3 wire for generator hookup

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  #1  
Old 06-25-07, 09:13 AM
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3 wire for generator hookup

I have a 3 wire marine cord and 4 prong plugs. My question is, can the plugs be used on the cord for a generator hookup? I will be using either a power transfer switch of if I can find one, a interlock.
 
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  #2  
Old 06-25-07, 09:25 AM
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Sorry. Try again. This time with a lot more detail.

What kind of cord? What size? How many conductors?
What exactly is a "4 prong plug"?
How big is the genset? What is the receptacle are you plugging into?
 
  #3  
Old 06-25-07, 02:23 PM
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Originally Posted by Speedy Petey View Post
Sorry. Try again. This time with a lot more detail.

What kind of cord? What size? How many conductors?
What exactly is a "4 prong plug"?
How big is the genset? What is the receptacle are you plugging into?
Sorry for the lack of info. cord is 10/3. the plug would match the outlet on the generator ( I don't know how else to describe it) Generator is 6750/8450 watt. Receptacle will be whatever works, as I have not purchased it yet.
 
  #4  
Old 06-25-07, 02:37 PM
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Your cable is borderline as #10 flexible cable really shouldn't be loaded beyond 25 amperes.

I assume this generator is rated for 240/120 volt output and at 6,750 watts it would be putting out 28.13 amperes at 240 volts. At peak output of 8,450 watts the current would be 35.21 amperes.

Furthermore, your gennie requires an equipment grounding conductor between the generator and the load. You need four conductors in the flexible cable. I would recommend a 8/4 type SO cable.
 
  #5  
Old 06-26-07, 04:48 AM
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Originally Posted by furd View Post
Your cable is borderline as #10 flexible cable really shouldn't be loaded beyond 25 amperes.

I assume this generator is rated for 240/120 volt output and at 6,750 watts it would be putting out 28.13 amperes at 240 volts. At peak output of 8,450 watts the current would be 35.21 amperes.

Furthermore, your gennie requires an equipment grounding conductor between the generator and the load. You need four conductors in the flexible cable. I would recommend a 8/4 type SO cable.

This is what I assumed after reading on here over the weekend. I was just hoping to not have to spend $$ on the wire. Thanks
 
  #6  
Old 06-30-07, 08:44 AM
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Should I use 8/4 for the outlet as well? Also, what size breaker?
 
  #7  
Old 06-30-07, 12:23 PM
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What outlet and what circuit breaker?
 
  #8  
Old 06-30-07, 12:58 PM
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Originally Posted by furd View Post
What outlet and what circuit breaker?
Sorry if I'm not using the correct terminology. The "convenience outlet" is where the cord from the generator plugs in, and the breaker is for that outlet. There will be a safety interlock so the main and generator breakers cannot be closed at the same time
 
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Old 06-30-07, 01:38 PM
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You want a "flanged inlet" connector to fit the "connector" on the cable from the generator. These need to be rated at an absolute minimum of 30 amperes and I would feel a whole lot better if they were rated no less than 40 amperes. They also need to be rated be for 120/240 volts and will have four wire connections (hot, hot, neutral and equipment ground) although they may be listed as "three pole, four wire, grounding" units. Forty ampere (and above) plugs, connectors and flanged inlets are not going to be as easy to find as will thirty ampere units.

The circuit breaker will need to be a 2-pole type "listed" for use with your panel and interlock device. It needs to be no less than a 40 ampere rating although the circuit breaker on the generator is the real overcurrent protective device (OCPD) and the circuit breaker on/in the panel is being used as a switch. You may use a higher rated circuit breaker in the panel if necessary.

Interconnecting wiring between the flanged inlet and the circuit breaker (switch) in the panel needs to be as stated in your local code, most likely #8 type THHN/THWN in conduit. Larger wiring is acceptable.
 
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Old 06-30-07, 03:55 PM
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Thank you for the detailed response. I was at Lowes today and saw 30A and 50A connectors, but no 40A. So I should go with the 50A breaker even though the outlet on the generator shows 30A? Does the interconnect wiring need to be in conduit if it is directly below the panel (same section of drywall, between the same 2 studs)? Any idea where I can find 8/4 wire for the cable? All they had at Lowes was 10/4. Or should I just make one?
 
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Old 06-30-07, 04:29 PM
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Since the continuous output of your gennie is less than 30 amperes you could use the 30 ampere plugs, connectors and inlets. It is the peak output of the generator that suggests that a higher rating would be preferable.

As I previously stated, the ampere rating of the circuit breaker that will connect the generator inlet to the panel is relatively unimportant because it will not be used as a OCPD but only as a switch. It MUST be rated higher than the generator's circuit breaker.

The 8/4 cable (with a type SO jacket or equivalent) may not be available from the "big box" stores but is readily available at electrical distributors. You might also want to try RV suppliers or marine stores.

I personally prefer that the interconnect between the inlet connector and the panel circuit breaker be made using conduit (flexible is fine) and individual type THHN/THWN conductors. Remember that you will need to have an electrical-rated box for that inlet connector and probably some kind of weather shield that will protect the connecter-inlet combination from rain when in use.
 
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Old 06-30-07, 05:01 PM
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I will go with the 50A breaker and connectors, if for nothing else than upgrading to a larger generator in the future. But I'm a little lost on the inlet connector, it will be inside the garage (where the panel is) so I do not need it to be in conduit, or weather resistant, correct?
 
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Old 07-01-07, 09:10 AM
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I hope you are not planning on running that gennie while it is in the garage.

If all you want is a place to plug in the flexible cable from the generator then you can get by using a short section of that flexible cable with a compatible (to the flexible cable from the generator) plug on one end and the other end connected to the interlocked circuit breaker in the panel. Use an "approved" cable clamp where the flexible cable enters the panel enclosure.

The box, conduit, weatherproof enclosure, etc. is for when the inlet connector is mounted outside.
 
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Old 07-01-07, 10:29 AM
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Originally Posted by furd View Post
I hope you are not planning on running that gennie while it is in the garage.

If all you want is a place to plug in the flexible cable from the generator then you can get by using a short section of that flexible cable with a compatible (to the flexible cable from the generator) plug on one end and the other end connected to the interlocked circuit breaker in the panel. Use an "approved" cable clamp where the flexible cable enters the panel enclosure.

The box, conduit, weatherproof enclosure, etc. is for when the inlet connector is mounted outside.

I would never run a generator in the garage. My breaker panel is in the garage about 15' from the door, so I am going to run the cable under the garage door. My plan is to run the wire straight down from the panel (behind the drywall) to a box with the recessed outlet/plug.
 
  #15  
Old 07-01-07, 12:20 PM
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Once again, Do not install a plug. You need a flanged inlet. You then make a standard extension cord for the generator. The male ends plugs into the generator, and the female end plugs into the flanged inlet.
 
  #16  
Old 07-01-07, 04:07 PM
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Originally Posted by racraft View Post
Once again, Do not install a plug. You need a flanged inlet. You then make a standard extension cord for the generator. The male ends plugs into the generator, and the female end plugs into the flanged inlet.
Sorry for incorrect terminology again. Flanged inlet is what I am going to do.
 
  #17  
Old 08-01-07, 04:42 AM
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Is there a way to put a 30a 4 prong connector (for generator) on 50a wire (6/4 I believe)? The plugs at home depot and lowes do not look like there is enough room for the larger wire.
 
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