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I recently purchased an 8kW generator (Briggs and Stratton). It has a 4-wire twist lock outlet that can handle 30 amps.

Suppose I were to:

  • Run a 10/3 NM cable from the panel in the basement out to the garage. Not actually connecting anything, just running the wire along the basement ceiling, where there are other visible NM cables (so I assume it's within code), out to the garage. The length of the cable run is about 50ft
  • Hire an electrician to terminate the cable with a 4-prong outlet in the garage, and connect it to the panel with a 30-amp breaker. The purpose of the outlet (and the entire circuit) would be to connect to the generator to power the panel during power outages.

First and foremost -- yes, I know that the main breaker MUST be turned off when backfeeding the panel from the generator. This is the most important consideration. The instructions for using the generator would be as follows (clearly outlined on a placard next to the panel, with pictures, and appropriate breakers labelled clearly):

  1. Switch off the main breaker
  2. Switch off all non-essential circuits, which will be labelled. Most important are the sump pump, well pump, HVAC blower, and refrigerator
  3. Switch on the generator breaker (the 30-amp circuit mentioned above)
  4. Power on the generator and connect it to the outlet in the garage

My questions are:

  • Is that a reasonable plan? Has anyone tried anything similar?
  • Should I use 6-gauge or 8-gauge cable instead of 10-gauge? 10 is rated for 30amps, but would voltage drop be a concern?
  • Is it correct to assume that it's OK to run NM cable along the (unfinished) basement ceiling? I see other NM cables from the other branch circuits there so I assume it's within code
  • What are the considerations for transitioning the cable from the basement ceiling out to the adjacent garage floor? There is ductwork that makes the transition from basement-to-garage through this wall currently, so I think I can "follow" the duct out through to the garage. I assume I should install some PVC conduit to run the wire through this transition?
  • Is this just a bad idea and I should just get a transfer panel installed?
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This is exactly how my generator is hooked up for occasional use. For safety (and probably legality/code compliance), you should have a generator interlock kit for your panel. If you're going to have an electrician do the inlet box for you, I would ask him/her then. –  JoeFish Dec 27 '12 at 21:12
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+1 for very well formed question - sorry to say it's a bad idea as @tester101 said –  The Evil Greebo Dec 28 '12 at 13:30
    
@JoeFish some jurisdictions would prohibit your interlock kit because removing the cover defeats the interlock. with a real transfer switch, the isolation mechanism is not defeated if the cover is opened. –  longneck Dec 28 '12 at 16:45
    
@longneck quite true, which is why I suggested asking the electrician. Every codebook has its own quirks. –  JoeFish Dec 28 '12 at 16:50

1 Answer 1

NO.

What you are describing could potentially kill the folks that are trying to help restore power to your home. You're also creating a situation where you could easily overload your generator.

To do this the right way, you'll need to install a transfer switch. Transfer switches allow you to switch between two source of electricity, while mitigating any hazards associated with using a secondary source of power.

The transfer switch will be wired in such a way, that backfeeding and/or overloading the generator will be prevented (without a lengthy start up procedure). Once the transfer switch is installed, you'll simply have to...

  1. Connect the generator to the inlet in the garage.
  2. Start the generator.
  3. Flip the switch(es) at the transfer to the GEN position.
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What Tester said. You should never ever create a circuit that even has the POTENTIAL to be hooked up the wrong way. Instructions saying, "Don't do this!" are useless. If you had a big red button saying "End of the world button, DO NOT PRESS" the paint wouldn't even have time to dry before someone wondered what it did. –  The Evil Greebo Dec 28 '12 at 13:29
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+1 for doing it right. It might cost a bit more, but gives a LOT more safety - people might not read the placard in the dark in the middle of the night when they just want power. –  Grant Dec 28 '12 at 13:33
    
@TheEvilGreebo, you mean like the history eraser button? –  JoeFish Dec 28 '12 at 16:52
    
Thanks for all the comments -- I put a call in to an electrician and waiting to hear back. (I live in a hurricane Sandy affected area, so I imagine the electricians are quite busy... especially with so many idiots like myself having panic-purchased a generator in the days leading up to the storm) I would like to go the interlock-switch route but I'll see what he says. –  thedudeabides Dec 28 '12 at 20:37

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