Im looking for a third opinion from a fellow electrician. From reading some older posts, I get the feeling that may be you. While Ive been out of work, (electrical work is real slow here in Atlanta, Im on my 6th week furlowed ), I have had a bunch of side jobs. I met this guy at Highland Hardware ( www.highlandhardware.com )who has a small 5 man cabinet-shop. We got to talking and he had a company come out and price putting in an emergency shut off system for all his machinery. It would have 8 E-stops, anyone of which would shut off ALL of the machinery. The company that gave him the price is a real sleezey outfit. Its one of those electrical contractors that will man a job with one guy that knows what hes doing, with as many minimum wage guys as they can find, and hope they dont burn the building down.
I asked what they proposed, and he said they wanted to put in a contactor-bank and reroute all of the machinery through it. Seeing if I could give him a better price I went to his shop to have a look for myself. What I found was that all of his machines were fed out of a dedicated 150A sub-panel. I figured it would would save him a hell of a lot of money to just change out the main on the sub-panel with a "shunt-trip" breaker, and run the E_stops in parallel.
finally...the question: A buddy I was talking to at our union meeting last night said you werent allowed to use a shunt trip: A)out of "line of site" of the panel it controls
and B) multiple actuators.
I have searched the NEC and I cant find anything saying that that is or isnt the case. Are you familiar with a situation like this? Was I completly off my rocker for thinking of a shunt trip breaker? Have I been shown up by a "Romex Ranger"? (east coast slang for a low quality electrician :+ )
" I do not regret the tools I have bought, but those I have yet to afford. "
I was thinking the exact same circuit,however the question needs to be asked :::::: Are the shop lights and auxilliaries on this same panelboard? If so then you have another problem unless it is truly an "E" Stop and you want to dump every thing and fix the problem later. You must have some Battery Operated egress lighting (OSHA) and some maintenance circuits if you want to get back on line if its dark of night or a dimly lit area in normal operating hours.
Seems to be an easy fix but we need all the rules
good luck........BTW,I spoke with Sonny by 'E' mail and he tried to get back to you but the forum was down so he is not avoiding the issue and will probably offer some thoughts as well,when he gets his 40 winks in.
I agree with you that the first guy was padding his pocket.
Hey bud. Sorry to here about the long furlow. That stinks.
Like I said, attempt 4 to respond. *@&#$^%(@!
Gary gave you your basic motor starter configuration. A MEMA 3 contactor I believe would do you.
My concern with this is:
5 guys running different operations. Suddenly somebody cuts the power because they have a problem.
So how many machines are going to kick back??? Maybe a shaper? One or two tablesaws?
Suddenly you have say 3 out of 5 guys with various injuries. Boxer breaks to the hands. Launched wood.
There's quite a bit more to think of beyond "OH CHIT!" cut the power.
The ability to do an ESO (emergency shut off) remotely is a good idea.
Interlocking stop stations for different operations in safe areas is good.
But to suddenly cut all power to all machines, not just the one in trouble, could really be dangerous.
So the machine spicific ESO with some safe area big red pushbuttons is a better idea.
Say #1 is doing something that the outflow is goint to #2 who is outfeeding to #3. OK, #1 has a button to stop his and #2 if #2 has a problem. #1's PB stops his and #2's machine.
This would be a seperate PB from #1's normal start/stop machine function.
Key here is EMERGENCY shut off.
But you go cutting ALL machine power, folks could get hurt.
A friend of mine, Kevin, whom I walked through subpaneling and wireing his shop, experianced a boxer break to his hand because he was ripping and his wife plugged in a second worklight in a seperate room in the basement and tripped the basement circuit.
A wicked kickback (in the dark, no less) bushed the joint on his little finger of his right hand.
Think it through. Sometimes to make something safe reguires a lot of senerio thinking. Thinking beyond just through the switch to everybody.
If I can be of help to you designing the scheme feel free to email me.
Also contact Dick Laxton as well for his engineering input.
We'll also need to know your experiance with industrial control schemes.
Sonny has made a goodpoint,however in a commercial shop if one operation depended on the other there should be interlocks with time delays already present and secure/safty shutdowns schemes in place.
Like Sonny said between the 4 of us ,for that matter the forum, we can make that shop stand on its head, get us all the rules and we will get you a package that the shop owner can't turn down and you make a name for your self....who knows automating shops may be your next career.
Say Isaac ........I don't know of a Code requirement that states anything about a shunt trip application...yay or nay.... with multiple loads.I am not at work today but will see if I can find something or another interpretation tomorrow.
If the main breaker or the shunt trip are lockable, the within sight of statement, is not an issue. I will also check on that for you.
Dick- The reason I was thinking of the shunt trip was because the subpanel ONLY feeds his machinery, so "sudden delumination"
wouldnt be much of a problem. (I always liked that phrase)
Sonny- What you said about the potential danger of turning off all of the machines is something I didnt think about. He said all of the changes he was making was for his insurance, i wonder if his insurance agent thought of those risks? As for my control experience, Ive done control work, for:
The Atlanta Pepsi Bottling plant (Im a Coca-Cola man myself :9 )
Krispy Kreme Doughnuts (nothing like one 5secs after being frosted :9 )
Lighting control for most Atlanta area Target stores
Southern Brush Manufacturers
Who knows how many Fire Alarm and suppresion systems
And... When I got furlowed, I was working on the "Lab Waste Steralization Tanks" At the Center for Disease Control. You know the tanks they boil the anthrax in before they dump it into our local water supply. (just kidding they dont dump it in our water supply, thats further up river, its just Alabamas water supply.)
So I do have a good bit of control work experience. What can I say, I always bitchh and moan whenever I get put on a job running recepticals. Id rather be outside digging a ditch for a service entrance than hooking up light fixtures. My control experience does come in handy. My employer is bidding a job, installing a small powerplant, maintaining the power plant, then removing it, for a National Parks restoration job. The job just happens to be on...big gasp... an island, 70 miles off the coast of Key West. Guess who will be the head apprentice on that job? :) Ill be getting alot of rustic furniture practice on that job. Keep your fingers crossed for me.
Anyway, with the safety concerns brought up, I may not be doing anything for this guy. But he did say he had a large order coming up, and I could help out if I was still out of work and needed the money.So thanks to all.
" I do not regret the tools I have bought, but those I have yet to afford. "
Sometimes any work is better than no work, on the big order coming in on the side.
Far Key West? I don't want to hear no more bitchen from you feller. :)Hope it pans out for you!
And I'll keep my finners crossed as well for you. Hang in there, things get better. Chin up. :)
Let me stick in one more thought..where do you stop the line??If you are in an "E" shutdown situation to keep from cutting off your hand and you pull the plug and only cut off your finger isn't that the intent we saved the hand.
I'm sure the insurance underwriters have established minimums as well as OSHA for this. Good luck in how ever it goes and send some pics of the Island if you go
I understand Sonny's point well, but the idea of master shut downs has merit in that anyone could quickly shut down the whole shop. It could be that worker A is in trouble on a machine and can only yell something. Worker B on the other side could shut down all machines before anyone else could get to worker A.
Like the example of the wire wheel comming apart. If you have to go to the machine to shut is down that could be a major injury for both the original operator and the rescue worker. Something to think about.
There are lots of ways to configure the system to shut it down from multi locations. I would not have the mushroom switches at each machine but have a number of Emergency shut offs around the shop in easy to reach locations, but not near the exit...
I've been in lots of industrial plants. E-stops usually shut the entire process down, as the purpose of it is for an emergency. If your getting dragged into a machine, chances are you won't be able to punch the e-stop so you have to count on someone else punching one somewhere for you.