Help with CM ½ ton electric hoist trouble shooting
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  1. #1
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    Default Help with CM ½ ton electric hoist trouble shooting

    My ½ ton CM electric hoist stopped working and I could use some help with trouble shooting. It is single phase, 110V, and is the older model that is silver in color, not painted. The hoist just buzzes when the up or down buttons are pressed. When it first started to have an issue, down still worked, not up. Now neither is working. It is relatively heavy so I will probably try and repair it while I am up on a ladder, so knowing what to check would help a lot. I am thinking it sounds like a contactor is not engaging.

    -Dave

    img_4600.jpg

    img_4597.jpg

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    My WAG is, because it's a single phase unit that must often start in a UP mode fully loaded that it's a start capacitor gone sour or a set contacts for the start cap circuit.

    Without taking it down and pulling it apart you just guessing. Unless you're motor savvy, a local motor shop would be your best bet..IMHO.

    Stuart

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    Centrifugal switch.

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    Well, it would help if I knew the difference between a hoist contactor and a reversing contactor...

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    Well...post a picture of the pendant at the very least. Otherwise folks will have to do all the legwork of finding out how a CM 1/2 Ton hoist operates. I mentioned this in my previous post but I'll say it again, nothings going to happen with the hoist slung on the ceiling, bolted together and plugged in. You're going to have to do exploratory surgery..on the table.

    I find it hard to believe there isn't an electrical schematic for that thing somewhere in 'cyber-world'.

    Stuart

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    Yeah, well it sounds as if it IS a contactor issue, and not necessarily a capacitor issue, since it worked one way and not the other for a while.

    The reversing contactor probably swaps ends on the start winding, including the capacitor, if any. If the contacts for one direction went out first, that would explain the first stage, when it worked in one direction. Then if the other set went out, it might not work either way.

    The question then becomes WHY they would go out like that? usually that occurs because either there is a missing or damaged transient suppressor, or because too much current is being drawn, which can damage a suppressor.

    Too much current could be from a bad capacitor. So you might have a couple bad parts. Or you could just have broken wires, possibly from vibration, if the thing gets a lot of use.

    I suppose it could even have a gearbox problem, that jams the gearbox, first in just one direction, and now in both, maybe a piece of "stuff" got in there in a bad place.

    You are just going to need to take it down and get a look at the possible bad parts inside.

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    Worked on a number of hoists and most were CM. Have one that is 110 but it may be 1/4 ton.
    What you describe may be a problem in the pendant switches. Replacement of the pendant
    was the easiest cure since the shop would order what I wanted. Cleaning the contacts with
    the power off (!) might help but likely will be a temporary fix.
    Assuming here that the chain is not at the full limit of travel and then the limit switches are
    not faulted.
    John

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    Asking, not quibbling here.....

    Are the pendant switches multiple? As in one contact for power and one for reverse? Yes, I see that if so, then the pendant switch being bad could close the power but not the start winding (reversing) relay. Seems like I have seen that setup, and I forgot about it until you commented.

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    Just two push buttons, one up one down on three phase units. No power switch on three or single phase. Once the switch is closed the the motor is energized and so is a solenoid that releases the brake. Power loss collapses the field in the solenoid so the brake clamps. Safety feature.
    What I thought was something in the hoist turned out to be the pendant for three hoists. I put my meter away and called over one of the electricians and they called it every time.
    One had a cracked brake plate so the load would spool the motor backwards when the button was released.
    Don't believe it is the solenoid for the brake as the problem was described as a directional problem and the brake solenoid would have worked in the down direction.
    Easy access to the electric while it is hanging. Pull the end cover and the schematic should be pasted inside. Push on spade connectors so easy to look for something loose. Got numbers for the wires? The schematic if present is easy to decipher.
    On another I reset the limits and cleaned the micro switches.
    Could be something else but I'm drawn to the pendant from the description and repeat failures on older equipment.
    John

    Push buttons on the 110, one rocker (fancy for two push buttons) for the three phase.

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    Here is the circuit diagram. I phoned CM and surprisingly the design of the L series hoist has not changed in the 30 years since this unit was built. The pendant has two momentary contact pushbutton switches.

    screen-shot-2017-12-01-9.09.15-pm.jpg

    For some reason I can't get the size of this image to match what I have on my screen. If you want a larger copy PM me and I will email it. The "solid state reverse switch" is a bit unexpected, I would like to know what it does.

    I think the hoist is probably at the lower limit, which may be why the down button no longer works ;<) Since the hoist makes the same buzzing noise for both buttons, I am thinking perhaps the problem is that A) the hoist is all the way down so the limit switch is engaged, and the up limit switch is stuck. I think the first thing is to remove the end bell where the limit switches are located and see if they are opening/closing. I'm installing cabinets in the shop tomorrow so will take a look Sunday.
    Attached Thumbnails Attached Thumbnails screen-shot-2017-12-01-11.46.55-am.jpg  

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    The brake lining is likely to be asbestos. It is not directly exposed. However, the end bell cover stores the wear particles from the lining. These particles will have settled on the horizontal surfaces. Expect some debris to drop out when removing the cover.
    Important to know since you will be working close to face level if the hoist remains on the trolley.
    Weight should be 62 or 79 pounds, depending on chain length.
    Is the CM a Model E ?
    Attached are schematics, the one you posted and also for a model E.
    lodestar-single-phase.jpgmodel-e-schematic.jpgbrake-limit-switches.jpgsolid-state-reverse-switch-test.jpgtroubleshooting.jpg
    All attachments are sourced from here:Literature, Catalogs, Manuals, CAD Drawings, Wiring Diagrams | CMCO
    Then I choose the downloadable pdf :CM Lodestar classic electric chain hoist (627-T)English
    John

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    John, it is a model E, but it predates all of the hoists in the current manual. Instead of a solid state reversing switch, it has a centrifugal switch with two contacts. When the motor is started, one contact is broken, depending on direction of rotation. Here are a couple photos:

    img_4606.jpgimg_4608.jpg

    I suspect the capacitor is bad, it is an old sprague 200mfd 110V capacitor with a paper casing. I have ordered a modern replacement.

    img_4611-2-.jpg

    I found a source of information I did not know I had. There is a circuit diagram inside the other end bell, dated 1964:

    img_4610-1-.jpg

    Now I really want to know what CM stood for. Was it Chisholm-Moore or Columbus-McKinnon?
    Attached Thumbnails Attached Thumbnails img_4613-2-.jpg  

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    Quote Originally Posted by rimcanyon View Post
    The hoist just buzzes when the up or down buttons are pressed.

    -Dave
    How convenient, the company rebranded itself as CM without any change in stationary.
    Diagnosis tip:
    Okay, it's apart now. Re-assemble it electrically and leave the brake side end bell off.
    Energize the unit up or down (buzzes both directions?) and source the location of the buzz.
    What you hear is likely the brake solenoid sound that is masked by the normal motor noise operation.
    While energized the function of the brake release action of the solenoid can be observed. If the
    solenoid cannot shift the clamped brake pads to a clearance position the the motor will not rotate.
    The motor does not have the torque to overcome the brake.
    John

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    It's pretty simple to pull the leads off the capacitor and check it with an ohmmeter....takes about 30 seconds and will tell you if the cap is good or bad!

    Stuart

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    Before you start replacing parts, I would take the push button station apart and look for burned contacts.

    It may have 2 burned, power to the run winding so the buzz is caused by the start circuit.

    If you think you have a bad capacitor, just short it while it is still in circuit. The motor will start and run but not have as much starting torque.

    Bill

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    Replacing the old paper-covered sprague capacitor solved the problem. The hoist is back together and runs great. Thanks for your help.

    The only issue I ran into with the install was that the modern replacement cap was shorter by an inch or so than the original Sprague. I found a piece of tubing that I could press onto the cap so the length remained the same. That was needed to use the same spring to hold the capacitor in place.

    -Dave

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    Dave,

    I have a model C hoist The remote control and power were disconnected so I am trying to rewire. I am having trouble identifying the orange connections to the Electric Brake. I have only one orange wire from the wiring harness connected. The other post is empty. According to the drawing, there should be another orange wire, but I cannot tell from the drawing where it originates. Would it be possible for you to check your unit and let me know the source of the second orange wire.

    Thanks for you help.

    Frank


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