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

Javed Iqbal eee.javed at gmail.com
Thu Oct 30 00:27:31 PDT 2014

```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> 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]
> *Sent:* Wednesday, October 29, 2014 6:51 PM
> *To:* Bernie Hont; 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
> <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
> *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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