[Equest-users] LEED Comment for FAN EFLH--help please

Thu Mar 30 14:37:50 PDT 2017

To answer an unanswered (I think) part of your query:  Yeah it’s totally fine to have substantially different FLEH’s for LEED projects – you just need to be able to rationally explain the why to yourself and your reviewer.  Be mindful diving a sum of instantaneous power draws into annual energy consumption is an arbitrary (if still useful for QC) metric – can miss a lot of nuance.  You should also in due diligence explore & address the cited requirements and ensure the actual prescriptive language is reflected in your models’ behavior.

Suggested exercise before diving very deep into hypothetical causes – Line up your hourly fan end-use draw on EM1 (library report:  File --> Export --> Hourly results) for your proposed and baseline case in Excel, and plot a line graph overlaying both series together.  Stretch the graph out so you can see what’s happening on a weekly/daily/hourly basis, and observe how the two lines are different.  Should be visually pretty apparent if & to what extent one case is cycling more during the evening/daytime and weekdays/weekends.

You might also observe the curves are pretty darn similar in shape, just very different in magnitude, which would suggest their equivalent runtime hours are actually similar and the root cause is largely in the power inputs.

That should help you as a starting point to filter through the many possibilities of how & why your FLEH’s are different.

~Nick

[cid:image001.png at 01D2A973.29185780]
Nick Caton, P.E., BEMP
  Senior Energy Engineer
  Regional Energy Engineering Manager
  Energy and Sustainability Services
  Schneider Electric

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From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Pasha Korber-Gonzalez via Equest-users
Sent: Thursday, March 30, 2017 4:22 PM
To: Michael Mantai <mmantai at systemworcx.com>
Cc: eQUEST Users List <equest-users at lists.onebuilding.org>
Subject: Re: [Equest-users] LEED Comment for FAN EFLH--help please

thank you Bill & Michael for some insights.

The Baseline model is Pkg VAV units with hot water heating
The Proposed model is VAV with heat recovery chilled water and hot water heating with condensing boilers.

When I read the SS-L reports I can see some differences in the run hours of the fans, but I don't really know what to explain about the differences that I'm seeing from the Proposed & Baseline models.  All the eQuest related info doesn't really tell me where these values in the SS-L reports are generated from.  Below is the Proposed SS-L for AHU-1 and the Baseline SS-L for one of the Baseline systems.  One thing at the bottom of the report shows that the fan elec kWh is noticeably smaller for the proposed system versus the baseline system.

[Inline image 1]

[Inline image 2]

On Thu, Mar 30, 2017 at 2:23 PM, Michael Mantai <mmantai at systemworcx.com<mailto:mmantai at systemworcx.com>> wrote:
What type of HVAC systems do you have in the baseline vs. proposed?  As noted in the comment, the baseline system fans should run continuous during occupied hours and cycle at night.  If your proposed case system has dedicated outside air systems, those fans would run continuously during occupied hours but other fans could cycle on temperature.  I’ve done schools that use a DOAS unit coupled with fan coils or heat pumps.  In the proposed case I set the DOAS to run continuous and set the fan coils/heat pump fans to cycle on temperature, which would result in less fan hours.  I’m also surprised your proposed fan kW is that much higher than baseline, so you might check that.

From: Equest-users <equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org>> on behalf of Pasha Korber-Gonzalez via Equest-users <equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>>
Reply-To: Pasha Korber-Gonzalez <pasha.pkconsulting at gmail.com<mailto:pasha.pkconsulting at gmail.com>>
Date: Thursday, March 30, 2017 at 3:51 PM
To: eQUEST Users List <equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>>
Subject: [Equest-users] LEED Comment for FAN EFLH--help please

Hello fellow eQuesters,

I'm sure we all get the standard LEED review comment regarding Fan equivalent full load hours (EFHL).

I received this one on my current project (elementary school in Ohio with heat recovery units.)  I have confirmed that my fan schedules for both models are exactly the same.  But I do have drastically different EFLH values for the baseline (over 3,000) and proposed (less than 1,500).

I have made changes in my models, but I cannot seem to get the proposed hours over 1,600 of run time.

QUESTION:  Do any of you have any experience of suggesting to the LEED Reviewer that it is possible to have this significant of difference between the two models hvac systems AND how can I show justification for these run hours??  Any advice & suggestions are welcomed at this time.

Here is the LEED comment I received with highlighted notes:
. Table EAp2-5 of the form indicates that the equivalent full load hours for interior fans in the Proposed and Baseline model are 1,200 hours (57,951 kWh/48.31 kW) and 3,702 hours (130,702 kWh/35.31 kW), respectively; however, it is unclear if the HVAC fans are modeled as cycling to meet the cooling and heating loads of the building during unoccupied hours. Table G3.1.4 in the Proposed building column requires that HVAC fans that provide ventilation air in the Proposed model must be modeled as operating continuously during occupied hours and cycled to meet the cooling and heating loads of the building during unoccupied hours, unless one of the exceptions of Table G3.1.4 are met. In addition, Section G3.1.2.4 requires that supply and return fans reflected in the Baseline model must be modeled as operating continuously during occupied hours and cycled to meet the cooling and heating loads of the building during unoccupied hours,
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