Microprocessor Controller for DOAS
7
Sequence of Operation
Sequence of Operation
communications, the user can also directly command
the supply fan speed. The following sequences are
selectable for supply fan control. The fan speed in
constrained by its min and max speed set points.
•
Constant Volume:
Supply fan operates at a constant
speed based on a constant volume set point based
on occupancy.
•
0-10 VDC:
The supply fan is enabled by the unit
controller. An external field-supplied 0-10 VDC signal
is responsible for modulating the supply fan’s speed.
•
CO
2
Control:
The supply fan modulates to maintain
CO
2
set point based on a sensor located in the space
or return duct. A CO
2
sensor or BMS communicated
value is required for this sequence.
•
Duct Static Pressure Sensor:
The supply fan
modulates to maintain an adjustable duct static set
point based on a sensor located in the supply duct. A
static pressure sensor or BMS communicated value
in required for this sequence.
• Space Static Pressure:
The supply fan modulates to
maintain a space static pressure set point based on a
sensor located in the space. A space static pressure
sensor or BMS communicated value in required for
this sequence.
•
Single Zone VAV :
The controller will control the
supply air temperature and supply fan speed in order
to maintain the space temperature.
Heating Mode-
The supply temperature set point
will be increased before increasing the supply fan
speed in order to maintain the space temperature set
point. If the calculated supply temperature set point
is greater than the current space temperature, the
supply fan speed will be increased while the supply
temperature set point is increased.
Cooling Mode -
The supply temperature set point
will be decreased before increasing the supply fan
speed in order to maintain the pace temperature set
point.
•
Two Speed:
The supply fan is enabled by the unit
controller. An external field-supplied digital contact is
responsible for enabling high speed operation.
Exhaust Fan VFD Sequence
The factory installed VFD is wired to the controller.
Exhaust fan speed needs to be set during test
and balance of the unit. If equipped with BMS
communications, the user can also directly command
the exhaust fan speed. The following sequences are
selectable for exhaust fan control. The fan speed
constrained by its min and max speed set points.
•
Constant Volume:
Exhaust fan operates at a
constant speed based on a constant volume set point
based on occupancy.
•
0-10 VDC by Others:
The exhaust fan is enabled by
the unit controller. An external field-supplied 0-10
VDC signal is responsible for modulating the supply
fan’s speed.
• Space Static Pressure:
The exhaust fan modulates
to maintain a space static pressure set point based
on a sensor located in the space. A space static
pressure sensor or BMS communicated value in
required for this sequence.
•
Supply Fan Tracking:
The exhaust fan proportionally
modulates based on the supply fan speed plus an
adjustable offset.
•
Outside Air Damper Tracking:
The exhaust fan
proportionally modulates based on the outdoor
air damper modulation. (This sequence requires a
modulating outdoor air damper.)
Outside Air and Recirculated (Recirc) Air
Damper Control
If equipped with a modulating OA and recirculated air
damper, the recirculated air damper will operate inverse
of the OA damper. The OA damper opens to its min
position. If the controller is configured to modulate the
supply fan speed, the min and max OA positions can
be reset based on supply fan speed. If equipped with
BMS communications, the BMS can directly control
the outside damper position. The damper position is
constrained by its min and max set point positions.
•
CO
2
Control:
The controller will proportionally
modulate the OA/RA dampers based upon a
comparison of the CO
2
set point to the actual CO
2
level reported from the sensor. As the CO
2
level rises,
the controller will proportionally modulate the OA
damper open, between the min OA damper position
and max CO
2
position.
•
Space Static Pressure:
The OA/RA dampers will
modulate based upon the signal from a building
static pressure sensor. The controller will modulate
the dampers, between the min and max OA
positions, based upon a comparison of the building
static pressure set point to the actual building static
pressure level reported from the sensor.
•
0-10 by Others:
An external field supplied 0-10 VDC
signal is responsible for setting the damper position.
•
Two Position:
An external field supplied digital
contact is responsible for setting the damper to max
position.
