transformer? buzzing inquiry

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  #1  
Old 10-21-15, 10:13 PM
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transformer? buzzing inquiry

At my workplace in the utility room by the electrical panels there is a box with what I believe is probably a transformer type unit (photos below) which I noticed is starting to make a definite and fairly loud and steady buzzing sound. Perhaps someone here could advise me by looking at the photos to help me identify more specifically what this unit is called (transformer or called something else) and whether it would be typical for it to buzz loudly and if not whether this means it may be failing or should otherwise receive some rather immediate attention/diagnosis by a qualified electrical person before I take the opportunity to contact one. Any comments appreciated. Thanks.





 
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Old 10-21-15, 10:48 PM
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That's a fairly old lighting contactor. Allen Bradley four pole. One switch could control multiple lighting circuits and from a distance. It's fairly common for them to buzz. If you walk over to it and tap it with a piece of wood it'll change pitch and may even get quiet.

When it's turned on it probably makes a pretty loud bang when it engages.
 
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Old 10-21-15, 11:07 PM
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ok thanks PJ. I don't really recall ever hearing/noticing a loud bang from it (although likely it does and just never really heard it or took much notice otherwise), but I'm also fairly certain it controls the outside lighting which turn on automatically when it gets dark outside. I did try thumping it with my knuckle and it did quiet down. Maybe I shouldn't worry much about it then? That would be fine with me. Thanks again!
 

Last edited by sgull; 10-22-15 at 12:29 AM.
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Old 10-22-15, 01:25 AM
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Since that switches the outside lighting.... it will be controlled by a photocell or timer. You'd hear it bang when the outside lights came on.
 

Last edited by PJmax; 10-22-15 at 05:09 PM.
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Old 10-22-15, 09:47 AM
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Yep there's a photocell outside for that lighting. And now that I've been informed that the old "buzz-ard" is called a lighting contactor I did some googling and came up with plenty of info about such -- including the following thread which provides some enlightening info in regard to what causes the buzz and some options I might consider to eliminate/fix the buzz if so inclined: Light Contactor humming. - ECN Electrical Forums
Again, thanks!
 
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Old 10-22-15, 04:52 PM
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Yes, it's a contactor and yes, it is being used to control lighting so I suppose you could call it a lighting contactor. There are specific lighting contactors availabe that are silent in both electrically and mechanically held types. Your contactor appears to be electrically held. Definite purpose contactors are electrically held and also sometimes used to control lighting and definiely give a BIG bang when they close.

The most popular mechanically held lighting contactor was the ASCO 917 series (also was sold under GE, Siemens, Cutler-Hammer names) which has been superceded by the 918 series.

http://www.emersonnetworkpower.com/e...hCircuits.aspx
 
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Old 10-22-15, 05:40 PM
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Thanks Joe, I appreciate the additional clarification/elaboration. Next time when/if I'm around to hear it bang I won't wonder what the heck that was and go into panic mode or something.
 
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