50 Amp Cord, Pwr Reel, Cord Ext, AutoFrmr w/srge/fire contrl

Mex,

That suggests resistance loss to me. Assuming you measured a 30A cord you had a long length in a tight environment that minimized heat loss with a 83% load. Wire specs generally include ambient temps of straight cord so I don't know how to calculate the expected heat loss with your environment.

Sometimes when I stop my cord is in the 140 degree range from engine heat and it doesn't seem to be a problem.

I have measured to Delta T of sixty five degrees F in a tightly coiled 60' motorhome cord running at about 25-amperes. This is excessive.

70F - 135F Two measuring instruments. Measuring the cord within the center of the coil not the ends.

Dusty R wrote:
I have a friend with a TT. Where he parks it sometimes, is a long ways to where he can plug it in. It takes the full length of the attached cord plus an extension cord of about the same as attached cord. It appears that the extension cords that are readily availably are the same size the attached cord.
When staying in it with AC running it melted the plug between the 2 cords.
I believe that the length of the attached cord is the maximum length for that size cord and any extension cord should be at least 1 size larger.

Dusty

Actually length is dependent upon voltage, wire size and amps. And of course the condition of the plugs.

The recommended sustained load (ie running ACs) is 80% of the plug rating. So on a 30A plug you are now down to 24A which is easy to exceed. Worn plugs, low voltage and high loads are all so common on 30A.

80% on a 50A circuit would mean not exceeding 40A on each hot leg. That is a lot of power (40A*2*120V = 9,600W) that few are likely to exceed. Not to mention the 12,000W limit.

I've used 40A maximum on one 50A leg. I'm sure I could draw more with: 3 ACs, aqua hot electric heat, 2 ceramic heaters, MW and a few other goodies...

I have and use a 25' 50A extension and a longer extension with reasonable loads would not present a problem. 30A plugs and cords tend to be a completely different kettle of fish.

I have a friend with a TT. Where he parks it sometimes, is a long ways to where he can plug it in. It takes the full length of the attached cord plus an extension cord of about the same as attached cord. It appears that the extension cords that are readily availably are the same size the attached cord.
When staying in it with AC running it melted the plug between the 2 cords.
I believe that the length of the attached cord is the maximum length for that size cord and any extension cord should be at least 1 size larger.

Dusty

tvman44 wrote:
So many old wives tales floating around on these forums and so many people believe them.

Totally AGREE!!

B.O.

So many old wives tales floating around on these forums and so many people believe them.

I carry a 25' 50A extension cord that is in a plastic tote box and it's rarely used. Actually it's used at my house and a few times we've reversed parked in a site because of the view.

I chose the PI HW50C power protector which provides protection that a autoformer doesn't but does not boost the voltage. Perhaps you want both. Low voltage is common on 30A pedestals and not so common on 50A pedestals.

"fire control" ??? Common in a boat bilge but where would you put it on a RV? Engine area, refer area, HW area, furnace area or? Smoke and propane detectors are common on a RV.

Golden_HVAC wrote:



The reel will act like a transformer to some extent. You will have 4 wires going around the reel, however if it is really long part wound up on the reel, then it can overheat and act like a transformer. It is best to wind out most of the cord - especially on a hot day, and avoid leaving more than 2 winds left on the cord reel. Say that the cord is 1/2" diameter and the reel is 5" wide, leaving space for 8 or 9 cords side by side, and two layers would leave about 10 - 20 feet of cord on the reel, and still not get hot. But if you leave it all on there, it can overheat. something to check on a warm day, when 2 A/C units are running.. . .

Have fun camping!

Fred.

How did you deduce this piece of info?

I do have Glendinning power cord which gets coiled inside a drum and have never experienced any of the effects you mention

DrewE wrote:
A power cord on a reel does not act like a transformer. It may heat up due to resistive heating, and being confined to a smaller area than if it were strung out, but there is no net inductive heating because the net current within the cable is zero. (The current that flows one direction through the hot conductor(s) flows back the other direction through the neutral, and they cancel each other out.)

If the cable is properly sized and rated for use on the reel, it shouldn't get too hot even at maximum rated current. That's basically what being properly sized and rated means, after all—it's suitable and safe for its application.

X2 Good accurate information.

A power cord on a reel does not act like a transformer. It may heat up due to resistive heating, and being confined to a smaller area than if it were strung out, but there is no net inductive heating because the net current within the cable is zero. (The current that flows one direction through the hot conductor(s) flows back the other direction through the neutral, and they cancel each other out.)

If the cable is properly sized and rated for use on the reel, it shouldn't get too hot even at maximum rated current. That's basically what being properly sized and rated means, after all—it's suitable and safe for its application.