Lacing secondary Cables

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JOECPQ1 Active Contributor Join Date: Dec 2009 Location: Woodstock GA Posts: 17	Lacing secondary Cables 12/19/2009 1:10 PM
	What is the purpose of lacing together all th phase and neutral conductors in a CT Cabinet for a 1000 amp service? __________________ JS CPQ
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redfred Guru Join Date: Dec 2008 Location: Long Island NY Posts: 15602 Good Answers: 982	#1 Re: Lacing secondary Cables 12/19/2009 8:39 PM
	Sorry, but there's not enough information here to give you a single definitive answer. But I do have a few suggestions: Identify and isolate primary and secondary circuit wires Distribute mechanical loading of cables to multiple connections Reduce magnetic field loop size To show off the wireman's technique To baffle people outside of the trade Those are just a few of my ideas. The best way for you to find the real answer is to ask the wireman why he/she did it. __________________ "Don't disturb my circles." translation of Archimedes last words
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JOECPQ1 Active Contributor Join Date: Dec 2009 Location: Woodstock GA Posts: 17	#4 In reply to #1 Re: Lacing secondary Cables 12/20/2009 6:46 AM
	He did it because the electrical inspector made him. It is the CT can secondary wires, 1000amp service, actual max load is 450 amps , heavest load two stage ac unit with 90 amp breaker. If the mounting bar broke ph A could still get into B or C could contact N. If moisture accumulated on the rope could that lead to tracking between phases? __________________ JS CPQ
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Tornado Guru Join Date: May 2009 Location: Richland, WA, USA Posts: 21017 Good Answers: 795	#2 Re: Lacing secondary Cables 12/19/2009 10:49 PM
	In the case of large fault currents such as direct shorts, the magnetic forces between adjacent conductors can become quite large. This requires proper bracing for bus bars and the like. In the case of cables, such unbraced forces might pull them out of their connections. I'm only conjecturing here, but tying the cables together might reduce these effects. __________________ In vino veritas; in cervisia carmen; in aqua E. coli.
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dkwarner Guru Join Date: May 2006 Location: Placerville, CA (38° 45N, 120° 47'W) Posts: 6215 Good Answers: 248	#3 Re: Lacing secondary Cables 12/20/2009 1:56 AM
	At that kind of current, the magnetic attraction between the wires can cause considerable buzz or hum. Lacing reduces the noise. __________________ Teaching is a great experience, but there is no better teacher than experience.
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vagabond Commentator Join Date: Nov 2007 Location: Third Rock from the Sun (?) Posts: 76 Good Answers: 8	#5 Re: Lacing secondary Cables 12/20/2009 9:19 AM
	What you are looking at is a fiberglass support bar that can easily withstand a 300 pound man jumping on it. The torque from that wire has as much of a chance of breaking that support as I do of sprouting wings and flying. Rope is not a brace. Even if the stuff was two inch howser cable it would still flex if part of the wiring gave way. Nope - - what you are really looking at is a small minded inspector that has intimidated a wireman that is totally unsure of what he is doing into wasting a lot of time and rope on something that absolutely can't be enforced if it were protested to this idiot's Supervisor. In fact, if you do get a short in this junction box ( I don't see any signs of CTs or CT wiring in the photo) the rope will only provide flammable material to improve the burn rate of the insulation. Some inspectors should be fired! __________________ vagabond
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redfred Guru Join Date: Dec 2008 Location: Long Island NY Posts: 15602 Good Answers: 982	#6 In reply to #5 Re: Lacing secondary Cables 12/20/2009 10:43 AM
	Now that a picture has been provided, I've come to the same conclusion that vagabond has come up with. This is a bogus, capricious inspector's requirement that might actually make failure more likely. I had assumed that the lacing was to bundle and/or support the wires in groups of each downstream load. This is doing nothing but adding more flammable fuel to the cabinet and providing a possible short circuit path that can wick moisture. I would protest this and ask to see in writing the "local code" that the inspector is applying. GA vagabond __________________ "Don't disturb my circles." translation of Archimedes last words
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Anonymous Poster	#7 Re: Lacing secondary Cables 12/20/2009 7:28 PM
	The inspector was obviously a Navy guy and wanted everything tied down.Been doing electrical work over 35 years, never seen this before.
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Patrick Whowha Power-User Join Date: Nov 2009 Location: Nnewi,Anambra,Nigeria Posts: 146	#8 Re: Lacing secondary Cables 12/21/2009 6:19 AM
	Well done Vagabond.I extend my handshake to others too. Patrick Whowha __________________ Patrick Whowha
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Anonymous Poster (1); dkwarner (1); JOECPQ1 (1); Patrick Whowha (1); redfred (2); Tornado (1); vagabond (1)

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