BAC-1xx63/1xxx63 Series (6 Relays and 3 Analog Outputs) Section 37 Application Guide L
Ventilation Startup
If OA Purge is set to zero (default) and motion/occupancy is sensed
during the rst 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
aer scheduled Occupied mode begins.
Normal Ventilation
During occupied mode, unless conditions warrant a dierent DCV
mode, the default Ventilation mode is NORMAL (aer Pre-purge, Start-
up, or Recovery modes have nished 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).
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 o 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 o for Fan Max O (30 minutes default).
Aer the fan has been o and starts due to a heating or cooling call,
Max Fan O, or high CO
2
level, the ventilation rate shall be increased
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 seing 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
2
concen-
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 aer 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 O Timer, keeps track of the
elapsed time in minutes the supply fan was o 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 aer an o 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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