[Equest-users] Crazy High Unmet Heating Hours on ASHRAE 90.1 Baseline Model

Jones, Christopher Christopher.r.Jones at wsp.com
Wed Aug 1 08:18:02 PDT 2018

The heating setpoint is 70° F. 90.1 says to size the system based on a 20° F delta T between space temperature setpoint and supply air temperature. Base on that, I revised the A1Sys Heating tab:

[cid:image001.jpg at 01D42989.4E13B600]

This reduces the total unmet heating hours for that system from 40348 to 3148.

I would then increase the minimum flow percentage and reheat delta T in the remaining problem zones. Q = 1.08 * (cfm * delta T). To meet the heating loads either the supply flow or delta T have to be increased.

Christopher R Jones, P.Eng.
T+ 1 416-644-0252

[cid:image005.png at 01D42989.4E13B600]

From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Dana M. Savage via Equest-users
Sent: Monday, July 30, 2018 3:09 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Crazy High Unmet Heating Hours on ASHRAE 90.1 Baseline Model

Good afternoon everyone!

I am working through the process of creating an ASHRAE 90.1-Appendix G baseline model and cannot understand where I've gone wrong in the design.  I have done a number of energy audits using eQuest but have never been through the LEED process and thus this is my first attempt at dealing with 90.1 directly.  Any help you may offer would be much appreciated and I am more than happy to compensate any time spent.

The building is a System Type 7 - VAV with Reheat - and my cooling hours are 0.  However, I can't seem to get my VAV terminal units to provide enough heat at any time during the year.  When I allow eQUEST to size the capacities on their own, not enough heat is added and temperatures throughout the winter and in all zones remain below 60F.  But when I specify a Maximum Heating Rate at the Zone Terminal the addition rate doesn't change!  I've tired increasing the throttling range, which had some effect.  The only thing that had a significant effect on the unmet heating hours was increasing the Heating Design Temperature for each Zone.  But this also had the effect of dramatically increasing the cooling unmet hours!  Finally, and most confoundingly, my heating energy consumption in the winter is significant!  Where is it all going?? I am at a total loss.

I hope I was clear in articulating my issue and again appreciate your assistance.

Dana M. Savage :: Mechanical Engineer
CONTACT :: DSavage at cfrengineering.com<mailto:DSavage at cfrengineering.com> :: C: 301.717.0003
ADDRESS :: 20251 Century Blvd. Suite 120 :: Germantown, MD 20874


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