[Equest-users] Pump Power Limit (19W/gpm & 22 W/gpm)

[Bernie Hont]

Based on everything I have read through various sites and opinions it to take the loop flow from the PV-A report for condenser water and chilled water and use that as the basis for the flow. Multiply that flow by the W/GPM to get the maximum allowed. Then make sure that the sum of the power (KW) for all pumps under the PUMP section on that system do not exceed that maximum.

So in your case, you would use 500 GPM to determine the maximum. Thinking about it logically that would make sense. If you have a variable primary pumping system rather than a primary/secondary the total head for the variable primary at 500 GPM should be close to the split head of 500 GPM through the primary and the secondary loops separately.

From: Bishop, Bill [mailto:bbishop at pathfinder-ea.com]
Sent: Monday, November 03, 2014 9:18 AM
To: Javed Iqbal; Bernie Hont; DavidEldridge
Cc: equest-users at lists.onebuilding.org
Subject: RE: [Equest-users] Pump Power Limit (19W/gpm & 22 W/gpm)

So, does the ASHRAE interpretation IC 90.1-2007-14 imply that the "gpm" used in the calculation should be only the flow rate of the primary loop (or alternatively, only the secondary loop)? For example, if you have a CHW system with 500 gpm flow in the primary loop and 500 gpm flow in the secondary loop (they are only equal if the loop delta-t is equal), is the "gpm" in "22W/gpm" 500 gpm or 1000 gpm? I have not seen this explicitly defined anywhere.

Thanks,
Bill

William Bishop, PE, BEMP, BEAP, CEM, LEED AP | Pathfinder Engineers & Architects LLP
Senior Energy Engineer

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From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Javed Iqbal
Sent: Thursday, October 30, 2014 3:28 AM
To: Bernie Hont
Cc: equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: Re: [Equest-users] Pump Power Limit (19W/gpm & 22 W/gpm)

Here is the ASHRAE interpretation on this issue.

Hope this helps!

On Thu, Oct 30, 2014 at 6:08 AM, Bernie Hont <bhont at girard.com<mailto:bhont at girard.com>> wrote:
Thanks, I think I got it. Take the loop flow from the PV-A report for chilled water and condenser water systems, multiply by 22 and 19 respectively, and make sure the sum of pump energies for all pumps on each system matches the allowable.

From: David Eldridge [mailto:DEldridge at grummanbutkus.com<mailto:DEldridge at grummanbutkus.com>]
Sent: Wednesday, October 29, 2014 6:51 PM
To: Bernie Hont; equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: RE: Pump Power Limit (19W/gpm & 22 W/gpm)

Not quite, I think you are close though - try it this way: use the total plant GPM x W/gpm factor, and that gives your total watts to spread across any number of primary and secondary pumps (even if there was only one of each type). It is up to you to reasonably assign that power between multiple secondary and primary pumps.

As an example, if there are two equally-sized chillers and each has a dedicated primary pump, then each primary pump will have the same W/gpm for its half share of the flow.

If you assigned the secondary pump 15 W/gpm as an example, then 7 W/gpm would be left for each of the primary pumps, based on each pump's own gpm.

Total power and gpm are additive for pumps in parallel, but not W/gpm. W/gpm is additive for the total of the primary and total of the secondary, and should equal 22 W/gpm.

Likewise, assuming two dedicated condenser water pumps, each condenser water pump would have 19 W/gpm for its own share of the total gpm...gpm and total power will be additive, not W/gpm.

David


David S. Eldridge, Jr., P.E., LEED AP BD+C, BEMP, BEAP, HBDP
Grumman/Butkus Associates



From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Bernie Hont
Sent: Wednesday, October 29, 2014 4:49 PM
To: equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: [Equest-users] Pump Power Limit (19W/gpm & 22 W/gpm)

For systems >300 tons where 2 chillers and therefore 2 primary chilled water and 2 condenser water pumps are present: do the 19 and 22 limits for condenser and chilled water pump energy apply to all pumps together? For example, would I take the W/gpm for the secondary chilled water pump and then add both the W/gpm for the two primary chilled water pumps to get to 22 total? Same for the condenser pumps, the sum of the W/gpm for both pumps should equal 19? This question has been answered numerous times before and the consensus has always been the sum of a single primary and single secondary should equal the limit, but I cannot find an instance where it was answered regarding multiple primary pumps.

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Javed Iqbal, LEED AP, CEA
Sr. Energy Analyst





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