Greenhouse wiring

Discussion in 'General Electronics Chat' started by Cajunbubba, Dec 25, 2009.

  1. Cajunbubba

    Cajunbubba Thread Starter New Member

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    I am wiring up a greenhouse that we built. I have installed 2 - 20 amp GFCI breakers and will use 12 guage wires. Because everything is in conduit I am trying to minimize wires. Here are my circuits:
    1- recepticles on a timer switch for grow lights (about 1000 watts)
    2 -(a)Exhaust fan and shutter motoers on a thermostat and reosatat (about 500 watts) & (b)additional recelpticles for possible heating pads

    I am in the process of planning my wire pulls. I am using 3 wires Black (hot), White (neutral), Green (ground).

    Main conduit runs overhead and drops down to various recepticles and stuff.

    I would like to splice off the green and whites and run down to the recepticle but not back up to the main conduit. The black will go down and back up. (hopefully I have painted a picture). My qusetion is this going to create an inbalance for mu GFCI?
  2. Cajunbubba

    Cajunbubba Thread Starter New Member

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    do my wires (pigtails included) need to be all the same to avoid imbalance?
  3. lmartinez

    lmartinez Active Member

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    Follow NEC 2008. :D
  4. Cajunbubba

    Cajunbubba Thread Starter New Member

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    Really did not answer my question.
  5. lmartinez

    lmartinez Active Member

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    A schematic might be of help............
  6. Cajunbubba

    Cajunbubba Thread Starter New Member

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    I will post one in 16 hours
  7. SgtWookie

    SgtWookie Expert

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    I really don't like to be critical, but...

    Your project really requires the on-site scruitiny of a professional electrician.

    I am NOT a professional electrician.

    Furthermore, no professional electrician worth his or her salt would be able to give you proper advice remotely.

    You need a professional electrician to look at your requirements and to keep you safe.
  8. Cajunbubba

    Cajunbubba Thread Starter New Member

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    ok here is a basic view of what I want to to do. These are single 12 gauge wires. Seeing that I am proposing different lengths and junction points will this cause problems with my 20 AMP GFCI?

    Attached Files:

  9. Bill_Marsden

    Bill_Marsden Moderator Staff Member

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    The GFI is basically a circuit hanging off your wiring, it shouldn't have a problem, as long as you aren't trying to use it to feed the other circuitry. If you are, don't. Use a GFI as if it were an outlet for each outlet.

    This is the image you posted, cropped to fit.

    [​IMG]

    You should also be aware which pin is hot, and which is neutral, it is important.

    [​IMG]

    For what it's worth, I agree with Wookie completely, this is not a job for an amateur.

    Attached Files:

  10. jpanhalt

    jpanhalt E-book Developer

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    One thing to consider is how you are going to tap into the neutral and ground, if that is really what you mean to do. Remember that such taps must be in an accessible box.

    Many electricians will simply run all three wires to the receptacle box (use a sufficiently large one) and make the taps or pigtails there. Be sure to consider that the box, if metallic, will also need to be grounded.

    John
  11. Cajunbubba

    Cajunbubba Thread Starter New Member

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    Thanks folks. The circuit diagram I supplied is fed from a 20 Amp GFCI breaker. the pigtails to be wired to be nutted at junction boxes. There will be about 8 receptacles on this circuit. I will have another circuit just like it on another 20 AMP GFCI breaker. Can I use common neutral throughout?
  12. Bill_Marsden

    Bill_Marsden Moderator Staff Member

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    NO!

    The GFI is a circuit. It monitors both hot and neutral, and hot and neutral are the outputs of the GFI. The GFI will turn the hot lead off if there is a problem, and possibly the neutral (not sure about that one, but a little research says it is probable).

    http://en.wikipedia.org/wiki/Residual-current_device

    This is why you need a professional, cutting corners can kill in this case.
    Last edited: Dec 26, 2009
  13. jpanhalt

    jpanhalt E-book Developer

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    Get Wiring Simplified, 42 edition (2008) for $5.90 at your big box store. See page 116, Figures 10-13, 10-14, and 10-15. They explain why you cannot use a "3 wire" circuit based on what you have described. However, if you modify the circuit to use both poles/legs of a 220V household (USA) supply, then you can use a 3-wire circuit.

    In brief, using two live wires and one neutral from a single pole, the neutral potentially carries the combined currents of both live wires. Could you increase the gauge of the neutral appropriately and do it from just the one leg? I don't know. That is a question for a qualified electrician. If you use both legs of the 220 service, then the neutral cannot carry more than either leg (see: Figure 10-15) because of the phase difference.

    I think everyone here has given good advice and many, if not all of us have done household or limited commercial wiring. For simple wiring tasks, I believe a homeowner should be allowed to it, if he or she follows the simplified code to the letter. If you want to deviate from that, then you need an expert.

    John
    Last edited: Dec 26, 2009
  14. CircuitsvilleEngineer

    CircuitsvilleEngineer New Member

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    One thing to consider is the temperature expected.
    I wasn't able to find your location, but summer heat may cause trouble with the
    wires.
    Heat can degrade the insulation over time.
    That is some of the things covered in NEC 2008, or more recently NEC2010 if it is out.
    NEC is the National Electric Code, also called NFPA 70 (National Fire Protection Association) This assumes you reside in the USA.
    There are different insulation grades for different uses and areas of installation.
    There may also be directions for installing GFI.
    In USA, your local community college may have a class in it.
  15. Cajunbubba

    Cajunbubba Thread Starter New Member

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    location is western washington state. So I do truly need to come out of the back of each GFCI breaker with it's own hot & neutral as opposed to what I have sketched here (not I left the ground off to simplify drawing).

    Attached Files:

  16. jpanhalt

    jpanhalt E-book Developer

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    Your new circuit is still using one neutral for two hot wires of the same phase. That is not code as described above.

    John
  17. maxpower097

    maxpower097 Well-Known Member

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    +1 I've worked in environments like this and you have to be extra extra careful in your wiring. If you don't know exactly what your doing call in a pro. Last thing you want is to come home to a fire or get electrocuted standing a puddle. Which does happen with 1000w + lights. Also make sure you have surge protection from a lightning strike, lightning + 1000w light = hand grenade.
  18. Cajunbubba

    Cajunbubba Thread Starter New Member

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    here is my latest attempt at the 2 circuits each connected to a seperate 20 amp GFCI breaker. anyone see any issues?

    Attached Files:

  19. jpanhalt

    jpanhalt E-book Developer

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    I don't see any issues. Are you using plastic conduit and boxes?

    John
  20. Bill_Marsden

    Bill_Marsden Moderator Staff Member

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    OK, here is his drawing...

    [​IMG]

    I've basically stated my case. Please have a professional review your work when you're finished.


    .

    Attached Files:

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