[Equest-users] Appendix G "riding the pump curve"

[Maria Karpman]

Bill,

 

As far as I understand G3.1.3.5 stems from the following prescriptive
requirement of 90.1:

 

6.5.4.1 Hydronic Variable Flow Systems. HVAC

pumping systems that include control valves designed to

modulate or step open and close as a function of load shall be

designed for variable fluid flow and shall be capable of reducing

pump flow rates to 50% or less of the design flow rate.

 

There is also this example in 90.1 User Manual:

 

Example 6-LLL-Variable Flow Hydronic System

Q

A hot water system has two-way valves at most coils, but occasional
three-way valves are

provided at the end of branches to ensure flow through them. Does this
design comply

with the Standard?

A

Yes, provided the total flow through three-way valves does not exceed 50% of
design

flow. While these end-of-line valves are allowed, they are not usually
required except

perhaps in very large campus systems. Water piping is generally designed for
water

velocities that are high enough so that the time it takes for chilled or hot
water to leave

the plant and reach the control valve will be seconds or minutes, a small
enough time

that the system will not be "starved" and no discomfort will result. To
minimize energy

use in variable flow systems, limit the use of three-way valves to one or
two to prevent

pump dead heading.

 

I typically follow the approach that you described on LEED models, but
arguably the minimum flow can be increased to 0.5 based on the above. I am
curious to hear what others think!

 

Maria

 

From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On
Behalf Of Bishop, Bill
Sent: Thursday, November 20, 2014 4:32 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Appendix G "riding the pump curve"

 

I'm reposting my question below as it has been a few days with no reply.

Thanks!

~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


 <mailto:wbishop at pathfinder-ea.com> bbishop at pathfinder-ea.com
<http://www.pathfinder-ea.com/> www.pathfinder-ea.com


http://png-5.findicons.com/files/icons/977/rrze/720/globe.pngCarbon Fee and
Dividend - simple, effective, and market-based.

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Bishop,
Bill
Sent: Wednesday, January 26, 2011 2:33 PM
To: Omar Katanani; equest-users at lists.onebuilding.org
Subject: [Equest-users] Appendix G "riding the pump curve"

 

To model variable loop flow with a single-speed pump, at least one 2-way
valve is needed in a loop. How are people approaching the requirement for
"riding the pump curve" in HW and CHW loops per G3.1.3.5 and G3.1.3.10? Set
all system/zone valves to 2-way and use the default loop-mimimum-flow ratio
of 0.05?

 

Thanks,

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   

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