© 2018 Littelfuse Fresh Water Pumping
Littelfuse.com/Pump-Protection
32
Three-Phase Pump Protection
Fully Programmable
777-P2 / 777-KW/HP-P2 SERIES INSTALLATION INSTRUCTIONS
LP -
Low Power (for KW/HP versions) setting is used to shut
down the motor or pump on an underload condition (that is
based on power instead of solely on current). LP can be set in
either kilowatts (kW) or horsepower (hp) as determined by the
PWS setting. Setting LP to 0 disables the underload trip feature.
NOTE:
PWS must be set before setting LP.
CUB -
Current Unbalance. Littelfuse recommends contacting
the motor manufacturer for a specific setting. Current unbalance
is calculated the same way voltage unbalance is calculated (see
formula under VUB).
Setting CUB to 999 will disable current unbalance and current
single-phase protection.
TC -
Trip Class. Determines how quickly the unit will trip when
an overcurrent (overload) condition is detected. TC is a dual-
function setting—both a thermal trip class (NEMA standard) and
a linear trip delay (in seconds) can be set.
While the standard trip classes are 5, 10, 15, 20, and 30, TC can
be set from 2–60, with or without jam protection. The trip class
setpoint is the time in seconds that the device will take to trip
when any phase current is greater than or equal to 600% of the
OC setpoint. These additional “non-standard” trip classes allow
the unit to follow a trip curve in-between the “standard” trip
class curves shown in Table 11.
Trip classes 2–60 can be set from approximately the 7 o’clock
to 10 o’clock position with the DISPLAY/ PROGRAM knob. Trip
classes J02–J60, which include jam protection, can be set from
approximately the 10 o’clock to 1 o’clock position. This additional
jam protection feature, when enabled, is initiated 1 minute after
the motor starts and provides a 2-second trip delay for motors
exceeding 400% of the OC setting.
The linear overcurrent trip delay can be set from approximately
the 1 o’clock to 5 o’clock position from 0–60 seconds (L00–L60)
or to “oFF.” If TC is set to L00, the unit will trip off within 1
second after motor current reaches the OC setpoint. If both trip
class and linear trip delay settings are programmed, the unit
will follow the faster trip time. For example, TC is set to J15 and
L20, and the amperage is 200% of the OC setting. Following
the trip class 15 curve, the unit will trip off in approximately 100
seconds. Thus the unit will follow the linear trip delay setting,
because it is faster, and will trip off in 20 seconds.
The motor manufacturer should be contacted for an exact TC
setting. Table 11 describes the trip classes, and Table 5 (page 20)
shows the trip class curves.
Table 11: Trip Classes
TRIP CLASS
APPLICATION DESCRIPTION
5
Small fractional horsepower motors where
acceleration times are almost instantaneous or
where extremely quick trip times are required.
10
(Fast Trip) Hermetic refrigerant motors, compressors,
submersible pumps and general purpose motors that
reach rated speed in less than 4 seconds.
15
Specialized applications.
20
(Standard Trip) Most NEMA-rated general purpose
motors will be protected by this setting.
30
(Slow Trip) Motors with long acceleration times
(>10 seconds) or high inertia loads.
J Prefix
Programming any of the trip classes with the J Prefix
will enable jam protection. This additional protection
is enabled 1 minute after the motor starts and
provides a 2 second trip time for motors exceeding
400% of the OC setting, regardless of trip class.
Non-Standard
Trip Classes
Trip time in seconds when any phase current is 600%
of OC. Time is approximately 90% of the TC setting
RD1 -
Restart Delay One. Rapid-cycle timer, in seconds (default).
The purpose of this timer is to provide protection against short
cycling and to allow adequate cool-down time between motor
starts. This timer is initiated when power is first applied to the
unit. If no voltage fault conditions exists, the output relay will
energize (the NO will close and the NC will open) as soon as
RD1 timer expires. In most cases, this is set to 20-30 seconds.
This should provide adequate protection for successive power
outages or short cycling caused by other motor controls. This
timer is also initiated when motor current goes to zero. Setting
RD1 to zero will turn off this feature and ensure that when an
alarm circuit is used, an alarm will sound only when there is a
fault or power to the unit is lost.
RD2 -
Restart Delay Two. Referred to as a motor cool-down
timer, in minutes (default). RD2 is used to restart the motor
after a trip due to a current unbalance, current single-phasing,
or an overcurrent condition. A setting of 5-10 minutes will give
most motors adequate time to cool down after an overcurrent
condition. The motor manufacturer should be contacted for an
exact value.
RD3 -
Restart Delay Three. This timer, in minutes (default), only
initiates after an undercurrent/low power trip and is referred
to as a dry-well recovery timer in pumping applications. This
is set according to the time it takes for the well to recharge
after pumping dry. This setting varies widely by application and
there is no typical setting. RD3 can be set from 2-500 minutes
or to A to enable the automatic Dry-Well Recovery Calculator.
