December 08, 2010 9:28 AM
To: Nick Caton
Cc: John Aulbach; equest-users
Subject: Re: [Equest-users] Systems /Zoning question.
All/Nick -
I thank you all for the valuable input. It cleared some of my doubts
but also created more.
I am not clear with zones, zone groups and assigning HVAC's to zone
groups. If I have 70 apartments, each apartments is one zone, i group
all these apartments into one zone group and assign the PTAC unit I have
created.
Does assigning the PTAC to the zone group mean that each zone within the
zone group is assigned to one PTAC unit?
That depends entirely on whether your PTAC is defined as 'system per
zone' or 'system per site' etc... not by what's in the zone group
screen. I found this unintuitive myself when I first encountered it,
but the zone group screen's system assignment pulldown does not mean you
do or don't wind up with one system in that group. The question is
easily explored if you simply finish the wizards and observe what's
generated by eQuest under the different options.
As an aside, for a building with this many systems/zones, you should
probably consider whether you can use a floor multiplier for the 2nd and
3rd floors to reduce the sheer size of the model.
Screen 13 and 14 in DD wizard seem to be conflicting. I entered all the
data on screen 13 for the whole building.
But after I group my zones on screen 14 the activity area allocation
uses the percentages on screen 13 for each zone group.
I am attaching screen shots of screen 13 and 14.
Screen 13 sets the default values and the available occupancy types for
screen 14. Any different percentages entered in 14 override screen 13
for the corresponding zone group. I tend to only use screen 13 to
define the occ. types I need, then use screen 14 to say a given zone
group is "100% office" or "90% corridor, 10% restroom" and so on.
Please advise on the above questions.
Thanks for all the advise.
Pranita.
On Tue, Dec 7, 2010 at 5:22 PM, Nick Caton <ncaton at smithboucher.com>
wrote:
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 I have 70 apartments do I have to create 70 PTAC(Could I use Zone
groups here).
Does the zone groups option assign each zone within the group one system
each (of the system which is assigned to the zone group)
You should only have to create one system type in the wizard - eQuest
can create all 70 individual systems if you 'choose system per zone.'
Zone groups exist primarily to help you assign/refine occupancy types,
exhaust (if any) and assign a corresponding system type. Whether you
end up with one or multiple systems is determined in the first screen of
the HVAC system dialogs. Again, finishing the wizards and observing the
results (look to the components tree under the air side systems tab)
will be the fastest way for you to grasp the possibilities if this isn't
crystal clear ;).
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.
How could I assign mutliple systems to one zone?
You cannot do this directly. I'm describing a method to get around that
fact - define two zones, each with it's own system, then define or
revise the connecting partition to an 'air' wall to effectively connect
the two zones thermally, making them behave together as one. I think
this will effectively allow the multiple systems work in tandem to
handle the combined loads.
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 <http://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
--
- Pranita
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