I'm interested in when it is allowed (NEC) and advisable to make a
connection in an electrical box of a wire to a screw terminal by
looping the wire around and then using the free end for another
connection. Here's what I think I know:
1) It is NOT allowed to do this with the hot or neutral conductors and
the screw terminals on a device. Use pigtails.
2) It is allowed to do this with the EGC and the grounding screw of a
metal box or strap. This is a good idea, because it makes a
neater, tighter installation.
So I think this only leaves the case of the EGC and the ground screw
on a device. Is looping allowed here? Is it a good idea?
P.S. FWIW I'm just contemplating my three gang switch box and how to
handle the 8 grounds (5 cables and 3 screw terminals). One option
would be loop a ground around each of the 3 devices, and use a wire
nut on the 5 ground wires. Another is to use 3 pigtails; joining the
8 ground wires would require splitting them into two groups and using
two wire nuts with a jumper between them.
If you are using a metal box, splice your grounds together and to the box.
Don't put them on switches. The neutral of a multiwire circuit (two hots
sharing a neutral) cannot be dependent on a device, but if you are looping
wire like you describe, it's not
Could be a 2002 110.3(b) violation. I just checked the instructions
on a box of NM-B and found it says to make connections at the end.
With some inspectors(I've heard of), that's is more than enough to
fail an inspection
Could you elaborate on what that section covers? Does it deal
specifically with NM cable?
With conduit installations it's commonplace when running wires from box
to box to simply leave a loop in each box and cut off some insulation
from the loop and hook it around the screw terminal.
Any NEC quotes are summaries, please read the code for yourself:
No, it's a general instruction: "Installation and Use of Equipment".
You need to follow the manufacturer's instruction. If the manufacture
says to only connect at the ends of insulated conductors, then you
need to do so.
Can't say it's too common. Simple since other people I run into, and
how I was taught, you cut, pigtail, and wirenut. If you are using a
greenie, then just cut, and wirenut. Now with the free end goes to
the ground screw.
The knawing of insulation in the middle of the wire run seemed to look
lazy/unprofessional, so I'm guessing an inspector can hit you as a
2002 NEC 110.12 violation. :(
Remeber i'm still learning, so I listen to what hapens to other
electricians and take note.
I have switches like this, a single hot comes in, and it daisey
chained from one switch to another without ever being cut. It is the
ONLY time I have found a terminal screw used in my house. Everything
else is BACK STABBED. :(
OK, based on the comments so far, let me try to revise what I think I
know about looping a wire around a screw terminal (and continuing to
1) It is not advisable to do this with an insulated conductor,
although I'm not too clear on the reasoning. One thing that is clear
to me is that if this is done, the requisite 6" of conductor should be
left before the first looped connection.
2) It is advisable to do this with the EGC and the grounding screw of
a metal box or strap, because it makes a neater, tighter installation.
So that still leaves me with the question of whether it is a good idea
to do this with the EGC and the ground screw on a device.
Specifically, for a light switch, I'm considering looping the EGC of
the cable with the outbound switched hot around the ground screw of
the switch that serves it. What's the downside?
As long as you remove a suffucuent length of insulation without nicking the
wire, it is hard to see ant downside. It should actully be very slightly
preferable as the total resistance to the last device on the line will be
slightly less. Each junction adds a little resistance.
On Mon, 14 Mar 2005 11:52:01 -0600, Wayne Whitney
Many residential grade (cheap) wiring devices have holes where a 14
gauge solid wire can be "stabbed" in and a spring clamp will hold it in
place. It's a labor saving feature that can result in intermittent
"back stabbing" is what I call when you strip the wire and push
through the tiny holes in the back of a device(switch, receptacle,
etc) that only uses spring pressure to hold onto the wire. So all you
do is stab it into the hole.
This is different from what I call 'back wiring' where you insert the
wire into the back, under a pressure plate and tighten a screw.
Back stab connections are legal. However the perspective is
human safety. Code is only concerned with human safety. You
have other concerns beyond human safety. Concerned not
addressed by code.
Intermittents created by back stab connections do not
adversely affect lights. But they can be catastrophic to
computer data. Notice the difference. Back stabbing is just
fine from the perspective of human safety. But a disaster for
data safety. Perspective.
David Combs wrote:
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