Resistance Checks - Pentair MYERS MSK75 Installation And Operator's Manual

Maintenance
Using an ohmmeter
To be sure wires are not burned off or broken, use an
ohmmeter to perform resistance checks. Set ohmmeter
scale to R X 1 scale and check meter by putting both
meter leads together and adjusting the needle knob until
meter reads zero. If meter cannot be adjusted to zero, the
batteries in meter must be replaced.
NOTICE: Always reset meter to zero [0] when going to a
new scale before making any measurements.
If wire is OK, meter needle will go to near zero and stay
there. If meter needle does not move, the wire has an
open and the wire must be repaired or replaced.

Resistance Checks

1. For single phase (1ø) pumps, attach one meter lead
to the white cord wire of the power cord and the
other meter lead to the black cord wire. This reading
should match the resistance shown in Winding
Resistance Chart, 1ø, 230V.
Model Start Winding
MSK75 6.63 Ω
MSK100 8.57 Ω
Winding Resistance Chart, 1ø, 230V
For three phase (3ø) pumps, repeat the above
procedure for white and red wires as well as red
and black wires. Each of the three separate readings
should read approximately the same and should
match the resistance shown in Winding Resistance
Chart, 3ø. If no resistance is obtainable for any of the
three phases, either a wire is broken, there is a bad
connection or the winding is defective. Skip Steps 5
and 8 if resistance is OK.
200V
Any one
Model
phase
MSK75,
7.31 Ω
MSK100
Winding Resistance Chart, 3ø
2. Remove plug (3) from top of housing (4) and pour
oil into a clean glass container. If oil is clear, it
will indicate motor is not burned and there has
been no water leak into the motor. If oil is black,
it will indicate a burned stator. If oil is cloudy, it
will indicate water in motor oil, so all seals should
be replaced.
Run WInding
3.06 Ω 9.69 Ω
2.35 Ω 10.92 Ω
230V 460V
Any one Any one
phase phase
9.66 Ω 38.65 Ω
3. After draining oil, remove the hex head cap screws
(7) that attach motor housing (4) to volute (11).
Slide motor housing upward 5 to 6 inches in order
to expose power cord wire connections to motor
(5). Disassemble power cord wire connections from
motor and then disassemble power cord from motor
housing. Using the wire leads from the motor, check
the winding resistance with an ohmmeter.
For Single Phase (1ø)
4. Attach one meter lead to the white cord wire and the
other meter lead to the black cord wire. See Winding
Resistance Chart, 1ø, 230V for an appropriate
resistance reading. Repeat this procedure for the
black cord wire and red lead wire. This reading is the
start winding resistance. Also repeat this procedure
for the white cord wire and the red cord wire. This
reading is the total motor winding resistance. If no
resistance is obtainable for either the start or main
winding, either there is a bad connection or the
winding is defective.
Total
For Three Phase (3ø)
5. Twist the three leads of one end of the power cord
together. Then at the other end, with an ohmmeter,
check any two leads. Check the third lead with either
of the first two. If a zero reading is indicated for
any wire, the wire is broken and a new power cord
assembly must be installed.
6. Ground check on stator should be performed using
ohmmeter with scale set to R X 100K. Connect one
meter lead to one lead of the stator and touch the
other meter lead to the housing (4). If the resistance
to the ground is less than 500,000 ohms, there is
moisture in the winding or leakage through stator
insulation. The stator must be dried out and then
575V
rechecked on the ohmmeter. If the resistance is still
Any one
less than 500,000 ohms after drying, the stator must
phase
be replaced. A zero reading indicates a direct short,
60.39 Ω
and the stator will have to be replaced.
6