[Equest-users] Modeling Chiller Efficiency
John Aulbach
jra_sac at yahoo.com
Thu Feb 11 11:02:11 PST 2010
Reniel:
The EIR input is at full load.
To answer your other question, here is the text from the Online DOE-2 Help menu in eQuest, which speaks so much better than I:
Rated vs. Design Conditions
The program allows chillers to be specified at either the:
Rated conditions – as specified by ARI or other rating organizations. For all chiller types, ARI rates the evaporator conditions as 54°F entering and 44°F leaving chilled water (which corresponds to 2.4 gpm/ton). For water-cooled chillers, the condenser conditions are 85°F entering condenser water at a flow of 3 gpm/ton. Air-cooled chillers are rated at 95°F entering outdoor drybulb temperature. Chillers with remote condensers, are rated at 125°F saturated-condensing temperature.
Design conditions – the actual conditions at which the chiller is sized and designed to operate.
When specifying a chiller, it is important to distinguish whether the stated chiller performance (capacity and energy consumption) are defined at the rated or actual conditions. Most chiller types can be specified at either the ARI rated conditions, or the actual design conditions. However, for centrifugal chillers, it may not make sense to specify performance at the ARI rated conditions, as the chiller may not be able to actually operate at those conditions.
For example, consider a water-cooled centrifugal chiller serving a building in a relatively cool, dry climate. The engineer specifies the chiller capacity and efficiency at 46°F leaving chilled water and 76°F entering condenser water. To achieve the specified efficiency at minimum cost, assume the chiller manufacturer configures the the impeller and heat-exchangers to exactly meet the design conditions. If this chiller is then operated at the more extreme ARI conditions of 44°F/85°F, the compressor may not be able to overcome the pressure differential between the evaporator and condenser, and the chiller will surge if it tries to deliver water at 44°F. To operate successfully at 85°F entering condenser water, it will have to deliver water warmer than 44°F.
For this reason, the program defaults assume that centrifugal chillers are specified at the design conditions. All other chiller types are assumed to be specified at the rated conditions, unless you specify otherwise.
So I THINK if you specify ARI conditions and ran the chiller in your climatic condition, it would be a correct simulation.
Others input please...
John R. Aulbach, PE, CEM
Senior Energy Engineer
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1990 E. Grand Avenue, El Segundo, CA 90245
W: 888-826-1216, X254| D: 310-765-7295 | F: 310-817-2745
www.ptrenergy.com| jaulbach at ptrenergy.com
________________________________
From: reniel barroso <renielbarroso at yahoo.com>
To: equest-users at lists.onebuilding.org
Sent: Thu, February 11, 2010 2:21:27 AM
Subject: [Equest-users] Modeling Chiller Efficiency
To eQuest users,
Only EIR is required for the chiller efficiency input.
This can be converted easily to COP from which most of the manufacturers specify this on their cut sheets/catalogues to get the EIR.
Questions are:
1. What is this COP/EIR input in eQuest?
Is this for Full Load or Partial Load?
2. Does anybody know how to convert the ASHRAE Chiller's ARI Condition listed in ASHRAE 90.1 to our weather condition here in Dubai?
Or is there a formula in converting the ARI Condition to the local weather where the project will be built?
Any related help from their own experience will be helpful.
Thanks in advance
Reniel
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From: "equest-users-request at lists.onebuilding.org" <equest-users-request at lists.onebuilding.org>
To: equest-users at lists.onebuilding.org
Sent: Wednesday, February 10, 2010 23:16:38
Subject: Equest-users Digest, Vol 23, Issue 16
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Today's Topics:
1. Re: Circulation Loop Warnings (Shaun Martin)
2. Re: Hrs exceeding throttling range on T24 baseline
(Sundharam, Premnath)
----------------------------------------------------------------------
Message: 1
Date: Wed, 10 Feb 2010 09:14:30 -0800
From: "Shaun Martin" <smartin at shaunmartinconsulting.com>
To: "'Katie Tuttle'" <Katie.Tuttle at hei-eng.com>,
<equest-users at lists.onebuilding.org>
Subject: Re: [Equest-users] Circulation Loop Warnings
Message-ID: <CF0A26C4519A450CADAF753921C1BBA9 at Shaun>
Content-Type: text/plain; charset="us-ascii"
The CURINV warnings you see are mostly related to pumps. What equest does
with its pump and loop calculations is a mystery and a bit of a joke (I
frequently see autosized flow rates 5 to 10 times the design). Chances are,
if you specify kW, flow and head together, you'll end up seeing the errors
you are getting here. Start with just the pump kW. Add head if eQuest
complains. You'll have to enter the head that the program calculates or,
again, you'll get more warnings.
Shaun Martin LEED AP
Principal
Shaun Martin Consulting
Suite 200 - 420 West Hastings Street
Vancouver, BC V6B 1L1
c: 604-789-1095
e:smartin at shaunmartinconsulting.com
_____
From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Katie
Tuttle
Sent: Wednesday, February 10, 2010 7:29 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Circulation Loop Warnings
Has anyone been able to resolve warnings that occur with circulation loops?
Please see attached for simulation warnings.
Thanks,
Katie
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Message: 2
Date: Wed, 10 Feb 2010 13:16:00 -0600
From: "Sundharam, Premnath" <psundharam at DLRGROUP.com>
To: "Hwakong Cheng" <hwakong at hotmail.com>,
<equest-users at lists.onebuilding.org>
Subject: Re: [Equest-users] Hrs exceeding throttling range on T24
baseline
Message-ID:
<175AB2D86809FE429E67032E0D05DC59010147FD at dlremail.dlrgroup.com>
Content-Type: text/plain; charset="us-ascii"
Hey Hwakong,
Thanks for the response.... I realized the hard way that the capacities
doesn't matter....
Our system does not have any preheat or reheat coils. The proposed is a
SZRH that is connected to CHW and HW Loop (This is in essence to
simulate a THREE Deck Multi Zone System). T24 Standard system for this
zone is PSZ.
There are both heating and cooling unmet load hrs, but on one zone the
heating unmet load hrs is 1300 and the rest of the zone are minor. This
single handedly is what is probably causing the problem.
This zone is similar to many other zones in use, geometry and so on and
except for this one every other zone of similar nature functions
perfectly well....
The same zone on the T24 Proposed appears perfectly normal.... See image
below....
So again, T24 standard uses a PSZ and the T24 Proposed uses a SZRH....
It is impossible for a zone to have a minimum temp at -57.8 F in May in
San Diego...... the T24 Standard is doing something wrong! I tried many
things, like increasing the Hot Water Entering Zone temp., deleting the
system for this zone and re-assigning to a new system.... Nothing seems
to solve the problem....
Any help would again be greatly appreciated....
Thanks
Prem
From: Hwakong Cheng [mailto:hwakong at hotmail.com]
Sent: Wednesday, February 10, 2010 11:59 AM
To: Sundharam, Premnath
Subject: RE: [Equest-users] Hrs exceeding throttling range on T24
baseline
In my experience, insufficient capacity in primary equipment (chillers,
towers, fans, etc) is seldom the cause of hours out of throttling range.
I would look more at reheat capacities, presence/absence of preheat
coil, presence/absence of reheat coils, and other control issues. These
are not autosized by eQUEST - for example, sizing the reheat coil
capacity is done in DOE-2 by specifying the reheat delta T. Sometimes
there are different system types between the proposed and standard
models that can cause differences in unmet load hours between the two.
Are your hours out of throttling due to insufficient cooling,
insufficient heating, or both? Is it one zone or many? You probably need
to review the detailed and hourly reports for the standard model to
understand what's not working right in that run... and then figure out a
way to fix that in the original model.
We always see low heating energy in our T-24 proposed runs. We think
it's an artifact of eQUEST rather than a reflection of reality.
________________________________
Date: Wed, 10 Feb 2010 11:11:24 -0600
From: psundharam at DLRGROUP.com
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Hrs exceeding throttling range on T24 baseline
Hello All,
I am doing a Title 24 Compliance through eQuest and I am just trying to
do a reality check to see if the model is performing correct.
Based on the T24 proposed and standard output files, it appears that the
T24 standard building has 17.6% outside of throttling range, where as
the T24 proposed has only 0.4% outside of throttling range.
One thing I don't understand is, if the program calculates its own
capacities, then how could T24 standard have such a huge unmet load
hours.
Anyways, is there a way to fix the T24 standards unmet load hours even
though the model complies with T24?
Also another question.... How do I check the heating capacity of the
system designed in Btu per sf in the output files... we typically see
around 20 Btu per sf as the heating capacity required in Phoenix...
assuming similar condition in inland San Diego... I wanted to check the
heating consumption against capacity, the program is showing a really
low heating need in San Diego which I seriously doubt... see attached
compliance report...
Any help would be greatly appreciated.
Thanks
Prem
Premnath Sundharam, Assoc. AIA, LEED AP
Architectural Designer | Senior Associate
psundharam at dlrgroup.com
DLR Group
Architecture Engineering Planning Interiors
o: 602/381-8580
6225 North 24th Street, Suite 250 Phoenix, AZ 85016-2020
dlrgroup.com <http://www.dlrgroup.com/> | listen.DESIGN.deliver
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