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Air compressor contactor/wiring problem. Need help please!

CITIZEN F16

Titanium
Joined
May 2, 2021
If it is getting proper voltage that is not getting pulled down and wired correctly I think your motor is toast. Just Google on how to test a motor, I still am suffering concussion symptom and don't want to read back through this thread or post instructions. Too much critical thinking makes my head hurt.
 

SAF

Stainless
Joined
Jul 20, 2014
Location
MI USA
The starter is chattering again. In your temporary wiring make sure that your control circuit power taps are NOT CONNECTED to your generated phase.

Like I said before, if you got a roll of orange tape to mark the generated wild leg, you could avoid these problems. Refer back to my earlier posts to where the wild leg needs to be terminated.
 

Ltk

Plastic
Joined
Sep 24, 2021
The starter is chattering again. In your temporary wiring make sure that your control circuit power taps are NOT CONNECTED to your generated phase.

Like I said before, if you got a roll of orange tape to mark the generated wild leg, you could avoid these problems. Refer back to my earlier posts to where the wild leg needs to be terminated.

The generated leg is not connected to the control circuit in any way, I’ve confirmed that and read back through this thread again, performing all tests. Does it make sense that the motor can run perfectly unloaded and start with the starter but not act properly under load? I’m going to test the leads in star pattern and report back my findings this evening. Is the pressure switch wired correctly? One terminal going to L1, the other going to the back side of the switch (L3)?
 

CITIZEN F16

Titanium
Joined
May 2, 2021
The generated leg is not connected to the control circuit in any way, I’ve confirmed that and read back through this thread again, performing all tests. Does it make sense that the motor can run perfectly unloaded and start with the starter but not act properly under load? I’m going to test the leads in star pattern and report back my findings this evening. Is the pressure switch wired correctly? One terminal going to L1, the other going to the back side of the switch (L3)?

I thought the starter issues were cured. Yes a motor can run fine unloaded and then skid to a halt with a load applied if it has problems. Do you have a megometer or just a multi-meter?
 

SAF

Stainless
Joined
Jul 20, 2014
Location
MI USA
Take the belts off and see if it works with no load. If it does I would suspect that you are getting low voltage under load.

Install some voltmeter leads onto the starter load side terminals and check the readings while under load. It appears that the sluggish motor and the chattering contactor are both telling you that you have low or intermittent voltage under load.

Check all of the connections in your new service and on your RPC. If you keep chattering the starter you will burn it up.
 

SAF

Stainless
Joined
Jul 20, 2014
Location
MI USA
The generated leg is not connected to the control circuit in any way, I’ve confirmed that and read back through this thread again, performing all tests. Does it make sense that the motor can run perfectly unloaded and start with the starter but not act properly under load? I’m going to test the leads in star pattern and report back my findings this evening. Is the pressure switch wired correctly? One terminal going to L1, the other going to the back side of the switch (L3)?

What you describe for the pressure switch wiring sounds incorrect, it may be your description, I can't tell. Follow the drawing I made earlier. One lead goes to the on/off switch, the other lead goes to terminal #3 on your auxiliary contact.

Compressor Control.jpg

The generated leg belongs on L2, feeding the starter.
 

Ltk

Plastic
Joined
Sep 24, 2021
What you describe for the pressure switch wiring sounds incorrect, it may be your description, I can't tell. Follow the drawing I made earlier. One lead goes to the on/off switch, the other lead goes to terminal #3 on your auxiliary contact.



The generated leg belongs on L2, feeding the starter.

Okay I double checked all my wiring, I am 100% positive everything is wired exactly to your schematic.

I also disconnected all windings and tested them in star configuration for low voltage.
- No shorts to ground from any lead.
- T1-4 = 0.3 ohms
- T2-5 = 0.3 ohms
- T3-6 = 0.3 ohms

- T7-8 = 0.5 ohms
- T7-9 = 0.5 ohms
- T8-9 = 0.5 ohms

- T6-9 = OL
- T4-7 = OL
- T5-8 = OL

The only thing I believe I’m confused on is the generated leg.

I’m feeding my 3 leads from the phase converter into a 3 phase subpanel. From there is where my compressor is hooked to a 60 amp breaker. Will include pictures. How do I know which lead is the wild leg once it enters the panel? This may be my problem?
 

Ltk

Plastic
Joined
Sep 24, 2021
***White wire with purple marking is the manufactured leg from the phase converter
4f79d187e3b261a66083891c06b0e518.jpg

87199355cf001917aa9a512a7e56114f.jpg
 

Ltk

Plastic
Joined
Sep 24, 2021
I disconnected my sub panel and fed the compressor directly from the phase converter, ensuring that the wild leg was feeding L2 on the compressor starter. Not getting chatter, but the motor is turning slow still
 

Ltk

Plastic
Joined
Sep 24, 2021
I thought the starter issues were cured. Yes a motor can run fine unloaded and then skid to a halt with a load applied if it has problems. Do you have a megometer or just a multi-meter?

Just a multimeter and an amp meter. The motor runs great unloaded, could there be a problem with the motor or is the RPC underpowered?
 

Ltk

Plastic
Joined
Sep 24, 2021
Low voltage under load would indicate the RPC being the culprit? All connections are good on the service and the RPC, also RPC to the load center. I will test the under load voltage tomorrow and report back my findings.
 

SAF

Stainless
Joined
Jul 20, 2014
Location
MI USA
To me it appears that your wiring is too small in your photos. Feeding the RPC and feeding your panel.

Just because your lathe starts, doesn't mean that the compressor should. A compressor is a hard stating load.

You could measure the voltage at your starter load terminals, while trying to run it as I suggested earlier.

For a 20HP RPC If it were my job I would size the supply wire @ 54A x 1.732 x 1.5 = 116.78A A #1 AWG
From the RPC to the panel I would use 54A x 1.25 = 67.5A A #4 AWG as a minimum
For the compressor 28A x 1.5 = 42A A #6AWG

It appears that your wiring looks smaller than that. But prove it to yourself by measuring the voltage at the starter load terminals first and then at motor terminals, to see what your voltage drop really is.
 

Ltk

Plastic
Joined
Sep 24, 2021
To me it appears that your wiring is too small in your photos. Feeding the RPC and feeding your panel.

Just because your lathe starts, doesn't mean that the compressor should. A compressor is a hard stating load.

You could measure the voltage at your starter load terminals, while trying to run it as I suggested earlier.

For a 20HP RPC If it were my job I would size the supply wire @ 54A x 1.732 x 1.5 = 116.78A A #1 AWG
From the RPC to the panel I would use 54A x 1.25 = 67.5A A #4 AWG as a minimum
For the compressor 28A x 1.5 = 42A A #6AWG

It appears that your wiring looks smaller than that. But prove it to yourself by measuring the voltage at the starter load terminals first and then at motor terminals, to see what your voltage drop really is.

I believe you’ve hit the nail on the head! Incoming power to starter is 141v between L1 and L2, 215v between L1 and L3, 141 between 2 and 3.

Load terminals to the motor are slightly lower. Wiring it temporarily with #4/0 (0000) AWG aluminum and if that’s the case, I’ll buy the proper copper wire and run the circuits permanately!


Sent from my iPhone using Tapatalk
 

Ltk

Plastic
Joined
Sep 24, 2021
Still no luck, I even brought a friends known working compressor over, same exact model, and it will not start. It's definitely the phase converter being under powered..
 

SAF

Stainless
Joined
Jul 20, 2014
Location
MI USA
Tell us more about your service and feeder to the garage. If i remember correctly you said that you put a 200A feeder and panel to the shop. What can you tell and show us about that?

If your supply is weak to the RPC, the RPC can’t make up for that Measure the voltage to your power panel where the RPC is tapped from while trying to start the compressor. If voltage is low here during starting you can’t really blame the RPC.
 

Ltk

Plastic
Joined
Sep 24, 2021
Tell us more about your service and feeder to the garage. If i remember correctly you said that you put a 200A feeder and panel to the shop. What can you tell and show us about that?

If your supply is weak to the RPC, the RPC can’t make up for that Measure the voltage to your power panel where the RPC is tapped from while trying to start the compressor. If voltage is low here during starting you can’t really blame the RPC.

Yes sir I ran 4/0 aluminum to the shop and a 200amp sub panel. Got a new meter. I called american rotary after I was still unsuccessful and they specifically told me that my model will not start a 10 hp compressor without purchasing about $800 worth of equipment to turn it into the “hard starting model” which is the ADX20 vs. my AD20..

I stumbled upon a new in box 10 hp single phase baldor on ebay for an incredible price and purchased it. Can I still use my size 2 starter just with 2 leads rather than 3 obviously? Or am I better off buying a new starter?

I also have another size 2 starter off a seperate 10hp compressor


Sent from my iPhone using Tapatalk
 

SAF

Stainless
Joined
Jul 20, 2014
Location
MI USA
To answer your question on the starter size, you just need to look at the tag on the face of your starter. It clearly tells you that the size 2 starter is rated for 7.5HP @ 230V 1Φ.

If you plan on running the machine hard,frequent starts, It may behoove you to looking into a continuous run unloader setup for the operating control. Large single phase motors fail early when subject to these conditions. Start capacitors and centrifugal switches, don't take well to this type of service.
 

Ltk

Plastic
Joined
Sep 24, 2021
To answer your question on the starter size, you just need to look at the tag on the face of your starter. It clearly tells you that the size 2 starter is rated for 7.5HP @ 230V 1Φ.

If you plan on running the machine hard,frequent starts, It may behoove you to looking into a continuous run unloader setup for the operating control. Large single phase motors fail early when subject to these conditions. Start capacitors and centrifugal switches, don't take well to this type of service.

It says 7.5hp for single phase, but it also says 45amp. If my single phase 10hp motor is 39amp at FLC is this safe to use, assuming I change the heaters?

So are you sure the pump is in good condition and spins over freely by hand? Sounds like it could be dragging the motor down due to possible mechanical issues??

Yes I am positive. I loaded the compressor onto my truck and took it to a shop with a 75hp RPC and it runs flawlessly. That is ultimately what made the decision to source a 10hp single phase motor instead of replacing or upgrading my RPC.
 








 
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