Electrical data, connections and wiring
Compressor models
SM/SZ084 - 090 - 100 -
110 - 112 - 120 - 124 - 147 - 148 - 161 have been
provided with an internal overload motor
protection to prevent against excessive current
and temperature caused by overloading,
low refrigerant flow phase loss or incorrect
motor rotation. The cutout current is the MCC
value listed in section "Three phase electrical
characteristics".
The protector is located in the star point of the
motor and, should it be activated, will cut out all
three phases. It will be reset automatically.
While not compulsory, an additional external
overload protection is still advisable for either
alarm or manual reset.
Then it must be set below MCC value (at max
operating current):
• when the motor temperature is too high, then
the internal protector will trip
• when the current is too high the external
overload protection will trip before the internal
protection therefore offering possibility of
manual reset.
Compressor models SY/SZ 240 - 300 - 380
and SM/SZ115-125-160-175-185 J, K, P, S,
U, W, X, Y versions
are delivered with a pre-
installed motor protection module inside the
terminal box. This device provides for efficient
and reliable protection against overheating and
overloading (as well as phase loss/reversal for SY/
SZ 240-300-380).
The motor protector comprises a control module
and PTC sensors embedded in the motor
winding. The close contact between thermistors
and windings ensures a very low level of thermal
inertia.
The motor temperature is being constantly
measured by a PTC thermistor loop
connected on S1-S2 (called 1-2 on SM/
SZ115-125-160-175-185).
Compressor models SM/SZ175 - 185
R & C
versions
have been provided with a bimetallic
single-pole, single-throw thermostat located
in the motor windings. In the event of motor
overheating caused by low refrigerant flow or
improper motor rotation, the thermostat will
open. Because the thermostat is an automatic
reset device, it must be wired within a lockout
safety circuit with a manual reset to restart the
unit. For over-current and phase loss protection,
an external overload protector must be used.
The external overload protector can be either a
thermal overload relay or a circuit breaker:
A thermal overload
relay should be set to trip
at not more than 140% of the compressor-rated
load current.
A circuit breaker
, on the other hand, should be
set at not more than 125% of the compressor
rated load current.
The rated load current is the maximum current
expected during operations of the considered
application.
Further requirements for the external overload
protector are:
•
Over-current protection
: the protector must
trip within 2 minutes at 110% of the Maximum
Must-Trip current (MMT).
•
Locked rotor protection
: the protector must
trip within 10 seconds upon starting at a locked
rotor current (LRA).
•
Single-phasing protection
: the protector
must trip when one of the three phases fails.
Motor protection
The table below shows the protection method for the various compressors models.
Recommended
Required
No test or additional safeties required
REQ
REC
Overheating protection
Over current protection
Locked rotor protection
Phase reversal protection
SM/SZ 115-125-160-175-185
R & C version
Internal thermostat
External overload protection
Reverse vent.
SM 112- 124-147
Internal motor protection
Phase sequence detector
SM/SZ 084-090-100-110-120-148-
161 - SZ147
Internal motor protection
Reverse vent.
SM/SZ175-185
J-K-P-S-U-W-X-Y version
Electronic module located in terminal box
Reverse vent.
SY/SZ 240-300-380
Electronic module located in terminal box
REC
REQ
21
FRCC.PC.003.A5.22
Application guidelines
