GE Multilin 239 Motor Protection Relay 2-9
2 INSTALLATION 2 INSTALLATION
2
jumper wire is connected between the access terminals all setpoints and configurations can be
programmed using the keypad. Once programming is complete the jumper will normally be
removed from these terminals or the connected keyswitch left open. When this is done all actual
and setpoint values can still be accessed for viewing; however, if an attempt is made to store a
new setpoint value the message
illegal access
will appear on the display and the previous set-
point will remain intact. In this way all of the programmed setpoints will remain secure and
tamperproof.
• EMERGENCY RESTART (39/44): When production or safety considerations become more
important than motor protection requirements, it may be necessary to restart a tripped motor. If it
is desired to override relay trips or lock-outs and restart the motor, a normally open keyswitch
should be installed between the emergency restart terminals 39 and 44. Momentarily shorting
these terminals together will cause the thermal memory of the 239 to discharge to 0% used. The
emergency restart terminals can be used to override a trip lockout caused by a running overload
or locked rotor start. This option should be used only when an immediate restart after a lock-out
trip is required for process continuity or personnel safety. Discharging the thermal memory of the
239 gives the relay an unrealistic value for the thermal capacity remaining in the motor and it is
possible to thermally damage the motor by restarting it. Shorting the Emergency Restart termi-
nals together will have no effect unless the motor is stopped (no phase or ground current
present). Having these terminals permanently shorted together will cause the memory to be
cleared whenever the motor stops. This will allow for an immediate restart after an overload trip.
Caution is recommended in the use of Emergency Restart input since the thermal protective
functions of the 239 will be over-ridden and it is possible to damage the motor.
• EXTERNAL RESET (40/45): An external reset switch which has the same effect as the front
panel RESET key or a serial port reset command can be connected to terminals 40 and 45 for
remote reset operation. The switch should have normally open contacts. Upon the momentary
closure of these contacts the 239 will reset any latched alarm, latched auxiliary relay output, or
trip providing it is not locked out. Installing a jumper wire permanently across the external reset
terminals will cause the 239 to reset any latched alarm or trip whenever motor conditions allow
for automatic reset.
• OPTION SWITCH 1 (41/46) & 2 (42/47): Two option inputs are provided. These switch inputs are
considered active when closed. The state of these input switches can be monitored by the serial
port for process signaling. They can also be programmed to provide an alarm, trip, alternate
motor control setpoints or process control after a programmable time delay. Programming for
these switch inputs, if used, is found in
63527(&7,21?6:,7&+,13876setpoints.
f) THERMISTOR INPUT (21/22)
A motor can be equipped with a single thermistor in the end turns or three in the stator windings for
overtemperature detection. Either positive thermal coefficient (PTC) or negative thermal coefficient
(NTC) type thermistors may be directly connected to the 239. PTC thermistors are preferred because
3 thermistors can be connected in series to monitor each of the stator phases. This is not possible
with NTC thermistors because all three thermistors must be hot to obtain an indication. Select ther-
mistors that have a resistance between 100 to 30 000 Ω at the intended alarm/trip temperature.
Either linear thermistors or those with a sharp change in resistance at the required temperature can
be used. If no thermistor sensing is required, these terminals can be left disconnected and the ther-
mistor feature programmed OFF.
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