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What gauge wire from manual generator transfer switch to outlet in garage?

What gauge wire from manual generator transfer switch to outlet in garage?

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  #1  
Old 12-18-13, 03:06 PM
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What gauge wire from manual generator transfer switch to outlet in garage?

Our current home is wired for a manual generator with a GE manual transfer switch and a subpanel. we start generator and pick and choose the equipment we need to run, turning breakers on and off. Generator is 5000 watts.

I wish to replicate this in the home we will be buying soon.

From the main panel (200 amp), there is a 100 amp double pole breaker with stranded 3 AWG wire to transfer switch. Then to the generator subpanel, there is also 3 AWG stranded THWN wire for hots and neutral from transfer switch.

However, the insulated equipment ground (green stranded) that goes from main panel to transfer switch and from transfer switch to generator panel is a much smaller gauge. I cannot read the writing on it.

Also, the wire that goes from the generator transfer switch is a black "romex" type wire where the red, black, and white wires are stranded, and the ground is bare solid copper. All conductors are then wrapped in black insulation. That is why I called it "romex-type" in that all conductors are sheathed in the heavy black insulation.

The twist-lock outlet in garage is 20 amp.

My questions are:
What gauge insulated equipment group is appropriate for the application, and what wire gauge is appropriate for the black romex-type cable that goes to the 20 amp generator outlet?

Thank you
Dave
 
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  #2  
Old 12-18-13, 03:09 PM
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I hope you mean an inlet and not an outlet. An outlet would require the use of a suicide cord.

For a 20 amp inlet you need #12 wire. You will not be able to power much with so small of a source.
 
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Old 12-18-13, 03:54 PM
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Sorry. Not sure of terminology. The connection in garage is recessed and round and has 4 exposed brass blades. The flexible cord that goes from generator to inlet in garage wall has a smooth round white connector which mates with inlet. It is marked 10/4.

Whatever the electrician ran between the transfer switch and the inlet in garage is very heavy duty. Maybe 6/3? It is black. All colored conductors (red, black, and white) are stranded, but ground wire is solid. I am sure he oversized it. Any idea of the gauge based on the black jacket?

We are able to run our boiler, air handler and a refrigerator and a few lights.
 
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Old 12-18-13, 04:07 PM
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Sounds like it is larger than #10, if it was installed in the last 10 years or so. The stranding make me think it might be #8.
 
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Old 12-18-13, 05:00 PM
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Thanks. Forgive my ignorance, but with a 5000 watt generator putting out the max via 220 voltage, does that mean each conductor carries a max of 23 amps? (5000 /2=2500 watts per conductor). Then 2500/110= 22.7 amps?
 
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Old 12-18-13, 05:23 PM
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Actually it would be 5000240=20.83 amps. However if the plug is 240 not 120/240 you won't be able to run any 120 volt loads. Did you have 120v loads to run? Any motors to start? If so how many amps?
 
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Old 12-18-13, 05:28 PM
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Yes. We run 120v loads. The generator and inlet are 240v. The inlet then powers a typical load center (circuit breaker panel) with both 120 and 240v loads. There is a transfer switch in between the inlet and panel.
Only motor is refrigerator.
 
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Old 12-18-13, 07:08 PM
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The generator and inlet are 240v.
The generator voltage must be 120/240 (2 hots, 1 neutral & 1 Grd) or why would your present flexible generator cord be 4-wire?

The flexible cord that goes from generator to inlet in garage wall has a smooth round white connector which mates with inlet. It is marked 10/4.
 
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Old 12-18-13, 07:38 PM
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Which of these matches your generator receptacle?

Name:  6-20r.jpg
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Size:  8.0 KB Name:  14-30r.jpg
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Note: Second photo is 30 amps.
 

Last edited by Posternine; 12-18-13 at 07:54 PM.
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Old 12-18-13, 07:41 PM
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The second photo is correct.
 
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Old 12-18-13, 07:53 PM
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The second photo is correct.
The second is a 120/240 receptacle not a 240v receptacle. It is rated 30 amps. Are you sure it is a 5000 watt generator?
 
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Old 12-18-13, 09:40 PM
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The generator and inlet are 240v.
Your generator is supplying 120/240V current through the coed and inlet. That's the same power you get from your power company. The real difference is that the generator you have can only supply a fraction of what your POCO is providing.
 
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Old 12-19-13, 03:51 AM
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Thanks I understand now because of the neutral, it is 120/240. The generator is definitely 5000 watts, which supplies our needs for the few times power goes out.
The connectors in the inlet are as such.....3 brass connectors are curved, and one is L-shaped. It says 20 on the plug.

I guess my question is what gauge should the insulated ground connector be that goes from main panel to transfer switch if conductors between main panel and transfer switch are 3 AWG? These are oversized conductors for what the generator can put out, but I want to do everything to code. Ground is much smaller gauge....maybe 8?

I have figured out that lead from generator to inlet is 10/4.
 
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Old 12-19-13, 04:30 PM
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A 5,000 watt generator should have an L14-30 240/120 volt receptacle. The interconnect cable should be four conductor #10 type S plus other letters but in my opinion not an SJxx cable for reasons of severe usage. The wiring from the inlet connector to the transfer switch, transfer panel or interlocked circuit breaker should be no less than #10 copper as well.

What size wire from a service panel to a transfer switch is dependent upon the rating of the switch itself and the loads served by that switch when on utility power. The circuit breaker in the service panel should be sized according to the switch, loads and wiring. If the switch is rated at 60 amperes you cannot have a 100 ampere circuit breaker feeding that switch.

Pictures of your installation might help. Be sure they are well-lit and in focus.
 
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