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plummerscarin 
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 Topic: Another electric motor question
Posted: 29 Oct 2022 at 7:08pm |
I have been the opportunity to use a grain bin this year with a dryer fan. Trouble is, the fan won't run unless I hold the toggle switch in the start position. As soon as I let go to the on position the fan stops. My thinking is the relay has failed but looking for options before either swapping parts or request a service call. Ideas? 
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steve(ill)
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Location: illinois
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Posted: 29 Oct 2022 at 7:38pm |
Im not sure its a "MOMENTARY START SWITCH"... Most of them are an ON- OFF switch.. You enengize the the solenoid and it pulls in the contacts.. You turn the switch OFF and it cuts the power... THINK of the STARTER SWITCH/ RELAY on your tractor.. Only engages when you have the switch ON... You let go, and it kicks out..
I would try a new switch that is ON- OFF and see how that works. ( even a bedroom wall light switch might work )
If it was a momentary switch, how would you turn the fan back off ??
Edited by steve(ill) - 29 Oct 2022 at 7:41pm
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Like them all, but love the "B"s.
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bigal121892
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Posted: 29 Oct 2022 at 8:23pm |
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I'm guessing the momentary switch was part of a latching relay circuit, but looks like the relay is missing. Or somebody replaced parts, and didn't know what they were doing. But, that never happens.
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Glenn (NJ)
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Posted: 29 Oct 2022 at 9:29pm |
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If the fan runs when holding the momentary switch the contactor (relay) is working correctly. What should happen is that the coil is then energized through the overload protection (hold circuit). If the overload opens no power goes to the contactor coil and it opens stopping the fan. Your momentary switch should have a second position which also opens the coil circuit stopping the fan. You know the coil works, you know the contactor pulls in and the fan runs but the hold circuit is open. Check the small wire from the motorside of the overload to the coil for a break or bad connection. FYI, the overload is the unit below the contactor on the left side of the unit in your photo.
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Coke-in-MN
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Posted: 29 Oct 2022 at 9:34pm |
Lot of wires , couple different circuits , looks like a receptacle in bottom of box 1 thermal overload only on one leg of 220 motor ? One set of heavy wirens and one size smaller wires exiting in same run but hooked to ? Evidently someone knows what is what - if you don't - get a electrician to figure it out and MARK things so you know next time . The contactor coil needs constant supply voltage to hold it in and a switch to allow it to open when electric is shut off . 3 wires on the 4 pole switch and route seems to put 2 on same leg with one pole open
1 / 4 wires look like start wires - 2 / 3 wires being smaller UNSURE if run - but normally a single phase motor is internally switched by centrifical force internal switch for start and run .
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Life lesson: If you’re being chased by a lion, you’re on a horse, to the left of you is a giraffe and on the right is a unicorn, what do you do? You stop drinking and get off the carousel.
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plummerscarin
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Posted: 30 Oct 2022 at 8:30pm |
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Overly complicated to guarantee a service call? IDK. Didn't spend any time on it today. My accountant wanted to clean up a mess from a collapsed garage five years in the making and needed to get the M3 back here for maintenance. Will keep you posted
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Les Kerf
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Posted: 30 Oct 2022 at 8:31pm |
 Glenn (NJ) wrote:
If the fan runs when holding the momentary switch the contactor (relay) is working correctly. What should happen is that the coil is then energized through the overload protection (hold circuit). If the overload opens no power goes to the contactor coil and it opens stopping the fan. Your momentary switch should have a second position which also opens the coil circuit stopping the fan. You know the coil works, you know the contactor pulls in and the fan runs but the hold circuit is open. Check the small wire from the motorside of the overload to the coil for a break or bad connection. FYI, the overload is the unit below the contactor on the left side of the unit in your photo. |
Yup. Glenn knows his stuff. There are lots of momentary start switches in industrial starter controls.
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DaveKamp
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Posted: 30 Oct 2022 at 9:55pm |
What Glenn said... with a couple additions-
The MOL only needs to be on one leg of the system to do what it does...
The MOL MIGHT be bad... meaning... the START circuit will bring the motor up, but once you release the START switch, the contactor's HOLD circuit SHOULD keep it running, but the MOL isn't allowing the contactor to hold...
IF the motor is SINGLE PHASE, and is using either a capacitor start, or it's a THREE Phase motor, running off a single phase supply (using a capacitor start, and run capacitors in a 'static converter' arrangement, it could have failed somewhere in the RUN capacitor circuit.
(I make this point specifically because my north grain bin has a 15hp 3phase motor that is capacitor-start, and capacitor-run, from single-phase supply...
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Ten Amendments, Ten Commandments, and one Golden Rule solve most every problem. Citrus hand-cleaner with Pumice does the rest.
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plummerscarin
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Posted: 31 Oct 2022 at 12:37pm |
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FWIW, the tag indicates single phase.
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DaveKamp
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Posted: 31 Oct 2022 at 8:05pm |
Then you have either a 'start' button that pulls in a 'latch-and-hold' circuit that ain't holding (the Motor Overload contact, or some other contact or wire problem), or you've got a RUN winding or RUN capacitor that's not doing it's job.
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Ten Amendments, Ten Commandments, and one Golden Rule solve most every problem. Citrus hand-cleaner with Pumice does the rest.
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plummerscarin
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Posted: 02 Nov 2022 at 7:47pm |
Well I got with my coworker electrical inspector and conned him in to coming out to have a look. I think the curiosity got the best of him and maybe he owed me a favor? Anyway, he determined the motor was fine since it did run. The wiring was fine but couldn't figure where the hold circuit is. Finally saw where the main contactor on the left side when activated, pushes down on another contactor that is the hold. I got it out tonight, took it apart and found a bug and dirty contact.   Cleaned it up, reassemble and is working as it should now. Thanks for the replies. It was very difficult to find that 3rd contactor in such a small space
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