Motor Control Wiring

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goldstar

goldstar

Senior Member
Location
New Jersey
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Electrical Contractor
Had a service call yesterday at a local dry cleaners for a compressor that wouldn't run. It turns out that the contactor/starter would not pull in. It was a 3-phase, 208V, 5HP motor with a GE starter. There was 208V single phase present at the coil but it wouldn't pull in. If you push in the contactor handle and held it the motor would start. I changed out the starter and installed this CH starter :http://pe.eaton.com/search/ECN0511EAA . Rewired the starter and threw the safety switch but motor wouldn't start. When I pushed in the handle the contactor held, the motor ran and shut down when the tank reached 120 lbs. However, the motor would not automatically restart. There is 208V at the coil.

I'm thinking I mis-wired something or there is an internal setting that has to be changed for this unit to operate automatically. It seems pretty basic. There's a 2-wire external control switch in series with the air pressure switch. When the switch is turned on it is supposed to energize the coil and the pressure switch de-energizes the coil. Any thoughts would be appreciated.
 
Were you testing coil terminal to EG, then second terminal to EG, or terminal to terminal?

Sounds like you may have wired the pressure switch in series with the holding contact, but that would not account for the voltage across the coil. Is there a pilot light in use?
 
ptonsparky said:
Were you testing coil terminal to EG, then second terminal to EG, or terminal to terminal?

Sounds like you may have wired the pressure switch in series with the holding contact, but that would not account for the voltage across the coil. Is there a pilot light in use?
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Did not pull the wires off. Checked right at the coil terminals. No pilot light involved
 
It sounds like your seal-in aux contact is in series with the pressure switch.
A compressor that runs start/stop via pressure switch needs to use 2 wire control (not 3 wire). I'm guessing it probably has a selector switch to turn it on/off, not momentary push buttons.
 
I think I might have figured it out. There is a factory installed jumper between the L2 and the # 96 terminal. There's a note at the bottom of the connection diagram that states Separate Control "Remove wire C if supplied and connect separate control lines to the # 1 terminal on the remote pilot device and to the # 96 terminal on the overload relay". I'll find out today and post it if I'm correct. Thank you all for attempting to help. The older I get the more brain cells I start to lose:slaphead:
 
goldstar said:
I think I might have figured it out. There is a factory installed jumper between the L2 and the # 96 terminal. There's a note at the bottom of the connection diagram that states Separate Control "Remove wire C if supplied and connect separate control lines to the # 1 terminal on the remote pilot device and to the # 96 terminal on the overload relay". I'll find out today and post it if I'm correct. Thank you all for attempting to help. The older I get the more brain cells I start to lose:slaphead:
Click to expand...

RTFM syndrome strikes again! It is not communicable but seems to strike everyone at some time or another.
 
What still doesn't make sense to me is regardless of what may be mis-wired, if you measured 208 volts across the coil terminals, then the coil should be drawing current unless it is open circuited, and that would pull the armature in and close the motor contacts.

Is possible you were not measuring directly across the coil and there is an open switch somewhere between your measurement points - such as the motor overload contact.
 
kwired said:
What still doesn't make sense to me is regardless of what may be mis-wired, if you measured 208 volts across the coil terminals, then the coil should be drawing current unless it is open circuited, and that would pull the armature in and close the motor contacts.

Is possible you were not measuring directly across the coil and there is an open switch somewhere between your measurement points - such as the motor overload contact.
Click to expand...
Yes, we’re missing some minor detail.
 
Well, I was close but no cigar. It turned out that I was, in fact, not measuring across the coil but actually across an open contact. One side side of the contact was wired to one side of the coil (which I could not see and which would end up being phase 1 after going through the pressure and control switches). Internally the opposite side of the coil was wired to phase 2. So, when I pushed in the plunger for the contactor it locked in (through the contact), ran the motor until the tank reached its capacity and then shut down. Got on the phone with the supply house and they walked me through it. It turns out that I had to land the return wire from the pressure and control switch on the same side of the contact as the internal wire.

I looked at the diagram 20 times and it didn't seem clear to me. This is what the controller looked like :

http://www.eaton.com/Eaton/Products...tarters/FreedomSeries/FreedomSeries/index.htm

I thought the coil was on the right side of the contactor but it was, in fact, located behind it and I was not able to see. This was the wiring diagram that came with the controller. I'm used to diagrams with more detail.

 
goldstar said:
Well, I was close but no cigar. It turned out that I was, in fact, not measuring across the coil but actually across an open contact. One side side of the contact was wired to one side of the coil (which I could not see and which would end up being phase 1 after going through the pressure and control switches). Internally the opposite side of the coil was wired to phase 2. So, when I pushed in the plunger for the contactor it locked in (through the contact), ran the motor until the tank reached its capacity and then shut down. Got on the phone with the supply house and they walked me through it. It turns out that I had to land the return wire from the pressure and control switch on the same side of the contact as the internal wire.

I looked at the diagram 20 times and it didn't seem clear to me. This is what the controller looked like :

http://www.eaton.com/Eaton/Products...tarters/FreedomSeries/FreedomSeries/index.htm

I thought the coil was on the right side of the contactor but it was, in fact, located behind it and I was not able to see. This was the wiring diagram that came with the controller. I'm used to diagrams with more detail.

Click to expand...

That's what I was trying to convey in post #7.

Glad you got it fixed!
 
Thanks. Glad I got it corrected as well. In all fairness, for those of you who are not accustomed to interpreting these wiring diagrams, would you know that you would have to run the control wiring between L1 and the # 3 terminal ? Especially when there is already a wire terminated on the # 3 terminal. Obviously if I have to wire another one of these again I'll know what to do but IMHO the drawing leaves room for improvement.
 
Experience is what you gained.

Some years ago we converted a small hay mill that was built in the 50s &60s to PLC control. Their control was based on a limit(s) of varying types, being in series with the holding or seal-in contact. The Start button was parallel to them. Pressing the Start would start the motor if the overloads were not tripped. Problems with the holding contact or limits would cause the motor starter to open as as soon as the Start button was released. That was a quick method to determine where they first needed to look for problems. Divide and conquer, so to speak.
 
goldstar said:
Well, I was close but no cigar. It turned out that I was, in fact, not measuring across the coil but actually across an open contact. One side side of the contact was wired to one side of the coil (which I could not see and which would end up being phase 1 after going through the pressure and control switches). Internally the opposite side of the coil was wired to phase 2. So, when I pushed in the plunger for the contactor it locked in (through the contact), ran the motor until the tank reached its capacity and then shut down. Got on the phone with the supply house and they walked me through it. It turns out that I had to land the return wire from the pressure and control switch on the same side of the contact as the internal wire.

I looked at the diagram 20 times and it didn't seem clear to me. This is what the controller looked like :

http://www.eaton.com/Eaton/Products...tarters/FreedomSeries/FreedomSeries/index.htm

I thought the coil was on the right side of the contactor but it was, in fact, located behind it and I was not able to see. This was the wiring diagram that came with the controller. I'm used to diagrams with more detail.

Click to expand...
What other detail do you want? That diagram is a generic label from the starter manufacturer that shows how the starter was configured when it left the factory, they don't know what it will get connected to in the field, and only give you a few of the most common examples of what you may run into for basic control schemes. Anything more complex would have to be drawn by whoever put the thing together.

NEMA starters typically do have "L2" connected to the overload then the coil if coil voltage is a line to line voltage (208,240, 480), if it is a line to neutral coil volatage (120, 277) then "wire C" isn't installed and you need to land control voltage neutral on terminal 96, which is sort of an IEC terminal identification, others are still calling the overload contact terminals X1, X2.
 
kwired said:
What other detail do you want? That diagram is a generic label from the starter manufacturer that shows how the starter was configured when it left the factory, they don't know what it will get connected to in the field, and only give you a few of the most common examples of what you may run into for basic control schemes. Anything more complex would have to be drawn by whoever put the thing together.

NEMA starters typically do have "L2" connected to the overload then the coil if coil voltage is a line to line voltage (208,240, 480), if it is a line to neutral coil volatage (120, 277) then "wire C" isn't installed and you need to land control voltage neutral on terminal 96, which is sort of an IEC terminal identification, others are still calling the overload contact terminals X1, X2.
Click to expand...
You've obviously wired these before and it sounds like you're talking from experience. But, try looking at this from a novice's point of view. I've wired many different types of controls from fire alarm systems to motor controls for large AC units. As a general rule I would never land a wire on a terminal that already had a wire on it. In this case I had to. The symbol shown for a coil is not what I'm accustomed to seeing and that's what threw me off. Thanks for your input.
 
goldstar said:
You've obviously wired these before and it sounds like you're talking from experience. But, try looking at this from a novice's point of view. I've wired many different types of controls from fire alarm systems to motor controls for large AC units. As a general rule I would never land a wire on a terminal that already had a wire on it. In this case I had to. The symbol shown for a coil is not what I'm accustomed to seeing and that's what threw me off. Thanks for your input.
Click to expand...
All I can say is the terminals in question are ordinarily designed to land up to two conductors on them and that if you go to other brands of NEMA starters they are wired pretty much the same way and their schematic is fairly similar in that they show approximate physical locations of components as drawn. True the coil isn't using a conventional coil symbol on that one but I think they put more focus on showing where the terminals are physically located in relation to other components.
 
kwired said:
All I can say is the terminals in question are ordinarily designed to land up to two conductors on them and that if you go to other brands of NEMA starters they are wired pretty much the same way and their schematic is fairly similar in that they show approximate physical locations of components as drawn. True the coil isn't using a conventional coil symbol on that one but I think they put more focus on showing where the terminals are physically located in relation to other components.
Click to expand...
Well, like you now I can speak from experience. After taking a closer look at the drawing I can see the logic in the wiring. I still think they could have done a better job on the drawing or provide a better wiring explanation. IMHO.
 
Notwithstanding the exhaustive detail of the starter, I'm still waiting for an explanation on how OP could get 208 volts and not having the coil pulled in.
 
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