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#3163 CBECC-Com 2019: Question on DCV
WontFix
None
Other
CBECC-Com
Medium
CBECC-Com 2019.1.1
2020-01-24
2020-01-15
No
User - Question on Demand Control Ventilation: the language of Section 120.1(d)3 “Required Demand Control Ventilation” specifies that DCV controls are required for spaces with a design occupant density of at least 25 people per 1000 SF, if “the system serving the space has one or more of the following…” – does the word “system” include a dedicated outside air system (DOAS) or just the space conditioning system (i.e. a zone system like a WSHP or 4-pipe FCU)? Does it make a difference if the DOAS is decoupled from the zone system, or if OSA is ducted directly into or into the return plenum? Does it make a difference if the DOAS provides fully conditioned OSA vs tempered or unconditioned OSA? This assumes the DOAS is >3,000 CFM (one of the three listed system requirements).
For example, would a 1,000 SF space with 25 people per 1000 SF, which does not meet any of the exceptions to 120.1(d)3 with 500 CFM of OSA but with tempered OSA provided by a 5,000 CFM DOAS unit, require DCV?
Discussion
Technically, I don't think these systems are required to have DCV, because according to 120.1(d)3A, a prequisite is an air economizer, and these systems are 100% outside air. I think that this is a Standards question, not a compliance software issue, and I would seek guidance from the CEC. I don't see why the systems couldn't include DCV, but if we exempt them from the mandatory requirement, it may require a software change. The baseline would include DCV in either case.
1/21/2020 CEC - For 2019, the requirement change from ‘and’ to ‘or’, meaning if any of the 3 options are part of the system, then the requirements would apply.
So it may not have an economizer, but if it also doesn’t have modulating air control or >3,000 CFM, then it would be exempt. So in their example, the DOAS is 5,000 CFM, so DCV would apply. And it would apply whether the DOAS is conditioned or unconditioned air, because the point of the requirements is to reduce the conditioning of OSA.