6.7.7 Wiring checks and installation
Before making the final surface wiring connection of the
submersible drop cable to the control box or control panel, it is a
good practice to check the insulation resistance to ensure that the
cable and splice are good. Measurements for a new installation
must be at least 200 megaohms. See the table below.
If the insulation resistance of the cable and splice is measured at
higher than 200 megaohms, run the submersible drop cable
through the well seal with a conduit connector to prevent foreign
matter from entering the well casing.
Always protect the submersible drop cable with conduit from the
pump to the control box or control panel. See the figure Wiring and
installation diagram above.
Finish the wiring and make sure that all electrical connections are
made according to the wiring diagram.
Make sure that the control box or control panel and high-voltage
surge arrester are grounded.
Route conductors properly such as in conduit where called for by
Local Code to protect the conductors.
Related information
6.7.8 Insulation resistance and ohm value chart
6.7.6 Control box or panel grounding
6.7.8 Insulation resistance and ohm value chart
The insulation resistance in a submersible pumping system is a
measure of the ability of the motors and/or cables to withstand
normal - and transient voltage without breakdown and failure. An
"adequate" level of insulation resistance is not a constant value, but
depends on the installation voltage and conditions, and whether the
measured resistance is lowered by a specific weak point or by
widely distributed conductance such as in cable insulation material
itself. For this reason, values for acceptable resistance cannot be
specific.
Insulation resistance measurements
Measure the insulation resistance at the time of initial motor
installation and then periodically. In deep set submersible
installations, take measurements throughout the installation process
to detect potential cable insulation or connection damage before the
unit is completely installed. The insulation resistance table in this
section describes the condition of the insulation system for a
submersible motor system of 600 V or less, based on
megohmmeter readings.
Measure the insulation resistance according to local
codes and regulations.
The table below indicates suggested values of insulation resistance
and the test voltage in relation to the rated voltage of the motor.
Rated voltage
≤ 500 [V]
> 500 [V]
Condition of motor and cable
[MΩ]
[MΩ]
New motor without submersible
drop cable
≥ 200
≥ 200
Used motor which can be re-
installed in a well
≥ 10
≥ 10
New motor in a well
≥ 20
≥ 20
Motor in good condition in a well
≥ 0.5
≥ 1
Damaged insulation
< 0.5
< 1
If the rated motor voltage is less than or equal to 500 V, the
insulation resistance must be measured at a test voltage of 500
VDC.
If the rated motor voltage is greater than 500 V, the insulation
resistance must be measured at a test voltage of 1000 VDC.
7. Startup
After the pump is set into the well and the wiring connections have
are made, go through the following procedures:
1. Attach a temporary horizontal length of pipe with installed gate
valve to the riser pipe.
2. Adjust the gate valve one-third of the way open.
3. On three-phase units, check direction of rotation and current
imbalance according to the instructions below. For single-phase
units proceed directly to section Developing the well.
4. Do not operate the pump with the outlet valve closed. This can
result in damage to the motor and the pump due to overheating.
Install a properly sized relief valve at the well head to prevent
the pump from running against a closed valve.
Related information
7.1 Startup with three-phase motors
7.1.1 Check the direction of rotation
Three-phase motors can run in either direction depending on how
they are connected to the power supply. To make sure the motor is
running in the proper direction, follow the procedures below:
1. Start the pump and check the water quantity and pressure.
2. Stop the pump and interchange any two leads.
3. Start the pump and again check the water quantity and
pressure.
4. Compare the results observed. The wire connection which gives
the highest pressure and largest water quantity is the correct
connection.
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