I have a borewell with a 3-phase submersible pump that I want to control with a water level controller (when the overhead tank is empty, it should start the motor and when the tank is full it should stop the pump, automatically).

On the advice of the sales staff, I purchased a controller rated for 415 volt which (according to the staff) was the most suitable for my 3 phase pump. (Technical info of the GIC Water Level Controller here - PDF file).

Now, I am confused as to how to connect the mains to the controller. The circuit diagram for my requirement shows -

enter image description here

  • Neutral being connected to A2 terminal and Line to A1 and 15 terminal in the controller.

But since my controller is rated for 415 volts, should I instead connect the 3 Lines (RYB of 3-phase) individually to the A2, A1 and 15 terminal, as otherwise the single phase (neutral and line) will provide only 230 volts?

FYI: Single phase supply in my country is 230 volts and three phase is 240 / 415 volts at 50 hz.

(The service engineer who can clarify my doubts is not reachable for a few days and hence my post here).


Page 186 of the technical sheet of the controller has this connection diagram:

connection diagram

which clearly shows that the input supply should be 110v / 240v / 400 volt (+ or - 20%) depending on what the controller is rated for. As I said before, the sales person insisted that the 415v rated controller is what I need for a 3-phase pump.

The controller has this printed on its side:

controller detail

This input supply of 415 volt is the source of my confusion as residential single phase supply in my country is 230 volts only. (And that is why I assumed that I have to use more than one phase as input to provide the 415v).

  • Am I misunderstanding something very obvious or did the sales person give the wrong advise and I should have got the 240v rated controller?

Since some of you have asked about the motor controller - the unit has a contactor, relay and single phasing protection relay (SPPR - SZ5). Circuit Diagram:

Mu-G6 Motor Controller Circuit

I was advised to remove the loop between D1 and D2, and connect terminal 18 (of the water level controller) to D1 and connect terminal 16 (of the water level controller) to D2. This would ensure the water level controller would automatically start or stop the pump through the motor controller.

  • Why are you using that diagram as you say you are switching 3-phase? Do you have the 3-phase contactor? The 3 sensor choice seems fine though.
    – Solar Mike
    Jun 10, 2019 at 8:13
  • Yes, I do have a 3 phase motor controller. That's the wiring diagrams given in the technical sheets (you can refer to the PDF file I have linked to in the question), and my source of confusion, as it only shows a single phase input for all 3 types of controller which only seem to vary by ratings (110v, 240v and 400v).
    – sfxedit
    Jun 10, 2019 at 8:46
  • Diagram p184 top left clearly shows the 3-phase contactor... which is what I referred to in my first comment. I asked whether you had a 3-phase contactor, not the level controller, which, I assumed you had already as that is the component you are talking about.
    – Solar Mike
    Jun 10, 2019 at 8:48
  • Oh ok. If you notice though, that doesn't matter much as the controller will be wired to the start / stop switch of the motor controller (i.e. to the contactor). My confusion is why did the sales person recommend the 400v rated controller if that expects a SINGLE phase supply of 400 volt, which obviously I cannot provide. Since the voltage between the lines of 3 phase is 415v, I was wondering if I it is meant to connect L1, L2, L3 to A2, A1 and 15 terminal instead of the neutral and line as shown, to provide 3 phase compatibility?
    – sfxedit
    Jun 10, 2019 at 9:23
  • 1
    See my edits in my answer. Nice improvement on the question BTW. Jun 10, 2019 at 19:10

2 Answers 2


I certainly don't see any reason why not. All the heavy switching is done by the contactor. The controller couldn't care less what kind of current actually powers the motor: 3-phase, Japan 100V, hydraulics, pneumatics, Lackawanna 3000VDC, 4-phase early 1900s power, Detroit street lighting DC, clutchable drive shaft, warp plasma, or any darned thing you can find a contactor for.

The contactor fully isolates the controller's voltage from the power that actually runs the pump.

You do not hook multiphase mains (or air, or warp plasma) to the controller normally. But in this case, you seem to have specced a 415V controller for some reason. The only way to get that is to connect 2 phases line to line. For that connection you will not use the third phase.


You actually have a problem here. All the other wires here are phase wires. The circuit from 15/18 to the contactor needs to be <=250v otherwise you will exceed the rating of the relay. That means you must use single-phase line to neutral (or really, anything the contactor can use, as long as it’s less than 250V).

Now in this drawing, they have inelegantly shown taking the neutral from the pump mains supply. This is wrong in all cases and violates the "currents must be equal/balanced" rule. As you know, current flows in loops, that is a very bad loop!

Normally I would say "The contactor coil should get its neutral from controller supply, e.g. from A2 on this drawing". But in this case, your controller will need 415V line-line, and so neutral will not be present.

If this is "wye" power you may be able to bring over neutral. If it is "delta" power simply use a different circuit.

If the relay coil is 415V you cannot use iqt because 415>250. Regardless, you need a 3-pole contactor, because it's 3-phase.

* to those who believe all 3-phase delta is "240V wild leg delta" with neutral centered on a leg, this is Europe and there's no such thing. Also even in America not all 3-phase delta is that.

  • Doesn't the controller need an input supply of 415 VAC? Please see the additional info added to the question and clarify.
    – sfxedit
    Jun 10, 2019 at 18:16
  • The relay that controls the contactor coil is plainly only rated to 250V, so you will need 230V for the circuit from relay to contactor coil. The controller itself is sold in 120 or 230 or 415, you seem to have the 415 version, which will be awkward because you will need to connect the source-pin15-contactor-pin16-source circuit to 230V. Jun 10, 2019 at 18:38
  • No, it's Made in India. Page 183 of tech sheet suggests there are 3 models of this controller - one is rated for 110 vac input supply, the other for 240 vac, and the third for 415 vac (with a margin of + or - 20% to accommodate voltage fluctuation). I guess I'll have to talk with the service engineer to see why I was asked to get the 415 vac model.
    – sfxedit
    Jun 10, 2019 at 18:52
  • 1
    No. The 15/16/18 relay is still only rated for 250V. Yes, really, even on the 415V model. You cannot use the same power for the controller itself vs. the source-18-15-contactor-source loop. If it has to go in today, then use a separate 230V circuit for that contactor loop. Jun 10, 2019 at 19:08

Two long for a comment:

You are getting control voltage mixed up with the power for the motor, the controller can be any voltage for example 24vdc is common the controller is doing just that, monitoring and controlling the output, your print is single phase see the wiring to the motor there are only 2 wires a L & N , the controller monitors the sensors in the tank and based on these inputs it sends a signal to the contactor (or relay for most non sparkys). The control voltage out of the controller can be anything but needs to match the voltage on the contactor. The a1 & A2 terminals on the contactor is where the power goes when the controller turns on. This voltage must match the controller output, for example most residential systems I work on use line voltage so the coil is normally 120v but many larger systems use 24v to be safer for troubleshooting, when I first started if the system ran on 480v the control voltage was 277 or 480. Today you never see that or very rarely because of safety concerns and costs, it is less expensive to use lower voltage control circuits and the only difference to the contactor is the size of coil installed in a1-a2, I had a tough time following your question since the drawing is single phase so I am trying to explain how control circuits work. The power across the coil turns on the contactor as mentioned before the power to terminal 15 is power that the controller runs on. So the controller voltage should be listed and connected to the correct voltage (the only part of the circuit that needs to be 3 phase rated is your contactor but it can be controlled by a different voltage (and usually is a different voltage than the 3 phase leg to leg voltage).

  • Please see the additional info added to the question and kindly update and clarify.
    – sfxedit
    Jun 10, 2019 at 18:17

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