He said he didn’t INSTALL used materials, not that existing in-place materials aren’t reused.
And wiring fished in existing walls does not have to be secured.
When is code going to change on backstabbing
- Thread starter Rdcowart
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He said he didn’t INSTALL used materials, not that existing in-place materials aren’t reused.
And wiring fished in existing walls does not have to be secured.
That is your hint what happened.
All mechanical joints cannot have a resistance less than the wire itself. Bus bars are supposed to have a contact area 3-5 times larger than the bus bar itself at a joint for that reason.
So now let’s apply some simple logic. If we have a fault in the system the breaker is designed to protect the wire. But occasionally we see normal surges, somewhat overloaded appliances, hair dryers. All of these temporarily overload the circuit then pass. The breakers only trip if the WIRE is in danger of being damaged.
Now consider what causes that wire to heat up. It has resistance or more specifically impedance. It gets hot proportional to the impedance and the square of the current. So that joint has a resistance several times higher than the wire itself. If you land it on a brass screw strapped to a piece of metal, all that surface area is contributing to radiating heat that is more or less open air. If you stick only the end with no exposed insulation down into a PVC plastic pocket everything is thermally insulated. The heat can’t escape. So it starts to soften at a mere 135 F, in the overload scenario the plastic is going to get scorched. The side screws are not only better at radiating heat by nature but the wire isn’t laying right up against the plastic the way it is routed so any melting going on is going to be mostly visible only on the wire itself. Even if it is not technically overloaded but the springs on the sockets for the plug get loose they get hot and again with the wire joint being the warmest area, guess where we expect to see faults?
Does overloading affect the integrity of the receptacle? I would hope UL tests for this. So it might be that some browning or scorching is OK but not a severe case. We see this going on inside breakers and contactors where the arc chutes discolor over time BY DESIGN.
So i don’t disagree that there are probably wiring errors with back stabbing but you can’t inspect the joint except with a “tug test” or if you are a breaker or motor shop a micro ohm meter but I don’t see many residential electricians with a tool that costs more than all their other tools combined. So no way to tell if it engaged the teeth, was stripped back the right amount, etc. With a screw terminal you can see it very easily and tell if it’s wrapped far enough, screw is tightened properly, etc. A lot more things can go wrong compared to just pushing a wire in but they are highly visible. Maybe that’s why Leverlocks do better than wire nuts or push terminals and why even the push terminals that are sold tend to be clear for inspection.
In fact I’ll go one step further. Spring clip joints have been common in electrical work for decades and have proven to have similar installation issues but still work great if used properly but there is one big difference with the industrial ones. We use all stranded wire so we can’t stab it in. Instead there is a screw driver slot that opens the jaw. You can even look down inside and see it open. Much better design. And a third option would be insulation displacement...no stripping at all and everything is sealed so much less chance of failures.
So I’m not in the camp of throwing the backstab JOINT under the bus. Too many industrial and residential systems work just fine with this type of spring clip system. I just don’t think the implementation is all that great, or we need to re-educate electricians that where there is smoke, it’s just smoke, if this is by design.
James L
Senior Member
- Location
- Kansas Cty, Mo, USA
- Occupation
- Electrician
Huh? I don't get it. Maybe I do...
If I'm installing wire, it's all new. I never install used wire. Even if a wire was pulled wrong on a rough-in and pulled out, I don't re-use it.
And when I do put new wiring into an existing house, I have a ZERO DAMAGE aim. I'm that good, I fully expect to do no damage. About .002% of the time it can't be avoided, but really I scratch my head when people start talking about damage.
Really? You ain't no better than that?
goldstar
Senior Member
- Location
- New Jersey
- Occupation
- Electrical Contractor
I think that's just as big a problem as the back-stab. The back-stabs are used for speed in installation. I mostly see them in condos or track built homes. If it's a duplex receptacle in a 1-gang plastic box - no big deal. But, when you have a gang of switches in a multi-position box there's not much space between the screw heads and the slightest tilt one way or another can cause an arc. Tightening the screw heads down so they are properly seated takes time. When you're getting the same amount of $$$ for each home or condo you're wiring, saving an hour per job is a savings (I guess).
I'm glad I don't have to think that way. I very rarely use the stabs and only when I don't have a choice. Using a stab on a switch for a small lighting load is one thing but cascading 8 receptacles on a circuit is another. HO's don't understand that just because you see a duplex receptacle on a wall it doesn't mean you can plug in anything you want to. HO's are plugging in heavy duty free standing heaters and the receptacle back-stabs won't hold up. The other thing you can't expect a HO to understand is that the first receptacle on the string of back-stabbed receptacles is taking the heat for all the others down-stream. But, the track builder electrician doesn't care about that. As long as UL states that the back-stab is an acceptable form of wiring he's off the hook (maybe legally but not morally IMHO)
Multiply that by the number of devices in a typical home, and couple that with the über-competative resi market, and doing so will price you out of the market. Resi roping in tract housing is down to the penny.
ptonsparky
Tom
- Occupation
- EC - retired
IMO, those devices were damaged because of some sort of abuse not relevant to back stabbing. Installer error or kids beating the switch.
kwired
Electron manager
- Location
- NE Nebraska
In those cases the receptacle contacts and/or the cord cap itself don't always hold up. Space heaters are about the worst thing that can be cord and plug connected into 5-15 receptacles, even good quality receptacles.
jeff48356
Senior Member
- Location
- Livonia, Michigan
Hair dryers, too. They both draw the same amount of current.
Frank DuVal
Senior Member
- Occupation
- Electrical Contractor, Electrical Engineer
At least hair dryers (the hand held version) are short operating time. Space heaters can be on 24 hours a day.
hillbilly1
Senior Member
- Location
- North Georgia mountains
- Occupation
- Owner/electrical contractor
Exactly! The ones I have replaced, that were broken like that, worked intermittently, and the HO kept hitting it to make it work, eventually breaking it. Usually starts out as burnt switch contact, not the push in contact.
- Location
- Illinois
- Occupation
- retired electrician
In my opinion, you get what you pay for. I have never seen a what I would call a quality wiring device with back stab connections....they are always the 59 cent cheap junk type of devices.
However they are listed products and you can use them if you want to.
I don't believe the place to change this would be in the NEC. I think the change would have to be made in the product standards. When the push in wiring devices were redesigned to prevent their use with 12AWG, that change was made in the product standard.
However they are listed products and you can use them if you want to.
I don't believe the place to change this would be in the NEC. I think the change would have to be made in the product standards. When the push in wiring devices were redesigned to prevent their use with 12AWG, that change was made in the product standard.
- Location
- Illinois
- Occupation
- retired electrician
Probably when they forced a 12 AWG conductor into the hole that is sized for a 14 AWG conductor...
I'm asking a serious question here - when has anyone ever backstabbed a switch in such a way that the switch cracked?
jeff48356
Senior Member
- Location
- Livonia, Michigan
Yes, that's true. But that also reminds me of another Code change that I'd like to see. Since running two hair dryers at the same time, even on a 20A circuit, will trip the breaker, I would also like to propose a change that each bathroom outlet must be on its own circuit. As it stands right now, all bathroom outlets in the house can be on the same 20A circuit, as long as no other loads are on them. Whenever I wire a house, I always run separate circuits for the outlets in each bathroom.
So in other words, any house that I've wired can potentially have several teenage girls and their parents, and two girls could be drying their hair in the main bath and power room at the same time as their mother drying her hair in the master bathroom -- without tripping any breakers.
So you're going to install GFCI breakers and single receptacles?
jeff48356
Senior Member
- Location
- Livonia, Michigan
No, I just install GFCI receptacles in each bathroom. Usually the main bath and powder rooms have only one outlet, and that's a GFCI receptacle on its own 20A circuit. The master bath has two outlets because it has two sink basins, so the first outlet is a GFCI and the other is wired downstream from that in order to receive GFCI protection. That is also a 20A circuit separate from either of the first two.
So you can still plug two hair dryers into one circuit. Nothing gained.
jeff48356
Senior Member
- Location
- Livonia, Michigan
Nothing gained from within the master bathroom, but it won't affect either of the other two bathrooms.
Send your documentation of such to the NFPA when you make the Proposal.
hillbilly1
Senior Member
- Location
- North Georgia mountains
- Occupation
- Owner/electrical contractor
The likelihood of two hair dryers running side by side is much lower than the likelihood of two running in different bathrooms that are on the same circuit, so nothing gained is not a true statement.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Another scheme would be two circuits, each feeding one GFCI receptacle in the master and fed through to another bath.
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