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#4113 09/11/01 04:49 AM
Joined: Oct 2000
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CanadianSparky;
probably the most prevalant 3 ph is 208/120Y folowed by 480/277Y .
Virgil;
i worked for a lot of different contractors here that knew nothing of safety practices or PPE, they would simply joke that i was not to get paid for 'welding'. Some would even make up service drops bare handed. It took me quite a while to realize my upbringing in this trade was outragoeusly flawed, so don't be impressed with my ignorance. [Linked Image]
Today if i visit similar situations i will ask the customer if he/she would like me to trace out the circuit or shut the main off, and i'll usually leave one of my computer generated panel scheduled for them.
There are, however, situations that require that i do live work. A common case in point is making on an overhead service drop, i would be interested in how others go about this. [Linked Image]

#4114 09/11/01 06:18 AM
Joined: Mar 2001
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Quote
Originally posted by Nevin:
Years ago I once was working On a 277v lighting circuit which I thought was de-energized. I had a ballast cradled in my arms while disconnecting or reconnecting it. I still don't know what touched what but what i do know is that baby became very uncomfortable in my arms.

You probably DID shut it off, but it was likely the neutral of a multi-wire ckt. that got you. This is pretty common in lighitng ckts.

#4115 09/11/01 06:23 AM
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I just got another of those NFPA conference mailings, for a meer $695 , and airfare for most of us, we can all learn to be safe!

#4116 09/11/01 06:30 AM
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My day job as an E & I Tech. in a chemical plant has a very in-depth, although not necessarily always followed, procedure manual for working on electrical systems. This policy works in conjunction with NFPA 70E. Unfortunately, it took 3 deaths before any formal policy was implemented at all.
This policy includes everything from LOTO to flash suits and designated flash-zones. Mostly, to test or diagnose anything 240 volt or below, you must wear leather gloves and safety glasses, anything over that, voltage-rated gloves, flame-proof clothing, and an arc-shield for facial protection at a minimum. This is a VERY simple overview of the policy. If anyone is interested in this sort of program, let me know, and I will send copies of our procedures.

[This message has been edited by Redsy (edited 09-11-2001).]

#4117 09/11/01 08:05 AM
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I won't work on anything live unless absolutely necessary.

If you do have to do, have two journeyman there only one working at a time, take turns.

Tag and lock out the circuit you are working on. Don't use masking tape use a physical lockout, preferably one with a padlock. I carry the Klein one in my truck. You would be surprised how many times somewill will attempt to energize the circuit while you are working on it. "hey my ac is out, oh here's the prblem it's shut off" no realizing you are on the roof working on it.

#4118 09/11/01 03:31 PM
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If you can also lock the room where the panel is. I have had jerks cut off a lock to turn on a breaker. One time a doctor did that so he could turn on his computer. Hung me up on 120 volt outlet circuit untill a fellow worker kicked the ladder out from under me. If you can't lock out the breaker and door remove the wire from the breaker.


ed
#4119 09/11/01 05:26 PM
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I sometimes do a live panel change in domestic premises here to avoid a call-out from the local utility. That's 240V to ground, rather than 277V though. I occasionally work live in a 3-phase 240/415V panel to add/change circuits.

I certainly wouldn't try a big 3-phase panel change live though, or a 3-ph. outlet replacement - Too many "hot" wires with 415V between them to keep an eye on.

#4120 09/11/01 07:33 PM
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Nevin Offline OP
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Ever have someone come up from behind and "goose" you while you were working on a live panel?, bump your ladder when working on a live circuit? These in themselves are good reasons to not work live. It dos'nt matter how good or steady you are if things like that happen.

#4121 09/11/01 08:52 PM
Joined: Oct 2000
Posts: 2,722
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I also do the "Hot" test to verify the meter [tester] works, then open the circuit and re-test.
LOTO the heck out of any and all disconnecting means, even pull fuses out of switches if there's any possible jokers [Linked Image].

Got hit once from 277 VAC, and it hurt plus shook me up quite bad! Glad to say only hit once [also glad to be alive today to say I got hit once!]

Canadian Sparky,
As to your question about the 347Y/600 Wye system, you guys in the "Real Great White North" [the one that Bob and Doug are from, plus the one north of Washington, Idaho, North Dakota, Wisconsin, Etc.] are the only North American country with it.
Down here, we have a 3 phase 3 wire Delta, which is 600 VAC, but the only low voltage [under 1 KV] 4 wire Wye systems are 208Y/120 and 480Y/277.

Depending on the size - in square feet - of a commercial / industrial structure, the system voltage from the utility company could be 208Y/120, 480Y/277 and upto 4160Y/2400. All this to get the required KVA into the building.
Of course, normal office lighting would be dangerous at 2400 VAC - switches would be killing people left and right!, so the better lighting voltage for large structures is 277 VAC.

Scott SET


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!
#4122 09/12/01 02:55 PM
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As to your question about the 347Y/600 Wye system, you guys in the "Real Great White North" [the one that Bob and Doug are from, plus the one north of Washington, Idaho, North Dakota, Wisconsin, Etc.] are the only North American country with it.
[/B][/QUOTE]

Ah... That's something I was getting curious about too. I have several references to 347V heaters, 347/600V connectors etc. in a U.S. catalog, but hadn't seen any mention of that system in here before.

Any particular reason why Canada adopted it, or has the origin been lost in the mists of time?

Nevin:
Your point about getting bumped when working live is a very valid one. If I do have to do a live changeover, I always insist that the area around where I'm working is kept clear of other people until I'm done.

At the same time, I won't do it if I'm completely alone on a site - Just in case.

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