Start-Up; Initial Checks; Unit Components; Description Of Unit Protection Devices - Carrier 38XTZ 007-024 Installation, Operation And Maintenance Instructions

START-UP

Necessary checks/precautions before start-up:
- Confirm that the electrical power source agrees with the
unit nameplate rating.
- Ensure that the power connections between speed and
thermostat have been made and correctly tightened.
- Check that there are no refrigerant leaks in the soldered
refrigerant lines, and that the refrigerant and oil charges
are correct.
- Check the 40ABZ/ALZ drain connection and that the
water is drained correctly.
- Ensure that the unit is level and well-supported.
- Check for proper fan rotation direction
- Check the condition of the ductwork in case damage has
occurred during installation.
- The air filter should be clean and in place.
- All the panels should be fitted and firmly secured with the
corresponding screws.
- Make sure that compressors float freely on the mounting
springs.
WARNING: The compressors are mounted on vibration
isolators. Do not loosen or remove the support mounting
bolts.
IMPORTANT: Actual start-up should only be done under the
supervision of a qualified refrigeration mechanic.

Initial checks

With the unit in operation, ensure that the values shown on the
high and low pressure gauges are within the normal limits. It is
advisable to simulate unit shutdown due to high and low
pressure, in order to make sure that the pressurestats work
properly. To do so, proceed as follows:
- High pressure shutdown: Completely cover the outdoor
air inlet, or disconnect the outdoor fan and motor. The unit
should stop at a pressure of 2844 kPa.
- Low pressure shutdown: Cover the indoor air inlet, or
disconnect the indoor fan and motor. Observe the low
pressure gauge. The unit should stop at a pressure of 265
kPa.
The pressure switches are automatically reset. As this takes
some time, the unit will stop, the pressures will equalise, and
then the unit will be reset and will start up again.
Check that the motor and compressor consumptions are
approximately the same as those shown in the fan performance
curves and in the cooling capacity tables, for the unit operating
conditions (indoor and outdoor temperatures, air flow and static
pressures, based on the speed, etc.).

UNIT COMPONENTS

The 38XTZ and 40ABZ/ALZ units incorporate the following
components:
- Three-phase hermetic reciprocating compressors with
internal thermal protection in the 38XTZ units.
- Refrigerant-to-air heat exchangers (evaporators and
condensers) made of copper tubes and pre-treated, water-
resistant aluminium fins.
- All-copper refrigerant circuit. R-407C refrigerant control
in the 40ABZ/ALZ indoor units using thermostatic
expansion valves or throttle valves depending on the
model.
- High and low pressure switch and filter drier (38XTZ).
- Fan high pressure switch (38XTZ 014).
- Soldered copper refrigerant connection lines at the unit
outlets.
- Complete internal wiring. Main on/off disconnect switch
in the 38XTZ outdoor units. These units also include the
complete electrical boxes with compressor and indoor fan
motor contactors, transformers (depending on the model)
and other components. Thermomagnetic disconnect
switches for compressors and fan motors.
- Master Link I electronic control board for sizes 38XTZ
016 to 024.
- Fans:
The 40ABZ/ALZ indoor units have centrifugal fans driven
by three-phase motors with adjustable belt-pulley drives.
The 38XTZ outdoor units have direct-drive propeller fans.
- Thermal and acoustical insulation. Flexible shock
absorbers in all moving components.
- Air filters in the 40ABZ/ALZ indoor units.
- Pre-painted galvanised sheet steel casings.

DESCRIPTION OF UNIT PROTECTION DEVICES

The unit includes the following compressor protection devices:
- Internal compressor protection device for all 38XTZ
units to avoid superheat.
- Short-cycle protection standard for units 38XTZ 007-014.
- Short-cycle protection included on the Master Link I main
electronic board for units 38XTZ 016-024
- Indoor fan motor thermomagnetic switch in the 38XTZ
unit control box.
- Thermomagnetic compressor and indoor fan motor
disconnect switch, in the 38XTZ unit control box.
- High pressurestat: This protects the unit against excessive
condensing pressure.
The high pressurestat has factory-fixed non-adjustable
settings. To check, see section Initial checks.
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