Carrier WeatherExpert 48LC B14 Series, Installation Instructions Manual

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37
SEQUENCE OF OPERATION
General
The Carrier Integrated Staging Control (ISC) is intended for use
with the VAV-RTU Open controller. After initial power to the
board, a Green LED will blink with a 1 second duty cycle indicat-
ing the unit is running properly. In the event of the ISC board fail-
ing, the Green LED will be OFF or continuously ON. When the
unit is not running properly, the Green LED will blink along with
Red LED lights. The Red LED light configuration will indicate
the type of error the board has identified. See Fig. 51 for LED lo-
cations and Table 8 for a list of status codes.
The ISC board can be remotely shutdown by removing Jumper 4
and wiring to the Remote Shutdown terminal. The Smoke Control
Module can shutdown the unit by removing Jumper 3 and wiring
to the Smoke Shutdown terminal. The Smoke Alarm terminal on
the ISC Board provides a pass-through connection should a smoke
alarm signal be connected. The VAV-RTU Open controller pro-
vides the signal which is passed through the ISC board to the
Smoke Alarm terminal.
The crankcase heater will run at all times except when the com-
pressors are running. An auxiliary power supply (24Vac) available
at TB-4 Terminal is provided to power auxiliary equipment. An
optional Phase Monitor Relay can be wired to the PMR terminal
by removing Jumper 5. An optional Condensate Flow Switch can
be wired to the COFS Terminal by removing Jumper 7.
Static Pressure Control
The supply fan VFD will be controlled using a PID and an ana-
log input from a duct static pressure transducer. The supply fan
will modulate its speed to maintain the desired duct static pres-
sure setpoint.
Field Test/Commissioning
The control will provide BACnet test points to activate specific
test modes that can be used to commission the rooftop and the sys-
tem. Test modes will be available in the Service Test screen on the
Property pages and shall also be available on the local Equipment
Touch device for standalone commissioning. Tests include: Fan
Test, Low Heat Test, High Heat Test, Cooling Test, Power Exhaust
Test, and an Economizer Test. When any test is active, the appro-
priate Linkage mode will be sent to the system’s terminals. This
will ensure appropriate system operation and airflow during any
test mode.
Ventilation
In the Ventilation/Fan Mode (G), the indoor fan will run at low
speed and the damper will operate at minimum position.
Supply Air Temperature Control
The control will maintain the desired supply air temperature set-
point whenever cooling is required. A user configurable setpoint
will be provided (default 53°F [12°C]). The control will use the
appropriate method (economizer cooling, mechanical cooling, or a
combination of both) to achieve this setpoint whenever the zone
temperature is greater than the current cooling setpoint (occupied
or unoccupied). If Supply Air Reset is enabled, the reset algorithm
will calculate a proportional reset value between the Occupied
Cooling setpoint and 1°F above the Occupied Heating setpoint.
The amount of reset (reset ratio and maximum reset limit value) is
user configurable.
Minimum Ventilation
The economizer minimum position will be adjusted as required
based on the supply fan speed. Two user configurable minimum
economizer positions will be provided. The economizer will be
positioned at the “Low Fan Econ Min Pos” when the fan is oper-
ating at its slowest speed. When the fan is operating at its maxi-
mum speed, the economizer will be positioned at the “Vent
Dmpr Pos / DCV Min Pos”. For any supply fan speed between
these two points, the economizer minimum position will be cal-
culated proportionally.
Demand Controlled Ventilation (DCV)
Whenever the unit is in an occupied mode and “DCV Control” is
set to enable, a unique economizer minimum position will be cal-
culated based on the output of the DCV calculation. Two user con-
figurable values are provided; the “DCV Max Ctrl Setpoint” is the
differential CO
2
setpoint that is used as the control point and a
“DCV Max Vent Damper Pos” provides the ability to limit the
maximum amount of outdoor air being introduced into the unit
through the economizer by the DCV control. The economizer will
be positioned at the greater of any minimum economizer position.
Demand Controlled Ventilation can be used in either a differential
mode where both the indoor air and outdoor air CO
2
levels are
provided to the control or in a single indoor air mode with only the
indoor air CO
2
level. In the latter case, the outdoor air CO
2
level is
assumed at 400 ppm.
Mechanical Cooling Cycle
The control will operate three stages of mechanical cooling in or-
der to maintain the desired supply air temperature whenever econ-
omizer cooling operation is unavailable but cooling is required.
This condition will be determined if the OA has high enthalpy or
at a temperature above the Economizer Lockout temperature. The
two compressors will be staged in a binary fashion so that three
stages of cooling are provided. Mechanical cooling stages will be
added as required to meet the desired SA setpoint. The number of
stages will depend on the return air conditions and the system load
(airflow through the coil). Stages will be added or dropped as re-
quired to maintain the setpoint while also maintaining the mini-
mum on time and minimum off time for compressor operation.
Anytime the SA falls below the desired SA setpoint, stages will be
dropped until only stage 1 is operating. At that point, should the
SA fall below 45°F (7°C), the economizer will modulate to in-
crease the amount of outdoor air in order to maintain this mini-
mum SA temperature. Should the economizer reach the maximum
OA position and if the SA is still below the minimum SA tem-
perature, the first cooling stage will be disabled and the economiz-
er will return to the minimum position.
Integrated Cooling Cycle
If economizer cooling operation is insufficient to maintain the de-
sired SA setpoint, mechanical cooling will be activated to supple-
ment the free economizer cooling. This condition will be deter-
mined if the OA has low enthalpy but is at a temperature at least
5°F above the desired SA setpoint and below the Economizer
Lockout temperature. Mechanical cooling stages will be added as
required to meet the desired SA setpoint. The number of stages
will depend on the return air conditions and the system load (air-
flow through the coil). Stages will be added or dropped as required
to maintain the setpoint while also maintaining the minimum on
time and minimum off time for compressor operation. Anytime
the SA falls below the desired SA setpoint, stages will be dropped
until only stage 1 is operating. At that point, should the SA fall be-
low the minimum SA temperature, the economizer will modulate
to increase the amount of return air in order to maintain this mini-
mum SA temperature. Should the economizer reach the minimum
OA position and if the SA is still below the minimum SA tem-
perature, the first cooling stage will be disabled.
Economizer Cooling Cycle
The control will provide the ability to utilize outdoor air for main-
taining the supply air setpoint should the outdoor air be suitable.
The economizer control will utilize an OAT temperature check, a
RAT temperature check if RAT is available or a SPT temperature
check comparison and optionally, an OA enthalpy check to deter-
mine if OA conditions are suitable for economizing. Economizer
operation, if available, will begin whenever cooling is required.
The economizer will modulate the position of the OA damper to
maintain the desired calculated economizer setpoint. The econo-
mizer will be controlled to meet CEC Title 24 requirements so that
it will remain open 100% during integrated cooling and only par-
tially close if required.