[Bldg-sim] DES Option 1 Pump Power

[Bishop, Bill]

Kevin,
Here's my interpretation of the LEED comment: An Option 1 heating loop is equivalent to a primary loop upstream with a secondary loop downstream. However, Appendix G requires heating loops to be modeled as primary-only. The baseline pump power allowance is based on a primary loop only, and there is no way (according to the LEED comment) to separate the primary loop pump power (which is excluded) from the secondary loop pump power. Therefore, the reviewer wants to see identical heating loop pump power in baseline and proposed.
However, in your case, your district/campus loop is a steam loop which you could argue has no pump power, which could potentially justify modeling 19W/gpm for the baseline heating loop and your actual separate steam and HW loops (from a steam-to-HW heat exchanger, correct?) in the proposed. Unless you get a more thorough review comment or find a CIR explaining it better, I would try that approach and explain it in detail with the revised submission.

Regards,
Bill

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

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From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Kevin Kyte
Sent: Wednesday, December 18, 2013 3:43 PM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] DES Option 1 Pump Power

Hello, I am reviewing an energy model and associated LEED comment for a DES project that is modeled using Option 1 (stand-alone scenario), there is no specific reference to pump power within the guidance document.  The LEED comment states:

"Since the project follows the DES guidance Option 1, only the Baseline secondary distribution loop from Appendix G, with the relevant pump and loop parameters from that secondary loop must be modeled. Additionally, since the distribution loop for hot water is a primary-only loop that includes both upstream and downstream equipment, this option is not available for purchased steam or hot water, and the Baseline Case hot water pumps must be modeling identically in the Baseline and Proposed Cases based on the Proposed Case values.

I believe the directive here is to model the baseline pumps identical to the proposed and equal to the proposed values.  The LEED review comment states that the loop includes upstream equipment when Option 1 is specifically to exclude upstream equipment and model stand-alone.  The energy source is purchased heat.

I think the problem is that I see that the steam coils in the roof-top units are modeled in the same loop as the HW terminal units.  If I separate these into two loops I should be able to claim energy savings for the pump power associated with the HW terminal units.  Is this correct or is it still required to model the HW terminal unit pump power identical in baseline and proposed cases?
Thank you.


Kevin J. Kyte, PE BEMP LEED AP
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