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skip 01-12-2004 12:42 PM

powerlines, 30amp vrs 50 amp
I want to extend the reach of my power cord. what are the pros & cons of 30 amp cord vrs 50 amp. also wondering @ the increase in resistance when the length is extended. I have seen cords from 25 to 50 ft. Is their an optimun length? Would the junction of the plugs also be a consideration?????

I have had times in my '73 ambassador ( now in a new home) that the plug would feel hot to the touch in the mornings after running the A/C all night. This was a direct connection to a recepticle with no adapter. Would this be more likely with an extention?

Are there any adapters I should have on board? In the past we have never had to use one. If this is just beginners luck, I don't want to push it.

We have brought along my generator a couple of times. It ain't the way to go !! Must weigh over 200# & takes up too much romm in the truck. TALK @ WORKING TO HAVE A GOOD TIME........

RoadKingMoe 01-12-2004 02:47 PM

If you just want to extend your trailer connector 25' there's no reason not to get a 10 gauge 30A extension cord. While the 6 gauge 50A extension cable may have slightly lower resistance, it is much heavier, stiffer, and harder to work with. Not only are each of the wires larger, but you pick up another 6 gauge wire that you won't even use.

The heat you are experiencing at the 30A plug is because of worn 30A outlets in campgrounds, which are notorious for burning up the prongs on RV plugs. To save their original RV cable, some RV owners make up a short cable with a cheaper, sacrificial 30A travel trailer male plug with short cable going to an electrical box with a 30A travel trailer outlet or spliced onto a female 30A travel trailer plug with short cable.

If there's a great site with a bad 30A outlet and a good 50A outlet, a 50M to 30F Adapter will let you plug your 30A stuff into the 50A outlet.

If you are at a site with only 15-20A power, which includes most rallies, a 15M to 30F angle adapter or 15M to 30F straight adapter will let you use at least some of your 120VAC stuff as well as keep the batteries charged.

RoadKingMoe 01-12-2004 03:55 PM

It also just occurred to me that with the age of your trailer, the prongs on your trailer plug may be so burned up that they no longer have the thickness to get a good grip in a socket and that could contribute to the heat problem.

skip 01-12-2004 08:02 PM

Thanks Maurice
25 feet should be enough for what I would need. The 10 ga would be less expensive. Sounds like I would also need a 50 M to 30 F.

When hooking up to 50-20 A power (or any power source), is there any advantage to use a straight or an angled plug?

The plug on my current A/S is new. It is a 79 Sovereign I purchased from Ken Smillie. The plug replacement is obviously new. I am really pleased with everything that he did with this unit.

Thanks for the answers. This gives me a better idea of what I need.

RoadKingMoe 01-12-2004 08:41 PM

Although I have one, the odds of needing a 50M to 30F are pretty low.

You will almost certainly need the 15M to 30F sooner or later. The one that's 90 degree can only be used in the bottom of a duplex outlet if someone else is going to share it. The one that's straight in works best for sharing, but it also tends to pull out the most, especially if the duplex outlet is horizontal.

There's a third one that's just a plastic block with a 15M to 30F, but it also can only be used in the bottom of the duplex outlet and it tends to pull out. Worst of both worlds, but it's the one I have. If I had it to do over again, I'd have both of the first two for more flexibility.

Did you ever see this New Owner Shopping List thread?

skip 01-13-2004 05:44 PM

What a great source of information ! Although I have many of the things on this list, There are a lot of things I would never have thought of .........until I needed them.

Especially helpful were the links to Campers World catalouge. Like they say, "One picture is worth a thousand words." I have often looked at the variety of items, that serve the same function & wondered which had the best application. This really helps!

Although this is our third streamer in the last couple of years, we are just beginning to really get in to it. Previously we just towed to where we were hunting or fishing & left it parked for months at a time. I am just beginning to realize what a great fraternity streamers are. It is probably time we signed on with a local club.

wahoonc 01-13-2004 05:49 PM


Originally posted by skip
What a great source of information ! t a time. I am just beginning to realize what a great fraternity streamers are. It is probably time we signed on with a local club.
I am sure Ken Smily will welcome you with open arms:p :D

You may even run across us down there one day:rolleyes: if we ever get done with the rehab...and don't move!


skip 01-13-2004 06:15 PM

You sure right @ Ken.
Ken is a great guy with boundless energy. Also seems to be very active with the "Low Country" club. I bought my current ' 79 Sov. from Ken. He did a great job on everything. I'm real pleased with it.

Where are you in N.C.? I grew up there & went to school at U.N.C.

wahoonc 01-13-2004 06:22 PM

Check you PM;)


Janets Husband 01-21-2004 03:24 PM

Extension Cords
I think you got a little wrong info on the capacity of extension cords.
According to the NEC Table 400-5(A)
a 3 conductor SO cord (just about all other types also) with 10awg conductors has a rateing of 25amps, a 8awg cable is 35amps and 6awg cable is 45 amps.
The conductor is derated from its free air capacity because it is bundled with other conductors. Heat disipation.
Overloaded extension cords are a leading cause of electrical fires.
I know a bigger cable is harder to work with but it is safer to work with a cable which will give you your needed capacity.

Heat in an extension cord is telling you something.
Hot Cable- overloaded
Hot Connector- overloaded or damaged.
Hot Plug- overloaded, damaged recepticle or worn out plug.

As for length a 25' cable should not cause too much of a voltage drop, or heating problems if you don't overload it.

Deal with the problems as they come and we all will get home safe.
Buy the biggest and best cord you can for the job.
Buy the best adaptors you can and derate your whole cable by 10% for the adaptor.

Be Safe
That's my $0.02

john hd 01-21-2004 05:45 PM


what do you consider "hot"?

there will be a tempature rise in any conductor under load.

so cord gets hot just sitting in the sun.


RoadKingMoe 01-21-2004 06:59 PM

OH MY GOD! AIRSTREAM (and every other RV manufacturer who's ever been in business) has been using 10/3 for 30A cables for years! Even back when I was an RV tech.

Worse yet, that cord runs up inside the trailer, where it gets even hotter when the trailer's closed up in the summer!

It must be a conspiracy! Underwriter's Labs lists these cables as safe.

There must be millions of dangerous RVs out there on the road.

N O T !

Janets Husband 01-22-2004 08:39 AM

Update on info
I double checked the NEC Article 400 Table 400-5(A) and the ampacities I listed are as stated in the book.
These rating are given for a cable in Ambiant Air at 30degC/86degF.

It has been said manufacturers have used 10/3 cable for years.
Ok. The NEC now states its rateings in Table 400-5(A).
Take it for what its worth to you.

How hot is too hot, that you'll have to answer for your self.

I consider a cable too hot if it is hot to my touch."Whatever that is" I deffinatly worry if the cable or plug starts to discolor.

I consider my family's safety formost on my list. If I deem a cord to be unsafe I change it.
My motto is: If I make and error it will be on the side of Safety first.

john hd 01-22-2004 03:45 PM

good motto gary.

i try to size conductors for wiring projects at 3% voltage drop or less.

bigger wire yes, piece of mind definately!

i imagine rv manufactures take diversity factor into account when sizing the power cords and undersize them slightly.


Janets Husband 01-22-2004 03:56 PM

Dear John
Always wanted to have a subject line just like that.

I'm going to look into the sizeing of factory AC power cables to the trailer. I think it might have something to do with it being a feeder cable. I just don't know the thinking was on their chooseing that size cable.

I know that a lot of manufacturers of extension cords have down sized their ratings 12awg = 15amp cord 10awg = 20amp cord....

I'm confused on this one, Are there any factory people out there who can shed some light on why the AC feed lines don't match what the NEC says on ampacity.

john hd 01-22-2004 04:54 PM


my guess without digging out my lineman books would be that the mfrs figure 60% to 80% use max.

we certainly size transformers that way at the power company.

meaning that with the univolt on and the ac running and the odd lightbulb or two would add up to 20 amps.

that would leave you with 10 amps for corrosion, loose or otherwise crappy connections. or too long extension cords.

there are short term overloads to factor in such as compressor starting or some one hosting a party and runnin 3 nesco roasters in the kitchen.

go figure!


skip 01-22-2004 07:28 PM

So, Maurice,John, Gary, et al...
Where exactly are we on this? I have already purchased a 10/3 extension with a 30 amp plug. However I certainly have no reservations about exchanging it. I am only an hour from the Myrtle Beach Campers' World.

My primary concern is also safety, but what about the existing 10/3 cable that came with this 1979 Sovereign? The over heating plug was on my '72 International 31'. I haven't used this '79 very much.

In the limited time I have spent in camp grounds, I don't recall seeing cables heavier than 10/3. Is this an acceptable standard?

john hd 01-22-2004 07:52 PM

lets do some math...

lets do some math, o.k. lets not!

lets use the handy dandy wire size calculator instead...

now lets look at the varibles:

120 volts, copper wire, single phase, 30 amps 50 foot run (assuming 25 foot cord on the trailer and 25 extension cord)

lets see what we get...

thats right, 8 gauge!

of course that is calculated for 3% voltage drop, insuring no damage to your ac compressor.

now, without the extension you would be o.k., with it, are you going to overload? probably not.

as suggested elsewhere, actually checking the circuit with a clamp on ammeter would tell you for sure how much load is on that cable with everything running.

also it all depends on what your voltage at the outlet is to begin with, the lower you start with the less you will have in the end. the load in the trailer is essentially fixed, the lower voltage, the higher the current draw will be. ohms law!

if it was my setup i would try to find ways to avoid use of the extension if at all possible.

-but- if you find yourself with no other way to get power to the trailer i would not hesitate to use it sparingly.

you are right on the edge of capacity.

just keep that in mind!


wahoonc 01-22-2004 08:04 PM

Re: lets do some math...

Originally posted by john hd
... actually checking the circuit with a clamp on ammeter would tell you for sure how much load is on that cable with everything running...


I quit doing that the answer scared me too much:p After measuring voltage at the campgrounds on a couple of weekends. One holiday we were getting around 106v at the freakin box, didn't even try to run the AC that weekend. Just used a bunch of cheap fans. I have wondered if one of the "soft start" kits for my AC might not be a bad idea, the ones that help smooth out the voltage. BTW I use the 10 ga cables for extensions, just grab ahold of one every now and again to make sure the connections aren't hot. Watch the cords being sold at Wally World they had a bunch of 30 amp cords the other day that were 12 ga..."I don't think so Tim!"


skip 01-22-2004 08:20 PM

Thanks John,
I think I'll take the 10/3 back & go with 8 ga.

The only question I have is the availability of 8/3 with 30M plug on one end & 30F on the other. It also seems that every time you use an adapter plug you increase the potential for problems. (debris,wear, disconnect, etc.)

Am I just overlooking ready made cords or should I just fabricate one ? I haven't checked CW catalogue, but I didn't see any in stock this past wk. end. Lowe's didn't have anything like that either.

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