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Re: [EnergyPlus_Support] Real world HVAC question - DCV using CO2 sensors with VAV dampers
Dear Jean,
I have some understanding of the origins of CO2 control, which are almost
exclusively based on occupant perception, not health. (Think "body odor"
or "Staleness").
As a result, I do not place a high priority on CO2 control schemes which
use more outdoor air than whatever is needed to maintain about 1000 ppm.
That means I favor something like your Scheme #3, in which the controls
treat the CO2 concentration as a maximum limit.
Keep in mind that any modern control system should not be "erratic"; it
should be able to produce consistent and smooth control of outdoor air to
maintain whatever setpoint you choose.
> This question has nothing to do with simulation as such. What is the best
> way to use / control a Demand Control Ventilation (DCV) System which uses
> a combination of CO2 sensors and motorized Variable Airflow Volume (VAV)
> dampers.
>
> I will suggest a control stradegy to illustrate the question:
>
> CO2 sensors report the zone CO2 level at given timestep.
> Allowable upperbound CO2 level is 800ppm.
> Outdoor Air (ODA) CO2 level is 400ppm.
> Minimum damper position allows at least 0.3 of fully open flow.
> Maximum damper position is fully open, i.e. 1.0 of full flow.
>
> Stradegy 1::
> Control is such that at 400 ppm, Damper will be at 0.3 of full flow.
> At 800 ppm or more, Damper will be fully open.
> Damper is linierly actuated between 0.3 to 1 as the level of zone CO2
> increases from 400 ppm to 800 ppm.
>
> Stradegy 2::
> Damper remains at 0.3 untill CO2 level reaches 750 ppm, then linierly
> opens from 0.3 to 1.0 as the level increases to 800 ppm.
>
> Stradegy 3::
> Erratic opening and closing of damper only when level reaches or goes over
> 800 ppm.
>
> Stradegy 4::
> Exponencial, or other curve to control damper other than liniear.
>
> Origional question...how are these systems controlled in practice?
> Anyone with experience, here?
>
>
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