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90.1 PRM: G3.1.1 Single Zone system type exception based on Internal Load AND EFLR #1526

Open eringold opened 1 year ago

eringold commented 1 year ago

@dmaddoxwhite @lymereJ @weilixu

In model_differentiate_primary_secondary_thermal_zones, it appears that both the maximum internal load check AND the equivalent full-load hours check are used to determine whether a zone is removed from the primary system type: https://github.com/NREL/openstudio-standards/blob/d332605c2f7a35039bf658bf55cad40a7bcac317/lib/openstudio-standards/standards/ashrae_90_1_prm/ashrae_90_1_prm.Model.rb#L2892-L2912

if max_load_diff >= load_limit && eflh_diff > eflh_limit

This seems to differ from the language of both 90.1-2016 Appendix G:

image

as well as the Standard 90.1-2016 Performance Rating Method Reference Manual: image

Should Line 2901 be if max_load_diff >= load_limit || eflh_diff > eflh_limit, or has there been a new interpretation of this part of Appendix G?

dmaddoxwhite commented 1 year ago

The tests are done in three steps, since each time we eliminate a zone, it affects the "average of other spaces". In the first step we eliminate zones that meet both criteria (hence the "&&"). In the second step we check EFLH, and in the third step we check load. This logic was added to the draft 90.1-2019 PRM reference manual, but it looks like that hasn't been published yet.

eringold commented 1 year ago

Hm, I see that now as I read farther in the code.

This is ultimately causing me to hit https://github.com/NREL/openstudio-standards/issues/1523, because for a building which operates 24/7, I have data/electric rooms with high internal loads that area already served by FCUs in the proposed model being included with the primary system type in the baseline model. The EFLH check isn't capturing them, but I was expecting the internal load check would.

I'll have to do more digging. Thank you for clarifying!