[Equest-users] Air cooled chillers versus water cooled chillers

Thu Oct 29 22:12:39 PDT 2015

Hi Sambhav,
I got that and was a typo error in my previous mail. The issue is not about 22 W/gpm in baseline case, whether an air cooled chiller can perform equivalent to a water cooled centrifugal chiller. I have got the same type of results for two of my projects and meeting the mandatory requirement for LEED is depending on these results. Therefore, i am concerned.
Regards,Rathnashree

     On Thursday, 29 October 2015 1:13 PM, Sambhav Tiwari <tiwari.sambhav at gmail.com> wrote:

 Hi Rathanashree,

22W/gpm is the requirement of baseline model not for proposed case and it has to be modeled for both primary & secondary pump in baseline.
Warm RegardsSambhav
On Wed, Oct 28, 2015 at 5:03 AM, Cam Fitzgerald <cam at energyopportunities.com> wrote:

Good morning, all! A little insight on this issue. There is an ASHRAE Interpretation ASHRAE/IES IC 90.1-2007-14 that indicates the chilled water pump power allowance is to be split between the primary and secondary pumps in the Baseline model. I am unsure of the date the interpretation was issued, but if using Appendix G modeling protocol for any other purpose other than LEED projects, this guidance should be followed from the issue date on. This ASHRAE Interpretation was implemented for LEED projects by LEED Interpretation 10299 which was issued on 01/01/2014 and all projects registered after that date must follow this protocol as described in the interpretation. Hope this helps.  Cam Fitzgerald Energy Opportunities/a 7group company   From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Rathna Shree
Sent: Wednesday, October 28, 2015 1:39 AM
To: David Eldridge; Bosch, Crina; Bishop, Bill; Sambhav Tiwari
Cc: Equest Users Mailing List
Subject: Re: [Equest-users] Air cooled chillers versus water cooled chillers Sorry, i meant primary and secondary pumps.  Now the main issue is my proposed case with variable primary and air cooled chillers are performing equal or better than the baseline case. Is this possible?  On Wednesday, 28 October 2015 2:42 AM, David Eldridge <DEldridge at grummanbutkus.com> wrote: I didn’t follow this thread all of the way earlier, but the idea might be that in the baseline case the 22 W/gpm is split between the primary and secondary pumps in some manner. The proposed case has the design values to go from, and may be primary only or primary secondary – whatever the proposed motor power and configurations is, use that. David                                                                                                  David S. Eldridge, Jr., P.E., LEED AP BD+C, BEMP, BEAP, HBDPGrumman/Butkus Associates                                                                                                  From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Bosch, Crina
Sent: Tuesday, October 27, 2015 3:32 PM
To: Rathna Shree <rathnashreep at yahoo.in>; Bishop, Bill <bbishop at pathfinder-ea.com>; Sambhav Tiwari <tiwari.sambhav at gmail.com>
Cc: Equest Users Mailing List <equest-users at lists.onebuilding.org>
Subject: Re: [Equest-users] Air cooled chillers versus water cooled chillers Rathnashree,  I didn’t understand your statement that “22W/gpm has to be split between base and proposed case based on a ASHRAE interpretation.”As Bill mentioned below, for the Baseline Model The CHW pump power must be calculated as 22 W/gpm. Usually , you check in PV-A report your autosized gpm and that way you can calculate you pump power and see if it’s input correct. The Proposed Model Pump power must be input as scheduled per design which is totally different than ASHRAE requirement.   Hope this may help, Crina.   cbosch at karpinskieng.com  From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Rathna Shree
Sent: Tuesday, October 27, 2015 3:49 AM
To: Bishop, Bill; Sambhav Tiwari
Cc: Equest Users Mailing List
Subject: Re: [Equest-users] Air cooled chillers versus water cooled chillers Dear Sambhav/ William Bishop Thank you for the replies. I have modelled the baseline case as per the requirements of Appendix G (Pumps, cooling tower power etc is modeled as per ASHRAE 90.1 2007). Just to confirm, 22W/gpm has to be split between base and proposed case based on a ASHRAE interpretation. With the exact modeling, i am getting result where variable primary pumping system - air cooled screw chillers are performing almost equal or better than baseline centrifugal chiller. These results seem little surprising. So i am unsure whether it is correct.  It would be really helpful if the experts can confirm the results. Thank you. Regards,Rathnashree    On Monday, 19 October 2015 7:27 PM, "Bishop, Bill" <bbishop at pathfinder-ea.com> wrote: Rathna,There are several inputs in eQUEST that impact your CHW plant pumping energy as modeled for Appendix G:1.)    CHW pump power should be 22 W/gpm per G3.1.3.10. I don’t recall how “official” it is but many on this forum interpret this as for the entire primary/secondary pumping, meaning it should be split between the primary and secondary pumps. (For example, 10 W/gpm for the primary loop pump and 12 W/gpm for the secondary loop pump.) Splitting vs. not splitting is one of the major influences of Baseline pump power.2.)    CW pump power should be 19 W/gpm per G3.1.3.11.3.)    CHW coils should use CHW-VALVE-TYPE of TWO-WAY to facilitate variable flow through the secondary loop, regardless of using a variable-speed drive for the secondary loop pump (for cooling capacity ≥ 300 tons) or “riding the pump curve” with a single-speed pump (cooling capacity < 300 tons).4.)    The loop HEAD-SETPT-CTRL and HEAD-SENSOR-LOCN have major influences on pump energy. There is no requirement in Appendix G. that specifies the type of control. In order of least to best efficiency, the settings are:a.      FIXED; AT-PUMPb.      FIXED; ENTERING-LOOPc.      FIXED; AT-COILSd.      VALVE-RESET; n/aI think FIXED, AT-COILS is a reasonable setting for both the Baseline and Proposed models, unless the Proposed design has the controls to survey the positions of all coils and implement the VALVE-RESET strategy, and then I use that in the Proposed.5.)    LOOP-OPERATION impacts all CHW end-uses (cooling, pumping, heat rejection) especially if cooling is not needed year-round. This is also not specified in Appendix G. STANDBY keeps the CHW plant running when any systems with CHW capability are running. DEMAND-ONLY turns the CHW plant off unless there is a coil or process load for that hour. I think either setting is fair as long as it is kept identical between the Baseline and Proposed models.Besides pumping energy, there is an easily-overlooked Baseline requirement per G3.1.3.11 of axial fan cooling towers with two-speed fans. Table 6.8.1G shows the minimum performance requirement of ≥38.2 gpm/hp. You have to calculate the fan kW from this based on the autosized tower flow and enter it as FAN-KW/FLOW or EIR. The eQUEST default EIR of 0.0105 for open towers is actually more efficient than the Table 6.8.1G requirement. Regards,~Bill William Bishop, PE, BEMP, BEAP, CEM, LEED AP | Pathfinder Engineers & Architects LLP
| Senior Energy Engineer |    |
|   |
| 134 South Fitzhugh Street                 Rochester, NY 14608 |
| T: (585) 698-1956                        F: (585) 325-6005 |
| bbishop at pathfinder-ea.com             www.pathfinder-ea.com |
| Carbon Fee and Dividend - simple, effective, and market-based. |

 From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Rathna Shree
Sent: Monday, October 19, 2015 1:03 AM
To: Sambhav Tiwari <tiwari.sambhav at gmail.com>
Cc: Equest Users Mailing List <equest-users at lists.onebuilding.org>
Subject: Re: [Equest-users] Air cooled chillers versus water cooled chillers Hi Sambhav, Does that mean, air cooled chillers with variable primary pumping system performance is almost equivalent or better than the ASHRAE 90.1 2007 defined water cooled centrifugal chiller system? Regards,Rathnashree  On Saturday, 17 October 2015 12:57 PM, Sambhav Tiwari <tiwari.sambhav at gmail.com> wrote: Hi Rathanashree, For me the results seems to be alright 1 Being a air cooled chiller with less COP than baseline water cooled your compressor energy consumption is increasing which is clear from the results . 2 Now there is a debate going these day to replace ( constant primary & variable secondary pumps) with variable primary pump system although many HVAC experts  advocate against it that it can have negative impacts on chiller too.But definitely it will save energy consumption under pumps which is clear from your results your proposed case is left only with VFD based primary pump compared with baseline of ( constant primary+variable secondary+constant condenser water pumps) therefore pumps energy is too less and justified to me. 3 Your cooling tower energy consumption will be nil in proposed case being a air cooled system that is also fine. But the main driver or  you can say main ECM in your analysis is variable primary and no secondary chiller which is contributing siginifant savings in pumps along with no cooling tower present hence your over all energy saving are positive. Hope this may help. Warm RegardsSambhav On Fri, Oct 16, 2015 at 11:50 PM, Rathna Shree <rathnashreep at yahoo.in> wrote:
Dear All, A project has 14 floors and 3.5 lakhs sq.ft. of conditioned area. The project is going for LEED certification. The baseline HVAC system will be Variable air volume system with water cooled centrifugal chiller of COP 6.1. LPD is maintained at 0.7W/sft. Building envelope is more or less equal to baseline case. In this scenario, the proposed HVAC system is air cooled screw chillers with variable primary pumping system. Even though the project is getting negative results in cooling category, there is a huge savings from pumps which is compensating for the negative in cooling energy consumption. Ultimately, the overall plant energy consumption (Cooling, heat rejection, pumps) is lesser in proposed case than base case. I am surprised with the result as i believe for such a building, water cooled chillers work more efficiently. For more clarity, the results are given as below: Base case: Cooling: 14,26,659 KWH, Heat rejection: 1,23,357 KWH, Pumps: 426,506 KWHProposed case: Cooling: 17,89,814 KWH, Heat rejection: 0 KWH, Pumps: 62,264 KWH These are results are for default chiller curves in both the cases. If air cooled part load values are used, then cooling energy consumption further reduces in proposed case. Then can it be concluded that air cooled with primary variable pumping system is a good alternative to use.  Is this conclusion appropriate? Are the results correct? Please help. Regards,Rathnashree
_______________________________________________
Equest-users mailing list
http://lists.onebuilding.org/listinfo.cgi/equest-users-onebuilding.org
To unsubscribe from this mailing list send  a blank message to EQUEST-USERS-UNSUBSCRIBE at ONEBUILDING.ORG

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20151030/bb467e6c/attachment-0002.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image002.jpg
Type: image/jpeg
Size: 1647 bytes
Desc: not available
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20151030/bb467e6c/attachment-0004.jpg>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image003.png
Type: image/png
Size: 3864 bytes
Desc: not available
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20151030/bb467e6c/attachment-0002.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image001.jpg
Type: image/jpeg
Size: 1517 bytes
Desc: not available
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20151030/bb467e6c/attachment-0005.jpg>