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Hello,
There
are three options for values in the min-air-sch.
1. A fraction value (ex: 0.36) in any given
hour sets the MINIMUM air as a fraction of total system air flow for
that hour. The economizer is enabled in this
case so the actual outside air could be greater than the minimum if
cooling is needed and outside conditions favor the use of the economizer.
NOTE: Be careful, even if you set the minimum OA ratio in the system
screen, you should still use that same ratio in the schedule. Using a
value of 1 will give 100% of the total system OA, not 100% of the minimum
OA.
2. A zero (0) value closes the outside air damper
AND disables the economizer. This is usually used for optimum start
periods.
3. A Flag value (-999) asks DOE to calculate the
minimum amount of outside air needed based on the number of people in the
occupancy schedule and the OA cfm/person specified in the thermal zone.
The economizer is enabled in this case so again the
actual outside air could be greater than the minimum if cooling is needed and
outside conditions favor the use of the economizer.
For
demand controlled ventilation, I've used an OA schedule flagged 24/7 (except
during optimum start periods = 0). For constant OA during occupied
periods and closed OA dampers when unoccupied, I use the minimum OA
fraction during occupied periods, "0" during optimum start, and Flag all
unoccupied hours to ensure economizer availability.
Hope
this helps.
Sheila
Sagerer
Energy
Opportunities, Inc
-----Original Message-----
From: postman@xxxxxxxx [mailto:postman@xxxxxxxx]On Behalf Of Aulbach, John Sent: Thursday, March 20, 2003 1:16 PM To: BLDG-SIM@xxxxxxxx Subject: [BLDG-SIM] Simulation of Demand Controlled Ventilation What
does -999 do in the Min-Air-Sch? Doesn't that "vote" on what OSA is needed, and
also yield to the economizer as well?
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