Fixing AC polarity issues.

I acknowledge that many of you will never have the need to do a modification like this one to your TC. If you only connect to mains power at your home or at an established RV park, you will most likely be connecting to a correctly wired (30A) electrical outlet.

However, in my case, I never-ever stay in RV parks or campgrounds and I get my AC power when and where I can find it. In addition, my TC's mains power cord has been modified and now has a NEMA 5-15 plug on it, rather than a traditional 30A RV plug. For example' A few weeks ago it we stayed at a rustic site at Lake Santa Margarita park (near San Luis Obispo, CA,) and last week we camped at a private summer camp near Guernville, CA... at both locations the electrical outlets ware incorrectly wired with a hot/neutral reverse. As it turns out, about one-third of the places where I choose to use mains power the outlets are incorrectly wired, and my beeping inverter and AC circuit tester are quick to point out the problem to me.

For the past year or so I have been remedying the issue by manually re-wiring a small jumper-cord between the outlets and my mains plug. However I have finally had enough of this wiring and re-wiring and I decided to fix the issue in a way that was easiest for me.... So I installed a 20A double-pole double-pole switch (in place of my previous single-pole-single throw switch) so that I can now correct polarity issues from inside the TC. In addition, I installed an AC polarity tester at the switch location so that I can verify polarity before closing the switch.

Here's a few photos of the install:

Switch is a Hubbel HBL1386I

Drilling switch wall plate to accept neon indicator lamps

Indicator lamps installed

Circuit board assembly

Final switch and polarity indicator assembly. Switch UP is normal polarity and Switch DOWN corrects a hot/neutral reverse condition. The center position is off.

Of course this type of polarity test lamp cannot test for all wiring issues. For example, it cannot detect a bootleg ground (nor a reverse bootleg ground), but that is a much more uncommon situation than a hot/neutral reverse or a floating neutral/ground.

Cheers,
-Mark

Truck Campers

Cannon_George
Explorer
Aug 24, 2015
This is a great project. Note that the switch specified Hubbel HBL1386I is "Center off," this provides the "break before make" closure (otherwise you might see sparks fly!)

I learned once the hard way that Norcold refrigerators won't work properly on AC if the hot/neutral leads are reversed - another reason to support this project if you encounter this condition with AC......
2oldnslow
Explorer
Aug 24, 2015
RickW wrote:
msiminoff wrote:
Gripnriprod wrote:

Another solution might be to carry a well marked reverse polarity extension cord about 1 foot in length. Deploy only when needed.

I like that idea! :)

I have not seen reversed polarity (yet), but then I seldom plug in.
bigfootford
Nomad II
Aug 24, 2015
Added this to my todo camper bucket list.... Nice mod!

I always check shore power plugs prior to plugging in....
Only seen a problem of reverse polarity one time.... I went around to the empty sites to check. Went to the office and told them.... They probably never did anything about it...

Thanks for the IDEA!

Jim
azrving
Explorer
Aug 23, 2015
msiminoff wrote:
RickW wrote:
A concern I have is the ease of access to your switch. If I were a curious 12 year old, I would flip the switch to see what happened.

My 10 year old son know's what the switch does, he understands AC and DC polarity, and he can interpret the indicator lamps using the little chart above the switch.
IF he ever did flip the switch (he won't, but I might accidentally), nothing would happen... except the inverter/charger would beep-beep-beep indicating that the hot/neutral were swapped.

rjxj wrote:
1/3 of the places seems like a surprisingly large number. Do you trust their water?
Yep, it's shocking how often I encounter this. But again, I don't stay in campgrounds.

NO! I don't trust the water! As a matter of fact I'm far more vigilant about where I take on water than where I get ac power.

-Mark

I seldom plug in so power isn't an issue but I started using a Berkey filter when I considered how many places I get water from. Things get wired wrong, things get plumbed wrong.
msiminoff
Explorer II
Aug 23, 2015
RickW wrote:
A concern I have is the ease of access to your switch. If I were a curious 12 year old, I would flip the switch to see what happened.

My 10 year old son know's what the switch does, he understands AC and DC polarity, and he can interpret the indicator lamps using the little chart above the switch.
IF he ever did flip the switch (he won't, but I might accidentally), nothing would happen... except the inverter/charger would beep-beep-beep indicating that the hot/neutral were swapped.

rjxj wrote:
1/3 of the places seems like a surprisingly large number. Do you trust their water?
Yep, it's shocking how often I encounter this. But again, I don't stay in campgrounds.

NO! I don't trust the water! As a matter of fact I'm far more vigilant about where I take on water than where I get ac power.

-Mark
RickW
Explorer III
Aug 23, 2015
msiminoff wrote:
Gripnriprod wrote:
So, where in the circuitry did you place the DPDT switch?

The DPDT switch is in the mains cord... before the inverter/charger. The circuit tester is wired to the input of the switch, so it will indicate an issue prior to me turning it on.

Yes of course, this does mean that I am responsible for placing the switch in the center (OFF) position prior to plugging in the cord to mains power, but this is still a big improvement over the setup I previously had.

Here's a simplified wiring diagram;

It was not apparent to me at first that your switch had a neutral position, but electrical is not my native language.

A concern I have is the ease of access to your switch. If I were a curious 12 year old, I would flip the switch to see what happened. :E

Another solution might be to carry a well marked reverse polarity extension cord about 1 foot in length. Deploy only when needed.
azrving
Explorer
Aug 23, 2015
1/3 of the places seems like a surprisingly large number. Do you trust their water?
Gripnriprod
Explorer
Aug 23, 2015
Thanks for clarifying this. With every mod like this there are a set of "operating instructions". Again, a great mod.
msiminoff
Explorer II
Aug 23, 2015
Gripnriprod wrote:
So, where in the circuitry did you place the DPDT switch?

The DPDT switch is in the mains cord... before the inverter/charger. The circuit tester is wired to the input of the switch, so it will indicate an issue prior to me turning it on.

Yes of course, this does mean that I am responsible for placing the switch in the center (OFF) position prior to plugging in the cord to mains power, but this is still a big improvement over the setup I previously had.

Here's a simplified wiring diagram;
Gripnriprod
Explorer
Aug 23, 2015
So, where in the circuitry did you place the DPDT switch? The instant you plug in you will have a current path to your camper's equipment unless you have placed the camper A/C isolation switch in the "off" position. Or am I missing something?

BTW, what a great idea and nice execution!