Question about Outlets and terminals/push-in(real question, not a troll)

Discussion in 'Electrical Forum discussion & Blog' started by cswilson, Nov 4, 2010.

  1. cswilson

    cswilson New Member

    Messages:
    2
    Location:
    North Bay, ontario, canada
    Is it allowable to use BOTH screw and push-in's on the same receptical?

    My situation is this, I have 3x 14/2 romex running into a 12.5ci (2"x3"x2.5") box.
    the Ontario electrical code allows 6 conductors and 0 or 1 marret in that size of box.

    If I can use both screw terminals and 1 push in I would need no marrets, but if I can't I will have to try and find a 2x3x3 box.


    I personally use marrets and pigtails normally when connecting outlets, but because this box is a little small it has raised this issue
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,013
    Location:
    New England
    There are receptacles that have rear contacts that rely on a screw to clamp it in place. Those are fine for your application. I've never liked the ones that relied on spring pressure to hold it in place. Otherwise, maybe a bigger box is the safer way to go.
  3. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
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    Location:
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    UL has tested the push-in connections on the back of receptacles and switches at their rated load and has approved them for this use.

    Should anyone come along and try to sell you the idea that the push-in connections are bad then they are trying to say that they are smarter than UL.

    What your propose is just fine and legal
  4. jimbo

    jimbo Plumber

    Messages:
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    Location:
    San Diego
    jw..........what you say is of course completely accurate. But in the same vein, there are plumbers who use plumbqwik one piece stop/riser combos, and push on valve/riser combos....because they are UPC/IAPMO listed, and they speed up new construction. Some of the plumbers on the forum would never use such products, because experience tells us that these products do not have the same long term reliability as better ( slower install types) products do. It is just a personal choice. Which product to use can also of course be a stricly business decision.

    I am sure you have read or even posted on question from consumers trying to find why some of their outlets and switches do not work...and the answer often is a faulty push in connection. So you are correct....but those who might recommend sturdier products are also correct.....n'est pas? as Frenchy the electrician would say!
  5. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
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    Location:
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    You are correct Jim in so much as ignorance builds a fear that can’t be explained away.

    From 1979 through 1987 about 98 percent of the work I did was apartment townhouses and condominiums. For this nine year period I carried the maintenance contract on all but two of these projects. The smallest project was 125 units with most being between 225 and 250 units. Each unit would have between 40 to 50 devices (switches and receptacles) that were installed using the stab-loc connection included with the device.

    Over this nine year period of installations I would estimate somewhere around 10 thousand units were wired with somewhere around three to four hundred thousand devices wired.
    Now I must ask if this stab-loc was so bad why I didn’t experience a massive failure back when the twenty amp circuits were included in the stab-loc.

    On the few failures (less than 50)and we almost always found portable electric heating equipment in use on the failed device. In the years of carrying the maintenance contract on these units not one switch failed. I am of the opinion that when there is a .0001 percent failure rate that the failure rate is nonexistent.

    What I have come to the conclusion of concerning the stab-loc connection is that all failures are the direct result of either misuse (overload) or improper installation.

    When these devices are properly installed and the circuit is not overloaded these type installations are just as safe and efficient as one wrapped around the screw. It has also been my experience that when the screw was used and the device overloaded the device would get to where the cord would not stay in the receptacle which is a blade being stabbed into the tension of the receptacle. Is this not the same principle as the stab-loc? So to say that the holes in the back of receptacles are bad, would not the holes in the front of the receptacle not be just as bad?????????

    As to the plumbing I have no answer as I do no plumbing or do I do research as deeply as I have the stab-loc devices.
  6. Thatguy

    Thatguy Homeowner

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    Location:
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    Hardly any organization ever admits they screwed up. You should have seen the gyrations the Patent Office went through when they failed to find a previous valid patent and so granted a new patent for the same invention.

    The customer is the ultimate testing lab and only statistically significant [hypothesis testing, double-blind studies, etc.] results count.
    Last edited: Nov 6, 2010
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
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    Location:
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    The plug on a cord has MUCH more surface area, and spot heating and resistance is less on heavy loads. The prongs on a back-stabbed device have much less surface area (but higher pressure). Given a choice, I'd prefer a device with a larger contact area, and that means a screw or a screw and clamp. Especially in a feed-through situation, I prefer a better connection than those small spring prongs.
  8. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,641
    Location:
    Cave Creek, Arizona
    I had a friend call yesterday, who has three outlets in the master bedroom which do not work while the other three do. After talking to him, it appears that the only source of the problem must be where those three attach to the other three. AND, since the wiring is done with "back stabbing", the inference is that one of them must be faulty. I also told him to plug a lamp into the bad outlets, because the simple process of removing the receptacle from the wall, COULD move the bad connection sufficiently to reenergize it. If that were to occur and he did not have a lamp which would illuminate when it happened, he would still not know where the problem was when he went back and retested the outlets and they were then working.
  9. Thatguy

    Thatguy Homeowner

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    Location:
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    And just pushing on and releasing the outlets while the lamp is plugged in may reveal the bad outlet.

    Has Mike Holt taken an official position on back-stabbed outlets? He seems to come close with AFCIs.
    Last edited: Nov 6, 2010
  10. ballvalve

    ballvalve General Engineering Contractor

    Messages:
    3,261
    Location:
    northfork, california
    You do not need Einstein to see that the tiny surface contact area of a stab in device is a problem waiting to happen. If pulled back hard when inserted and twisted a bit, it might be good forever. On high amp draws they likely arc until they melt together at which time they become "safer"

    Back stab with a SCREW on the side seems to be the way these days except on the cheapest outlets.

    But I have used them years ago and always felt a bit regretful. I have had call backs for bad connections. Often a whack or touch or twist will reconnect them. Sounds like TROUBLE to me.

    Never more!
  11. Thatguy said a lot yesterday in two short paragraphs. Every post here has said pretty much the same thing. Thanks to the wisdom of crowds, I now vote against the jwelectric point of view. I might receive a failing mark if I were forced to take his course. It is true that ignorance "breeds" a fear.
  12. jwelectric

    jwelectric Electrical Contractor/Instructor

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    Location:
    North Carolina
    Yes I agree that with the CPSC, NFPA, and all the other NRTLs throughout America that should UL miss something that all these other testing labs and the Consumer Protect Protection Agency would just sit in silence and let the public be at risk.

    The area of contact of a stab-loc device is the area that is required for the 15 amp device to safely carry 12 amps which is the most that is allowed to be carried by any device installed on a 15 amp circuit installed in any manner in which it can be installed.
    Should more amperage be allowed on this circuit there will be a failure somewhere on the device carrying the current which is a DIRECT VIOLATION OF BOTH THE NEC AND THE LISTING OF THE PRODUCT.
    Every time this question is posted someone comes along with a friend that had one fail yesterday and cost millions of dollars in property damage and lost time. What no one has ever posted was what caused the failure. Without a doubt it is because one of two reasons, 1- improper installation, 2- overload. Which was the case with your friend?

    Take a look at 210.21(B)(2) of the NEC to see that a high amp draw is in violation.

    A prime case of the blind leading the blind and the blind is blindly following;
    My friend it is not the view of JW Electric but instead it is the view of
    Underwriters Laboratories
    Met Laboratories
    Intertek Group
    National Technical Systems, Inc.
    Wyle Laboratories
    Nemko
    National Electrical Manufacturers Association
    Just to mention a few and then we also have the Consumer Protect Protection Agency which orders a recall when a product is dangerous and causes all this damage that these uninformed people keep preaching about simply to make everyone think they know something that their jaw is proving they know nothing or little about.

    So my friend it is not something that JW Electric is saying but the greatest electrical minds in the country and those minds who are charged with our safety are saying.
    It is not me that those who think that the stab-loc is bad is arguing with but instead it is those who are charged with listing and labeling the product they are arguing with.
    It is not me that they are turning up their noses at but those charged with mine and your safety they are looking down at.

    Now the choice is yours. You can believe those who post of forums such as this one or you can believe those who spend millions of dollars each year testing the products we use everyday.
    I would suggest that if you are going to take the word of the individuals who post on these forums that you take action to destroy all those fools who put their labels on the products saying they are safe to use.
  13. Thatguy

    Thatguy Homeowner

    Messages:
    1,459
    Location:
    MD
    I found out about this "possibility" the hard way
    http://en.wikipedia.org/wiki/Regulatory_capture
    The newspaper code words for Capture are ". . .this agency is too cozy with the industry it regulates."

    The agency I tried to blow the whistle on has been in the papers twice since 2002. It turns out that 600 to 6000 preventable fatalities in the US each year is "down in the noise."

    In another flap at another agency I read that one guy actually said that "not enough people have died yet. "
    I thank him for his honesty and hope I see him someday in a very hot place presided over by a guy with horns, a tail and a pitchfork.

    The good news is, the thousands I spent for a lawyer in a vain attempt to keep my job were tax deductible. Wow!

    http://www.imdb.com/title/tt0078966/
    Last edited: Nov 7, 2010
  14. ballvalve

    ballvalve General Engineering Contractor

    Messages:
    3,261
    Location:
    northfork, california
    Originally Posted by ballvalve
    You do not need Einstein to see that the tiny surface contact area of a stab in device is a problem waiting to happen. If pulled back hard when inserted and twisted a bit, it might be good forever. On high amp draws they likely arc until they melt together at which time they become "safer"

    From jwelectric: Take a look at 210.21(B)(2) of the NEC to see that a high amp draw is in violation



    NEC= Numb-nuts excreting crap. "high amp draw is a violation?" Huh?

    What on earth does violation have to do with everyday reality?

    Tell it to your kid that stuck his fire truck ladder in the outlet, or mom that plugged in the 1800 watt heater to the 15 amp circuit that actually drew 2200 watts because of Chinese sabotage, along with the American dope that used a 20 amp breaker on the line.

    Hey! its okay to design and install 12 million devices that will arc and spark rather than blow a breaker because if they do its a "violation".
  15. Furd

    Furd Engineer

    Messages:
    446
    Location:
    Wet side of Washington State
    JW posted:
    Please cite the source of these statements, especially "...12 amps which is the most that is allowed to be carried by any device installed on a 15 amp circuit..." It seems to me that you are confusing the requirement that continuous loads may only be a maximum of 80% of the circuit rating with the non-continuous rating of a device. To my knowledge there is NO limiting factor of 80% that must be applied to all devices in any and all service conditions.

    Or to put it another way, any device rated at 15 amperes should be able to carry that 15 amperes for a period of up to, but not more than, three hours of continuous operation without failure.
  16. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,534
    Location:
    North Carolina
    Now there is a bunch of bull shi... if I have ever seen any! What the hell does China have to do with this conversation?
  17. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,534
    Location:
    North Carolina
    210.21(B)(2) Total Cord-and-Plug-Connected Load. Where connected to a branch circuit supplying two or more receptacles or outlets, a receptacle shall not supply a total cord-and-plug-connected load in excess of the maximum specified in Table 210.21(B)(2).

    Table 210.21(B)(2) Maximum Cord-and-Plug-Connected Load to Receptacle

    Circuit Rating (Amperes) Receptacle Rating (Amperes) Maximum Load (Amperes)
    15 or 20 15 12
    20 20 16
    30 30 24


    No it seems like I might know what I am talking about here.
    This is the Standard that UL has set forth for the manufacturing of these devices and the load at which they are to be tested.

    When a 1500 watt portable electric heater is plugged into one of these 15 amp devices they heat and the device is destroyed. 1500 divided by 120 volts equals 12.5 amps. Let this device be in series with other devices that are carrying a load of their own and now we have more than one device that is being affected.

    Now couple this with the trip curve of a breaker and we see that it is possible to load that receptacle to enormous amounts of heat and failure will occur. A general rule for the trip curve of a breaker is it will carry six times its rated current for two full seconds. It will carry three times it’s rated current for up to five minutes.

    As for all this area bull hockey that has been spread around in a futile attempt to prove that back-stabbing is some awful miscarriage of the electrical trade take a look at the end of a #14 conductor and tell me what the area of that conductor that under certain circumstances can carry 20 amps continually and explain to me again about all this contact area. Are you trying to say that the contact area for a conductor must be larger than the conductor in order for the conductor to carry current? Come on now let’s get real in this discussion.
  18. jwelectric

    jwelectric Electrical Contractor/Instructor

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    Location:
    North Carolina
    [​IMG]

    This is a little better. It is from the NEC

    Here is a picture showing the area of contact and as anyone can see the area of contact is the same as when under the screw as though this would really matter as the only area of contact is the wire itself

    [​IMG]


    Notice how the area is about the same as when under the screw unless you are so blind you can only see one side of the contact.

    Also notice that the blade of the plug is a pressure contact. When overloaded this contact point also gets weak and the plug gets to falling out, another type of failure due to overload
    Last edited: Nov 8, 2010
  19. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,013
    Location:
    New England
    I'd still rather have the wire underneath a properly torqued screw or double-sided clamp. The area of contact assumes that the wire is straight (the rest of the structure requires it to be fairly straight) and the spring pressure. If the wire was slightly curved, it would still fit in, but may only make contact on a small area. Yes, this is a workmanship issue, but it is still an issue (to me!). Especially when the receptacle is being used as a junction, with the screw connections and the stab being used, I'd rather not rely on the back-stabbed connection. I've had more than one in my home that became intermittent and replaced it, and no, I don't use portable heaters or other heavy load devices on them. Do I believe that they work, yes. ARe they the better solution, no IMHO. I prefer a bigger margin of error.
  20. Thatguy

    Thatguy Homeowner

    Messages:
    1,459
    Location:
    MD
    Work on it. Ask people. Do Google searches. Open your mind.

    And read
    http://www.amazon.com/Being-Certain-Believing-Right-Youre/dp/0312359209
    You are too sure of yourself.

    BTW,

    "Since push-in wiring connections do not grip the wire as securely as binding head screw terminal connections, the push-in wiring connection may be disturbed as the wired receptacle is mounted. Thus, a need exists for a contact termination memberthat securely retains an inserted wire within the electrical receptacle, while providing a quick and easy connection between the wire and electrical receptacle.

    Another problem with push-in wiring connections is that the single spring arm is movable from outside the electrical receptacle to release an inserted wire. The spring arm may retain subsequently inserted wires less securely within theelectrical receptacle after being deformed to release a previously inserted wire, thereby causing an unsafe electrical connection. This results in poor or failed electrical connections, which may cause a fire due to the poor connection. "

    from
    http://www.patentstorm.us/patents/7270581/fulltext.html

    so check if your backstabbed receptacle shows patent numbers this old or newer. It may decrease your odds of a fire.
    Last edited: Nov 8, 2010
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