To plug or not to plug into a GFCI outlet

Discussion in 'Electrical Forum discussion & Blog' started by DIY, Apr 6, 2009.

  1. Thatguy

    Thatguy Homeowner

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    Happier, yes. . .
     
  2. Bill Arden

    Bill Arden Computer Programmer

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    You are not taking harmonic noise into account. The power line voltage waveform is not a sine wave and the extra frequency's add to the current.

    And then there is the long range power utility communication systems. These can add quite a bit of noise spikes. The worst is the DCSI TWACS system (90 amp pulses at the house), then there is the cannon EMETCON(9Khz to 12Khs) and the L&G TS2 system(560Hz).

    All these can add quite a bit of current and that is why the Capacitor & diode power supplys have a series resistor to limit the current from higher frequencys.
     
  3. jwelectric

    jwelectric Electrical Contractor/Instructor

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    Boy we sure made a big jump here from a MOV to the power company’s grid and the harmonics found on that grid.
    The important part of this is the fact that we are not affected by the primary harmonic currents of the power grid. The transformer at our house only steps down voltage and not current. The amount of current draw at our homes is solely based on the loads we have not how much current the primary lines are carrying.

    Once again not on the circuits in our homes. The TWACS system is a software system that was designed by Distribution Control Systems, Inc. (DCSI), a subsidiary of ESCO Technologies Inc. and is mostly used as a load control program to ensure the end customer always has power.
    The newer version NG 3.0 can often times detect a grid outage and reset the breaker before the homeowner knows the power was out. It can detect this so fast that a lot of electronic clocks never stop working such as the clock on microwaves.

    Again Brother Bill the amount of current on the primary lines of the utility company in no way affects the current on a 120 volt branch circuit that is protected by a GFCI device in our homes. The harmonics on the utility primary power lines does not enter our homes either. These harmonics are lost at the step down transformer that supplies our homes.
     
  4. Ian Gills

    Ian Gills Senior Robin Hood Guy

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    I have a GFCI on my sump pump and it has never tripped by accident.

    Similarly I have a GFCI on my condensate pump.

    Each life can be valued at about US$2 million. To protect me and those around me, these are a pretty good investment.

    All within 6 feet of water source.
     
    Last edited: Apr 14, 2009
  5. Bill Arden

    Bill Arden Computer Programmer

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    1. When you draw currents from a outlet that WILL affect the voltage since the transformer has both resistance and inductance. The higher the frequency the less current you need to change the voltage. At 10Khz it does not take much current to change the voltage.

    2. the DCSI TWACS system includes a AMR(Automatic meter reader) component and that meas that it includes a module that mounts inside the house electric meter. That unit uses a Triac to pull 90 amps just before the zero crossing. These pulses of current can cause problems and is part of the reason the AMR part of the system has been banned from some states.

    3. There is a "voltage noise test" that units have to pass and that is probably why the 0.09 uF value was stated. It's not that 0.09 uF will trip a GFCI, but that it MIGHT trip a GFCI.
     
  6. Thatguy

    Thatguy Homeowner

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    .09 uF @ 60 Hz is 30kΩ, 120v/30kΩ = 4 mA, which is just about the trip threshold for a GFCI.
    ROMEX® has about 100 pF/ft, so 900' of ROMEX® should trip a GFCI.
     
    Last edited by a moderator: Dec 7, 2011
  7. jwelectric

    jwelectric Electrical Contractor/Instructor

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    Bill I know that you are trying hard but the simple answer is none of this will affect a GFCI.

    If other than the 60 Hz sine wave would affect a GFCI then there would never be a listing on items such as the X10 control systems sold to control lights throughout a home. These devices send signals across the electrical wires that are different than the 60 Hz sine of the voltage being controlled.

    The automated meter readers you have referred to in your post is connected in parallel with the home so any currents or harmonics introduced by this item would end at the point of use and not be transmitted into the home.
     
  8. Micheal

    Micheal New Member

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    My personal experience is this... If you have a GFCI on an appliance the chances of it tripping is higher. UL states that you can but like everything appliances do get old and also bleed power to the ground because of the motor or compressor. The GFCI does its job by detecting this and trips out. Problem is this happens and no one notices until too late. Another thing is GFCI circuits are typically connected to outside receptacles and if they get wet or fail it will also trip the GFCI. No one is saying you can't plug your appliance to a GFCI receptacle but it is suggested that you don't. I too have a refrigerator in my garage and I ran a separate circuit to it because the only available outlet was a GFCI.
    As far as Surge suppressors... connect your Laptops and PCs to UPS backups system... LED tv's same thing. Most TV's now use little wattage and are smart TV capable. UPS backups are great cause it provides you with some protection and the ability to shut things down properly.
    All my electronics are connected to backups its a wise investment in the lightning capital of the world, Tampa Florida. Its great on Cable Modems and Wifi routers, cause it provides you with at least an hour of power during an outage so you can still be online if you work from home.

    GFCI receptacles do not provide surge protection. They are Ground Fault Circuit Interrupters they only detect electrical currents that go to ground. They do not protect your appliances from surges. They do not regulate voltages either. They do detect shorts like a breaker does. Always consult with a local electrician. All Electricians that are owners are master electricians. They are full of real life experiences. Instructors lose track of things over time. No pun intended. NEC book does get updated because of real life experiences. Remember safety first.
     
    Last edited: Apr 26, 2017
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