Legal to make a US two-plug power cord power strip?

Discussion in 'Audio Hardware' started by harby, Jul 27, 2021.

Thread Status:
Not open for further replies.
  1. harby

    harby Forum Resident Thread Starter

    Location:
    Portland, OR, USA
    You can go down to Harbor Freight and get one of these outlet multipliers:

    [​IMG]

    However, I'm not sure if the second plug is simply a "dummy".

    It is not forbidden to hook up two separate circuits and two phases to a two-outlet receptacle, and in fact, there are usually tabs to break off to separate the circuits:

    [​IMG]

    This could cause "poof!" if there's not a breaker in the plug on at least one of the circuits.

    [​IMG]

    I'm wondering, because I was comparing the poor US NEMA plug vs the sturdy UK plugs, and envisioning a power strip with not only robust "real receptacle" construction, but also a custom-manufactured big plug that plugs into and draws power from both receptacle outlets at the same time.

    One could also avoid electrical faults by having half the strip outlets wired to one receptacle only, but that wouldn't have as much electrical contact benefit.
     
  2. jea48

    jea48 Forum Resident

    Location:
    Midwest, USA




    VANGUARD
    6 Outlet, 3 Prong Side Entry Tap, White

    Outlet adapter converts two three prong outlets into six outlets, three on each side

    $2.79


    I assume one plug feeds 3 receptacles on one side and the other plug feeds the 3 receptacles on the other side.
     
    Last edited: Jul 27, 2021
    mackat, Lowrider75, Big Blue and 2 others like this.
  3. Ingenieur

    Ingenieur Just a dog looking for a home...

    Location:
    Back in PA
    It is UL listed
    They would not allow a product that may result in a line to line fault by simply plugging it in for use as intended
     
  4. harby

    harby Forum Resident Thread Starter

    Location:
    Portland, OR, USA
    Another idea that one would not dare release to the general public:

    A power strip with two cords.

    In an ideal case, you are able to reach two separate outlets with separate circuits on the same phase, and parallel them. Two different wall circuits, giving half the voltage drop back to the circuit breaker box.

    In a normal residential case, where all of a wall or even room is wired to the same circuit, you've enhanced the outlet contact and at least paralleled the power strip's cord.

    Plug it into two different phases, getting 240v between the plugs, and one must have robust protection circuitry in the strip that will trip, quickly protecting any household wiring and the cord gauge.
     
    Ingenieur likes this.
  5. Phil Thien

    Phil Thien Forum Resident

    Location:
    Milwaukee, WI
    Ah, but there have been devices designed to plug into two separate 120 receptacles, each wired to a different side of the load center, and provide 240.
     
  6. Wayne Nielson

    Wayne Nielson Forum Resident

    Location:
    My House
    US 240 volt circuits are not "2 phase", they are of the same phase (you can't blend voltages of different phases or you will get and arc flash explosion).

    US 240 is 120 + 120 volt in series. Our homes have (2) 120 volt lines and a neutral coming into them. Ground is made via a copper rod outside of the home.

    'ner
     
    Saint Johnny likes this.
  7. Wayne Nielson

    Wayne Nielson Forum Resident

    Location:
    My House
    You can't offer 240 volt with a 120 volt outlet.....or I don't get what you are trying to do.
     
  8. harby

    harby Forum Resident Thread Starter

    Location:
    Portland, OR, USA
    OK, replace "phase" with leg.

    The idea is just to parallel two receptacles or outlets together. Bonus if you can reach two different breaker circuits.
    240V would be the fault condition if you accidentally encounter outlets on opposite legs when doing so. Naive straight wiring without fault protection would run 240V through the power cords until one of the breakers tripped or a wire melted. Just inserting the second plug with the strip "switched on" could cause arcs, so perhaps electronic logic that didn't engage the second cord until proper voltages are detected at and between both.
     
  9. Ingenieur

    Ingenieur Just a dog looking for a home...

    Location:
    Back in PA
    That is an age old debate
    I consider it 2 phases 180 deg apart
    Some call it a split phase

    3 phase is 120 deg apart
    And 2 phases can be added and usually are.
    If the sec of the xfmr is wye you have 3 V's
    Assume 120/208 3 phase Y
    120/0 deg
    120/120 deg
    120/-120 deg

    adding 120/0 - (+ 120/120) = 207.85/-30 deg
     
    Last edited: Jul 27, 2021
  10. JamesRR

    JamesRR Trashcan Dream

    Location:
    NYC
    The adapter assumes the duplex receptacle is wired to the same circuit. It doesn't matter which one draws the power, it's not "twice" the power drawn because it's in two receptacles. They're wired together. They use two because it provides stability for the adapter once attached. It's all about how much draw is on a circuit - which is why it's dangerous to plug and use multiple power strips on the same circuit (e.g. in the same bedroom).

    Everything you're describing in connecting two outlets is asking for trouble - a power strip with two cords on it. As it is, extension cords and the like are a huge cause of electrical fires. If you need multiple strips and extension cords, your room doesn't have the proper number of receptacles or circuits required. It's why building codes (in the US) require a certain number of receptacles in a room in certain locations.
     
    classicrocker and Shawn like this.
  11. harby

    harby Forum Resident Thread Starter

    Location:
    Portland, OR, USA
    One thumbs through a Hi-Fi magazine in disgust at the $500 power cords and conditioners that still plug into a receptacle that can barely retain a plug, and still run through 80 feet of 50-year-old Romex back to a circuit breaker box. Plug in a hair dryer - or 1500W peak power amplifier - and you get a 5 volt drop.

    A better solution is possible and ponderable and a fire hazard if done stupidly. Not the flaky 2-to-6 adapter, but a full-on power strip.
     
  12. Wayne Nielson

    Wayne Nielson Forum Resident

    Location:
    My House
    The 2 legs of the 120 volt are in perfect phase to each other, therefor, they can be combined to form 240 volt.

    Each leg of 3 phase voltage can never touch each other, each having their own separate circuit, like in 3 phase industrial motors. If 2 of the legs would come in contact with each other, the resulting explosion would be hotter then the surface of the sun and spew atomized copper everywhere.

    NFPA-79e
     
    classicrocker likes this.
  13. Wayne Nielson

    Wayne Nielson Forum Resident

    Location:
    My House
    Also, why do we need such an outlet? Need is the mother of invention, but I see absolutely no need for such.
     
  14. Ingenieur

    Ingenieur Just a dog looking for a home...

    Location:
    Back in PA
    for 3 phase you are conflating 'phase' and 'line'
    In a wye all 3 phases are connected in the middle.
    In a delta at the corners.
    In a wye the sum of 2 phases = line V
    Line to line = short circuit

    if the legs of 120 were in phase, 1 phase:
    120/0 - 120/0 = 0
    You subtract because the center is tapped or connected to ground, so current flows out in opposite directions = opposite polarity, ie 180 deg out of phase. They meet at the N, only the difference returns on the N, if both = 10, 0 return.

    So if out of phase, it must have more than 1 phase, hence 2 phase.

    120/0 - 120/180 deg = 240/0 deg

    I know enough to be dangerous, lol

    [​IMG]
     
    Last edited: Jul 27, 2021
    BuddhaBob and BillWojo like this.
  15. WildPhydeaux

    WildPhydeaux Forum Resident

    Wait a minute, Doc. Are you telling me you built smelter out of a SquareD junction box?

    Cool,
    Marty
     
    Rolltide, wrat and Ingenieur like this.
  16. crn3371

    crn3371 Forum Resident

    Location:
    Glendora, CA
    While it is theoretically possible to configure a duplex outlet like you’ve described, no electrician in their right mind would ever do so.
     
  17. Phil Thien

    Phil Thien Forum Resident

    Location:
    Milwaukee, WI
    I am going to respectfully disagree on that.
     
  18. WildPhydeaux

    WildPhydeaux Forum Resident

    I'm not entirely up on current code and it will vary between states, but back in the day in Canada every kitchen had to have at least two "split plug" receptacles. So, fed Romex 14/3 from a two pole single throw breaker. If one side tripped, both went out. This is for service safety reasons.

    If the suggestion is a custom power bar with two feed cords, each to feed a couple duplex receptacles, fine in theory but I don't believe it meets code to have entirely separate circuits in a box not rated for it. And if you fed it from both sides of a split plug, you're sharing a neutral at the source,which isn't ideal if you plan to demand some current...

    Cheers,
    Robert
     
  19. Phil Thien

    Phil Thien Forum Resident

    Location:
    Milwaukee, WI
    Yep, that is code down here now, not sure when it was added.
     
  20. jea48

    jea48 Forum Resident

    Location:
    Midwest, USA
    If two circuits are used to feed a duplex receptacle


    NEC 210.7. I believe it was added to the 2002 NEC

    2020 NEC
    Quote:
    210.7 Multiple Branch Circuits. Where two or more branch circuits supply devices or equipment on the same yoke or mounting strap, a means to simultaneously disconnect the ungrounded supply conductors shall be provided at the point at which the branch circuits originate.
     
    Phil Thien likes this.
  21. priestman

    priestman Well-Known Member

    Location:
    North Carolina
    Not only is it theoretically possible to configure a duplex receptacle like that, it’s permitted by code. The two line wires can even share a neutral.
     
    BrentB likes this.
  22. Ingenieur

    Ingenieur Just a dog looking for a home...

    Location:
    Back in PA
    Yep
    MWBC
    it is done often, one ckt. being switched that lamps are plugged into, that way they can be left on and several controlled by one switch.

    I'd be very surprised if that outlet device is not 2 x 3 vs 1 x 6
    It is UL listed.
    I may buy one today just to play with.
    I would never use one.

    Harbor Freight here I come! lol
    I know I'll buy some other junk too ;)
     
  23. jea48

    jea48 Forum Resident

    Location:
    Midwest, USA
    Correct providing the branch circuit feeding the duplex receptacle is a multiwire 3 wire 120/240 circuit. ( Both Line 1 and Line 2 are required. The neutral will only carry the unbalanced load. The balanced load is in series with L1 and L2.)


    Here is a video that explains how a split phase secondary winding of a single phase power transformer works.

     
    priestman likes this.
  24. harby

    harby Forum Resident Thread Starter

    Location:
    Portland, OR, USA
    The NEC is concerning itself with permanent installations. One can't control what receptacles a consumer might plug a temporary device into, even one with two power cords:

    [​IMG]

    Rather, I'd think one would find it would be consumer regulations permitting sale or permitting use in particular locations. For example, hospitals that require clear power cords for inspection of internal faults.

    UL seems not obligatory for temporary devices: The UL certification is a North American Product certification that comes from Underwriter Laboratories. It shows that the product in question was tested by UL, and that it meets US and Canadian safety standards. Products displaying this mark are likely to meet standardized minimum requirements for safe operation and this can help with sales and marketing...

    Such a power strip, featuring two cords, one of which can be connected in parallel to the same power strip receptacles as the other by "smart circuitry" (when of compatible phase), only has the unique quality that it potentially can deliver up to 30A to a single receptacle without causing overheating hazard in residential wiring or setting a breaker. The NEMA receptacle, though, is not manufactured or specified for 30A availability, so the strip device must logically also have its own breaker, as most power strips do, after circuits are combined. This also protects against overcurrent in neutral in a case where one of two separate circuits might have a broken neutral and someone has plugged more than 15a worth of devices in.
     
    Last edited: Jul 28, 2021
  25. jea48

    jea48 Forum Resident

    Location:
    Midwest, USA

    The two power supplies of the amp are not paralleled together. They are independent and separate from one another. The only thing they have in common is the EGC. ( Hot and neutral of the IEC connectors are not internally tied together.)
     
Thread Status:
Not open for further replies.

Share This Page

molar-endocrine