How to identify the ground core if the wires are the same color?

  • Mar 15, 2021

This question, already 64 in a row, with just such a title, was asked by the reader Yuri. If you have your own answer to the question, then write it in the comments below. I and other readers will be happy to read it.

The text of the question itself read literally as follows:

Hello. An old Soviet water pump has an electrical plug cut off. All wires are the same color. How to identify a grounding conductor. Thank.

I considered the issue and consulted Yuri within the framework of my knowledge and qualifications as follows:

Good day!

In principle, there is nothing complicated here, to determine the protective conductor you need the pump itself and multimeter (tester), if there is neither a multimeter nor a tester, but there is a megohmmeter, then you can use and him.

To check, follow this sequence of actions:

  • Strip the ends of the three cores that protrude from the pump so that you can clearly touch them with the probe in turn, excluding the contact of the probe with adjacent cores.
  • Then set the tester to the continuity mode, connect the test leads to the corresponding terminals of the multimeter.
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  • Secure one dipstick to the pump housing. It is important that the installation site has good contact, therefore, if there is paint, a thick layer of dirt and other obstacles to the flow of electric current into the case, they need to be cleaned or another a place.
  • With a second feeler gauge, as shown in the figure below, touch each core of the pump power cord alternately.
  • The core that shows the circuit with the case is the protective conductor. Accordingly, the other two are the phase conductor and the neutral conductor.

This method is relevant for checking a working pump, if the insulation of the windings of an electric machine has a breakdown to the case, then not only the PE conductor will ring with the ground. As for the megohmmeter, the test method is identical with the difference that you have to roll the insulation between the case and each wire. The one that will show a short circuit will be the protective conductor.