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Old    Pound (snyder)      Join Date: Feb 2006       01-12-2012, 12:54 PM Reply   
Bought a generator w/240/120v NEMA L14-30 (twist-lock) outlet. I want to connect it to the 120V 30a 3 prong plug on my camper.
Instead of buying a converting plug, I decided I'd do it myself. So I bought a panel box w/a 120v 30a female plug for the camper to go into (specifically for campers/RV's i guess), I bought 10' of 10/3 cord and a male L14-30 plug.
The wiring diagram of the 4 prong outlet on the generator shows (clockwise from top) Neutral, Hot, Ground, Hot where it can provide 240V by using both hots, or 120 on each side.
How do I wire this plug so that I'm only getting 120V. Do I just pick one of the hots? Does it matter which one? will this cause an unbalanced condition? This for some reason is really hard for me to find info on in the interwebs.
Old    Pound (snyder)      Join Date: Feb 2006       01-13-2012, 8:07 AM Reply   
I think I have my answer, just doing some tripple checking. Here's a diagram of what I've got.
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Last edited by snyder; 01-13-2012 at 8:12 AM.
Old    John Anderson (fly135)      Join Date: Jun 2004       01-13-2012, 10:45 AM Reply   
That's looks good. You also had a question about the generator being unbalanced. I would guess that it's designed to run 120V, but you may reduce the rated capacity by only pulling off one leg. I would check the manual for the generator.
Old    Pound (snyder)      Join Date: Feb 2006       01-13-2012, 10:58 AM Reply   
Thanks John. It's amazing how unclear this actually is... I guess I'm making more of it than I need to. The manual says this:

"Use NEMA L14-30 plug with this receptacle. Connect a 4-wire cord set rated for 250 Volt AC loads at 30 Amps (or greater). You can use the same 4-wire cord if you plan to run a 120 Volt load.

This receptacle powers 120/240 Volt AC, 60 Hz, single phase loads requiring upto 6,000 watts of power at 25 Amps for 240 Volts or two independent 120 Volt loads at 25 Amps each. The outlet is protected by a two pole rocker switch curcuit breaker."

and I found a discussion on an RV forum where someone pointed out this disclaimer on a converter plug set:

"PLEASE NOTE: A 30 amp 7500 watt generator normally runs 30 amps to each hot blade on the receptacle. Since the RV TT-30 is a 125-volt only device, only ONE hot leg of the plug is wired, and the other would be inactive. Connecting this adapter to your generator for long periods of time may cause the windings of the generator to run imbalanced which could potentially shorten the life of the generator. GenTran is not responsible for any damage caused by the use of this cord."

But I don't know A.) what "long periods of time" means, and B.) is this just CYA stuff? So I called Troy Bilt and they said it's designed to run on either one or both legs. and it should be fine... Also, they sell cords specifically designed to turn this 4 prong twist lock into 2 or more 120V extension cord plugs... so wouldn't it be doing the exact same thing, only running one hot down one side of the cord, and the other down the other. If I plugged into only one of them... same thing.
Old    Pound (snyder)      Join Date: Feb 2006       01-13-2012, 1:29 PM Reply   
Yeah, i'm pretty sure i've got this figured out... Basically, using only one leg of the 240 leaves the other leg unused, which to the generator is no different from all the other 120V unused plugs. So theoretically, what the maker of the adapter cord says above is kinda bogus. It would be analgous to saying if you only use one of the 120V 20a outlets on this generator you'll cause the windings to run imbalanced...etc.
I've beat this dead horse quite a bit, but another simplification is to think of the center tapped (common) neutral as basically dividing the generator windings into two seperate generators. each with 120v but in exact opposite phase. If you want to use 120, just tap into either side. If you want to use 240, tap into both sides (where the neutral is not really necessary). Just like your house is wired. You get two hots and a neutral (and a ground) from the power company. It goes into your breaker box and each hot goes to it's own bus bar.. providing two sets of 120v power. all using one common neutral. things that need 240 (like a drier) use a hot from each side. Otherwise normal 120V appliances use one side or the other...
I'm just trying to convince myself that i'm not going to wear out my generator permaturely... in reality, it'll likely only see a few hrs operation at a time and i'll probably never draw anywhere near it's full capacity...
Old    Pound (snyder)      Join Date: Feb 2006       01-17-2012, 2:29 PM Reply   
As a follow-up. The generator ran flawlessly. 18-20 hrs. used maybe 8 gallons of gas.
It was loud though. Now I'm looking for some good deep cycle batteries to replace the original so that I can get about 200 Amp Hours of stand by time. I figure that's enough to run the furnace and a light and possibly the fridge on propane for about 12 hrs. I was unable to run the furnace off battery alone because the original battery that came on the camper would discharge too fast. I shut the generator off at around 10pm and by midnight, I was back out there starting the genset back up to keep the furnace on (it got down to about 32 degrees overnight).
Old    Scott (crypted1)      Join Date: Jun 2009       01-23-2012, 4:26 AM Reply   
As an industrial Electrician your diagram is spot on. If you followed the diagram you are correct. All of your concerns in bold listed above, are just the legal mumbo-jumbo that businesses do to make sure that they can't be sued for what ever reason.
Old    Pound (snyder)      Join Date: Feb 2006       01-23-2012, 12:38 PM Reply   
Thanks Scott.


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