Hi All,
I'm modeling a system with DCV set to "DCV-RETURN-SENSOR." The help file says: "The program calculates the OA minimum requirement and sets the minimum damper position hourly based upon the sum of the ZONE requirements. Each zone OA requirement is calculated based upon the hourly maximum of either OA-CFM/PER (times the NUMBER-OF-PEOPLE adjusted by the hourly PEOPLE-SCHEDULE) or a minimum OA ventilation rate."
However, when I look at the hourly report for the zone, "Hourly zone OA CFM requirement for DCV calculation (cfm)" (Var 100), the CFM does not increase for high occupancy hours. My hand calculations show that when I multiply the OA-CFM/PER by the hourly occupancy, it should exceed the minimum OA ventilation rate for the zone (which I specified using OA-FLOW/AREA.)
I have set the zone minimum flow ratios to "DCV-RESET-UP/DOWN" and the zone minimum flow is increasing according to the occupancy.
Why is the zone OA CFM requirement not increasing with occupancy? Any thoughts are appreciated.
Thanks very much.
Kind regards,
Molly
Molly Curtz
Good Morning,
I'm modeling a building that uses fan coil units supplied via a central
boiler plant with out cooling any involved. I'm not sure how to model the
fan coils as terminal units in equest (what the correct input would be).
Thanks,
Colin
Hi Molly,
Based on what you describe, you have your eyes on all of the DCV toggles in eQUEST. One thing that you didn't mention though was the type of system you're modeling. In my experience, applying DCV to some system types results in hourly OA flow that's not responding to your OA-FLOW/PER and OA-FLOW/AREA inputs and occupancy levels. In a recent project, I had DCV operating correctly in a VAV system and a Single Zone Reheat system. Try changing your system to either of those types as a sanity check. Then if it makes sense, go ahead and model your system with that system type. DCV can have a significant impact on your space heating and space cooling, so it is important to get the OA flow sorted out and verified in the hourly report as you are doing.
Good luck!
Holt Cutler, EIT, LEED AP BD+C