[Equest-users] Again: eQUEST - serious trouble with LEED review

[Heinrich.ib-bauklima.de]

Bill,
 
I didn't oversize the chillers and boilers. I used 0.5 for the capacity
ratios of the chillers and boilers as you told me, more precisely 0.575 for
the 2 chillers and 0.625 for the 2 boilers.
You can see it in the eQUEST model.
eQUEST calculates this big capacities that create this poor part loads.
Don't you think part loads < 50% are a problem for the model review?
 
Heinrich
 

  _____  

Von: Bishop, Bill [mailto:wbishop at pathfinder-ea.com] 
Gesendet: Dienstag, 25. Januar 2011 18:20
An: Heinrich.ib-bauklima.de; equest-users at lists.onebuilding.org
Betreff: RE: Again: eQUEST - serious trouble with LEED review


Heinrich,
 
As Ravi Srinivasan suggested yesterday, don't oversize the chillers and
boilers. Use 0.50 for their capacity ratios. I believe the consensus in the
modeling community is to do the oversizing only at the system level,
adjusting the cool sizing ratio and heat sizing ratio (not the system sizing
ratio). It would not be surprising for the chillers and boilers to spend a
majority of the time at low part load, since they are autosized based on
total design loads and flowrates of all attached equipment and processes.
This is not a "problem" for the baseline.
 
Bill** 

  _____  

From: Heinrich.ib-bauklima.de [mailto:heinrich at ib-bauklima.de] 
Sent: Tuesday, January 25, 2011 5:41 AM
To: Bishop, Bill; equest-users at lists.onebuilding.org
Subject: Again: eQUEST - serious trouble with LEED review
 
Bill,
 
thank you for your advice.
I followed your instructions to change the model.
So I resolved the indicated reviewer comments.
Now there is no difference between secondary and primary chilled water loop.
 
But now I have the dilemma that chillers and boilers of Baseline are heavily
oversized and are not sized to 115% and  125% respectively according to
demands of ASHRAE-90.1 App. G.
For checkup you can look at the Screenshots of the PS-C report, PV-A report
and the SS-D report that I have attached.
The part load of the chillers is about 40%-50% meaning a size 200%-250% (see
pump secondary CHW in PS-C report). 
The part load of the boilers is about 50%-60% meaning a size of 167%-200%
(see pump HW in PS-C report).
 
So I still have a serious problem. Any help would heavily appreciated.
Can we solve this problem in eQUEST?
 
Heinrich
 
 

  _____  

Von: Bishop, Bill [mailto:wbishop at pathfinder-ea.com] 
Gesendet: Montag, 24. Januar 2011 19:49
An: Heinrich.ib-bauklima.de; equest-users at lists.onebuilding.org
Betreff: RE: [Equest-users] eQUEST - serios trouble with LEED review
Heinrich,
 
The chiller pumps requirement your reviewer is referring to is in Section
G3.1.3.11 (not G3.1.11). The model you sent currently has one primary CHW
pump attached to each of your two chillers, a separate primary CHW pump on
the primary loop, one secondary CHW pump and one condenser water pump. You
labeled your primary chiller pumps "Secondary Pump CHW 1" and "Secondary
Pump CHW 2", which is probably why the reviewer thinks you only have one
primary pump (the one on the primary CHW loop labeled "Primary CHW Pump"). I
suggest making the following changes:
*	Delete the separate pump attached to the primary CHW loop 

*	Relabel the chiller pumps to indicate they are primary loop pumps 

*	Add condenser water pumps for each chiller through the "Loop
Attachments" tab of the chillers; delete the other CW pump. 

*	Change both the primary loop and secondary loop sizing option to
"secondary" to allow eQUEST to size based on coil loads. 

*	Change the chiller capacity ratio for each chiller to 0.50. (Or use
0.575 if you want to oversize by 15% per G3.1.2.2 - I don't know if this is
supposed to apply to chillers.) Each chiller will be sized for half the
total load. 

*	Allow the chiller capacity to default (remove the 0.9 MBtu/h). 

*	Make sure you include both/all pages of the PS-C report - your
reviewer will then see that the secondary CHW pump is variable flow. (Your
zones have two-way valves already.) 

*	The PV-A report will show that the total primary CHW pump flow will
nearly match the secondary CHW pump flow. 
 
Regards,
Bill
 
William Bishop, PE, BEMP, LEEDR AP | Pathfinder Engineers & Architects LLP
Mechanical Engineer
 
134 South Fitzhugh Street                             Rochester, NY 14608
T: (585) 325-6004 Ext. 114         F: (585) 325-6005
wbishop at pathfinder-ea.com       www.pathfinder-ea.com
<http://www.pathfinder-ea.com/> 
P   Sustainability - the forest AND the trees. P** 

  _____  

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of
Heinrich.ib-bauklima.de
Sent: Monday, January 24, 2011 12:28 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] eQUEST - serios trouble with LEED review
 
Hi Everyone,
 
I got a review comment that got me in big trouble and I can't find the
solution yet.
May be there is no solution for this in eQUEST....!
I rate this forum as the very best address for difficulties with eQUEST and
LEED EAc1 simulation.
So please give me some guidance and feel free to testthe model attached.
 
Hereare the two comments of the reviewer.
"It appears as if the pumps and circulation loops were not modeled correctly
for the Baseline Case. It appears based on the PS-C reports that there is
only one primary chilled water pump and one condenser water pump for the
Baseline Case. However, ASHRAE 90.1 Section G3.1.11 requires that each
chiller be modeled with separate condenser water and chilled water pumps
interlocked to operate with each associated chiller. Please model two
primary chilled water pumps and two primary condenser water pumps in
accordance with Section G3.1.11. Also update the chilled water valves to
two-way valves so that the secondary chilled water loop operates as a
variable flow loop with pumps riding the curve. Provide updated PS-C reports
confirming that the changes have been made."
"It is unclear why the pump flow for the secondary chilled water loop is so
much larger than that of the primary chilled water loop when the temperature
differential for both loops is expected to be the same. It also appears
based on the outputs in PS-C that the secondary chilled water loop is
operated at the same load for every hour that it is on even though it is a
variable speed pump. Please update the secondary chilled water loop flow to
be consistent with the primary chilled water loop flow, and confirm that the
secondary chilled water loop is operating as a variable flow loop."
 
I have to say:
I didn't see any equest-model modeled with separate condenser water and
chilled water pumps interlocked to operate with each associated chiller. 
I manually resized the boilers and chillers with reference to SS-D report,
because auto sizing of eQUEST generated capacities that were double the size
of SS-D report. Resizing of the volume flow of secondary loop of chillers
according to primary loop of chillers generated warningmessages but changed
nothing.
 
Heinrich
 
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