Electrical data, connections and wiring
CC
L1 L2 L3
KM
Q1
A1
A2
DGT
HP
KS
KS
KA
KA
KA
LPS
LPS
KA
KS
KM
A3
180s
OCS
M
T3
T1
T2
F1
F1
Locked Rotor Amp value is the highest average
current as measured on mechanically blocked
compressor tested under nominal voltage. The
LRA value can be used as rough estimation for
the starting current. However in most cases, the
real starting current will be lower. A soft starter
can be applied to reduce starting current.
The MCC is the current at which the motor
protection trips under maximum load and
low voltage conditions. This MCC value is the
maximum at which the compressor can be
operated in transient conditions and out of the
application envelope.
The wiring diagram below is example for a
safe and reliable compressor wiring. In case
an alternative wiring logic is chosen, it is
imperative to respect the following rules: when
a safety switch trips, the compressor must stop
immediately and must not re-start until tripping
condition is back to normal and the safety switch
is closed again. This applies to the LP safety
switch, the HP safety switch, the discharge gas
thermostat and the motor safety thermostat.
Winding resistance is the resistance between
phases at 25°C (resistance value +/- 7%).
Winding resistance is generally low and it
requires adapted tools for precise measurement.
Use a digital ohm-meter, a “4 wires” method and
measure under stabilised ambient temperature.
Winding resistance varies strongly with winding
temperature; if the compressor is stabilised
at a different value than 25°C, the measured
resistance must be corrected with following
formula:
a + t
amb
R
amb
= R
25°C
_____________
a + t
25°C
t
25°C
: reference temperature = 25°C
t
amb
: temperature during measurement (°C)
R
25°C
: winding resistance at 25°C
R
amb
: winding resistance at tamb
Coefficient a = 234.5
The max. operating current is the current when
the compressors operates at maximum load
conditions and 10% below nominal voltage
(+15°C evaporating temperature and +68°C
condensing temperature). Max Oper. Current can
be used to select cables and contactors.
In normal operation, the compressor current
consumption is always less than the Max Oper.
A.value.
LRA (Locked Rotor Amp)
MCC (Maximum
Continuous Current)
Max. operating Current
Winding resistance
General wiring
information
Legend
:
Fuses .................................................................... F1
Compressor contactor .................................. KM
Control relay ..................................................... KA
Safety lock out relay ........................................KS
Optional short cycle timer (3 min) ......... 180 s
High pressure safety switch .......................... HP
Fused disconnect ............................................. Q1
Compressor motor ............................................M
Discharge gas temperature ....................... DGT
Safety pressure switch ...................................LPS
Control circuit ...................................................CC
Operating Control System ..........................OCS
13
FRCC.PC.022.A4.02
Application Guidelines
