Shore power cable puzzle

[oldcarguy]

The shore power cable on our 2307C was (more on that in minute) permanently connected, stored inside the street side lower storage bin, and had a molded on male plug - feeding the male plug through the small round access hatch in the bin door and wresting with the cable has always driven me nuts.

When the molded on cable end started to fall apart, it was time to convert to an external power inlet. Ordered the parts, installed the power inlet, cut the shore power cable, installed the trailer end in the power inlet and installed new cable ends on the now-disconnected shore power cable, being careful that the hot (black), neutral (white) and ground (green) leads went into the proper locations in the power inlet and both new plugs on the cable.

Plugged the new shore power hookup into the outlet I always use and.....the refrigerator refused to come up on ac. Plugged a 110 ac circuit tester into one of the 110 volt outlets inside the trailer - it said that hot and neutral were reversed. Spent an hour taking everything apart to make sure that I hadn't screwed up and reversed the connections somewhere - everything was correct. Plugged shore power back in, same result.

Decided to roll the dice and switch the hot & neutral leads in the new male shore power cable end. Swapped leads, plugged shore power back in, and everything (including the refrigerator) works properly.

Question is, why? There's never been any problem with any of the electrical circuitry in the trailer previously. The only wild card is/was the old molded cable end - since it had to be cut off the end of the cable I don't know what the orientation of the hot and neutral blades on the connector itself was, so I guess it's at least possible that they were the reverse of the positions on the new equipment. Probably should have kept it for reference until the new hookups were completed, but unfortunately, it got thrown out.

Curious if anybody's got any ideas.....

 

[JackandJanet]

Oldcar - from your post, it sounds like you never had this problem before if you plugged into shore power at home? And since you were careful to connect black to black, white to white, and green to green in the trailer, that would argue that your house power is wired properly.

This really leaves us with a miswiring situation IN the trailer, that was there when the trailer was manufactured. You COULD look at the AC wiring into the converter, and see if the black and white wires there are reversed. Or is it possible that the AC wiring to the refrigerator is reversed? Some other things are not strongly effected by a reversal, except you might feel a small electrical shock if you touch the body of something plugged into a wall socket that has been wired incorrectly.

If you have a simple AC circuit tester light, you could plug it into one of the AC outlets in the trailer. That would tell you if there is a fault at the converter or if there is a miswire to the refrigerator, because if it shows "reversed", you know the power entering the trailer is reversed. This would mean the wiring from the converter to the refrigerator is also reversed.

If the light shows normal, then the AC connections from the shore power cord are reversed at the converter.

- Jack

 

[oldcarguy]

Thanks for the follow up - we've had the trailer for about 4 years and have had no prior polarity issues when connected to wall power or a generator, either at home or on the road. When we have the trailer at home, it's always plugged into the same 20 amp circuit; we've lived in this house for 30+ years - there's never been a reversed polarity issue with the house wiring over that period.

The ONLY variables are directly related to converting the trailer's shore power connection: cutting the shore power cable into two sections at the point where it passes through the lower skirting, putting an in-wall male receptacle on the trailer side, a corresponding female socket on the cut end of the shore power cable, and replacing the damaged male plug on the wall power end of the cable.

The shore power cable was never disturbed at the connection to the the converter and the ac wiring to the refrigerator was never disturbed. When the refrigerator didn't activate on ac, I plugged a 110 ac circuit tester into one of the inside ac outlets - it indicated that the hot and neutral legs were reversed.

When the hot and neutral legs were swapped (white to black / black to white) at the shore power cable's wall plug, the circuit tester indicated the legs were connected properly, which is what makes this so puzzling.

The only logical answer would seem to be the one you suggested - that somehow the legs were wired in reverse from the factory. As long as the circuit tester says the reversed legs are wired properly when plugged into either wall power or a generator and the refrigerator and air conditioning work properly, I can't think of anything that would be negatively impacted by leaving it that way.

 

[JackandJanet]

The only potential problem is that you now have a cable that is wired backwards to the trailer and probably internal wiring to the converter that is also backwards. The old "Two wrongs making right" situation. Personally, I'd correct the wiring so that black went to black and white went to white. I'm sure the factory wired your converter backwards, at the internal connections to the AC supply lines.

But, until someone else replaces the converter or shore power cord again, there's no problem having them wired that way.

- Jack

 

[oldcarguy]

Yup, having the cable legs reversed at the wall power end is NOT a good long term solution.

Next time the trailer's home, I'm going to open up the converter and see if the shore power legs are reversed - if they are, I'll correct that issue and swap the leads at the cable's wall plug back where they belong.

If they're not, I'll swap the legs in the wall plug back where they belong, open up the receptacle in the skirting and swap the legs there - that way if the shore power cable ever has to be replaced, there won't be an issue with the cable not matching standard codes. If that winds up being the semi-permanent "work-around", I'll also tape a warning note inside the converter so anyone dealing with it in the future will be aware of the issue.

 

[oldcarguy]

This issue appears to be resolved - and I feel kinda stupid.

Brought the trailer back from storage to have another run at figuring out the issue with the shore power cable and to work on installing an access hatch in the lower front wall (more on that project later). The neighbor's kid was parked in front of our property, so the trailer had to be parked in a different spot than usual, which necessitated using a different extension cord than normal.

After connecting the extension cord and shore power cable (and before opening up the converter), I plugged the 110 v circuit checker into a trailer outlet, and it showed the legs reversed (last thing done in the course of trying to figure the cable issue out was to switch the legs at the trailer shore power cable plug - white to black / black to white - resulting in the circuit checker indicating that the legs were connected properly).

When the circuit checker told me today that the legs were now reversed, I opened up the shore power plug, switched the legs back to their proper positions, plugged back into the extension cord, whereupon the checker said everything was right with the world - which, of course, raises the obvious question - why? Something had to have changed, which is where feeling kinda stupid comes in - turns out the problem was the other extension cord, which had a replacement end put on it years ago - with the black and white leads reversed.

It's the simple stuff that always seems to bite me.

 

[JackandJanet]

*grin* It bites ALL of us, oldcar! I can't even begin to count all the times I've done stupid things that I even knew were stupid at the time, but I did them anyway. In your case though, it wasn't even stupid. Who would guess that the extension cord had been wired incorrectly? I wouldn't have - they're always reliable, right?

The trouble is, most things work fine with the AC power wires reversed, if you don't mind a bit of an electrical shock when using some appliances that is. I don't know, but if you plug in a 3-wire grounded device to such a reversed line, you may not even get the shock.

Anyway, I'm delighted (as, I'm sure, you are too) that you found and corrected the problem and now have a properly wired trailer. Happy camping!!

- Jack