Portable generator connection questions

Discussion in 'General Electronics Chat' started by jbaugh, Aug 11, 2010.

  1. jbaugh

    Thread Starter New Member

    Aug 11, 2010
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    To begin I must admit my abysmal level of knowledge concerning electrical circuit concepts. That is why I am seeking assistance here.

    I have a 4600 Watt portable generator in a shed just outside of my garage for use for emergency power generation.

    I'm concerned about how the electrician has configured the connection with the house circuit. He installed a double throw safety switch about 25 ft away on an interior garage wall. A heavy gauge cord with a 3 prong male end dangles from the switch box for connection to the power cord connected to the generator. When generated power is needed, a power cord is plugged into the 3 prong 125V outlet on the generator with the other end connected to the cord from the safety switch. I have run this configuration several times for testing and during brief power outages. It seems to work as long as the power draw from my house is kept relatively low ( two refrigerator/freezer combos, 8 or 10 75 watt light bulbs, computer, clocks and other low wattage items). Occasionally the generator seems to falter a bit and I notice the lights dim briefly.

    Is this the optimal way to transfer power from the generator to my house circuit? I notice there is a circular 3 prong locking outlet on my generator. According to the owners' manual this is a "120 V 30 A Twist-Lock" which "powers 120 Volt AC, 60 Hz, single phase loads requiring up to 2300 Watts of power." The standard 3-prong outlet is labeled "to operate 120 Volt AC, single phase, 60 Hz loads requiring up to 20 A or 2300 Watts of power."

    All this suggests to me that I can only supply up to 2300 Watts of power from my generator to my house through one of these connections and I am not getting the full potential 4600 Watts. Is my assumption correct? Is there a way to remedy this so that all 4600 Watts of my generator are available?
    Thanks.
    John
     
  2. marshallf3

    Well-Known Member

    Jul 26, 2010
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    You're probably getting full power, electrical connectors are by nature rather underrated due to safety issues. If the generator came with that style plug it had to pass some sort of approvals however if the one on the generator itself is rated at 30A that implies no more than 3,600W output.

    Are there multiple plugs on the generator?

    Consider the fact that your 4,600W may not be a continuous rating. What horsepower is the motor driving it, and can you read any specs off the generator (actually alternator) component of the device?
     
  3. jbaugh

    Thread Starter New Member

    Aug 11, 2010
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    0
    Rather than try to describe in words my set up I've posted a series of photos that might help. As you will see I actually have two different generators available-- a gasoline powered and a propane powered one.

    http://gallery.me.com/lcc6/100016

    Clicking on individual photos will enlarge them for detail.

    Currently I connect either of the generators to the switch box with a heavy gauge electrical extension cord running from the 120V 3- prong outlet on the generator to the cord hanging out of the switch box.

    I really wonder if I should somehow be connecting instead to the 12/240 V connector with the 4- prong twist on connector?
    John
     
  4. radiohead

    Active Member

    May 28, 2009
    474
    31
    4 prongs suggest two phase capability. Are the cables or terminals black, red, white and green? if so, your black is hot (one phase), the red is hot (the second phase), white is neutral (or return) and green is ground (a four-foot copper ground rod or a six-foot steel ground rod pounded into the earth). Please ground your generator correctly. You may get electrocuted if you fail to do so. If the "heavy gauge" extension cable you speak of is a standard electrical extension cord, you may want to consider running the generator's output power to a fused electrical breaker box using 12 gauge ROMEX solid core wire. Then branch it out to ganged 120VAC plugs if you so desire. If you draw too much current from an extension cord (you said you wanted to pull in excess of 4500 watts), and nothing is fused, and your generator is not properly grounded, I can sense a disaster looming in the not too far future.
     
  5. marshallf3

    Well-Known Member

    Jul 26, 2010
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    Yes, they are single phase 240V generators which are generally wired to put half the wattage out of one leg and the other from the other leg. To get the maximum at 120V only you'd need two "extension cords" - one leading from one hot to the neutral and the other from the second hot leg also to neutral. You would get half the power from one of the hot legs and the other from the other hot leg. You can't hook the two together either, one leg would have to run your refrigerator and the other run your lighting or something like that.

    These are made this way to make it easier to hook into your home circuit breaker box which, by nature, is 240V with a neutral floating inbetween the two hot legs.

    Think of a center tapped transformer as that's what your output configuration is.
     
  6. marshallf3

    Well-Known Member

    Jul 26, 2010
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    Last edited: Aug 12, 2010
  7. marshallf3

    Well-Known Member

    Jul 26, 2010
    2,358
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    Where's the "delete" button for when the website spaces out or you accidentally double post?
     
    Last edited: Aug 12, 2010
  8. nsaspook

    AAC Fanatic!

    Aug 27, 2009
    2,907
    2,165
    It looks like he has a single 120 leg powering both sides of the transfer switch. (black wire from cord to two red wires on a wire-nut. :() You need to get this guy back and do it right with the correct plug and 10 or 12 gauge wiring so you can get full power.

    http://www.stayonline.com/reference-nema-locking.aspx

    http://www.amazon.com/Reliance-Cont..._2?ie=UTF8&s=automotive&qid=1281626130&sr=8-2
     
    Last edited: Aug 12, 2010
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