KMC Controls FlexStat Application Manual page 37

Ventilation Startup
If OA Purge is set to zero (default) and motion/occupancy is sensed
during the first 20 minutes immediately following scheduled Occupied
mode, Ventilation mode is set to STARTUP and the fan is called for to
run with the OA damper open to OA Recovery Position as calculated
under the Ventilation Recovery Mode below. This mode ends 20 minutes
after scheduled Occupied mode begins.
(Unoccupied)
Scheduled
On Time
Cooling
Setpoint
Night Flush
(Economizer
Cooling)
Pre-purge
OAD
Position
(*Available only on FlexStats with motion sensors)
Normal Ventilation
During occupied mode, unless conditions warrant a different DCV
mode, the default Ventilation mode is NORMAL (after Pre-purge, Start-
up, or Recovery modes have finished and returned the ventilation rate
to "normal" operation). During Normal ventilation mode, the damper
modulates between OA Area (2% default) and OA Full (5% default) as
follows with an increase above OA Full as described below.
OA Area is the damper position required to provide the outdoor air
rate. (Note that this represents the damper position, not the minimum
outside air percentage.) The OA damper shall be at this position when
Space CO2 is at or below CO2 Base.
OA Full is the full damper position required to provide the combined
people and area outdoor rate. The outside air damper shall be at this
position when Space CO2 is at CO2 Max (1000 ppm default).
BAC-1xx63/1xxx63 Series (6 Relays and 3 Analog Outputs) Section
(Occupied) (Unoccupied)
Scheduled
Off Time
Occupancy Occupancy
Standby* Override*
Startup* Recovery
Standby
(Manual)
Normal Override
When Space CO2 is between CO2 Base and CO2 Max, the damper shall
modulate proportionally between OA Area and OA Full.
When Space CO2 exceeds CO2 Max, the damper shall increase propor-
tionally above OA Full limited by OA Max (40% default) using the same
proportional gain as above.
Ventilation Recovery
When the supply fan is off unless in Standby mode, a ventilation re-
covery mode with supply fan operation shall be initiated for a variable
length recovery period when either Space CO2 exceeds CO2 Max + 200
ppm or when the fan has been off for Fan Max Off (30 minutes default).
After the fan has been off and starts due to a heating or cooling call,
Max Fan Off, or high CO level, the ventilation rate shall be increased
2
to provide average ventilation that matches the ASHRAE Standard 62.1
ventilation rate for the prescriptive method.
Ventilation during this mode shall be limited to a maximum that is full
damper opening (100% open) when outside air is temperate relative to
space temperatures (typically between 65° F and 80° F) and ramps down
to the OA Full setting at either heating or cooling design temperatures
(20° F and 95° F respectively, adjustable). Ventilation shall operate for at
least 5 minutes up to a time related to the ratio of the space CO
tration at the end of the last fan operation period to CO2 Max and the
allowed ventilation rate for this fan cycle. Should there be a continued
call for heating or cooling after the recovery period is complete, Ventila-
tion mode shall return to NORMAL.
Whenever the supply fan stops, Space CO2 is recorded (Space CO2
Last) at the time the fan stops. A timer, Fan Off Timer, keeps track of the
elapsed time in minutes the supply fan was off during the occupied pe-
riod since the end of the last fan operation or the end of the last Standby
period.
Whenever the supply fan starts after an off period, except in Standby
mode, the ventilation shall be maintained at the following position, OA
Recov Pos:
1. If OA is above Clg Design Temp (95° F default) or below Htg Design
Temp (20° F default), the OA damper shall be set to OA Full.
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Application Guide L