Spec sheet

18
Unit Mounting (Outdoor)
Refer to the unit’s installation instructions for further details.
Support – A location which can bear the weight of outdoor unit.
Refer to the Physical Data section for weights, and base
dimensional drawings.
Unit Leveling – For reliable operation, units should be level in all
planes.
Clearances – Minimum clearances, as shown in Fig. 9, must be
provided for airflow. The outdoor units are designed for free−blow
applications. Air inlets and outlets should not be restricted.
Unit location – A location which is convenient to installation and
not exposed to strong wind.
NOTE: Do not install the indoor or outdoor units in a location
with special environmental conditions. For those applications,
contact your sales representative.
System Operating Conditions
OPERATING RANGE (Min / Max °F (°C))
Cooling Heating
Outdoor DB -13 / 122 (-25 / 50) -22 / 86 (-30 / 30)
Metering Devices
The outdoor unit has multiple electronic expansion valves to
manage the refrigerant flow to the different indoor fan coils
connected to that unit.
Refrigerant Lines
General Guidelines:
1. The outdoor units are shipped with a full charge of R−410A
refrigerant. All charges, line sizing, and capacities are based
on runs of 25 ft. (7.6 m). For runs over 25 ft. (7.6m),
consult long−line section on this page for proper charge
adjustments.
2. Refrigerant lines should not be buried in the ground. If it is
necessary to bury the lines, do not bury more than 36 inches
(914 mm). Provide a minimum of 6 inch (152 mm) vertical
rise to the service valves to prevent refrigerant migration.
3. Both lines must be insulated. Use a minimum of ½−inch
(12.7 mm) thick insulation. Closed−cell insulation is
recommended in all long−line applications.
4. Special consideration should be given to isolating the
interconnecting tubing from the building structure. Isolate
the tubing so vibration or noise does not transmit into the
structure.
Long Line Applications:
S No change in line sizing is required.
Unit
Size
Zones
Charge
oz. (kg.)
Additional Charge
Required
After ft. (m)
Additional
Charge
oz./ft. (g/m)
Total
Maximum
Piping
Length ft.
(m.)
18 2 70.55 (2.0) 49 (15) 0.16 (15) 131 (40)
24 3 98.76 (2.8) 74 (22.5) 0.16 (15) 197 (60)
30 4 105.82 (3.0) 98 (30) 0.16 (15) 263 (80)
36 4 162.26 (4.6) 123 (37.5) 0.16 (15) 328 (100)
48 5 162.26 (4.6) 123 (37.5) 0.16 (15) 328 (100)
NOTE: Additional Refrigerant Calculation Sum Total Liquid
Pipe ft. (m) Additional Charge Required After ft. (m.) x
Additional Charge oz./ft. (g/m) 0.16 (15).
NOTE: If the calculation results in a negative number, no
additional refrigerant is required.
Drain Connections
Install drains that meet the local sanitation codes.
Wiring
The main power is supplied to the outdoor unit. Four field supplied
connecting cables from the outdoor unit to each of the indoor units
are: L1, L2, Ground, and S for communication between the
outdoor unit and each indoor unit.
Control System
The 38MGR unit is equipped with a microprocessor control to
operate the system and give optimum levels of comfort and
operating efficiency. There are microprocessor boards and
thermistors located in both the indoor and outdoor units. The
thermistors monitor the system operation and control the operating
mode.
Sequence of Operation
NOTE: Simultaneous heating and cooling is not allowed.
The Heating Mode is the priority in the system and controls the
mode of operation for the rest of the indoor units connected to the
same outdoor unit. If any unit in the system is set into Heating
Mode the system switches to Heat. If any unit is setup in
COOLING, while any unit in the system is setup as Heating, the
ones on COOLING would enter in conflict mode and an error
message would appear on the units set as COOLING.
All units must be set in cooling or fan mode for the system to cool.
When a unit is set to COOL, HEAT or the DRY mode, the
electronic expansion valve is first initialized (closed) and then is
opened to a preset position.
Superheat heating for each fan coil (the ones that are energized) is
monitored and the position of the electronic expansion valve is
adjusted to ensure that each fan coil gets the appropriate amount of
refrigerant to maintain the required superheat. In the COOLING
mode, after the set point is satisfied, the electronic expansion valve
remains open for a specified time to ensure the system pressures
equalize. In the HEATING mode, after the set point is satisfied,
the electronic expansion valve remains open to ensure proper oil
flow back and keep low pressure.
When the system is set for COOL, HEAT or DRY mode, the
compressor speed is varied by comparing the indoor air
temperature with the set point and continuously adjusting the
compressor speed (to keep the compressor running as long as
possible) in an effort to maintain the greatest comfort possible.
The indoor fan can run in either the MANUAL or AUTO mode.
When the fan is runs in the AUTO mode, the speed is determined
by comparing the room temperature to the set point.
For High Walls and Floor Consoles Fan Coils, when the set point
is satisfied, the fan speed is reduced. For Cassettes and Ducted Fan
Coils when the set point is satisfied, the fan continues to run. The
Fan Coils are not de−energized.
When the unit goes through the defrost cycle, the indoor fans are
de−energized and the refrigerant is circulated through all the fan
coils (even if they were off or on standby before the defrost cycle)
to maximize the heat transfer surface area available for defrost
operation.