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Old 11-17-2013, 05:43 PM   #1
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30 amp "open neutral"

I parked at a site on Saturday night and when I plugged in my Progressive industries 30 am surge protector the 2 red lights came on. According to the instructions this means an open neutral. What is an open neutral on a 30 amp plug. In reading this Open Neutral its seems that it is more of a concern for 50 amp service as stated, If you only plug into 30-amp power you're significantly safer because an open neutral will almost always only result in lower voltage.

Thanks
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Old 11-17-2013, 07:21 PM   #2
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If you had an open neutral on 50 amp RV service you would have immediately introduced 220volts to EVERYTHING on mains power effectively toasting crispy your coach. As a rule never think of plugging in before you plug your little $3 test light in

We have a dis advantage over other brands as our shell is conductive without insulation. In the event of a reverse hot and you are a path to ground by having sweaty feet or being in wet grass.....
Bzzzzzzt you're dead in 1/60 of a second.
This is a deadly serious issue.
For what its worth... a surge protector will do squat to save your life in these cases!
Yes you are much safer from these faults with 30 amp service or split breaker 50 amp.
Be safe out there!
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Old 11-17-2013, 07:30 PM   #3
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On 30 amp there is a positive lead, neutral lead and a ground. The nuetral, or negative, leads electricity back to the electric source. In an open nuetral that lead is not connected somewhere to make a complete circuit. If nuetral and ground get crossed somewhere you can have a hot shell. Keeps out the riffraff though.
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Old 11-17-2013, 07:36 PM   #4
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neutral ground reversal will not cause a hot shell by itself , but will leave you with no protection if an appliance fails and a hot wire comes in contact with the neutral within the device. The lack of a ground could also cause problems if a hot wire came in contact with the ground within the device.
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Old 11-17-2013, 08:49 PM   #5
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The neutral side of an electrical circuit is simply the "return" side. There is no "positive" and "negative" side to an alternating current (AC) Circuit. By definition alternating current in the U.S. is 60 cycle or 60 hertz. 60 cycle current changes polarity "60" times per second.
In a 240 volt system there are 2 "hot legs" and 1 "neutral". I will use the letter "m" to depict the voltage. The letter "m" represents a 240 volt power source (the secondary of the transformer on the power pole) from the utility company.
If you read the voltage between the two outside legs of the "m" you will read 240 volts on a 240 volt system.
If you read the voltage between either of the outside legs to the center leg (or neutral) of the "m" you will read 120 volts or half of the 240 volts.
An RV wired for 120 volt 30 amps is wired in such a way that the letter "m" now becomes the letter "n". Where there is only 1 hot leg and 1 neutral.
If the plug on the shore power cord has three prongs, your RV is wired for 120 volts. It could be 30 or 50 amp.
It is wired like the letter "n". The left leg of being neutral and the right leg being hot.
If your RV has a 4 prong plug on the shore power cord. It is wired for 240 volts. Or the letter "m".
Most, if not all AC devices in RV's are 120 volt. In the larger RV's, such as those with 2 air conditioners, micro waves, washer and dryers. A larger amount of current is required. This the need for 240 volt 4 wire systems. Part of the devices are wired between the left outside leg and the center leg of the "m". The remainder of the devices are wired between the center leg and the right leg of the letter "m". Thus balancing the load.
If there is an electric dryer that is rated for 240 volts. It is only the heating element in the dryer that requires 240 volts. The motor and controls are 120 volts.
If you have a "open neutral" at the source. There will be no return path for any 120 volt device. Since they are all wired with one side being neutral.
An open neutral does NOT mean the 120 volt devices will have 240 volts applied. It means that WITHOUT a return path, the 120 volt device will not work.
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Old 11-17-2013, 09:01 PM   #6
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I beg to differ....
Should you remove the neutral there will most certainly.be 240 volts to the coach.

There are endless accounts of a missing neutral resulting in overvoltage an the destruction of all 110v appliances. Measure L1 and L2 = 240v

I dare you to cut your neutral on 50 amp RV service then plug it in to mains...

Additionally please cite a manufacturer who requires 220 for their product. I do not believe there is a single RV product that is 220 volts.
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Old 11-18-2013, 12:20 AM   #7
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There is 240 volts to the coach. Depending on the coach. Some use the hot legs separately, others have some 240 volt devices, ie electric dryers and perhaps air conditioners.

I rest my case!
http://i1166.photobucket.com/albums/...RVservice1.jpg

http://i1166.photobucket.com/albums/...RVservice2.jpg

Source: myRv.us/electric
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Old 11-18-2013, 07:21 AM   #8
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As I laid my head on the pillow last night. It came to me. That you are correct when it comes to an open neutral on a 240 volt circuit.
Since all of the 120 volt devices are still connected together on their neutral side. With the neutral being open at the pedestal. The full 240 volts would stand across any 2 devices that were turned on or had an inductor on the line side. It would cause component failure of at least one of those 2 components and could occur multiple times because of the difference in the impedance of those devices. Since the 240 volts would not be divided equally as it would be if the neutral was present. One device would see a higher voltage and be damaged.
This damage would not occur on a single power leg 3 wire circuit for lack of a return path.
What would occur is a shock hazard in the case of either circuit in a 3 wire system for sure and the four wire system if the breaker failed to trip. If you were troubleshooting this problem not realizing the neutral is open and happened to get between the neutral buss and the ground buss. You could be electrocuted. Since the voltage of the hot leg would stand at the open neutral.
It pays to check the power source at every location.
Being on this web site makes one think. It is a good place to keep ones mind fresh.
I believe this conversation and what is learned from it is invaluable to those who may not be as familiar with the electrical system in an RV.
SAFETY FIRST ALWAYS
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Old 11-18-2013, 07:29 AM   #9
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I full-time.....
This past year alone my little $3 tester has saved me from at least a dozen reverse hot neutral potentials. I have also seen 2 Streams toasted with the 50amp loose neutral fault.
Indeed we have to be careful!

I personally will stop anyone from just plugging in.... will check for them if they wont!

As I said above we have the extreme disadvantage of a non insulated at the ready fault staring us in the face!

Everyone needs one of these testers and needs to use it religiously.

Hope you didn't loose sleep!

Regards
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Old 11-18-2013, 08:17 AM   #10
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The open neutral occurred when I was out with my 1976 Sovereign, and I plugged the progressive 30 am surge protector in to the 30 amp plug at the pedestal, I did not check the 50 amp source. The Progressive 30 amp surge protector has a green light to indicate the surge protector is on an 2 red lights that light up to indicate open neutral, open ground and reverse polarity. The sequence for open neutral is that both the red lights will be on and that is what I encounter. I had not plugged the trailer power cord in just the surge protector, so I moved to another spot and tested and it was fine. Thanks for the input and information.

In my MH I have a progressive Industries 50 amp hard wired EMS system to hopefully catch these situations.
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Old 11-18-2013, 09:14 AM   #11
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My prior remark holds true to the original poster's condition when only testing a 30 amp service with an open neutral was indicated. I would not have hooked up to it either, as your appliances should not work with a missing neutral. I was referring only to the fact that: a open neutral does not directly cause a hot shell. I carry a tester which I plug into the potential outlet, to check it out, before I waste all my time backing into the site.
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Old 11-18-2013, 09:37 AM   #12
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The simple answer is an "open neutral" is a dangerous situation in both 120V and 220.
The ground is a safety feature mandated by code.

The neutral is used as the return line in 120V 30A should the neutral open the ground becomes the return. Your 120V electrical equipment will work but now there is no safe alternate return path and should you come in contact with the ground you can become the return path and be electrocuted.

A "lot" more serious than low voltage.

The Progressive 30 amp surge protector acts as a safety device and blocks current from passing to the RV.

220V is the same. Ground is for safety and neutral is used to carry the difference in current between L1 & L2 (the hot wires). A lot of damage to your electrical devices with an open neutral on a 220V system and possiable electrocution.
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Old 11-18-2013, 12:45 PM   #13
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Let me tell you from experience what happens at your home when the neutral opens. This happened to me 5+ years ago. It was a fault caused by utility digging that only opened the neutral. It put 240 vac across my 120 circuits. Any electronics that were not separately protected by a surge suppressor were toasted. That included such things as garage door opener, washer and dryer control boards, digital clocks, etc. My refrigerator thermal cutout protected the refrigerator. incandescent light bulbs that were on burned out. I had to replace every surge protector. My work experience was electric utility and I happened to be sitting at the dining table as it happened and ran for the breaker panel to disconnect the house. The utility paid for all damage. If I had not been home, I have no doubt that there would have been a house fire. This would not be the same issue on a 30 amp 120 v circuit as one leg open is only going to assure that no load works.
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Old 11-18-2013, 01:00 PM   #14
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Yup very very bad...
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