[Bldg-sim] Tolerance for unmet load hours

[Annie Marston]

I had the very same question and couldn't find the answer, but I was told that Trane Trace uses 1.1°F / 0.83°C. So we use that as a default when modelling for LEED. But the only thing I could find was as Michael Tillou says, it must be the same for baseline and design case.

I am interested to know what other people have experienced.

Thanks!

Annie

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From: Bldg-sim [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Michael Tillou
Sent: Wednesday, May 28, 2014 1:44 PM
To: 'King-Scott, Celia'; bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Tolerance for unmet load hours

Hi Celia,

ASHRAE 90.1 Appendix G would simply require that the tolerance be the same in both the baseline and proposed design energy models.

Cheers,

Mike


Michael Tillou, PE, LEED AP BD+C, ASHRAE BEMP
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From: Bldg-sim [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of King-Scott, Celia
Sent: Wednesday, May 28, 2014 1:38 PM
To: bldg-sim at lists.onebuilding.org<mailto:bldg-sim at lists.onebuilding.org>
Subject: [Bldg-sim] Tolerance for unmet load hours

Does anyone know what the ASHRAE limitation on the tolerance (in F) for unmet load hours is. Design Builder/EnergyPlus appears to have this tolerance for the heating and cooling setpoint. It is defined as the maximum difference from the heating setpoint when the reporting the time setpoints are not met (for both heating and cooling). If the zone temperature is below the heating/cooling setpoint by more than this value an unmet load hour will be reported.
There is a similar input in eQUEST called the 'Cool control range' and 'Heat control range'.
If you increase the value of this tolerance you will get smaller number of unmet load hours. I was told once that ASHRAE has a limit on what this tolerance is however I am unable to locate it.
Any help would be greatly appreciated.
Thank you!


Best regards
for KEMA Services Inc., USA

Celia King-Scott PE, BEMP, LEED® AP BD+C
Senior Engineer, Sustainable Buildings & Communities

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