General Information
16 RT-SVX21AC-EN
closing a field supplied contact installed in parallel with
the FOS.
If this circuit is closed before t
he compressor is started,
the
compressor will not be allowed to operate. Anytime this
circuit is closed for 1 continuous second during
compressor operation, the compressor for that circuit is
immediately turned “Off”. The compressor will not be
allowed to restart for a minimum of 3 minutes should the
FOS open.
Frostat is standard on multi-speed indoor motors and
si
ngle zone VAV products (SZVAV).
Electromechanical Option
This input incorporates the Frostat™ control (FOS)
mounted in the indoor coil circuit or on suction line before
equalizer port of TXV and can be activated by opening a
field supplied contact installed in series with the FOS.
If this circuit is open before
the compressor is started,
the
compressor will not be allowed to operate. Anytime this
circuit is opened during compressor operation, the
compressor for that circuit is immediately turned “Off”. The
compressor will restart when the FOS closes. Frostat™ is
standard on YSC036-060G electromechanical control
products.
Discharge Line Temp Switch (DLTS)
The DLTS is looped in series with HPC and LPC. It prevents
compressor from overheating (over 300 Fº dome temp) in
case of indoor fan failure (cooling) or outdoor fan failure
(heating).
Smoke Detector Sensor (Optional)
This sensor provides high limit “shutdown” of the unit and
requires a manual reset. The sensor is used to detect
smoke in the air conditioning or ventilation ducts.
Notes:
• The supply air smoke detector samples supply air. The
return and plenum a
ir smoke detectors sample return
air. The smoke detectors are designed to shut off the
unit if smoke is sensed. This function is performed by
sampling the airflow entering the unit at the return air
opening. Follow the instructions provided below to
assure that the airflow through the unit is sufficient for
adequate sampling. Failure to follow these instructions
will prevent the smoke detectors from performing its
design function.
• Ai
rflow through the unit is affected by the amount of
dirt and debris accumulated on the indoor coil and
filters. To insure that airflow through the unit is
adequate for proper sampling by the return air smoke
detector, complete adherence to the maintenance
procedures, including recommended intervals
between filter changes, and coil cleaning is required.
• Periodic checks and maintenance procedures must be
performed
on the smoke detector to insure that it will
function properly. For detailed instructions concerning
these checks and procedures, refer to the appropriate
section(s) of the smoke detector Installation and
Maintenance Instructions provided with the literature
package for this unit.
In order for the supply air smoke detector or return air
sm
oke detector
to properly sense smoke in the supply air
stream or return air stream, the air velocity entering the
smoke detector unit must be between 500 and 4000 feet
per minute. Equipment covered in this manual will
develop an airflow velocity that falls within these limits
over the entire airflow range specified in the evaporator
fan performance tables.
Phase Monitor
This sensor monitors voltage between the 3 conductors of
the 3 phase power supply. Two LED lights are provided:
• The green light indicates that a balanced 3 phase
supply
circuit is properly connected.
• The red light indicates that unit operation has been
prevente
d. There are two conditions that will prevent
unit operation:
• Th
e power supply circuit is not balanced with
the
proper phase sequence of L1, L2, L3 for the 3
conductors of a 3 phase circuit.
• T
he line to line voltage is not between 180 volts and
633 volts.
Single Zone Variable Air Volume /
Displacement Ventilation (Optional)
This sensor offers full supply fan modulation across the
available airflow range. In addition to full supply fan
modulation, the unit controls the discharge air
temperature to a varying discharge air temperature
setpoint in order to maintain Space Temperature.
Human Interface - 5-inch Color
Touchscreen (Optional)
The 5-inch color touchscreen Human Interface provides an
intuitive user interface to the rooftop unit that speeds up
unit commissioning, shortens unit troubleshooting times,
and enhances preventative maintenance measures. The
human interface includes several features including:
• Data trending capabilities by means of time series
gra
phs
•
Historical alarm messages
• Real-time sensor measurements
• On board system setpoints
• USB port that enables the downloading of component
r
unt
ime information as well as trended historical
sensor data
• Customized reports
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