Motor contactor wiring

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Old 09-27-15, 09:25 AM
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Motor contactor wiring

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I have a 3 phase air compressor that is controlled with a motor contactor. The contactor is controlled by an air pressure switch. I don't know what terminals the air pressure switch needs to be connected to. There are 2 terminals of the left (NO and A2) and there are 2 terminals on top (unmarked) behind the line side. The 2 black conductors in the photo go to the pressure switch (on /off) and are not connected to anything. The knockouts are also going to be filled with seals. Any help would be appreciated.
 
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Old 09-27-15, 10:08 AM
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Welcome to the forums.

The two terminals on the top are probably the coil. That lower piece looks like a heater element array. Those would be heater elements that got warm as the motor ran. If it drew too much power they would get hot and thermally trip an overload.

I need the part number for the contactor or a close up picture of the label.
Are there any other labels on that lower piece where the load connects ?

You also need to confirm the contactor coil voltage.
 
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Old 09-27-15, 10:24 AM
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Thank you

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Thank you so much for your help and information. I do have a clearish picture of the contactor information above. I was hoping the coil is 208 but if not I have a neutral in the disconnect above this box. It would make sense that it would be the top terminals. Unfortunately, I do not have a photo of them.
 
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Old 09-27-15, 11:02 AM
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I think I found them in the photo on the left of the contactor. I think it's called an auxiliary contact and requires 120 volts.
 
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Old 09-27-15, 11:11 AM
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The device to the left is an auxiliary switch and is most often used to "seal-in" the contactor when used with a three-wire (momentary) pilot control. I see NO contacts for the coil or any designation of the coil voltage.

Isn't there a wiring diagram on the inside of the cover?

Normal wiring would be from T1 to the pilot device (pressure switch) and from the pressure switch to one of the coil terminals. The other coil terminal would go to the pilot contacts on the overloads (all O/Ls in series) and then to T3
 
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Old 09-27-15, 11:29 AM
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I hosted a diagram for you. The two red wires are connected at the bottom. They should be connected at the top per the diagram. The pressure switch connects to points 1 and 3.

click on pic for full size.


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Old 09-27-15, 11:46 AM
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No wiring diagram unfortunately. That's interesting that the auxiliary isn't what I was looking for. There are 2 small terminals that are not pictured behind L1 and L3. One of them is connected to the NO(top red wire) on the 'heater element array" the other is empty.
 
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Old 09-27-15, 12:00 PM
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I'm guessing you didn't see my post ? You need to refresh the thread when you return to see the new posts. The contacts on the thermal unit are NC and X2.
 
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Old 09-27-15, 01:45 PM
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Wow! This is perfect! Thank you so much for your time and all your help!
 
 

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