What to do with wires when installing light switches/plugs

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Jadnashua

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As a side note, I suppose the 'area of contact' idea allows for side-wiring without looping the wire around the screw.
The cam action of the screw would make it a less than secure connection, but from an area standpoint, if it was secure, would be sufficient. Having a loop around it allows less pressure while providing a more secure connection. The back stabbing connection is held from side-to-side forces if it is stripped and inserted properly, providing a consistent contact point.
 

JWelectric

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As a side note, I suppose the 'area of contact' idea allows for side-wiring without looping the wire around the screw.

What we have to remember is any contact beyond the area of the conductor is doing nothing but looking good. Look at the end of the conductor and any contact beyond that amount of area is not needed as the current flowing through the conductor only has the area of the conductor to flow through. Wrapping the conductor around the screw in no way increases the area of the conductor.


If the area of contact with the conductor was a problem then we wouldn't have terminals that held the conductor with only a set screw. look at the larger size conductors such as the service entrance conductors that land in a terminal. Based on the receptacle conductor contact area shouldn't these conductors be wrapped around that terminal?
 

Wet_Boots

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I remember wires boinking out from under terminal-strip screws, while doing controller low-voltage wiring, but it seems that sort of thing isn't possible on a modern electric receptacle, given their geometry.
 

DonL

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I remember wires boinking out from under terminal-strip screws, while doing controller low-voltage wiring, but it seems that sort of thing isn't possible on a modern electric receptacle, given their geometry.


That is normally due to improper installation.

And using the wrong type of wire for the termination.

Connectors are rated for solid conductor or stranded for a reason.

Many terminal strips are made for a tongue connector, and not a direct wire connection.
 
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JWelectric

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I remember wires boinking out from under terminal-strip screws,
It might just be something around my area or the era in which I was born but I don’t see how a conductor could bonk at all. I think this was intended by our creator to be done between husband and wife in order to keep their gene pool alive.

while doing controller low-voltage wiring, but it seems that sort of thing isn't possible on a modern electric receptacle, given their geometry.
As Don pointed out, this is mostly due to improper installation just as most failures in electrical systems.

When I was going to school and studying electronics we were still working with vacuum tubes so this should tell you that I went to school many years ago. Yes I am familiar with modern technology but that is not the point I want to make.

Way back when we were still cutting trees to build the Ark there was a rule and a firm rule we followed that seems to somehow fell by the wayside, tin first. Yes I know that many in the low voltage today don’t even know what I am talking about but I bet there are many here that have a full understanding of that comment.

As to the geometric make up of low voltage terminals verses those on premises wiring devices there is one very major difference. The major difference is the amount of foot pounds mandated for the amount of pressure that holds the conductors in place and the type of conductors being held in place.

In the premises wiring of our homes the smallest conductor allowed is 14 but in low voltages we can use as small as 28 gauge conductors. In a lot of cases these small conductors are stranded and use a fine strand in the manufacturing process. Fine stranded conductors are harder to hold in place than solid conductors and this is the reason the NEC mandates that when fine stranded conductors are used the terminal used has to be listed for stranded conductors. We see the fine stranded conductors in photovoltaic more than any other place.

Now couple improper terminals with any human being and we have the equation for failure. Why you might ask. Well as humans we learned a long time ago to add erasers to our pencils for one reason or the other but I think it is because we aren’t perfect. Get my meaning?
 

Wet_Boots

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I was thinking that the terminal strip screws were probably not the undercut binding-head variety (and it didn't help that the original installations had little wire slack to allow easy maneuvering come repair time)

Some of the original controllers I worked with employed a single terminal strip for all connections, both line-voltage input and low-voltage output. Needless to say, the folks at the Underwriters Laboratory didn't think too highly of that arrangement.
 
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SteveW

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Brother Don you have hit the nail on the head with most problems found in residential wiring or at least let me say that it has been my experience.

Young journeyman stripping conductors twist the strippers to and fro breaking the insulation free, opps the damage is done but they don’t trim it off and start over they just continue on without a care in this world.
Grab the conductor in the wrong hole of the strippers and then move to the correct hole, sorry damage is already done to the conductor.
One of my most favorite is the fellow grabbing two conductors at one time with dime store strippers that are not designed for the purpose.

Taking a phrase from some who are against the stab-loc, “if I had a nickel for every time,†I have found a handful of white conductors joined with a wire nut and one or two in the middle would be broke completely free “I would be a millionaire.†This comes from ringing the conductor with the strippers and also causes the burning of the stab-loc connection. We like to bend the end so when we do damage the conductor it breaks off and tells us we goofed.

When having lab with one of the classes I watch for this and try to head this habit off before it ever gets started by holding the stripped part of the conductor in my lineman’s pliers and with a couple of bends it breaks clean.

People do it and aren’t aware that they are damaging the conductor. No concentration at all, to busy jumping around to the beat of that awful mess coming out of that radio blasting louder than the jack hammer in the background.
Geez what is this world coming to? Next thing you know they will be demanding a water cooler and a chance to run to the port-a-jon every 30 minutes. That ain’t the half of it, they will be wanting to get paid to drink that water so they will have a reason to run back and forth on payroll.


I'd like to follow up on this comment. If I'm reading this correctly, the problem with using backwired receptacles could be due to damaging the copper wire with improper stripping technique?

Just trying to visualize this. I imagine that in a case of bad stripping technique, the blades on the wire stripper will leave an indented/carved out ring around the conductor. Then, when the wire is inserted into the stab-loc, the ringed area on the wire gets caught by the stab-loc but since the ringed area isn't full thickness, the contact area is less than ideal, and thus creates potential for arcing/burning. Is this the concept?
 

JWelectric

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Your concept has a lot of merit in so much as the conductor is no longer a 14 but something less.

In a lot of cases not only with the stab-loc but with other methods the indention of the conductor causes the conductor to break causing arcing and a burned device. This damage is more evident when using a wire nut on several conductors at once. If damaged the conductor breaks off clean causing the installer to have to find the broke conductor.

Not pointing toward anyone but a lot of the stab-loc devices that have failed is due to overloading the device or as outlined above damage to the conductor but the electrician lacks experience to ascertain the cause of the damage and only sees what they are looking at thus the finding that the stab-loc failed.

Many people can see the area that is in contact with the conductor when wrapping around the screw but are not yet wise enough to realize that no matter how much contact is being made by the screw the conductor still has the same area under the insulation. The screw does not give the conductor any more area nor does it make the device able to carry more current.
 

Jadnashua

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The stab-loc is a ways inside the device, and if you nick the wire, it is usually at the point where the insulation ends, so no, it's not a case of it getting jammed at the stab-loc. It IS quite important to strip the proper amount of insulation to ensure two things: you don't have a lot of uninsulated wire sticking out, and two, it is fully inserted through the stab-loc and stabilized properly.
 

DonL

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The only way a nicked conductor would end up in the connector is if you strip it to short, then strip it again to the proper length. The built in strip gauge tells you the correct length for wire striping.

Not only does a nicked conductor change the wire gauge size, a Solid conductor will tend to break before its minimum bend radius is reached.

Just for test you can take a piece if solid wire with a nicked conductor, and it will be easy to break in two with a little bending.


Have Fun.
 
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