UNIT COMPONENTS
The 38UQZ and 40ALZ units incorporate the following
components:
•
Three-phase hermetic reciprocating compressors with
internal thermal protection in the 38UQZ 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 40ALZ indoor units using thermostatic
expansion valves or throttle valves depending on the
model. Thermal expansion valves in bypass mode with
a non-return valve and the expansion valves.
•
High and low pressure switch and filter drier (38UQZ).
•
Soldered copper refrigerant connection lines.
•
Complete internal wiring. Main on/off disconnect switch
in the 38UQZ outdoor units. These units also include
the complete electrical boxes with compressor contac-
tors. Thermomagnetic disconnect switches for compres-
sors, fan motors and crankcase heater.
•
Fans:
The 40ALZ indoor units have centrifugal fans driven by
three-phase motors with adjustable belt-pulley drives.
The 38UQZ outdoor units have direct-drive propeller
fans.
•
Thermal and acoustical insulation. Flexible shock
absorbers in all moving components.
•
Air filters in the 40ALZ indoor units.
•
Defrost control using a time/temperature-activated
thermostat. Compresor crankcase heaters. Liquid
slugging tank. Discharge line muffler and thermal
protection. Four-way reversing valve.
•
Pre-painted galvanised sheet steel casings.
•
The indoor and outdoor units can be used with the
accessory ambient thermostat in heat pump mode.
DESCRIPTION OF UNIT PROTECTION DEVICES
The unit includes the following compressor protection devices:
•
Internal compressor protection device
for all 38UQZ
units to avoid superheat.
•
short-cycle protection
standard for units 38UQZ.
•
Indoor fan motor thermomagnetic switch in the 38UQZ
unit control box.
•
thermomagnetic compressor, indoor fan motor and
crankcase heater disconnect switch, in the 38UQZ
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.
•
Low pressurestat:
This protects the 40ALZ units against
excessive low pressure in the evaporator or in the refri-
gerant lines. It is not operational in heat pump mode.
The low pressurestat has factory fixed non-adjustable
settings. To check, see section Initial checks.
•
Discharge line thermal protection.
•
Defrost control thermostat. Time and temperature
activated control. Defrost start and stop temperature
limit. Controls the time between defrost cycles and
defrost duration.
CAUTION: When any of these cuts out, the unit stops and
will not re-start until the contacts have been reclosed
after rectification of the fault, when resetting is automatic.
Table 8 - Pressure switch, overheat switch, defrost
thermostat and anti short cycle switch settings
Cut-out
Cut-in
Reset
High pressurestat
*2844 kPa
*1863 kPa
Automatic
Low pressurestat
*265 kPa
*363 kPa
Automatic
* Factory-calibrated
Discharge line thermal switch
*120°C
* Factory-calibrated
Anti-short cycle setting
3 minutes
Defrost thermostat or control
Defrost temperature:
Start
-3°C*
End
+19°C*
Time between defroat cycles (minutes)
30*
45
90
Maximum defrost time
12 minutes
* Refrigerant temperature in the outdoor heat exchanger.
WARNING: Alteration of factory settings other than the
design setpoint, without manufacturer’s authorisation,
may void the warranty.
Table 9 - Operating limits
Zone
Air temperature °C
Dry bulb
Wet bulb
Cooling operation:
Indoor
Maximum
+35
+21
Minimum
+19
+14
Outdoor
Maximum
+46
-
Minimum
19*
-
Heating operation:
Indoor
Maximum
+27
-
Outdoor
Maximum
+24
+18
Minimum
-10
-
Indoor air flow
Maximum
+15% of nominal value
Minimum
-15% of nominal value
Hot water coil (accessory/option)
Maximum water temperature
80°C
* With head pressure control, the unit will operate at temperatures below 19°C.
ATTENTION: Operation of the units at temperatures, air
flows, etc. outside the limits indicated in the table above
can cause serious damage to the units and will void the
Carrier warranty.
