Weird 120 VAC problem

[DaddyRV779]

Originally Posted by kwftlaud

I have a 2001 Itasca Sundancer 27P
I am having a electrical issue with my front AC circuit.

I know the circuit line. I have disconnected it.

If its hooked up to the circuit breaker it shorts out the AC line and sparks fly when I try to plug it in. If I measure the resistance on the line it reads open. If I read the resistance to ground and across the AC lines on the 30Amp plug I get a high resistance ( open ). When I connect the black wire from the bad leg I get a high résistance also so I'm not seeing any shorts.
Yet when I plug it in with that leg connected sparks fly, but doesn't trip the breaker.
I am really stumped because in my mind, if the resistance is in the 100's of kilohms I shoud not be seeing sparks fly.
Any idea what I'm missing here?
Thanks

Kip

Check you slide for cables that are showing bare wires - anything shorting to ground could throw sparks... BTW, where are the sparks showing? If at the slide , you have a short where you see sparks...seeing sparks that don't trip a breaker indicates a weak short...one that emits sparks, but is at a lower current than the listed value of the circuit breaker...look for worn insulation on your wires.

[OldWEB]

With the diagram provided by cbeierl, you could now further isolate each JB and outlet connections to narrow it down. As others wondered, how bad is the sparking, fine little sparklers or molten metal, arc welding meteor type sparks? TV plugged in? VCR/DVD player?

[TandW]

Originally Posted by Archer2

@Bigb56 I guessed that the OP was saying that the sparks flew when plugging the shore power cord into the power pedestal. Nothing else that I could think of made any sense. Of course checking the circuit with an ohmmeter doesn’t show any problem because the Converter doesn’t start drawing a load until it sees 120VAC at its input but when the 120VAC shows up then it’s “Katy bar the door!”
Also, @TandW I think you meant to say just the opposite of your description of how to interpret a multimeter when measuring resistance.

High resistance reading on VOM = continuity. So does low resistance. An open circuit produces Zero reading. Open circuit means no complete path for electron flow.

[Archer2]

I think I see what you’re saying. Using a VOM with an analog display (meter with a needle like a Simpson 260) if the needle is sitting against the left-hand stop then it’s 0V, 0 Amps but the scale printed on the meter says maximum resistance (open circuit). If the needle is full-scale and pegged to the right it’s max V, Max Amps but the scale says zero Ohms resistance (short circuit). So in terms of the meter's indicator, continuity is maximum meter deflection and an open circuit is zero deflection.
A digital VOM set on the resistance scale but not connected to anything will usually read “OL” for “overload” and when you touch the leads together it will read “0.00”.
Is that how you are looking at it?

[TandW]

VOM is switched to a resistance range. Touch leads together. Meter deflects indicating continuity. This test should always be done to check meter batteries. Connect meter leads to circuit to be tested. If no deflection, open circuit is indicated.

[bigb56]

Originally Posted by bigb56

I don't think the converter is the issue because he says the circuit in question "shares the breaker with the converter" so the converter is connected when he plugs in and gets no sparks. From what he is telling us so far there is no load that he can account for.
I would like to know more about the sparks, a load spark/arc is not exactly the same as "shooting sparks". I have seen a short that causes shooting sparks but clears itself before the breaker trips caused by a single strand shorting out and melting, but not numerous times.
I'll be standing by waiting for more info.

I don't think the converter is the problem, he said the problem circuit shares a breaker with the converter, no sparks happen when the converter is the only thing on that particular breaker, adding the second circuit makes the sparks.


With this line disconnected everything in my rig works ( all appliances and AC ) No sparks when I plug in.
When I connect it back up to the 15 AMP breaker ( that it shares with the converter ) I will get sparks when I plug in the shore power . The breaker does not blow.

[Ray,IN]

Originally Posted by TandW

VOM is switched to a resistance range. Touch leads together. Meter deflects indicating continuity. This test should always be done to check meter batteries. Connect meter leads to circuit to be tested. If no deflection, open circuit is indicated.

[kwftlaud]

I still haven't figured it out. Someone supplied me with wiring diagrams so I'll investigate some more soon.

But one thing I want to highlight.
The sparking was strong enough to make black marks all over the plug and socket. This is no slight arc.... its a massive short.
I would think I should be able to find somewhere a short to ground, but I cant.

I did do some work on the bedroom slide a few months ago, so, I am going to open that up and check out the 120 volt wiring there.

Thanks for all of the input.
Kip

[TandW]

By now you should have caught on. Other posters have responded with the very good and safe suggestion that you keep the pedestal breaker off, plug in and then turn the pedestal breaker back on. They also explained that your converter is drawing a lot of current when energized as its capacitors charge up. The only problem you are going to have is burned up spades on your power plug and or a burned up receptacle at your pedestal.

[Archer2]

@kwftlaud, as others have said what you are experiencing (and stubbornly insisting something is wrong) is exactly what happens if you connect or disconnect a circuit while it’s energized. It’s also the exact reason that you shouldn’t do it. Circuit breakers and switches are designed to positively make and break a circuit safely. Anytime you try to make or break a circuit while heavy current is flowing you will get some arcing-in fact, that’s how an arc welder works. The really heavy current in your case is only present for a fraction of a second and that’s why no breakers trip.
But maybe We aren't understanding what you are saying. Other than the arcing at the main power shore connector, does everything seem to operate OK? All the outlets work, converter is charging your batteries, appliances OK, etc?

[edge68474]

Another interesting electrical thread.
Thank you for sharing.


EDIT: I was just reminded and learned something, Wahoo!!

[SCVJeff]

I agree with Archer.. I didn’t read every word on all the replies, but what keeps standing out at me is “sparks fly and the breaker doesn’t pop”. To me that’s standard inrush current from a big inductor in the RV. A fan or a compressor motor, and certainly whatever you use as a charger has a nice big inductor in it (transformer). Those in-rushes are normal.. If you’re not popping a breaker, plug it in and see what happens. Probably nothing