Humming relay question

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All,
A while back I'd asked for advice on getting emergency stop switches going in the shop. Based on the advice from this group, I ordered these combo switches and normally closed contactor blocks, model E22JLB2N8B:
http://web1.automationdirect.com/adc/Shopping/Catalog/Pushbuttons_-z-_Switches_-z-_Indicators/Eaton_Cutler-Hammer_22mm_ (E22_Series)/Emergency_Stop_-z-_Mushroom_Pushbuttons_-a-_Stations/E22JLB2N8B
I then ran that over doorbell wire to a 24V transformer I picked up at my local electrical supply store, run off a 110V line from my primary subpanel ("Subpanel A"). I then ran a 30A line to a safety switch, from there to an Eaton 30A contactor, and hooked the doorbell line to the 24V hookup on the contactor. Finally, I hooked the output from the contactor to a new subpanel ("Subpanel B") and turned it all on.
Anyway, thankfully, after all that, it worked. :D
But, one question - the contactor hums. LOUDLY. It's only when the 24V is on; I can turn off the safety switch, but not hit an estop switch, and it'll hum. Is it supposed to do that?
Brett
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The way you have it wired, yes.
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George wrote:

You could have chosen to be helpful.
Which begs the question: why are you here in the first place? Is it to take what you can get and give nothing? Or are you simply a troll?
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WoofWoof wrote:

It had ocurred to me that I could get a switch which would control both the relay and the transformer, and cut power to both at the same time. Perhaps that's what he's talking about. However, the relay humming while I'm not around isn't much of a concern to me. It's distracting while I am there, but I can learn to live with it, if it's inevitable.
I'm more wondering whether the relay *should* be making that noise, if they all do that, or if mine's doing it because it's about to burst into flames, or something.
I was at least smart enough not to wire the transformer off of subpanel B :)
-BAT
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Brett A. Thomas wrote:

Perhaps it was. My point though was that, from his statement, he either knows why this is happening or believes he does and he could have supplied that information for you and other interested parties (like me). He chose not to contribute so you have to wonder why he participated at all.
I thought at first he was a simple troll but he actually seems quite a helful guy in other current threads here.
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If you're supplying constant hold-down voltage - the way you wired it - it will hum.
Had I wired it, I would have had the safety switch control my pull - down current (NO) to a spring-loaded solenoid which would break the current to the shop. This would allow multiple paralleled panic switches, but would require a reset after a panic stop.
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George wrote:

Yes, that makes sense. Thank you, that was very helpful.
-BAT
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Sorry I simply answered your question the first time. I'm prone to do that. Some give elaborate answers to their own questions instead, some just blast in with ad-hominem accusations, for reasons unknown.
Can't take credit for the solution. It's the way every wood shop I've ever worked in is wired.
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George wrote:

I think my complaint with it is that the failure mode is that, when you hit "stop," it wouldn't stop, since everything has to be intact in order to signal for a stop. But with what I have, the failure mode (an open in the wiring) is that nothing would work until it was fixed.
The downside is the hum. But, if the hum isn't detrimental and doesn't signal something Bad Wrong (i.e., if the contactor is supposed to sound like that when it's engaged, and is designed to be engaged and hum for hundreds of hours at a time), then it's really no worse than the flourescents and I can live with it.
-BAT
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know what you want. The emergency cut-off, obviously, assumes power is present, else it wouldn't be used to cut it off.
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Meant to include this. http://www.detroitcoil.com/PAGES/What%20Is%20A%20Solenoid.pdf
And check the reply to the provocateur for DC.

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As helpful as you?
http://www.detroitcoil.com/PAGES/How%20A%20DC%20Solenoid%20Works1.pdf In case you're not just the dog fart you sign yourself.
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George wrote:

I wasn't helpful to him because I didn't know the answer to his question (I was as interested as he to learn). You, on the other hand, did know but chose not to help initially.
I'll leave it to others to judge which is worse.

As always, I think that kind of name-calling says more about you than me ... but again, others can judge. But anyway: *plonk*
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"WoofWoof" wrote in message

Too bad, it will be your loss ... George and I aren't exactly enamored with each other, but plonking him is the epitome of cutting off your nose to spite your face, because you will learn something from his posts. So get pissed if you must, we all do, but don't cut off your nose ....
... well, you get the picture.
--
www.e-woodshop.net
Last update: 11/06/04
  Click to see the full signature.
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[snipperectomy]

It could be something as simple as an AC vs DC issue. Was the relay disigned for 24v AC? That'd be the route I'd chase. Then again.... *S*
00
Rob.
"This guy was a mean killer.... he used a kitten as a silencer.." (CSI)
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Humming relay question...
When I first saw the title... I had visions of 4 people, around a track, each running then humming a verse into the ear of the next guy...and so on... But I resisted expressing that vision in public.
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Robatoy wrote:

You didn't resist it very well. :) But thanks for your suggestion.
-BAT
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thank you for not sharing that.. *g*
mac
Please remove splinters before emailing
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wrote:

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"Brett A. Thomas" wrote:
<snip>

The output of a doorbell transformed is 24V A.C.. Is the relay designed for 24V A.C. or 24V D.C.?
-- Jack Novak Buffalo, NY - USA (Remove "SPAM" from email address to reply)
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