HVAC type for Exhaust Fans on parking lots

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A non-conditioned underground parking lot has exhaust fans with VSD which work according to CO2 levels.
How do I define this type of HVAC system?

Thanks
Claudia

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Claudia,

If you are doing a LEED/Appendix G model, I suggest modeling it as a
process load (Direct Loads - Interior), with the load equal to the fan
power and with a schedule that approximates when the fan will run based
on CO2. The load and schedule should be identical between your baseline
and proposed unless you can justify it through an exceptional
calculation. See Dakota Kelley's email, attached.

Regards,
Bill

William Bishop, PE, BEMP, LEED(r) AP

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As an extra suggestion, you can take the approach Bill is describing but
instead define the ventilation systems as a direct load on a sub-meter
to your default electric meter. The advantage to this extra step is you
can reference report PS-B to more easily document the garage ventilation
system demand/consumption on the EAp2 template as a process load
separate from your other "misc. equip" loads, the same way elevators get
a separate line. My last reviewer demanded this be broken out
separately.

Attached discussion describes the suggestion more thoroughly.

To my knowledge nobody has yet put forth a "standard" or "baseline"
schedule to use for garage ventilation, so I've always resolved to model
them identically thus far.

systems don't operate terribly often, even in busy garages. I suspect
the predominance of modern catalytic converters (fewer cars from the
70's and earlier are driven daily) has a lot to do with the ppm values
not getting approached.

~Nick

NICK CATON, E.I.T.

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