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Author Topic: Reverse polarity on surge protector?  (Read 615 times)

mrshernandez

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Reverse polarity on surge protector?
« on: November 27, 2017, 09:36:38 PM »
We are staying at Soledad Canyon RV park in CA most of the time. We are in a 37 ft class A, and usually plug into a 50 amp site. We have an adapter to use a 30 amp site, and have never had a problem using it at a 30 amp site in other parks.

At this park, every 30 amp site we have plugged into has read "reversed polarity" on the surge protector. Our son is an electrician and he said that is not good, so we have not used a 30 amp site here. However, there are many other class A's plugging into the 30 amp sites with a dog bone. When the campground is crowded, it would be nice to go into a 30 amp site (where it is generally less crowded) but we are afraid of damaging something in our Winnebago.

Any insights as to whether this would be a problem, and why?

Thanks
Kristin
2017 37' Winnebago Sunova 36z
Living for 10-11 months a year in our RV to avoid the cold !

lynnmor

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Re: Reverse polarity on surge protector?
« Reply #1 on: November 28, 2017, 02:26:50 AM »
Using your voltmeter, check the voltage as shown in the meter readings diagram on this page: http://noshockzone.org/accidentally-plugging-into-240-volt-outlet/

If the outlet is reversed, with voltage between the ground and neutral, ask that it be fixed or your money be refunded.  If you find that the outlet is OK, then do the same check on your adapter and replace it with a quality one if you find the fault there.

Rene T

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Re: Reverse polarity on surge protector?
« Reply #2 on: November 28, 2017, 04:43:47 AM »
If you find that the outlet is OK, then do the same check on your adapter and replace it with a quality one if you find the fault there.

The OP said their adapter works fine at other park but I guess it wouldn't hurt to check it anyway.
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lynnmor

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Re: Reverse polarity on surge protector?
« Reply #3 on: November 28, 2017, 07:46:51 AM »
The OP said their adapter works fine at other park but I guess it wouldn't hurt to check it anyway.

I know that it worked before but we need to completely rule it out before confronting the campground owner.  There is also a very slight possibility that the surge protector is giving an erroneous reading.  Of course the electricity will work either way, but safety will be compromised if the outlet is reversed.


 

Gary RV_Wizard

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Re: Reverse polarity on surge protector?
« Reply #4 on: November 28, 2017, 08:01:34 AM »
I don't think the voltage test described at noshockzone will provide any useful insight, especially on a 30A/120v outlet.  Reverse Polarity means neutral and hot are reversed, but the voltage is still correct at 120v (more or less).  The way to test for it is to put a voltmeter between the neutral and ground terminals and test for zero voltage. Then, to double check, put the voltmeter between the hot & ground and check for 120v (or at least somewhere between 105 and 126) (see attached photo).   Easier yet, use a 15A/30A dogbone adapter and plug in an outlet tester and read the lights. No expertise required.  Any home or hardware store will have an inexpensive tester, one like this:

https://www.amazon.com/Electrical-Receptacle-Outlet-Ground-Tester/dp/B0012DHVQ0/ref=sr_1_6

Most things still work when the polarity is reversed, but there are two potential problems:
1. Increased shock hazard
2. Some (few) things are polarity sensitive and not smart enough to verify the input power polarity. Those will either not work or go up in smoke.

I've attached a photo of a 30A outlet showing the proper polarity of the sockets.
« Last Edit: November 28, 2017, 08:05:51 AM by Gary RV_Wizard »
Gary
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Gary Brinck
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Home: Ocala National Forest, FL

mrshernandez

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Re: Reverse polarity on surge protector?
« Reply #5 on: November 28, 2017, 08:18:26 AM »
We are not plugged in to a 30 amp site, we have been using only 50 amp sites at this campground. It is a thousand trails campground, so you can choose your site and move around if you want.

The 30 amp sites are less crowded, so we tried a few of those sites, but the 10 or so we tried all said reverse polarity. When we use the surge protector on any of the 50 amp sites, it does not give the reverse polarity error.

There could be about 45 more 30 amp sites, and we did not try every single one, but we did try different sections of the campground. We see big class A's parked in those spots with adapters, but we are afraid to try it because we do not want to cause damage to our coach.

However, if there is no danger of damage, there are 30 amp sites that are more secluded and we would prefer that if we were confident it wouldn't cause an issue. What would it do to the coach? Would it just not provide the power we need, or would it actually damage some of the wiring in the coach? We have not seen anyone talking about this issue from anyone online so I can't imagine that every coach we see staying in those sites is getting damaged. This is a pretty busy campground so we keep thinking we can't be the only people who have noticed this problem (if it is a true problem at all).

Could our surge protector now be showing an error at every 30 amp hook up we try? It never has before, but I guess that is a possibility. We are moving in a week so we will test it at the next campground to confirm.

Thanks for your thoughts everyone.
2017 37' Winnebago Sunova 36z
Living for 10-11 months a year in our RV to avoid the cold !

John From Detroit

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Re: Reverse polarity on surge protector?
« Reply #6 on: November 28, 2017, 10:28:45 AM »
Your son the electrician knows what he is taliking about

on a 30 amp site; REVERSE POLARITY means the Hot And Neutral (Black and white) Wires are swapped.
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ChasA

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Re: Reverse polarity on surge protector?
« Reply #7 on: November 28, 2017, 10:32:44 AM »
It certainly could hurt something in the coach....YOU.
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Lou Schneider

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Re: Reverse polarity on surge protector?
« Reply #8 on: November 28, 2017, 11:30:51 AM »
You can't get reverse polarity on a 50 amp connection because the two hot leads are already have reverse polarity with each other.  It doesn't matter if the installer is dyslexic, the two hot wires can be connected to either of the two hot pins in the socket and still be correct.

But a 30 amp plug only uses one hot lead and the neutral.  If they are reversed at the outlet, you'll get the Reverse Polarity indication.

The neutral lead is supposed to stay at 0 volts, the hot lead contains the 120 volts that powers the equipment in the RV. 

Technically, since neutral and ground remain separate inside the RV, the plugs and appliances will work no matter which way the incoming power is wired.

The hazard is that appliances are made so that the power switch is on the hot lead and the rest of the appliance is downstream of that, on the neutral side.

With a proper connection, any stray voltages on the appliance are pulled towards the neutral connection at 0 volts so there's no shock hazard on the exposed parts.  If the polarity is reversed, so there's 120 volts on the neutral line, these stray voltages will drift upwards towards 120 volts, creating shock hazards inside the RV if you touch both the appliance and a ground. 

That park has a serious problem with their 30 amp outlets and it needs to be fixed.  You don't need a sophisticated surge protector to detect the flaw, like Gary said a voltmeter or a 3 light polarity indicator connected to a 30 amp adapter will do.
« Last Edit: November 28, 2017, 11:51:21 AM by Lou Schneider »

Gary RV_Wizard

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Re: Reverse polarity on surge protector?
« Reply #9 on: November 28, 2017, 07:23:44 PM »
Quote
You can't get reverse polarity on a 50 amp connection because the two hot leads are already have reverse polarity with each other.  It doesn't matter if the installer is dyslexic, the two hot wires can be connected to either of the two hot pins in the socket and still be correct.

Gosh, Lou, you don't think that dyslexic installer can't hook one of the hot wires to the neutral terminal and a neutral wire to a hot terminal? Or switch ground and neutral?  Never underestimate the human capacity for stupid mistakes...  :o
Gary
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Summers: Black Mountain, NC
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lynnmor

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Re: Reverse polarity on surge protector?
« Reply #10 on: November 28, 2017, 07:31:10 PM »
I don't think the voltage test described at noshockzone will provide any useful insight, especially on a 30A/120v outlet.  Reverse Polarity means neutral and hot are reversed, but the voltage is still correct at 120v (more or less).  The way to test for it is to put a voltmeter between the neutral and ground terminals and test for zero voltage. Then, to double check, put the voltmeter between the hot & ground and check for 120v

That is exactly what the web page shows.

Gary RV_Wizard

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Re: Reverse polarity on surge protector?
« Reply #11 on: November 29, 2017, 06:53:14 AM »
Quote
That is exactly what the web page shows.

Yes it does show that in the meter reading diagram, but the entire focus of the article is on avoiding 240v and distinguishing the old 240v dryer outlet from a 120v RV outlet.  Doesn't try to address outlets that have the correct 120v but reverse the hot & neutral wires. That has to be deduced from the meter reading diagram. I thought that Kristen probably needed a more explicit explanation and "how to".
Gary
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Summers: Black Mountain, NC
Home: Ocala National Forest, FL