My experience is that problems of this nature are usually - but not always - a loose connection in the panel, inverter or a receptical. You would be surprised how fast vibrations from an RV will loosen screws. The first thing is to check for loose connections and corrosion/arc damage on the connections. Go from there. JMO.

Bill,
Lots of folks think loose terminal connections when describing arc faults. You're right that they happen in connections too, but folks need to be aware that many in wall fires are not only due to loose mechanical connections, but also degradation of the wire's insulation itself due to mechanical damage on installation, or aging issues.

"The electrical shorts that cause these fires produce arcs. These miniature fireworks create sparks and temperatures that approach 10,000 F. This intense heat can rapidly ignite plastic insulation, wood, carpeting or any other combustible material in the vicinity of the arcing wires. Arcs happen frequently in appliance electrical cords where insulation has become brittle or is cracked. Hidden wires behind walls nicked by nails or pinched by fasteners can also be sources of sinister arcing. Loose connections where wires are attached to switches and outlets are often arc hot spots."

http://www.askthebuilder.com/320_New_Arc_Fault_Breakers..._Peace_Of_Mind.shtml

Jack's notion is the first one I would spend time on. The reason is that RV receptacles are usually made very thin to surface mount because the walls cannot contain a full depth outlet box. Because of this, the usual way that the wire is attached is just with pass though-push-in insulation displacement type connections. The wire is often a continuous piece from source to the last outlet in the chain and each outlet in between has the wire just pushed down flat into the teeth of the connection. A back cover holds the wire down.

Now, what happens to this sort of connection when a high current device, like an electric heater, microwave, etc., is used a lot on one of the outlets? You get the heating up that was talked about and you get a loss of spring temper in the metal that is supposed to be continuously making solid contact with the conductor. This connection is now likely to be a little loose when it cools down. From this point on, it can put noise on the electrical line whenever anything of any kind of load is plugged into it.

This noise can be confusing to things that actually monitor the line characteristics and not just the voltage. Some smart UPS units do this to keep clean power going to the computer and such.
One other source of this sort of problem can come from other 110 volt devices that are introducing noise onto the line. Things like light dimmers are a good source of this sort of noise, particularly if they are older ones. If it happens only when a specific light or device in the RV is turned on or maybe even just plugged into some other circuit then it is more likely induced noise rather than a bad electrical connection.

The best and complete way to find an outlet problem is to:

1. find all of the outlets that are on this circuit by finding the circuit breaker that its connected to, turn it off and then use your little plug in voltage/connection tester with the little lights to see what outlets are on this specific circuit.

2. Disconnect all power to the whole main 110 volt panel and the Inverter, too.. This means Shore power, gen, etc. because you are going to want to check out the circuit breaker for this specific circuit, too, as it could also have been compromised over time.

3. Open up each outlet on the line and check the connections. If they are the simple push in type or insulation displacement type then look for evidence of heating (discolored metals of bare wire (if visible), insulation, connection points that actually bite the wire and distorted plastic or blackened areas around the connection.

4. Finding even one outlet that the wires are not tightly gripped in means that there are probably more of them. The factory wiring crew combined with the quality of the specific outlet mfr, may gang up to make connections that are not completely and tightly seated as they are supposed to be. Also, some insulations are more difficult to puncture with an insulation displacement type of connector and keep it from seating.

5. Always replace any outlet that you find that has any indication of having been in service in a compromised installation or that has any evidence of heating up.


Now, you are still left with the inverter and depending on how the shore power is switched in it can mean that a high load on the output while connected to shore power, has also compromised the switchover relays and maybe also the connection that supplies it 120 volts ac.

Several good thoughts in this thread, so I'll be very interested to see what the answer may turn out to be.

If I am understanding, the problem is only with one specific outlet? The advice to make sure that it isn't effecting other outlets as well, but you just had not discovered it, is sound. The catch is that with an intermittent problem, it can be very difficult to get it to repeat and so to know what to check.

I think that Emery's advice is good, especially if you are unable to get the problem to repeat. If you can get it to repeat, you need to check all outlets supplied by the inverter as it is difficult to accept that it is connected tot he inverter and only effects one outlet, assuming that the inverter supplies more than one.

By all means, do come back and let us know anything new that you discover and especially so if you find the answer!

RV - "Ask the builder" does do a good, simple explanation for fires and AFCI requirements. Does not explain JoeZ's computer or oxygen concentrator problem.

Emery does a much better job explaining how this arcing may effect the "smarter" devices such as power supplies. (Hence my highlight in green for the original poster). I was not trying to give a dissertation on AFCI's, just a little background.

In my 35+ working years (30 as a licensed master electrician, 20 as an electrical engineer)in the heavy electrical usage plants 20 - 50 megawatts) and the personal investigation and repair of electrical faults and sometimes fires, 95+ percent of them have been loose connections. The insulation breakdown and charing has been that arcing heat.

Another cause has been condensation in pipe, wire in areas that go from hot to cold, condense, bridge between phases or corrode, back to arcing. (think air conditioning inside and air migrating (wind pressure) through various openings in walls and condensing in our rigs). I had that in one plant (cold storage room and steam on the other side) Plugs, switches lasted 6 months, had to go with outside covers and clay (ductseal) in the pipes.

Emery does a very good job also of remedy and repair. Personally, I throw a heater load and use a Thermo-cam, but not everyone has one. Works great on wall insulation to.

This message has been edited. Last edited by: Bill B,

While replacing a wall switch with a pilot light switch for the hot water heater, I was surprised at how flimsy RV rceptacles are. The romex was attached to the outlet not with screws, but with a knife like attachment that was part of the switch itself. This would never pass code in residential housing. As mentioned above, a standard wall box would need some modification in order to fit between the shallow walls.

Sorry Caseyj - Look at the back or better yet, tear apart one of the cheap receptacles. The kind that the "faster" electricians push the wire into. These things end up in many, many homes. Tiny tab brushing (latched) on the side of the wire and plastic on the other side. Now, think in one side and out the other 6 times to the last plug. Put space heater here (nice heavy, cycling load). Can you say OUCH

Wow! Not only did my question generate a lot of good suggestions, but also became a learning experience for me. I checked every outlet on the circuit with one plug under load (thanks for that lesson) - all were OK except the problem plug and it showed a very significant voltage drop when the load was on. No signs of arcing or overheating, but I did replace the receptacle and, so far, the problem has gone away - everything works on that set of plugs. Now we will see if the problem reappears. Thanks again for all the help.

quote:

all were OK except the problem plug and it showed a very significant voltage drop when the load was on.

Can we assume that you made that same test again after you put in the new outlet? If so and if it passed the test then I would bet you have the problem solved. But do keep us posted!

JoeZ - That plug may have had:

Bad connection to the wire

heavy load at one time (heater) and did as Emory suggested

been used enough (cheap contacts with no mechanical spring tension left) that it wore out. The really cheap ones are only good for a couple hundred uses, maybe. Unless I really, really have to use a special (cheap), I use a "spec grade' receptacle (costs 3-4 times more) but does a much better job.

Glad that you may have found your problem and Happy Trails to all.

Hello to all. Kirk, yes, I repeated the voltage with load test not only on the replaced plug,but also all the other receptacles.No voltage drop this tine.Found no evidence but I suspect there was a loose connection - everyone is right about cheaply made receptacle although I have seen similar ones in stick and bricks I've owned.Thanks again for all the advice.

Congratulations. You're the man for giving us closure on this problem.

Thanks.