30A to 50A Adapter Causes MH Fire

[steveclv]

Originally Posted by Lincolnboy2

So one should just lay the cord in a lot bigger loops in the bay then...

Yes, the larger the loop the lower the inductance by a square root law - if you can figure of 8 it by preference. Tightly winding it isn't a good idea and I suspect that the power reel instructions tell owners to unreel the whole cord before use.

[Lincolnboy2]

Thanks Steve, I have to work to get that cord wound up in it's half of the bay anyway, I'm more than happy to loop 8 it in the whole bay, that's a lot easier!

[Cubey]

Originally Posted by gemini5362

I do not know how you do your wireing or what kind of maintenance you do on it.

That goes for every vehicle on the road. I can't help but notice the MH that caught fire in this thread was some crazy expensive fairly late model rig. You can have a setup that cost you $300,000 but if you don't take care of it and/or do stupid things, threads like this pop up.

[Cubey]

Originally Posted by steveclv

The length of 30amp cable and any connectors between the Pedestal and the first 30amp circuit breaker in the RV are NOT protected by a suitable circuit breaker and that is in breach of code.

Unless I am mistaken, that is how (almost?) all RVs are wired. Now it might be the 50A rigs have an extra breaker in the compartment but I haven't heard of 20A or 30A ones having it.

(I had a 67 Shasta that was 20A, my 78 Xplorer now has 30A)

[myredracer]

My opinion as an electrical engineer is that it is extremely unlikely that the coiled cord had anything to do with this.

What likely happened is that the 30 amp cord was probably plugged in all the time when the supply was live. When you do this, the converter has a momentary inrush/charging current that causes pitting of the plug blades and the receptacle contacts. If you plug in live, you will hear a zap, and in the dark, a flash. Each time you do this, the pitting gets worse and eventually the resistance builds up high enough that the plug/receptacle connection overheats. If you are lucky, it will just melt. At the worst, it can cause a fire. You should ALWAYS turn the pedestal breaker off before plugging in. That's why sometimes you will find the pedestal breaker off when you get to your site. If you install a dedicated receptacle for your RV at home, you should install a disconnect switch at it. This is a little known fact that gets people into serious trouble sometimes. I burned out two 25' 15 amp extension cords twice at home from doing this and I eventually installed a dedicated receptacle in our carport. You could turn off the breaker in your house, but they aren't designed for energizing a load with a high inrush current. "Switching duty" breakers would be better but still not designed for this type of continual use.

If you have a detachable power cord, if you plug into the pedestal first all the time and then attach the cord to the RV live, you will be pitting the cord's connector and the power inlet on the exterior wall. I've seen photos where this has happened. If you damage these from overheating, it's an expensive repair. Or your RV will end up on fire.

NEVER plug your RV cord in live - period. If you continue to do it, it's an accident waiting to happen.

If an RV has a 30 amp main breaker inside in the panel, which it should, I don't understand how you could overload the 30 amp RV cord to the pedestal. You should be able to plug the 30 amp protected RV into a 100 amp or 200 amp receptacle with adapter and be fine.

Some things are done with RVs that would never be allowed in building construction by electrical code. You can buy adapters for adapting up, down and sideways. With one of them, you can use two adjacent 30 amp pedestal breakers with a wye adapter cord to make 50 amps. Some of them make me cringe.

A coiled 30 amp extension cord heats up because it does not get cooled properly and if multiple conductors are run together, they need to be derated. The more the number of coils, the more the derating factor needs to be. In building wiring, there are tables for derating wire ampacity (current rating) based on the number of wires in place together. If you have a coiled cord in a confined space in a hot location (eg, exposed to full sun on hot day) the cord can get pretty hot if running 30 amps through it.

Jacketted power cords have a temperature rating which is the max. temp. the cord can carry for the rated amps it has. The 30 amp Conntek cord on our TT has an "STW" exterior jacket with a temp. rating of 105 degrees celsius (221 deg. F) but the spare Marinco cord we have has the same "STW" jacket but a temp. rating of only 60 deg. celsius (140 deg. F). Not sure why this is. Both are CSA approved and STW insulation is an industry standard and the technical specs. should be the same. If you had the Marinco cord coiled up in a confined space, in full sun and on a hot day, you could easily exceed the 140 deg. F rating if running the cord at rated amperage. Should a Conntek cord be safer?? I don't know....

If the cord was melted or burned to a crisp, that would mean one thing, but if the plug and connector (or receptacle) was melted or burned to a crisp, that would mean another thing.

Some of the posts from people who have no formal training in electrical matters kills me!

[FlyingDiver]

Originally Posted by Cubey

Unless I am mistaken, that is how (almost?) all RVs are wired. Now it might be the 50A rigs have an extra breaker in the compartment but I haven't heard of 20A or 30A ones having it.

RVs are wired as needed for the draw they're designed for. The problem pointed out in this thread is that a 30amp RV is designed to plug into a 30amp receptacle and breaker. If you plug it into a 50amp receptacle (using an after-market adapter), you're technically doing something it's not designed for and could have a problem.

[FlyingDiver]

Originally Posted by myredracer

My opinion as an electrical engineer is that it is extremely unlikely that the coiled cord had anything to do with this.

So you don't think an inductive load from the coiled wires could have any effect?

I'm actually an aeronautical engineer, which is a hybrid discipline including electrical, mechanical, and aerodynamics. I would have also had an EE degree if the EE dept had been willing to give credit for equivalent courses taught by the Aero dept. They weren't. :(

[Lincolnboy2]

My shore cord is about 15' long. That is the cord I was talking about coiling up in the bay, not an extension cord.

I do have a 50' 30 amp extension cord and just out in the heat in the afternoon with no load on it it feels like its 100 degrees to start with.

Gil: I have installed the Progressive EMS-HW30C. I never plug the coach into a live circuit. Always make sure the breaker is off. However; my question is, the EMS is designed so that once I flip the breaker on, it allows power in the coach once it has analyzed it and says its ok. It has a 15 second "layover" then energizes the coach. So even if I did forget and plugged into a live circuit (which I haven't yet knock on wood) the EMS would take care of that oversight?

[steveclv]

Originally Posted by myredracer

Some things are done with RVs that would never be allowed in building construction.

And I think that pretty much says it all.

[BCooke]

OK, wow, the burnt cord was bad and glad only major damage was the cord.
I trust the 110 receptacles inside the camper about as much as I trust the pedestal.
For the electricians, are those RV outlets legal for use in a stick house? Is it ever within code to put 15 amp receptacles on a 20 amp breaker?

[Lincolnboy2]

Hey guys, I just came across this.....

Does a coiled extension cord overheat

Answer:
No, it will not overheat unless too much current is being drawn through the cable, but this can happen even with a cord that is not coiled. Example: The lightweight zip cords used for Christmas tree lights and other light-use appliances such as table lamps, are made to carry very little current, perhaps only a couple of amps. If somebody uses such a cord to power a circular saw, grinder or some other power tool which uses 12 amps or more, that cord will overheat and start to melt the insulation. Not only that, but the tool itself will be damaged because its motor will overheat.



A single conductor (one wire only) coiled up and with current passing through it may heat up. This, after all, is how older electric heaters worked. A single, high resistance wire was wound around a ceramic rod and current passed through it, causing it to glow red.


A power cord has two conductors (three if a grounding conductor [green] is included). Without a neutral (white or gray) the cord would be useless. This neutral wire negates the effect of heating that would otherwise be generated by the single conductor.


As a former electrical contractor, I had to attend electrical code classes every year to maintain my license. The electrical inspector who taught the class, used to take photos of code violations (some done by homeowners with little or no knowledge of electrical installations). In one of the photos a single conductor was passed through a cable connector and into a breaker panel. He said that when a current is passed through the conductor, the steel case of the breaker panel will heat up. A neutral, run with the live conductor, would prevent such heating. Obviously, the "electrician" who installed the single conductor must have already had a neutral at the device to which he was running the new conductor. Perhaps there was an open circuit in the live conductor, but whatever the reason, a single conductor must never be run by itself in any electrical installation because of the heating factor.


In a recent fire investigation, the fire marshal concluded that a coiled up power cord was the cause of the fire. That could be possible if the insulation was deteriorated and there was a short circuit between the live and neutral conductors. It will not happen in a cord in good condition. But such a short could cause a fire even if the cord was not coiled up.

[FlyingDiver]

Originally Posted by Lincolnboy2

Hey guys, I just came across this.....

Does a coiled extension cord overheat

He may be an electrician, but he's not a physicist. A tight coil of wire, with current running through it, is an inductor. The magnetic fields generated by the coil (think transformer) causes a load, therefor a resistance, which will cause the coil to heat up. The figure eight generates fields that cancel each other out, which eliminates the load.

You can test this yourself. Take an extension cord, coil it tightly, then put a heavy load on it. How hot does it get? Stretch it out with the same load. Does it get as hot?

[Lincolnboy2]

Originally Posted by FlyingDiver

He may be an electrician, but he's not a physicist. A tight coil of wire, with current running through it, is an inductor. The magnetic fields generated by the coil (think transformer) causes a load, therefor a resistance, which will cause the coil to heat up. The figure eight generates fields that cancel each other out, which eliminates the load.

You can test this yourself. Take an extension cord, coil it tightly, then put a heavy load on it. How hot does it get? Stretch it out with the same load. Does it get as hot?

Yes, I agree and he is saying with a heavy load on anything its going to get hot. I agree with you FlyingDiver, I think it is not a good idea to have it coiled, but especially not when pulling a heavy load, makes it even more dangerous.

[steveclv]

Well, what do you think??