Motor Connections

[jmellc]

I am hooking up an air compressor that has been on 240, changing to 120. As usual, nameplate gives diagram for low/high voltage. This motor has screw terminals in wiring box, ring terminals on leads. I know for sure terminals 1 & 4 connect to windings, as 1 & 4 are always used for incoming leads. 2 & 3 are used for 2 leads each under 1 hookup & 1 & 3 leads another way.

Question is; are terminals 2 & 3 merely there to splice the leads as needed or do they connect back to the windings? Motor is very old. #2 is rusted & I may not be able to remove nut without WD 40 or such & that still may not work.

Thanks for any help.

 

[templdl]

I am hooking up an air compressor that has been on 240, changing to 120. As usual, nameplate gives diagram for low/high voltage. This motor has screw terminals in wiring box, ring terminals on leads. I know for sure terminals 1 & 4 connect to windings, as 1 & 4 are always used for incoming leads. 2 & 3 are used for 2 leads each under 1 hookup & 1 & 3 leads another way.

Question is; are terminals 2 & 3 merely there to splice the leads as needed or do they connect back to the windings? Motor is very old. #2 is rusted & I may not be able to remove nut without WD 40 or such & that still may not work.

Thanks for any help.

Is there a wiring dia. on the motor? If so please post a picture of it.
Or if there's a connection diagram on the NP please post a picture of it.

 

[jmellc]

Is there a wiring dia. on the motor? If so please post a picture of it.
Or if there's a connection diagram on the NP please post a picture of it.

Sorry, don't have photos. Diagram is on motor name plate. Something like this:

Low

1. Line

2. Red lead & blue lead

3. Orange lead

4. Line

High

1. Line

2. Blank

3. Red, Blue & Orange leads

4. Line

Not precise, but something in that league. 1 & 4 have lug for spade terminal to fit on, as well as stud & hex nuts. 2 & 3 just stud & nuts.

I have seen similar setups to this or the usual loose leads to wirenut together as shown for various voltages.

 

[ActionDave]

Question is; are terminals 2 & 3 merely there to splice the leads as needed or do they connect back to the windings? Motor is very old. #2 is rusted & I may not be able to remove nut without WD 40 or such & that still may not work.

Thanks for any help.

How old is very old? I am approaching what I used to consider old. Very old used to be considered 1900 and before. Now it is 1950 all the way up to 1970.

Anyway, on dual voltage single phase motors there is often a dummy terminal that is used when the motor is connected High because all the windings are in series so you don't need both of the running windings going through the thermal.

 

[jmellc]

Probably about 50 years old, just a guess. I saw no manufacturing date of any sort.

 

[Smart $]

...

Question is; are terminals 2 & 3 merely there to splice the leads as needed or do they connect back to the windings? ...

In my experience at least one has connection to a winding (or other component of a start circuit).

 

[templdl]

From what the OP has presented it may be simple. There may be much ado about nothing. Configure the Orange, red, and blue wire so that they are terminated on terminals 2 and 3 and illustrated on the NP.
For the LV configuration I find it strange for the orange lead to be isolated from the red and blue leads if terminal #3 is not connected in some way to the internal motor circuit. But on the other hand landing the orange lead on terminal #3 may just be a convenient way of providing a place to terminate the orange wire if it is not being used rather than using a wire nut.

 

[jmellc]

From what the OP has presented it may be simple. There may be much ado about nothing. Configure the Orange, red, and blue wire so that they are terminated on terminals 2 and 3 and illustrated on the NP.
For the LV configuration I find it strange for the orange lead to be isolated from the red and blue leads if terminal #3 is not connected in some way to the internal motor circuit. But on the other hand landing the orange lead on terminal #3 may just be a convenient way of providing a place to terminate the orange wire if it is not being used rather than using a wire nut.

Thanks for this. I do not recall exact diagram, I should have copied it. Am going back today to drip WD 40 on terminals & hopefully be able to work nuts. I suspect the 2 & 3 terminals may be as you said, place to land wire terminals. I wish i had the same motor nearby with wires only & same diagram, - terminals. That would tell me OK. If I can work the terminal nuts this will turn into a moot issue. If not, I have to experiment.

 

[PEDRO ESCOVILLA]

i'm trying to follow this thread and help come up with assistance. am i reading the op correctly in that you only have 4 leads to work with?

 

[jmellc]

i'm trying to follow this thread and help come up with assistance. am i reading the op correctly in that you only have 4 leads to work with?

Yes, 4 leads. Red, orange, blue & black, with old style ring terminals. Wiring box had 4 screw terminals to land leads & incoming power leads. I now see I omitted the black lead in my earlier post. Me, the absent minded professor.

I am heading back there today & will try WD 40 on the terminal that is stuck with rust. Hopefully not too corroded. If the terminal is just a landing post, it won't matter & I can work without it.

Hadn't thought of this earlier, but if connected internally, I should be able to get an ohm reading from terminal to at least 1 lead or 1 other terminal. I will try that today.

I need to better learn the camera on my cell phone so I can post photos.

 

[templdl]

Yes, 4 leads. Red, orange, blue & black, with old style ring terminals. Wiring box had 4 screw terminals to land leads & incoming power leads. I now see I omitted the black lead in my earlier post. Me, the absent minded professor.

I am heading back there today & will try WD 40 on the terminal that is stuck with rust. Hopefully not too corroded. If the terminal is just a landing post, it won't matter & I can work without it.

Hadn't thought of this earlier, but if connected internally, I should be able to get an ohm reading from terminal to at least 1 lead or 1 other terminal. I will try that today.

I need to better learn the camera on my cell phone so I can post photos.

Photos are most awesome.
I remember the first time that I was blown away by that technology was back in the late 1990s when I was trying to solve a breaker with ground fault application for a guy at a gold mine in the frozen tundra of Russia. He was using our 4p 150af breakers with GF for use with heat trace cable to keep pipes from freezing. The only problem he had specified panel boards that didn't have enough room. Having run out of room he had suspended a few breakers in the wire way with some sort of cord.
I advised him what the correct X spaces that would be required to mount all of the 4p breakers properly which he then reordered.
It wasn?t for the pictures it would have been very difficult to solve his problem for something on the other side of the world.
I would have liked to share those picture with you guys but you know how it goes, I have no idea where I filed them.
Any time someone can include pictures of what they are asking questions about is a huge help in understanding what the issues are.

 

[jmellc]

Sorry, I am still a little behind the times with loading cell phone photos online & my teenage daughter is too busy to help Dad. I made a diagram on Word, close as I could and managed to copy it here. I was wrong, leads are black, white, red and orange. I listed a blue earlier. Sorry about that.

I now have another problem. I got the terminals open with WD40 & terminated for low. Motor will not run. I must have somehow broken an internal wire to terminal 4. I disconnected & ohmed the terminals. I got some readings but could not get anything from 4 to any other terminal.

Is it possible to gently break the bakelite mounting plate & splice with the inner leads coming to it? Anyone done this before?

Somehow my computer files have gone haywire. Add black to terminal 4 on HIGH. I put it there but it gets deleted when I save it. I corrected it & it did it again.

View attachment motor.doc

 

[ActionDave]

I now have another problem. I got the terminals open with WD40 & terminated for low. Motor will not run. I must have somehow broken an internal wire to terminal 4. I disconnected & ohmed the terminals. I got some readings but could not get anything from 4 to any other terminal.

That is a problem. You should have continuity to 1.

Is it possible to gently break the bakelite mounting plate & splice with the inner leads coming to it? Anyone done this before?

I would not do this. Better to unscrew it and see the other side and see if a connection can be re-soldered or otherwise fixed.

What kind of motor is this? Horse Power, cap-start, brand name? Was it running before you changed the connections?

 

[Smart $]

...

I now have another problem. I got the terminals open with WD40 & terminated for low. Motor will not run. I must have somehow broken an internal wire to terminal 4. I disconnected & ohmed the terminals. I got some readings but could not get anything from 4 to any other terminal.

...

It is common for one of the line terminals to only be jumpered to another terminal on the backside of the terminal board.

 

[jmellc]

Had been connected on 240. Customer said he last used it about 2 weeks ago.

 

[Smart $]

Had been connected on 240. Customer said he last used it about 2 weeks ago.

That's fine and dandy... but you are not giving us enough information to help you (that and what information you have given us is confusing or at best inconsistent).

 

[Smart $]

...you are not giving us enough information to help you...

Help us help you. Use a sensitive digital ohmmeter (at least tenths if not hundredths) and fill in the following table. Note there may be a capacitor start (you haven't told us otherwise) so you may get a varying reading on one combination. Reverse leads several times to make sure it consistently varies, as if a capacitor is charging and discharging.

 

[hurk27]

Without photos of the terminal board and the diagram for that motor its hard to armchair wire it, we can get close with knowing the basics of a capacitor start motor but some things very from manufacture to manufacture and can make the wiring confusing, it is best for you to understand the basics of a capacitor start motor so in the future you can judge by what you have as what you need to do.

here is the NEMA color standard for capacitor start motors with dual voltage and dual rotation:
T1 Blue Main run winding
T2 White other side of above
T3 Orange Aux run winding
T4 Yellow Other side of Aux
T5 Black Start winding circuit with cap and switch inline
T8 Red other side of start circuit

Here is a diagram that may help with what you have remember depending upon the manufacture as to which conductors they bring out to the terminal board, apply the above colors to it and it might make sense.

also to reverse the rotation is just a matter of reversing T5 and T8 which is the start winding circuit.

 

[hurk27]

Just a note to the above:

Most motors have a 5 or 6 terminal boards which indicates the start winding was brought out so it can be reversed for dual rotation.

other common things found if motors with only a single voltage will have only one main run winding so these terminals are not found on them.

The fact that you only have 4 terminals indicates to me that one of the above is missing on this motor and is not available for field wiring, also look closely for small copper straps that are supposed to be moved between the terminals such as the ones in the photo below:

 

[hurk27]

I have noticed that in post 3 you stated you have as follows:

Red/T8
Blue/T1
Orange/T3

But in post 10 you added a Black/T5 but do not say which terminal it lands on?

Red and Black are the start winding circuit that includes the start switch and capacitor.

There is a few ways that the run windings can be configured to achive the same results depending upon the manufacture of the motor but in all cases the start winding is parallel with the main run winding as the Aux run winding is left to be placed in series with the main for 240 voltage operation, this allows the voltage across the start winding to remain the same at both voltages that would otherwise require a differant capacitor rating for the 240 volt operation verses the 120 volt.

From the best I can figure for low voltage (120volt operation) with your supplied info is:

Terminal 1 L2(neutral)
Terminal 2 red/blue
Terminal 3 Orange
Terminal 4 Black/L1

Black could also land on terminal 3 with the Orange but this doesnt match my diagram as to what I think terminal 3 is connected to internally (T4 White) but it makes more sense if terminal 2 is T4 and terminal 3 is T2 and there is a slide jumper between Terminal 2 and 3 that you have to remove for 120 volt operation??? man My mind is getting fuzzy thinking about this.

It is like somthing is missing.