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the problem is a recurring
one, measure voltage with
recorder on a 24 hour basis.
d. Make sure the floats
are located away from
any turbulence.
e. Dry out the junction box
(if furnished); moisture
in the junction box
may cause relays to
energize intermittently.
6. Short cycling pump.
a. Check float controls.
7. Run light stays on.
a. Selector switch may be in
the Hand position.
8. Nuisance tripping of
overload on motor starters
or circuit breakers.
a. Check pump amp draw with
amp probe and compare to
nameplate amps on pump.
b.The impeller may be locked
up due to excessive debris
or solids.
c. Possible motor failure (fault
in windings).
d.Pump may be miswired to
terminal block.
e. Check for possible voltage
and current unbalance.
(Three-phase only).
Voltage unbalance on
three-phase power sources
can cause motor current
to become unbalanced
and excessive heating will
result. Tripping of the
overload protectors and
premature motor failures
can be expected if the
current unbalance exceeds
five percent.
Maximum Current
Percent
Difference from x 100
Current
=
Average Current
Unbalance
Average Current
To determine if motor current
unbalance is a function of the
motor or the power supply:
1. Label the leads and the
terminals 1, 2 and 3
respectively.
2. Record the amperage for
each lead.
3. Move each lead to the
next terminal (1 to 2, 2 to 3,
3 to 1).
4. Read the amperage of
each lead.
5. Move each lead to the
next terminal (1 to 3, 2 to 1,
3 to 2).
6. Read the amperage of
each lead.
7. If the unbalance moves
with the motor leads, the
unbalance is caused by the
motor. If the unbalance
remains with the terminals,
the unbalance is in the
power supply.
8. If the current unbalance
exceeds five percent,
nuisance tripping or
excessive heating
will result.
9. Connect leads for
the lowest percent of
current unbalance.
f. Check connections and
start components on single-
phase units.
1. Disconnect all power from
the panel before making
these checks.
2. Motor winding resistance
readings.
a. Disconnect all three
motor leads from panel
terminal blocks.
b. Using a volt-ohmmeter,
with the scale set on
RX1, measure the
resistance between the
leads with the chart.
Typical
Winding
Motor Leads
Main
Black to
White
Start
Black to
Next Lowest
Red
Both
White to
Red
3. Check capacitor.
a. Make sure the capacitor
is discharged. Use
extreme caution as a
spark might occur.
b. Disconnect the
capacitor leads and
connect an analog-type
volt-ohmmeter to the
capacitor terminals.
c. Set the meter on the
RX1,000 scale to check
the start capacitor.
Set the meter on the
RX10,000 scale to check
the run capacitor.
d. The meter should
indicate low ohms when
it is first connected, but
as the capacitor becomes
charged (by the meter),
it will return to a reading
of infinity (open circuit).
4. Check start relay.
a. Check the coil
resistance. It should be
3,000 to 15,000 ohms.
b. Install a clamp on amp
meter around the start
winding lead.
c. Set the amp meter
scale to at least 2 times
the pump motor full
load current.
d. Place the H-O-A switch
in the Hand position to
start the pump.
e. The meter should
read approximately 2
times full load current
during starting.
Resistance
Reading
Lowest
(Middle)
Highest
(Main &
Start)
5
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