[Equest-users] High pumps equivalent full load hours in the model

Fri Jan 25 12:04:19 PST 2019

If the energy (kWh) of the pump divided by the peak demand (kW) is something close to 8760, this indicates not only that the pump is running 24/7, but that the pump power does not vary. Some baseline loops are required to have VSD pumps. But even single-speed pumps are required to be “variable flow” by “riding the pump curve”. To model this, you have to use two-way valves. Alex Chapin mentioned this in his reply below. When you make the changes Alex describes below (and one more – remove the process load on the secondary chilled water loop), the EFLH drops down to around 6,000 hours for all three loops.
~Bill

William Bishop, PE, BEMP, BEAP, CEM, LEED AP
Senior Energy Engineer

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From: Equest-users <equest-users-bounces at lists.onebuilding.org> On Behalf Of Nicholas Caton via Equest-users
Sent: Friday, January 25, 2019 1:51 PM
To: Chapin, Alex N <Alex.Chapin at masonandhanger.com>; Morteza Kasmai <morteza.kasmai at gmail.com>
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] High pumps equivalent full load hours in the model

Not to make this more difficult than necessary, but could I take a step back and ask:  Can anyone comment regarding what exactly between LEED and/or 90.1 precludes 24/7 hydronic loop circulation?

This is NOT an uncommon control scheme to encounter in the real world, and the inherent simplicity of 24/7, constant-speed operations carry some real advantages with respect to system first-cost, simplicity / troubleshooting, and maintenance over time.

That’s not to say variable flow pumps, demand based on/off controls, and other schemes are a bad idea (I’m regularly implementing such strategies where it pencils out), but I’ve encountered a number of cases where variable-flow upgrades implemented badly can end up causing more harm ($$$/downtime) than good.

I am left sincerely interested to learn and understand what exactly the LEED reviewers may be expecting/requiring of hydronic system pumping operations.

Thanks,

~Nick

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  Energy and Sustainability Services
  Schneider Electric

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From: Equest-users <equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org>> On Behalf Of Chapin, Alex N via Equest-users
Sent: Monday, January 21, 2019 7:14 AM
To: Morteza Kasmai <morteza.kasmai at gmail.com<mailto:morteza.kasmai at gmail.com>>; equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: Re: [Equest-users] High pumps equivalent full load hours in the model

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Hi Morteza,

I looked at the file quickly and it seems that there are some changes that you can make to reduce the EFLHs slightly (I was able to get it to 8,146 hours/year by changing to two-way HW and CHW coils, moving cooling coils to secondary loop, readjusting pump flows and power after other changes, and setting loop operation to demand), but it seems like the underlying cause of the high EFLHs is probably due to having VAV systems which only serve interior spaces which are probably going to be in cooling mode year round.

Note that I think you can model the corridors on floors with residential as PTACs also. I believe that the reviewer should allow you to be flexible in how you define the corridor off of residential spaces. This might help reduce the pump EFLHs for primary and secondary chilled water pumps, assuming those VAVs which only serve core spaces are part of what is driving the high EFLHs.

Alex Chapin EIT, BEMP, LEED AP BD+C, O+M
Energy Engineer | Mason & Hanger
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From: Morteza Kasmai <morteza.kasmai at gmail.com<mailto:morteza.kasmai at gmail.com>>
Sent: Friday, January 18, 2019 1:29 PM
To: equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: [Equest-users] High pumps equivalent full load hours in the model

Hello all,

I received following LEED review comment:

“The Baseline model pumps equivalent full load hours (determined by dividing the total annual pumps consumption (45,761 KWH) by the pump peak demand (5.426 KW) reflected in the simulation output report) is 8,433 hours/year, which is unexpectedly high given the anticipated schedule of operation for the project.”

This is a 9 story residential building with unfinished retail space in the ground floor. Primary HVAC system in the baseline case is PTAC and the secondary system that serves non-residential spaces is System 7 – VAV with reheat and chilled water. HVAC system in unfinished retail space of the propose model is System 7 as well. Pumps equivalent full load hours for the proposed model is 8,089 hours/year (15,401/1.905), which is close to EFLH of the baseline case.

Is this high EFLH loads relate to the primary and secondary pumps in both of the models and are justifiable or there is something wrong with the models. Attached are inp and pd2 files of the baseline model from version 3.65 build 7173.

Thank you for your help,

Morteza Kasmaei
Senior Architect
LEED AP BD+C, GGP

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