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Thread: Contactor overheating

  1. #1

    Contactor overheating

    I have an Ingersoll Rand Type 30 air compressor. It’s 7-1/2hp single phase 240v.

    When I first turn it on, it will run for a few minutes until it pressures up to 150psi then shuts off. If you release all the air down to 0psi, it doesn’t come back on. You can force it on by holding in the little reset button on the contactor, but as soon as you release it it shuts back off. If you let it sit for about five minutes, it will then start back up.

    Is the contactor going bad? Any suggestions on how to trouble-shoot?

  2. #2
    A picture of what you have would help.
    But I will take a stab a what is going on and this is the manual for it.
    https://www.aircompressorsdirect.com...9ac4ffd206.pdf
    It does not look like you have a starter which differs from a contactor, A starter will have overload protection such as adjustable over loads or heaters.
    But a picture of your contactor or starter would certainly help.

    According to the manual you do have a low oil pressure switch cut out and a high air temp cut out.
    I would look at the low oil pressure switch and see if something is a miss there.

  3. #3
    It sounds like your pressure switch is faulty. When your compressor reaches full pressure the 120 volt to the contactor is turned off by the pressure switch. You can see this at the pressure switch with a volt meter. By pressing the reset button you are bypassing the pressure switch as long as you hold it in, so the comprssor runs.
    Last edited by Lee Schierer; 08-25-2019 at 8:34 AM.

  4. #4
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    I agree, faulty pressure switch.

    Charley

  5. #5
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    The other respondents may very well be spot on about the pressure switch, but seems odd for the pressure switch to 'cool off', and so go back to work. I'd be more inclined to suspect the air temp, but never owned one of these I-Rs. To be rigorous, get a cheap multi-meter.

    Look at the single phase schematic (pg.13) in George's link. Assuming this is what you have, problem could be any of the 'interrupts' in the circuit to and from the motor coil ('M').

    Run the compressor to its shut off point, then bleed the air off as you describe in your post. Verify it won't restart, and before it can cool off, test for voltage using the meter:

    If the meter has a clip on lead, clip it on an end terminal of wire #4; if just probes, hold one probe on the #4 terminal. Using the other probe, test these points:
    1. Test on wire #1, just to verify voltage (it ran, so this basically just verifies fuses are good and meter is working). Should read 240VAC.

    2. Test on wire #7, to verify ON/OFF switch. Should read 240VAC; if not, its a bad hand switch.

    3. Test on wire #8, to verify (air) pressure switch. Should read 240; if not, its a bad pressure switch (PS).

    4. Test on wire #9, to verify low oil level switch. ... no voltage = bad LOLS.

    5. Test on wire #6, to verify high air temperature switch. ... no voltage = bad HATS.

    6. Test on wire #5, to verify overload aux contact. ... voltage = bad OL. If there IS VOLTAGE, the OL is open/tripped.
    (This may be integral to the contactor, so possibly remove/replace entire contactor..?)

    Other possibilities: Is the run time to charge the air system too long? (Added new, bigger, or 2nd receiver?) Compressor's location is leading to over-heating? ...In the summer sun? Tight space (no cooling air flow)? Could the unit be 'slightly' low on oil? (starts OK when its all in the crankcase, but too low when its been running, ...then drains back and starts again?)

    Adder: Just to be clear - - and safe - - these voltage tests should show you what device is preventing re-start. It may be that the device is working fine and is properly preventing re-start, due to out-of-range process condition. So, find the device and then verify that the process condition it measures is in fact OK.

    Edit: I 'mis-blended' the other replies, about oil level/pressure switches. Hope my edit better represents their recommendations.
    Last edited by Malcolm McLeod; 08-25-2019 at 1:15 PM. Reason: mis-read other posts
    Molann an obair an saor.

  6. #6
    So...the pressure switch can overheat, and when it cools down start working again?

  7. #7
    Quote Originally Posted by Thomas C Barron View Post
    So...the pressure switch can overheat, and when it cools down start working again?
    No it probably just sticks at the high pressure point or the line I blocked so it takes a few minutes for the pressure to bleed off the switch.

  8. #8
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    Let's go back to step one. The compressor runs but instead of shutting off at the normal 175psi (is that correct?) it shuts down at 150psi. Then, it seems that something has to cool off before it will restart. That kind of behavior is typical of a thermal overcurrent limit in the starter or an overtemperature switch in the motor. Either of those would be caused by the motor drawing too much current. Wouldn't current be the first thing to check? That is, assume that the safety devices are working correctly and check the most obvious cause first.
    Beranek's Law:

    It has been remarked that if one selects his own components, builds his own enclosure, and is convinced he has made a wise choice of design, then his own loudspeaker sounds better to him than does anyone else's loudspeaker. In this case, the frequency response of the loudspeaker seems to play only a minor part in forming a person's opinion.
    L.L. Beranek, Acoustics (McGraw-Hill, New York, 1954), p.208.

  9. #9
    It sounds more like a thermal overload to me. After the motor cools it comes back on. Is the compressor newly installed? I had to move my T30 closer to the breaker box or install a larger wire because it was overheating and in winter struggled to start on very cold days. It was starved for power.

  10. #10
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    I would 1st check all the wiring connections to make sure they are tight. Any loose connection will cause heat..
    If all is good there you will need to further trouble shoot.

    Bruce
    Epilog TT 35W, 2 LMI SE225CV's
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  11. #11
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    Sometimes I've got to read things 6 times... Not sure about the 'reset' button on the contactor. Is this a true OL reset? Or, is it the mechanical over-ride to 'force' the contactor closed?

    If it IS a reset, then it's about 95% certain this is a over-current situation. OK, maybe 95.82476%.

    If mechanical over-ride, then my money is on a process safety switch, or the respective process.
    Last edited by Malcolm McLeod; 08-25-2019 at 4:21 PM.
    Molann an obair an saor.

  12. #12
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    Quote Originally Posted by Malcolm McLeod View Post
    Sometimes I've got to read things 6 times... Not sure about the 'reset' button on the contactor. Is this a true OL reset? Or, is it the mechanical over-ride to 'force' the contactor closed?

    If it IS a reset, then it's about 95% certain this is a over-current situation. OK, maybe 95.82476%.

    If mechanical over-ride, then my money is on a process safety switch, or the respective process.
    A mechanical override would perform as the OP indicated, i.e., press in and the motor runs, release and the motor stops. With a safety switch open (this includes the the OL) there is no latching action. An OL reset would (probably) allow the motor to keep running after it was pressed since it would clear the fault indication.

    Regardless of all that, it easy to check the current. To me, that's the first thing that should be done. If the current is too high then the problem is not the control circuits. If it's in spec then start looking at the sensors.
    Last edited by David L Morse; 08-25-2019 at 4:43 PM.
    Beranek's Law:

    It has been remarked that if one selects his own components, builds his own enclosure, and is convinced he has made a wise choice of design, then his own loudspeaker sounds better to him than does anyone else's loudspeaker. In this case, the frequency response of the loudspeaker seems to play only a minor part in forming a person's opinion.
    L.L. Beranek, Acoustics (McGraw-Hill, New York, 1954), p.208.

  13. #13
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    Quote Originally Posted by David L Morse View Post
    A mechanical override would perform as the OP indicated, i.e., press in and the motor runs, release and the motor stops. With a safety switch open (this includes the the OL) there is no latching action. An OL reset would (probably) allow the motor to keep running after it was pressed since it would clear the fault indication.

    Regardless of all that, it easy to check the current. To me, that's the first thing that should be done. If the current is too high then the problem is not the control circuits. If it's in spec then start looking at the sensors.
    Agree on the current test 1st, if OP has access to ammeter. I've never had need of one (make the sparkies do the big AC stuff), so tend to default to methods where I can use a multimeter.

    And at the risk of seeming to have the bit in my teeth on this......I keep going back to the I-R schematic. If the OL trips, then a mechanical override should not start the motor, since there is a OL primary contact in the path to the motor...? (Their start circuit is dirt simple - it has no parallel latching START/STOP PBs - just SPST ON/OFF.)

    This brings me back to the button being a 'reset'. And the OL internals must be hotter than a $2 pistol for it not to reset and continue running = = either over-current, or too many cycles on the OL wore it out. Bets are down!
    Molann an obair an saor.

  14. #14
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    Quote Originally Posted by Malcolm McLeod View Post
    If the OL trips, then a mechanical override should not start the motor, since there is a OL primary contact in the path to the motor...?
    This
    Annotation 2019-08-25 174830.jpg
    is the symbol for an overload heater. It is just a sensor. It's not a switch.

    This
    Annotation 2019-08-25 175419.jpg
    is the symbol for the switch contacts controlled by the heater. This is what opens when there's an overload.
    Beranek's Law:

    It has been remarked that if one selects his own components, builds his own enclosure, and is convinced he has made a wise choice of design, then his own loudspeaker sounds better to him than does anyone else's loudspeaker. In this case, the frequency response of the loudspeaker seems to play only a minor part in forming a person's opinion.
    L.L. Beranek, Acoustics (McGraw-Hill, New York, 1954), p.208.

  15. #15
    There wouldn't be anything on the pressure switch to sense temperature. It's just an on and off switch. If the compressor has any overload protection it would be on the motor or if it has a magnetic switch be included. It's better to have a magnetic motor starter between the pressure switch and the motor. I couldn't keep a pressure switch on my T30 until I installed a motor starter to mine and it has a 5 hp motor.

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