Daikin Maverick II MPS062E Installation And Maintenance Manual page 71

7. The compressor should operate continuously while there
is a call for cooling. If the compressor cycles on its low
pressure switch, do the following:
a. Verify that the circuit is not short of refrigerant.
b. Check for low airflow.
c. Check for clogged filters.
d. Check for restricted ductwork.
e. Check for very low temperature return air entering
the unit.
f. Verify that the liquid line components, expansion
valve, and distributor tubes are feeding the
evaporator coil.
g. Verify that all air handling section panels are closed.
h. Verify that the liquid line service valves are
completely open.
8. Verify that the compressors stage properly. As the circuit
loads up the second compressor (if available) will be
energized. For more information on staging sequences,
refer to IM 919 and OM
9. Verify that the condenser fans are cycling and rotating
properly (blowing air upward). When the compressor
starts, at least one condenser fan should also start. The
CCB1 should control the remaining condenser fans based
on ambient air conditions. Look at keypad menu Main
Menu\Commission Unit\Cooling Setup\ Cfan Out1 Spt =,
Cfan Out2 Spt =, Cfan Out3 Spt.
shows recommended setpoints based on the unit size.
Cond Fan1 controls BO5, Cond Fan2 controls BO6, Cond
Fan3 controls BO7, Cond Fan4 controls BO8. Refer to the
unit wiring diagrams and
10. After 15 minutes of run time, check the oil level in the
compressor sightglass. If low oil or heavy foaming is
observed, it is possible that liquid refrigerant is returning
to the compressor. Check the suction superheat (see
Expansion Valve Superheat
between 10°F (5.5°C) and 13°F (7.2°C).
11. Open S1. the compressor should stop. Place the unit
into the "Fan Only" mode through the keypad menu Main
Menu\Quick Menu\Ctrl Mode = fan only.
12. Check refrigerant circuit #2 by repeating steps 2 through
9, substituting circuit #2 nomenclature for circuit #1
nomenclature (CS2, TD2, CCB2, and compressor #2
(and #4).
13. Check the compressor oil level again, add oil if low.
14. Verify that the condenser refrigerant subcooling at full
capacity is between 13 and 20°F.
www.DaikinApplied.com
920.
Table 2 on page 14
Table 3 on page 14.
Adjustment). It should be
Check, Test, and Start Procedures
Expansion Valve Superheat Adjustment
It is very important that the expansion valve superheat setting
be adjusted to be between 8°F (-13°C) and 14°F (-10°C).
Insufficient superheat will cause liquid floodback to the
compressor which may result in slugging. Excessive superheat
will reduce system capacity and shorten compressor life.
Turn the adjustment stem clockwise to increase superheat.
Not exceeding one turn, adjust the stem and then observe the
superheat. Allow up to 30 minutes for the system to rebalance
at the final superheat setting.
On refrigeration circuits with multiple expansion valves, the
superheat adjustment should be approximately the same for all
valves in the circuit.
Checking Superheat
Following are recommendations for checking superheat:
1. Close the unit section doors. Running the unit with
its doors open will affect expansion valve and system
operation considerably.
2. For units with one expansion valve per circuit, check the
pressure and temperature at the compressor suction valve.
3. For units with multiple expansion valves per circuit,
check the pressure at the compressor, and check the
temperature at the suction header that is fed by the valve.
NOTE: If low oil level is accompanied by heavy foaming
visible in the oil sightglass, it is possible that excess
liquid refrigerant is returning to the compressor
depending on the rotation of the crank shaft. Check
the suction superheat and adjust the expansion
valve for 8°F (-13°C) and 14°F (-10°C) of superheat.
If proper superheat is obtained, sightglass foaming is
not a concern.
For RCS/RFS applications in which the condensing section
is remote from the air handling section, consideration should
have been given to proper piping between the sections, as
this can affect the compressor oil level. Refer to the
Handbooks" for more information on proper refrigeration piping
design and installation.
71
"ASHRAE
IM 991-2 • MAVERICK II ROOFTOP