Thanks to Fred and Dr. Li for their responses. I’ve think
got it now.
The Building Performance Team
James V. Dirkes II, P.E., LEED AP
1631 Acacia Drive NW
Grand Rapids, MI 49504
616 450 8653
From: EnergyPlus_Support@xxxxxxxxxxxxxxx
[mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of Walter Buhl
Sent: Monday, July 26, 2010 3:43 PM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: Re: [EnergyPlus_Support] Controller:OutdoorAir minimums
Minimum Fraction of Outdoor Air Schedule Name is the
name of a schedule whose values are flow fractions.
Minimum Outdoor Air Schedule Name is the name of a schedule whose values
multiply a flow fraction.
The normal way of specifying the minimum outdoor air flow rate is through the
input Minimum Outdoor Air Flow Rate.
This input is a fixed value in cubic meters per second. This input is converted
to a minimum OA flow fraction
by dividing by the system design supply air flow rate. This value can then be
modified by multiplying by the value
of Minimum Outdoor Air Schedule.
Some users found the flow rate input for min OA very inconvenient. Minimum
Fraction of Outdoor Air Schedule was
installed to provide an alternate method for inputting the min OA flow
rate: as a fraction of the design flow rate.
Minimum Fraction of Outdoor Air Schedule imposes a strict lower limit on
the OA flow. It overrides Minimum Outdoor Air Flow Rate
and Minimum Outdoor Air Schedule.
Fred Buhl
On Fri, Jul 23, 2010 at 1:33 PM,
jvd2pe <jvd2pe@xxxxxxx> wrote:
Dear Forum,
I'm trying to make sense of the I/O Reference description for two of the fields
that affect the minimum OA. (shown below)
Can someone explain how these are different from each other?
Field: Minimum Outdoor Air Schedule Name
The name of a schedule whose values are decimal fractions (0.0 – 1.0)
that multiply the minimum outdoor air fraction. This schedule is useful for
reducing the outdoor air flow rate to zero during unoccupied or start up hours.
If this field is not input, the minimum outdoor air flow rate remains constant
during the simulation period.
Field: Minimum Fraction of Outdoor Air Schedule Name
This is an optional field with the schedule values in decimal fractions
(0.0-1.0). This field enables the user to limit the minimum amount of outdoor
air permissible and thus also helps in getting at least the minimum amount of
air in.
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