Why is my magnetic switch not working?

[Mark Gibney]

I wired up this Sherndian MP-09 magnetic switch today, but I can't get it working. It's a 3-phase 240 V switch.

417398

When I press the green button, nothing happens. When I take the cover off and press the manual contactor override (my screwdriver is pointing at it) the switch works.
When I press the on switch with the cover off, nothing.

417399

I bought this switch last year, but am using it now for the first time, and I bought a second one recently for another machine. I wired the second one up and I also failed to get it working.

It's a pretty popular switch as far as I can see, so I'm hoping someone can tell me what I'm doing wrong.

Thanks, Mark

[Matt Day]

Are you using a vfd or do you have 3 phase from the street or RPC?

[Bill Dufour]

I would be suspect of the wiring to the stop switch and the switch itself. Check with a meter if the wires to and from the switch are not making a circuit. The stop switch is wired to be on at all times except when pressed. The ion switch could also be a t fault and not making contact when pressed.
Both these are simple to check with it unplugged.
Does it hum when you hold it closed so you know the coil is working?
Bill D

[Frank Pratt]

You'll need to give us a diagram of how you wired it so we can help out without just guessing.

[Mark Gibney]

Bill, when I press on the contactor override (with the cover off) the motor gets power and everything works fine, so the circuit is good.
There is no humming. And both switches, bought maybe 1 year apart, are behaving exactly the same.

Matt, I have 3-phase in the shop, no VFD.

Frank, I'll take some clearer photos today and describe the wiring this evening. It's very simple however, the line side are landed on the three "lugs" and the three load side wires are landed on their three lugs.

[Dan Friedrichs]

Mark, I can't tell from the picture, but is it possible the reset button is "out"? The overcurrent may be tripped, which would prevent the coil from getting power.

[Charles Lent]

Your problem is in the start/stop switch control circuit that operates the coil to pull in the contactor. Your power leads through the contactor are Ok since pressing in the contactor by hand operates your tool. We need to see how you wired the start/stop switches to be able to help you. Are there motor overload circuits involved? these would be keeping this control circuit from working too. Most of this circuit is a series string and any one of the switches and overload controls sould be causing your problem, or you just failed to hook it up correctly. Show us a wiring diagram and some close-up pictures.

Charley

[Mark Gibney]

Here are some more photos
417416 - this is the line side.

417417 - the load side.

417418 417419 - this little wiring schematic is the only “instructions” that came with the
switches.

If if you need more detail on any aspect just let me know. Thanks

[Frank Pratt]

Okay, the overload relay has 2 sets of contacts, one is normally open, the other is normally closed. It appears as though you are connected to one side of one set & the other side of the other set. So no matter what the contact state is, current can't flow to the coil. The normally closed (closed when not in overload condition) is the set you need to use.

You should have a wire running from one of the coil terminals to one side of the OL contacts, terminal 95. Terminal 96 should have a wire connecting it to one of the line terminals.

[Mike Kreinhop]

Here is a link to a similar contactor used by Grizzly. Your contactor should be wired the same way.

https://cdn0.grizzly.com/manuals/t20551_m.pdf

When you manually push the override with your screwdriver to close the contactor, does it remain closed (energized) when you pull away your screwdriver? If not, then there is a wiring problem with the Start/Stop switch circuit. If it does remain closed when you pull away your screwdriver, can you turn it off by pressing the red stop button? If so, then the problem is likely the Start switch.

The easiest way to determine if the Start switch is bad is to disconnect power from the contactor and connect an Ohmmeter across terminals 7 and 8 of the contactor. There should be continuity between these terminals only when the Start button is pressed. If you are confident in your electrical skills, another way to determine if the start switch is bad when power is connected is to use a short jumper wire to momentarily connect terminals 7 and 8 of the contactor. These are the latching contacts that are wired in parallel to the start switch.

[Charles Lent]

I kind of disappeared on you right in the middle of this (needed heart surgery), but I'm back and I agree with Frank's post #8. I think he figured out where your problem is. In the bottom of your electrical diagram are two horizontal lines that show the wiring of the control circuit for this relay. You have something missing in this circuit. Any open connection in this circuit will cause the relay not to operate. A jumper wire, a mis wired connection, etc. and I'm putting my bet on Frank.

Charley

[Steven Cooper2]

Not sure why it wouldn't stay on if you manually activate it, but it appears that you may have it connected backwards. The line side should be 1,3,5,and 7.

Since there would be no power to activate the contactor, it wont latch.

[Frank Pratt]

Line side is L1, L2, L3 (or 1, 3, 5). 7 and 8 are for the holding contact & it needs to be connected as per the diagram inside the cover.

An explanation: the start pushbutton has a normally open contact that upon being pressed, is momentarily closed, energizing the coil, which closes the motor contacts. But when the start button is released, the contactor would open again if not for the holding contact. It is connected in parallel with the start button, and when the contactor closes that holding contact closes, maintaining power to the coil after the start button is released.