480 volt contactor will not close.

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copper123

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Good Morning

I went out and looked at a problem for a friend yesterday. The electrical contractor had installed a 480-volt, 3 phase, 60 amp Square D contactor that drove an air-circulating fan. He had told me that the fan would not kick in upon closing the control ckt. The coil voltage was 120 volt and the control ckt distribution was right next to the controller. ( no voltage drop, voltage was nominal when metered). Anyhow, with the control ckt closed, X2,(neutral) was not feeding through and providing potential at the contactor coil terminals. Upon going through the old, faded schematic on the cover, I think the neutral side has a N/C contact point that might have some sort of overload protection. It sure seems like it, as the X2 side has a line and load terminal. It has a field landed terminal and a factory landed terminal that has a factory lead going to the contactor proper. Problem is, it just looked like a clear plastic terminal point built into the mechanism of the contactor. I only looked at it for a minute or two, but nothing really jumped on how to even take it out.
A couple of questions:
Do most contactors have an overload that is factory built in for the control side, I know this is an extremely general question but how about for the type of contactor I have described above. And why on X-2? I have seen them before when the contactor has a X-form, but with this gear, you have to bring it it.
If this is some sort of overload, IE, bi-metal strip or similar, where would the reset be? The front cover had a square black reset button in the middle of it, but this is for resetting the overloads for the motor itself that are installed in the contactor.
How common is it, to have control circuits built into the neutral (grounded) conductor of these control devices?
I am trying to find some information on the contactor, (explosion view or other) so I can just learn a little more
Also, I have been digging around in the code and trying to see if it is some sort of code violation not to have this contactor identified that it has two different voltages installed in the same enclosure. I will try and send a picture, If the picture goes through, the X-2 terminal is on the bottom and I installed the wirenut to by-pass the the terminal points to see if the contactor would close. It did so the problem is a N/O point at that terminal.
 
Unless I am missing something what you describe if very typical for a motor starter.

The grounded conductor of the control circuit is opened by a switch that is operated by the overload 'heaters'.
 
Is this more or less what you have?

types.gif
 
looks like the overload contact was bypassed, sorry missed the last line
Is the last over load on the right of the picture missing is so that would be why it's open
 
Yes I-wire, that looks pretty close. I sure hope that picture goes through. What a great way to exchange information. So it sounds like the cotrol ckt overload is directly apart of the line amperage overloads? When the thermal overloads of the motor conductors kick out, the N/C of the control circuit change position as well?
 
With a magnetic motor starter the thermals themselves do not open.

They do not break the circuit to the motor, all they do is drop out the coil of the magnetic starter.
 
From the pic it looks like a Square D overload relay. Sometimes it is necessary to depress the reset button more than once so that all of the trip fingers are caught on the ratchet wheels of the heaters. When reset the N/C contacts will read closed.
 
Thanks guys,
from the sounds of it, I had it all wrong. I was thinking the overloads for the motor actually tripped out and the reset on the cover was what set them back in. But from what you fellas are saying, when the overloads heat up, it trips out the N/C contact on the control ckt.
 
From what I can tell from the picture, the OL contacts have been bypassed. Look at the red wire lower left hand of the picture. It is wire nuted to the yellow wire. These wires should land on the terminal screws at the lower left.
 
Hey, I found the problem!
After going back and looking at the problem, I took a look at the fingers that actually are held in place by the cogs on the thermal overloads. When you push in the reset, the fingers are supposed to lock under the cogs and be held in place. When the are locked in, the N/O turns to N/C on the control power to the coil. Anyhow, one of the metal fingers would not hold in place on the thermal overloads. I got to looking, and for a proper installation, you need to have the metal fingers on the top of the thermal cogs when you install them. Then, when you push in the reset, they grab. The electrician installed one of the them with the fingers on the bottom of the thermal. My guess is he used a screwdriver or something and got it to stick somehow. It must have finely slipped off somehow, and opened the contact. With the finger on the bottom, you can't make the fingers latch in properly no close the contact. They have to be on the top.
Thanks for the comments.
Also, to the fella with the last post, yes, the contact has been jumped, I did it to make sure the coil was in good working order.
 
Copper123,Whats up with all the rubber cord .2-wire control circuit.3-wire power circuit.What is the red control wire doing attached to the line side of the t.o.l?
Rick
 
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