[Equest-users] Unmet hours BOTH htg & clg

[Chapin, Alex N]

Hi Pasha,

The unmet load hours are coming from AHU-15. I noticed the following items that may help you debug the issue:


1.      The SS-R report indicates that the zone L2ComputerLabZone is within the 100+ part load range for 8760 hours/yr. This is causing AHU-15 to not be able to reset its supply air temperature which means you are doing a lot of simultaneous heating and cooling in the other zones, especially at the perimeter. This could reduce unmet load hours and it will also reduce energy use if you put that zone on its own single zone system.

2.      You are using the Powered Induction Unit system type but have all of the zone terminal types set to Std VAV Terminal. You should set any perimeter zones to either Series or Parallel PIU terminal type. This will allow those zones to pull induced air from warmer core zones with the Std VAV Terminal terminal type. Note that if you want to keep L2ComputerLabZone on AHU-15, applying the correct terminal types may help also since that zone will have excess heat to share with other zones.

3.      You set OA ratio at the system level of 0.22 but the SV-A report states 0.454. If the correct value is 0.22, then you need to reduce the cfm/person OA input found at the zones because these will override the system level OA ratio.

4.      You might want to check that the supply airflow and design cooling supply air temperature and zone reheat delta T are sufficient for the loads. You are hard coding the supply airflow at the system, it might be helpful to set it at the zone if you know the required airflow per zone (I’ve found that eQUEST doesn’t do a great job at distributing airflow to the zones sometimes).

5.      Switching the zone thermostat type to Reverse Action from Proportional helps also (I did a quick test and overall unmet hours went from 65 to 55%).

6.      SS-O report seems to show more unmet heating hours in the morning, therefore it may be worth revising the fan schedule to include up to 6 hours of optimum start period (use a value of -999).

Good luck.

Alex Chapin PE, BEMP, LEED AP BD+C, O+M
Energy Engineer | Mason & Hanger
A Day & Zimmermann Company
O 804.521.7072
4880 Sadler Road, Suite 300 | Glen Allen, VA 23060
masonandhanger.com<http://www.masonandhanger.com/>

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From: Pasha Korber-Gonzalez [mailto:pasha.pkconsulting at gmail.com]
Sent: Tuesday, January 12, 2021 3:26 PM
To: eQUEST Users List <equest-users at lists.onebuilding.org>
Subject: [Equest-users] Unmet hours BOTH htg & clg

Hi guys/gals-- it's been a long time since I've posted, mainly because its been a loooong time since I've been working on energy models.

My skills might be a bit rusty, but you never forget how to 'ride a bike', truly...

I would like some help with trying to figure out why my hours out of throttling range are coming in like they are-- I've managed to reduce them, but they are not in compliance for the LEED review yet.  And I have virtually "peeled" back all of my design inputs in the HVAC systems (specifically for AHU-15) where the problems are occurring.

Can any of you please help me to take a second look at my file and see if you can find what aspect of the inputs are pushing out my throttling hours?  I appreciate any insight/info/time you can provide,  The attached file is in a cold Michigan climate, it has a college schedule, and basic loads with LED lighting system, so nothing internal should be pushing the loads and controls out of throttling range.  I'm available to chat about this if any of you would like too.  Ph 308-763-1593.

I've been struggling with getting the hours in range for a few months now... please help.  Thank you!
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