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Check that the currents in the individual phases of
a 3-phase system are approximately equal. Where
there is considerable difference between them, change
all 3 connections at the starter as shown below (so
that rotation remains the same) to obtain the most
consistent readings.
Starter L1 L2 L3
cable (1) black yellow red
cable (2) red black yellow
cable (3) yellow red black
Then subtract the average of the readings from the
highest. The difference, expressed as a percent of the
average must not exceed 10%. Note that the highest
reading must not exceed the maximum permissible
for the motor.
WARNING
FAILURE TO GROUND THE UNIT PROPERLY CAN
RESULT IN SERIOUS OR FATAL SHOCK. REFER
TO ELECTRICAL CODE REQUIREMENTS.
EXAMPLE:
Phase 1 54.0 amp
Phase 2 55.0 amp
Phase 3 60.0 amp
Average: 56.3 amp
% Unbalance = 60 - 56.3 x 100
56.3
= 3.7 x 100 = 6.6%
56.3
(a) Install additional riser pipe to place pump lower in
the well if possible.
(b) Use a cock or similar valve in the discharge line to
throttle the pump output to suit the yield of the well.
(c) Install FLOATLESS LIQUID LEVEL CONTROL.
(d) Use a pressure switch with a low water protection
or a separate low-water cutout switch. Neither of
these devices give as reliable protection as a fl oatless
liquid level control and both require careful application.
(e) Replace the pump with smaller unit to avoid over
pumping the well.
Damage can occur to both pump and motor, in addition,
air drawn into the pump can cause air-lock
.
H. ACCESSORIES WITH INSTALLATION
LIGHTNING ARRESTERS
Install lightning arresters to protect the motor from the
effects of electrical storms. Although they will not give
protection against direct stirkes they will ground the
surges caused in transmission lines by surrounding
storms.
One arrester is suffi cient for a single-phase unit, but
two are necessary for a three-phase unit. Install them in
accordance with the manufacturers separate instructions,
either in the control box on some single-phase systems,
or in the supply line immediately ahead of the control
equipment. Pay particular attention to the ground
connection. DO NOT USE GROUND ROD. Use the best
ground on the premises, which is usually the metal riser
pipe from the pump or other metal water pipe.
RELIEF VALVE
Always install a relief valve if the pump is capable of
developing pressures in the discharge system greater
than the pressure ratings of individual components. The
relief valve must be large enough to handle the pump
output at the relief pressure.
*CAUTION*
NEVER RUN THE PUMP UNLESS IT IS
COMPLETELY SUBMERGED IN WATER.
Should the unbalance exceed 10%, ask the power
company to improve the voltage balance between the
incoming lines.
5- Use a voltmeter to check the voltage at the starter while
the pump is running. The average must be within 10% of
the motor rating, and the maximum variation of any phase
of a 3-phase system for the average should not
exceed 1%.
6- Continue to run the pump until the drawdown of the
water in the well becomes stable. Should the water level
drop to the pump intake to admit air, use one or more of
the following methods to protect installation.
6