Electrical data, connections and wiring
The compressor will only operate properly in a
single direction. Use a phase meter to establish
the phase orders and connect line phases L1, L2
and L3 to terminals T1, T2 and T3, respectively.
For three-phase compressors, the motor will run
equally well in both directions. Reverse rotation
results in excessive noise; no pressure differential
between suction and discharge; and suction line
warming rather than immediate cooling.
A service technician should be present at initial
start-up to verify that supply power is properly
phased and that compressor and auxiliaries are
rotating in the correct direction.
MLZ/MLM015-038 scroll compressors are
designed to operate for a maximum of 150 hours
in reverse, but as a reverse rotation situation can
go unnoticed for longer periods, phase monitors
are recommended.
For compressors MLZ/MLM048 and larger,
phase monitors are required. The selected phase
monitor should lock out the compressor from
operation in reverse.
At brief power interruptions, reverse rotation can
occur with single phase compressors. In this case
the internal protector will stop the compressor.
It will have to cool down and will restart safely
afterwards.
For three-phase applications the voltage
measured at the compressor terminals for each
phase should be within ± 2% of the average for
all phases.
Phase sequence and
reverse rotation
protection
Voltage imbalance
Internal motor protection
MLZ/MLM scroll compressors are equipped with
an internal line break protector mounted on the
motor windings. The protector is an automatic
reset device, containing a snap action bimetal
switch.
Internal protectors respond to over-current and
overheating. They are designed to interrupt
motor current under a variety of fault conditions,
such as failure to start, running overload, and fan
failure.
If the internal overload protector trips out, it must
cool down to about 60°C to reset. Depending on
ambient temperature, this may take up to several
hours.
Three phase
Suggested wiring diagram
with "one shot" pump down
cycle and safety lock-out relay
Control device .................................................. TH
Optional short cycle timer (3 min) .........180 s
Control relay .................................................... KA
Liquid Line Solenoid valve .........................LLSV
Compressor contactor .................................. KM
Phase monitor ................................................ PM
Safety lock out relay ........................................KS
Pump-down control low pressure switch ..LP
High pressure safety switch........................ HPs
Fused disconnect ............................................Q1
Fuses ...................................................................F1
Compressor motor ...........................................M
Discharge gas thermostat ......................... DGT
M
DGT
HPs
180 s
TH
LP
CONTROL CIRCUIT
F1
F1
KM
KM
KM
KA
KA
A1
A2
A3
KA
KA
KS
KS
KS
L1
L3
L2
Q1
T1
T3
T2
LLSV
KS
Wiring diagram with pump-down cycle
PM
24
FRCC.PC.015.A8.02
Application Guidelines
