Protective Devices; Compressor Protection; Relief Device; Control Circuit, 24-V - Carrier 50FCQ 04-07 Series Service And Maintenance Instructions

PROTECTIVE DEVICES

Compressor Protection

OVERCURRENT
The compressor has internal line-break motor protection.
OVERTEMPERATURE
The compressor has an internal protector to protect it against ex-
cessively high discharge gas temperatures.
HIGH PRESSURE SWITCH
The system is provided with a high pressure switch mounted on
the discharge line. The switch is stem-mounted and brazed into the
discharge tube. Trip setting is 630 psig ± 10 psig (4344 ± 69 kPa)
when hot. Reset is automatic at 505 psig (3482 kPa).
LOW PRESSURE SWITCH
The system is protected against a loss of charge and low evapora-
tor coil loading condition by a low pressure switch located on the
suction line near the compressor. The switch is stem-mounted.
Trip setting is 54 psig ± 5 psig (372 ± 34 kPa). Reset is automatic
at 117 ± 5 psig (807 ± 34 kPa).
EVAPORATOR FREEZE PROTECTION
The system is protected against evaporator coil frosting and low
temperature conditions by a temperature switch mounted on the
evaporator coil hairpin. Trip setting is 30°F ± 5°F (–1°C ± 3°C).
Reset is automatic at 45°F (7°C).
SUPPLY (INDOOR) FAN MOTOR PROTECTION
Disconnect and lockout power when servicing fan motor.
The standard supply fan motor is equipped with internal overcur-
rent and over-temperature protection. Protection devices reset
automatically.
The high static option supply fan motor is equipped with a pilot-
circuit Thermix combination over-temperature/over-current
protection device. This device resets automatically. Do not bypass
this switch to correct trouble. Determine the cause and correct it.
CONDENSER FAN MOTOR PROTECTION
The condenser fan motor is internally protected against over-
temperature.

Relief Device

A soft solder joint at the suction service access port provides pres-
sure relief under abnormal temperature and pressure conditions
(i.e., fire in building). Protect this joint during brazing operations
near this joint.

Control Circuit, 24-V

The control circuit is protected against overcurrent conditions by a
circuit breaker mounted on control transformer TRAN. Reset is
manual.

SYSTEMVU CONTROL SYSTEM

The SystemVu™ control is a comprehensive unit-management
system. The control system is easy to access, configure, diagnose
and troubleshoot.
The SystemVu control system is fully communicating and cable-
ready for connection to the Carrier Comfort Network
Carrier i-Vu , and Third Party BACnet
®
systems. The control provides high-speed communications for
remote monitoring via the Internet. Multiple units can be linked
together (and to other Direct Digital Control (DDC) equipped
units) using a 3-wire communication bus.
The SystemVu control system is easy to access through the use of
a integrated display module. A computer is not required for start-
up. Access to control menus is simplified by the ability to quickly
select from 7 main menu items. An expanded readout provides de-
tailed explanations of control information. Only 6 buttons are re-
quired to maneuver through the entire controls menu. The display
readout is designed to be visible even in bright sunlight. See
Fig. 53.

SystemVu Interface

This integrated device is the keypad interface used to access the
control information, read sensor values, and test the unit. The in-
terface is located in the main control box.
Through the SystemVu interface, the user can access all of the in-
puts and outputs to check on their values and status, configure
operating parameters, and evaluate the current decision status for
operating modes. The control also includes an alarm history which
can be accessed from the display. The user can access a built-in
test routine that can be used at start-up commissioning and
troubleshooting.
Additional SystemVu Installation and Trouble-
shooting
Additional installation, wiring and troubleshooting information
for the SystemVu Controller can be found in the following manu-
al: "50FCQ 04-07, 50GCQ 04-06 Single Package Rooftop Units
with SystemVu™ Controls Version X.X Controls, Start-up, Oper-
ation and Troubleshooting."
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owners.
32
® (CCN),
building management
®1