Sequence of Operation
80
OAU-SVX006E-EN
Sequence of Operation
General
Text shown in
italics
are point names in the programming.
Typically, points ending with “Local” are hardwired
inputs, points ending with “Active” are determined by the
program and can’t be adjusted by the operator or BAS.
Discharge Air Temperature Setpoint Maximum
is
adjustable but cannot exceed 120°F for gas, heat pump, or
hot water heating, and 90°F for electric heating.
Program Control Type
can be determined using Multi-
State Value 13.
Note:
There is a 3-minute delay during compressor or gas
heater staging to allow the system to stabilize
before adjusting the cooling or heating capacity.
Program-Controlled Setpoints
Space Control and Single Zone VAV
Control
Discharge Air Temperature Setpoint Active
is reset by
comparing the
Space Temperature Active
to
Occupied
Cooling Setpoint
during cooling and
Occupied Heating
Setpoint
during heating. If a single setpoint is preferred,
use
Space Temperature Setpoint BAS
by putting it In
Service using Tracer TU or BAS.
Dehumidification Temperature Setpoint Active
is reset by
comparing the
Space Dewpoint
to the
Space Dewpoint
Calculated Enable Setpoint
minus 2°F.
If
Space Temperature Setpoint BAS
or
Space Temperature
Setpoint Local
(Thumbwheel) is In Service,
Occupied
Offset
is adjustable (2°F default). Otherwise, is determined
using
Occupied Cooling Setpoint
and
Occupied Heating
Setpoint
.
If
Occupied Cooling Setpoint
is below
Occupied Heating
Setpoint, Occupied Offset
is 1°F. If
Occupied Cooling
Setpoint
is above
Occupied Heating Setpoint¸ Occupied
Offset
is the difference between the two setpoints.
Space Dewpoint Calculated Enable Setpoint
is calculated
using
Space Humidity Setpoint
and
Space Temperature
Setpoint Active
.
Discharge Air Control and Multi-Zone VAV
Control
Discharge Air Temperature Setpoint Active
is controlled by
Discharge Air Cooling Setpoint BAS
during cooling
operation, and
Discharge Air Heating Setpoint BAS
during
heating. If
Discharge Air Temperature Setpoint BAS
is In
Service, the program will use this over the discharge
cooling and heating setpoints.
Dehumidification Temperature Setpoint Active
is
controlled by
Dehumidification Temperature Setpoint
.
Occupied Control
Starting Sequence
Occupied operation begins when the unit is placed in
Occupied via BAS or when OAUTS-7 & 8 is closed on the
field wiring terminal strip. The unit must not be in
Emergency Stop
to begin starting sequence. OAUTS-9 &
10 on the field wiring terminal strip are used as an external
Emergency Stop
for the unit. Cycling power to unit to may
not resolve alarm condition.
Refer to Multi-State Value
Occupancy Status
to determine
the active status of the unit.
Two-Position Outdoor Air Damper
will begin by
energizing relay OADR, opening the outdoor air damper.
The supply fan sequence begins once the end switch is
closed.
Two-Position Outdoor and Return Air Dampers
will
begin by energizing relay OADR, opening the outdoor air
damper and closing the return air damper. The supply fan
sequence starts immediately after the unit becomes
occupied.
Modulating Outdoor and Return Air Dampers
will
begin by adjusting the
Outdoor Air Damper Position
Command
to meet the
Outdoor Air Damper Minimum
Position Setpoint
. The supply fan sequence starts
immediately after the unit becomes occupied.
Supply Fan Sequence
Supply Fan Starting Sequence
begins by energizing
relay G and setting the
Supply Fan Speed Command
to
50%. The supply fan status switch (IFFS) closes, energizing
relay IFFR. If after two minutes there is no proven signal,
Diagnostic: Supply Fan Failure
will be displayed, and the
unit will shut down requiring a manual reset.
Constant Volume with VFD
After completing the starting sequence, the supply fan will
run to the
Supply Fan Speed Setpoint
, field adjustable
from 50-100% (defaulted 100%).
Constant Volume with ECM
After completing the starting sequence, the unit calculates
the
Supply Fan Air Flow Active
and adjusts
Supply Fan
Speed Command
to maintain the
Supply Fan Air Flow
Setpoint
(adjustable, factory set according to submittal).
Multi Zone VAV Control
After completing the starting sequence, the unit adjusts
fan speed to maintain
Duct Static Pressure Active
to
Duct
Static Pressure Setpoint BAS
. Supply fan speed is limited
between
Supply Air Flow Minimum Setpoint Active
and
Supply Air Flow Maximum Setpoint
(both factory set).
