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#127273 - 05/18/01 08:11 PM LOOPS IN BOX  
doc  Offline
Member
Joined: Nov 2000
Posts: 123
Texas
Well I have to say I have been guilty of making a complete loop in a box with bot the hot and the grounded conductor and have done it with more than one wire in the box have no idea why I stopped doing that and now just pull some extra and leave it un looped ,but have seen lots of electricains do this in the past that is where I learned it so now expand on why not to do it please


MAY THE SUN SHINE ON YOUR FACE IN THE MORNING AND YOU AWAKE WITH A SMILE

Tools for Electricians:

#127274 - 05/19/01 02:36 PM Re: LOOPS IN BOX  
Bill Addiss  Offline
Member
Joined: Oct 2000
Posts: 3,878
NY, USA
doc,

What makes you think that you can't or shouldn't leave loops in boxes? I'm just trying to understand the question.

Bill


#127275 - 05/19/01 06:56 PM Re: LOOPS IN BOX  
sparky66wv  Offline
Member
Joined: Nov 2000
Posts: 2,236
West Virginia
Bill,

Doc is referring to the thread here: https://www.electrical-contractor.net/ubb/Forum1/HTML/000199.html

gpowellpec has an interesting post on induction and choking that may come to play here.

-Virgil


-Virgil
Residential/Commercial Inspector
5 Star Inspections
Member IAEI

#127276 - 05/19/01 07:21 PM Re: LOOPS IN BOX  
golf junkie  Offline
Member
Joined: Apr 2001
Posts: 507
York, NE
gpowellpec has an interesting post on induction and choking that may come to play here.

I'm not buying that there is any appreciable inductance added to a circuit by a loop in a j-box.
If someone wants to do the math and can show that it affects breaker trip time with a fault I'll buy it.........otherwise, no way!

GJ


#127277 - 05/19/01 07:35 PM Re: LOOPS IN BOX  
Bill Addiss  Offline
Member
Joined: Oct 2000
Posts: 3,878
NY, USA
Thanks '66,

Didn't realize I was jumping in the middle of something here. This thread probably should have gone in the Theory section. My first thought might be that the loop wouldn't be a problem as long as the other conductors in the circuit did the same thing. I'm not sure of that though so don't jump on Me [Linked Image]

And gpowellpec did mention a spare 'conductor' in the singular so this may go along with his post also.

Bill


#127278 - 05/20/01 12:12 AM Re: LOOPS IN BOX  
doc  Offline
Member
Joined: Nov 2000
Posts: 123
Texas
ok Bill move it to the theory section and then give me some help on this subject LOL thanks sparky66 for grtting bill unconfused as to what i was talking about.From what I am reading this is something that could possibly happen but is not really wrong to do it or any prove of it being dangerous ? did not mean that statement as being mean or nasty just asking ?


MAY THE SUN SHINE ON YOUR FACE IN THE MORNING AND YOU AWAKE WITH A SMILE

#127279 - 05/20/01 12:44 AM Re: LOOPS IN BOX  
Bill Addiss  Offline
Member
Joined: Oct 2000
Posts: 3,878
NY, USA
OK,

For all that may be trying to follow this after the fact, this thread was moved to its' present location from General Area.

Scott,

Any thoughts on this?
Do you see any problems or what effect would a loop in a single conductor have and how about if all conductors had a loop?

Bill


#127280 - 05/21/01 02:20 AM Re: LOOPS IN BOX  
Scott35  Offline

Broom Pusher and
Member
Joined: Oct 2000
Posts: 2,708
Anaheim, CA. USA
Any coiled conductor carrying current will have an increased XL [Inductive Reactance], or simply a higher level of Inductance than if the conductor was run straight.
I Think that a tight loop [with a single loop coil of 1" diameter on 1 conductor], the L would be 4 times greater than straight line L.
For a 4" coil, the value might be more like 2.5 times greater than straight line [I'll need to pull out the EE books on this one, I'm just "Shooting From The Hip" here].

Now, if there's a loop with conductors carrying current that oppose each other [flow in opposite directions], that will cancel the cumilitive L on both of them, so even with many tightly wound coils, there wouldn't be a substantial increase of L in this circuit.

BTW: L = Inductance - I hate to write the entire word over and over, so luckilly we have ANSI/IEEE symbols!!

Once again, let me verify this stuff with the books and see what's up. The whole thing is equal to a single turn air coil inductor [in case you were wondering [Linked Image]], unless there are more than one turn, or there's currents flowing the opposite way.

Here's one for fun [Linked Image]:
Coil the wire for the job loop so there's like 4 layers thick and 20 stacks high, wrapped on a "Bobbin" of 1/2" GRC conduit [only one current carrying conductor].
Now run a wire through the GRC and wrap it through again and again - so it's covering the other winding.
Connect a DC source [Drycell or Battery] to the coil ran through the GRC.

?? What should happen to the AC flowing through the original coil ???

PS: Don't really do this!! Just explain what would be going on if this was done, and think of it as if you did it!
Otherwise........ Shokken Zeee Shi*zen out of ya!! could happen!!

Scott SET


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

#127281 - 05/21/01 08:26 PM Re: LOOPS IN BOX  
R.Legg  Offline
Junior Member
Joined: May 2001
Posts: 5
Coiled loops take up less room. The extra wire is appreciated if the box has to be pulled temporarily from its position or have additional branches introduced at a later date.

Its not an offering made to the Electric God.


#127282 - 05/21/01 11:33 PM Re: LOOPS IN BOX  
gpowellpec  Offline
Member
Joined: Dec 2000
Posts: 127
Irving, Tx USA
If you are counting on coiling the wires of the circuit together to cancel inductances, better include the ground. If there is a short to ground that is the conductor that is going to carry the high current back to the source, not the normal "return" conductor. Anything that slows down the operation of an OCPD in a short circuit situation should be avoided. Shorts can transfer a lot of energy to the wrong place in very little time.


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