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Tool Talk Discussion Forum

Re: Compressor electrical question

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Stephen Newell

01-04-2013 18:07:25

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Thanks for the help. This thing was why I hired an electrician in the first place and the guy didn't do it. I've been sitting here this evening probing the switch with an ohm meter trying to make some sense of it. For some reason L1 isn't doing anything. L2 and L3 work T2 and T3. The bottom part of this thing has a dial where you can adjust the amperage and is set on 26amps. The right side has a reset button. I don't know which side of it has the coil. Here is a picture of it.

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George Marsh

01-04-2013 20:18:45

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 Re: Compressor electrical question in reply to Stephen Newell, 01-04-2013 18:07:25  
Has anyone answered your question how to wire the contactor in the pic? What you have is a 3 phase contactor. L1,L2,L3 = 3 phase. It is possible this contactor was used on 3 phase 440v making the coil 440v. Is there any info about the coil?

This is only a guess, need to confirm with an ohmmeter. The red wire is a part of the control circuit. One control leg from the pressure switch will feed in on the long red wire, goes to NC, normally closed contact, which will open if the bottom section measures too much current. The power then is sent to T4 via the other short red wire. My guess is T4 is one side of the control coil. Now use your ohmmeter and try to determine which screw is the other side of the control coil, I would try T3. If it is T3, that will be the other wire going to the pressure switch.

If there is no info about coil voltage, make up a cord and apply 220v to the coil. Going to say that if you get it right, the blue section will pull inward when the coil is energized.

Then all you need to do is apply 220v to L2 & L3 and wire T2 & T3 to motor.

Now, don't forget to put all this inside an approved electrical box or the NEC COPS will give you a ticket and push you over a cliff.

If you can't get the contactor to work and you find out how much one is going to cost you may want to double up the switch like I said above. Then put the all air compressor inside a metal container, turning it into an appliance. Then make and break one side of the 220v. The metal container will make it safer, NEC approved appliance. You may want to put a grounding rod on the metal box too. Wouldn't want to upset the NEC cops.

By the way, a code is not the same as a law, except here. You can be arrested if you break a law. Never seen anyone get arrested for breaking an NEC code. If you could, I would be serving a life sentence.


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Stephen Newell

01-04-2013 21:10:28

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 Re: Compressor electrical question in reply to George Marsh, 01-04-2013 20:18:45  
I took the unit apart and found the model number of the coil and looked it up and found out it is a 110v coil. The long red wire is attached to one side of the coil. On the opposite side of the coil there is a contact A1. I'm wondering since the coil is 110v do I take power from L1 and run to A1 and then run the red wire to the pressure switch and out the other side to ground. I found a generic schematic online which runs the wire from L1 to L2 through the coil but I assume that would be for a 220V coil.

If I can ever get that figured out then I have the Overload Relay to figure out.

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George Marsh

01-05-2013 03:48:14

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 Re: Compressor electrical question in reply to Stephen Newell, 01-04-2013 21:10:28  
Here is the deal, what I tell you the NEC cops will tell you is wrong, you are going to blow up the world, kill someone, kill yourself, get a ticket for breaking the law and so on.

Then the advice I'm going to give you is worth what you are paying for it......

Secondly, the contactor you have is not the one that came with the air compressor. It is something so one got off a 3 phase device.

That said, the bottom half of your motor contactor is not set up for your motor and I would remove it using only the top contactor. Again, NEC cops will jump all over me for saying this.

I would get an extension cord and wire it to your pressure switch. Black wire on one side and white wire on the other side of the pressure switch. Use the ground wire if your 220v wire is not already grounded to the compressor. Then send the black wire from the other side of the pressure switch to A1 and the white wire to the other side of the coil. Plug in extension cord and see if contactor pulls in. If it does, you are half way home.

Wire the 220v to L2 & L3 and the motor to the terminals below T2 & T3.

Forget the overload protection on the contactor. I've never seen a motor that didn't already have it's own overload protection. Make sure your circuit breakers are the right size for your wire. Put the contactor in a metal electrical box. You should be good to go.

Hope I've been a help. Let me know if it works.

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Stephen Newell

01-05-2013 05:03:32

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 Re: Compressor electrical question in reply to George Marsh, 01-05-2013 03:48:14  
It may perhaps be the wrong magnetic starter for my compressor but I bought the compressor new directly from Ingersol Rand and that was the switch that came with it. The motor however went out a few years back and was replaced. You are right the new motor has its own overload protection where I don't think the original motor did. I did give out some bad info about the coil being 110v. I have since learned it is 220V. I also do need to be careful not to energize the compressor itself. The compressor is used outdoors where the ground often gets wet around it. All in all with everybodies help, I'm getting closer to understanding this unit. Thankyou.

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Greg K

01-04-2013 19:46:12

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 Re: Compressor electrical question in reply to Stephen Newell, 01-04-2013 18:07:25  
It looks to me like the 2 red wires are going through yur motor overload contacts. These wires need to be hooked up in series with the coil wires, so if the overload trips out it will not let the coil on the starter kick in. so from t2 there needs to be a wire to the pressure switch, from the other side of the pressure switch it hooks to the red wire that is loose on one end. Now from t3 there needs to be a wire the same size as the two existing red ones to the other side of the coil wire, I believe this terminal to be on the top right corner of the starter but NOT visible in the picture. Terminals 13 and 14? are just an auxiliary set of contacts and not used in this application. Now the feed goes to terminals L1 and L2 as was stated earlier. The motor leads connect to T2 and T3. When you press in the button on the cover of the starter box it will press the contacts together completing the circuit from L1 to T1 and L2 to T2. Also energizing the wires fromT2 to the motor overload contacts, through the contacts through the pressure switch(assuming it is calling for the need for power), and to the latching coil in the Starter. It will also complete the circuit from T2 to the other side fo the coil. This is assuming that there is a pushbutton on the case to depress the starter initially. If there is no push button, then the red wire that is not connected on one end should hook to one side of the pressure switch. The other side of the pressure switch will hook to L3. Now there will need to be a wire from L2 to the other terminal on the coil, which I believe to be on the upper right hand corner, but not in the picture. With this setup you will need a disconnect in sight of and within 50 foot of the compressor for sure.

If you could take some pictures of the sides of the starter it would help. Clear as mud now? Greg

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Stephen Newell

01-04-2013 21:48:17

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 Re: Compressor electrical question in reply to Greg K, 01-04-2013 19:46:12  

The pressure switch itself had a cut off on it and the sub-panel and breaker for the compressor is 3' away. Do you think I need a disconnect also? Here are the pictures of the sides of the starter. Also there is another of the overload. The flash on the camera tends to bleach the picture. The right side of it has the letters NC on it with the numbers 95 and 96 on it.

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Greg K

01-05-2013 06:45:53

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 Re: Compressor electrical question in reply to Stephen Newell, 01-04-2013 21:48:17  
No disconnect neededif the panel is only 3' away. I cannot see on this but I believe the other terminal to your coil is on the upper right corner, to the right of L1, L2,L3, but below 14. About in the same location of where the short red wire goes. I don't see anything on the labels that lead me in a different direction. George March is correct in that it is a 3 phase starter, however T1, T2, T3 are all motor leads and not a coil terminal, just as L1, L2, L3 are all input leads for 3 phase power. Gotta go to work now, but try and get me a pic of the top right looking down from the top and this will verify how wrong or right I am.

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Stephen Newell

01-05-2013 08:03:33

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 Re: Compressor electrical question in reply to Greg K, 01-05-2013 06:45:53  
Looking at the top of the switch under L1 there is A1 which is one side of the coil and below 13 and 14 is A2 which is the other side of the coil.

I expected the switch was made so it could either be used for single phase or three phase.

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Stephen Newell

01-05-2013 03:47:20

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 Re: Compressor electrical question in reply to Stephen Newell, 01-04-2013 21:48:17  

Maybe you can see the labels better with these pictures.

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Greg K

01-04-2013 19:55:45

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 Re: Compressor electrical question in reply to Greg K, 01-04-2013 19:46:12  
Oops posted that reply about the 110v coil in the wrong spot. It should be here

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