How do you deal with exception (b) to G3.1.1?
Do you apply a single-zone system (1) to spaces that have a COOLING or HEATING PEAK LOADS that differ more than 31.2 W/m2 to other spaces served by the main system (what I mean for "peak thermal loads" referred by the standard), OR (2) to spaces that have PROCESS LOADS that differ more than 31.2 W/m2 to other spaces served by the main system (unregulated load, that is the literal meaning of "process loads" even referred by the stadard a few lines before)?
I've noticed some relevant consequences:
- if (a) you do not know it before sizing runs, and with the 4 rotations you can have different single-zone system spaces for each rotation (and therefore issues in filling data in Air-side HVAC sheet of the MEPC - Minimum Energy Performance Calculator)
- if (b) you know it before sizing runs and you have the same systems configurations for all the 4 baseline rotations, but the evaluation is limited to cooling baseline design, and what about Occupancy and Lights, other fixed (=not varying with rotation) internal gain that produce cooling loads too?
Thank you for any insight
Alessandro
Ale g
building engineer2 thumbs up
March 4, 2021 - 3:15 am
No one about this?
Tyler Thumma
7GroupLEEDuser Expert
67 thumbs up
March 4, 2021 - 3:51 pm
Actually it seems to refer to the peak internal loads (inclusive of equipment, occupancy, lighting, etc) rather than the cooling/heating peak (which would include envelope loads) or the process equipment only. I don't have a copy of the 90.1-2010 User's Manual, but the 90.1-2013 User's Manual (which is based on identical language for this exception) states "the exception is triggered when the difference in internal loads is more than 10 Btu/h∙ft² (31.5 W/m²)". Similarly, the PNNL 90.1-2010 PRM Manual's (https://www.pnnl.gov/main/publications/external/technical_reports/PNNL-2...) heading for this exception is "internal loads".
Ale g
building engineer2 thumbs up
March 8, 2021 - 12:42 pm
Thank you Tyler for you replay.
At the end it could have three interpretations, all referenced by standard or other relevant document.
It seems not to be an engaging issue by leeduser community, therefore it passes to be not an issue to me too