Power Line One Panel Limits One Leg 50 Amp circuit to 30 Amps

[SteveG]

Another lesson learned! We registered at the KOA camp in Stark, Fl requesting 50 amps. We had an early afternoon appointment so had to hustle to get our 2004 36G Journey set up. So instead of checking the one panel after I initially plugged in and the Surge Guard activated power, I completed the setup and then noticed that the One Panel read 30 amps.

So I went to the office and asked the fellow who registered us if he would check our power for a problem and he turned to another guy who said, "You must have a Winnebago with a PowerLine panel?"� He then went on to explain that the site I was on was wired for 50 amps with a single leg (phase). He said that RV's without PowerLine, such as a Prevost, have no problem with this single leg 50 amp setup.

Having recently read a post about incorrectly wired electrical service, I protested. He said their electrical installation passed electrical inspections and used #4 aluminum wire so the wire was designed to carry 50 amps. He offered to move us to a site with two leg power but by then we were out of time so we stayed put.

Since this was a good learning opportunity I used Don's advice from his 06/21/07 post in how to measure for 220V which would be available if two legs were used to provide 50 amps service vs. 110V if only one leg is provided. The check is easy enough. To use Don's words, "Take a volt meter and check the voltage across the 2 hot terminals in the receptacle. If it reads 220V its OK; if it reads 0 volt it's not wired correctly."� And zero volts is what it measured.

Don also explained the potential problem of a single leg being used for a 50 amp service. "When the 50A service is wired incorrectly with both hots coming from the same leg (phase) from the panel, this is actually a dangerous condition which can overrate the neutral wire, as the two hots amperage will be additive to the neutral wire, and you will over-current the neutral and possibly cause it to overheat, melt and other bad things.'

So I think I have to conclude that the KOA design must have accounted for the additive amperage? Since the PowerLine panel is designed to turn on or turn off its load shedding capacity based on the presence of 220V, the design assumes that an 110V circuit would be designed as 30 amps. It also seems to me that the PowerLine panel protects the Park owner from themselves?

So next time I register at an RV Park I am going to ask the question, "Does the 50 amp circuit have a single or double leg?"� Might get some interesting responses...

[SteveG]

Another lesson learned! We registered at the KOA camp in Stark, Fl requesting 50 amps. We had an early afternoon appointment so had to hustle to get our 2004 36G Journey set up. So instead of checking the one panel after I initially plugged in and the Surge Guard activated power, I completed the setup and then noticed that the One Panel read 30 amps.

So I went to the office and asked the fellow who registered us if he would check our power for a problem and he turned to another guy who said, "You must have a Winnebago with a PowerLine panel?"� He then went on to explain that the site I was on was wired for 50 amps with a single leg (phase). He said that RV's without PowerLine, such as a Prevost, have no problem with this single leg 50 amp setup.

Having recently read a post about incorrectly wired electrical service, I protested. He said their electrical installation passed electrical inspections and used #4 aluminum wire so the wire was designed to carry 50 amps. He offered to move us to a site with two leg power but by then we were out of time so we stayed put.

Since this was a good learning opportunity I used Don's advice from his 06/21/07 post in how to measure for 220V which would be available if two legs were used to provide 50 amps service vs. 110V if only one leg is provided. The check is easy enough. To use Don's words, "Take a volt meter and check the voltage across the 2 hot terminals in the receptacle. If it reads 220V its OK; if it reads 0 volt it's not wired correctly."� And zero volts is what it measured.

Don also explained the potential problem of a single leg being used for a 50 amp service. "When the 50A service is wired incorrectly with both hots coming from the same leg (phase) from the panel, this is actually a dangerous condition which can overrate the neutral wire, as the two hots amperage will be additive to the neutral wire, and you will over-current the neutral and possibly cause it to overheat, melt and other bad things.'

So I think I have to conclude that the KOA design must have accounted for the additive amperage? Since the PowerLine panel is designed to turn on or turn off its load shedding capacity based on the presence of 220V, the design assumes that an 110V circuit would be designed as 30 amps. It also seems to me that the PowerLine panel protects the Park owner from themselves?

So next time I register at an RV Park I am going to ask the question, "Does the 50 amp circuit have a single or double leg?"� Might get some interesting responses...

[Hitchhiker]

Actually, with a CG wired in that manner, you'll only have available half of the amount of power as you would have if it were wired as a conventional two leg circuit and may be at risk of tripping the CG's 50 amp breaker. For example, on my trailer, I have two heat pumps and each will draw about 16 amps on separate legs when running. My refrigerator will draw about 10 amps, the electric water heater draws another 10 or 11 amps. If we run an electric coffee pot and maybe turn on the microwave... I think you can see where I'm going with this.

I could easily be drawing 50, 60, or more amps and that single circuit wiring just isn't going to handle the loads. I have my doubts that it was actually passed by a competent, licensed building inspector who wasn't biased in favor of the CG.

[DriVer]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by SteveG:
Another lesson learned! We registered at the KOA camp in Stark, Fl requesting 50 amps. </div></BLOCKQUOTE>Interesting! We've camped there several times in the past. I run a 50A Surge Guard and if it trips shut I usually feel comfortable with the power that I have.

I'll be sure to keep an eye on that if I camp there again. We did find a nice campground up on the 295 loop West of Jacksonville, Flamingo Lake.

Nice pull throughs and all new service equipment on unique looking pedestals that almost look like pagodas.

[Hillbilly2]

Hitchhiker, you are incorrect on the assumtion that you will have only half the power with that setup, the breaker only "sees" current, not voltage. You still can have 50 amps flowing on each leg, but you will have 100 amps flowing on the neutral, which is the dangerous part in which the wire would overheat. The exception to this is if they are useing a single pole breaker and jumpering the hot over to the other side of the receptacle. The only reason that I can think of why they only have 120 volts available is they ran three conductor wire instead of four conductor to the pedestal. Usually a larger feeder cable is run through the campground (200-400 amp capacity) then is split off at each pedestal, reduced down to the needed ampacity. As for inspections, unless its just obvious, most inspectors don't have the time or are unwilling to look at the installation that close. The Power Line One panel correctly detects this condition, and keeps the wiring from being overheated.

[Gary RVRoamer]

If you go to enough different places and check the wiring, you will find most every possible combination on a 50A receptacle. I've seen 220V with as little as 40A or 30A per leg and I've seen 30, 50 or 50A @ 120V feeding the two hots from a single source. And I've seen a 30A and a 20A masquerading as a 50A by feeding one hot from each (just like the "cheater boxes" do when you want 50 and only have a 30A/20A hookup). That's actually not too bad - most everything works fine and there is no overload on the neutral.

My American Tradition with its Smart Energy Mgmt System will read the power situation just like the Winnebago does, reporting it as a 30A hook-up and managing the load to match.

[John_Canfield]

I've seen just about everything like Gary in the above post (including an RV park in Alaska where the power was supplied by a large generator with a varying line frequency), but only one time in 30K miles of camping I found a 50 amp receptacle obviously wired wrong where there was only 30 amp indicated by my EMS.

Ironically it was near Gary's home base at Salt Springs!

Low voltage and low current are so common it's not even worth talking about

[Harry B]

Steve,

A single phase 50 amp service can be a legal configuration. However, if the EMS only sees one leg powered, it functions as if you have 30 amp service available and will shed loads to not exceed 30 amps as designed.

This only means that you are limited to drawing 30 amps of power on a circuit capable of supplying 50 amps. (saves on the electric bills for the campings).

You need both legs powered, to have the EMS indicate that you have 50 amps of service available, which if wired as such really means you have 100 amps available, (50 amps via each leg). Our coaches use each leg for 120 VAC at 2x 50 amps=100 amps and not 240 VAC at 50 amps, which is how 50 amp dual phase wiring is typically used. This is just something unique due to the wiring of motor homes.

A good indicator if wired properly or not would to determine if the circuit breaker at the hookup pedestal is a 50 amp single gang or 50 amp dual gang breaker. If it is a single gang breaker and it has the correct wire size feeding it, it is wired properly. On the other hand if you have a dual gang breaker and only a single leg powered, you have a problem.

I am just not sure if electrical code requires a different plug for single phase 50 amp service or not.

[Hillbilly2]

Actually it is not considered "Dual Phase" even if it's derived from a three phase system. It is still single phase even with both "hots" present. There is a thing called two phase, but it is as rare as hens teeth, and has not been used in this country for a long time. Most rural campgrounds are single phase 120/240. Yes, there are some real creative power systems out there!

[Pusherman]

Assuming the KOA in question ran 2 hot lines to each side of the RV receptacle, but both lines ran to a single 50A breaker (single pole) the setup would be 'safe' but I'm not sure it's legal. In this case, the amperage would be limited to 50A max, which would not overrate the neutral line.

The One-Place panel reads voltage to determine whether it's a 50A or 30A service. If it reads 220V across both legs, then it allows 50A. In the case above, the device only senses 120V and limits to 30A usage by shutting down devices, as if it were plugged into a 120V 30A shore service.

When wired correctly, a 50A service is actually a 220V service, even though the motorhome only uses 120V devices, and yes, you have 100A load capacity in this situation. These services are always 'fused' with a 50A double pole breaker which guarantees you're getting power from both legs of the panel, which are 180d out of phase with each other, which cancels on the neutral amperage, thus not overrating the neutral line.
Note, this assumes the pedestal's source is truly 220V power from 2 separate legs of the main power supply.

The test I described in Steve's original post still applies.

[SteveG]

We returned today from the KOA-Stark no worst for the wear and a lot better educated. Thanks to all for your replies. We watched the One Panel shed the loads as needed and we had a pleasant stay.

Since the Power Line One Panel protects our Motorhomes from a single phase wiring by limiting the amperage to 30 amps, what happens to the MHs that do not have the Power Line One Panel? As their current draws exceeds 30 amps possible exceeding 50 amps is the Motor Home at risk or just the camp wiring?

[Hillbilly2]

If the breaker at the pedestal is a single pole it will just trip, resulting in power loss to the MH. If it is a two pole, the power cord on the MH will start heating up, depending on the overall load. Prolonged overloading could damage the pedastal receptacle, plug on the cord and/or the distribution panel in the MH. Full load would likely be only temporary, most people would not have everything on at one time, at least not for an extended period of time.

[Jackm]

Hillbilly2,

Your responses suggest that you know more about electrical systems than most. I hope you keep contributing to this forum. Thanks.

Jack

[SteveG]

Trying to understand the RV electrical system I found the following paragraph from Progresive Industries Surge Guard:

"RV wiring is different than the wiring found in homes. The neutral and ground wires are isolated in an RV. In a home they are tied together at the service panel. The reason, homes have a bonded ground system and RVs do not. Therefore never bond the neutral and ground together for any reason. This will create a ground fault condition and may result in electrical shock and/or fire hazard."

Why are home and RV power supply circuits designed differently?

[Hillbilly2]

Code considers the neutral a hot wire, even though it is common with the ground. For practicality, the ground and neutral are bonded together at the service disconnecting means.(first breaker past power company meter) Which on older houses the main is also in the panel, so the grounds and neutrals are allowed to be connected together. In newer houses, the main is on the outside to allow firemen to safely turn power off to the home without entering it during a fire. This setup requires the neutral and grounds to be seperate in the panel, because the service disconnect is not in the panel. The reasoning behind all of this is,that if the neutral is being used as a ground also, that if for some reason it becomes disconnected or broke, everything grounded with it would become live to ground creating an electrocution hazard. If they are separate, and the neutral is broken, the shock hazard is greatly reduced. usually the circuit just quits working if its only suppling 120 volt loads, or with the case of 120/240 volt loads creates wild voltage swings destroying electronics or other equiptment. The RV neutral and the ground are bonded together, but not at the RV, but back at the power company service.

[SteveG]

Hillbilly2, thanks! I think I am finally understanding ground vs neutral. I think of "bonding"� as interconnecting all exposed non-current carrying metal objects together so that any fault currents in the system will not produce dangerous voltages which could cause an electric shock. And I think that I easily confuse "bonding"� with an "equipment ground."�

But I did find a pretty explanation of why RV's have neutral isolated from ground.
From: http://www.coachrepair.com/info1.html

"The big topic is safety mostly concerning the use of extension cords to connect your RV to a source of power. It is always stressed that you use a proper 3-wire extension cord of appropriate size "Wire Gage". The ground prong not only connects the RV to ground at the power source it also aligns the other prongs as to be in proper polarity. Now one of the most important things about the internal wiring of a RV is that the neutral wire is floating, or in other words is not connected or "Bonded" to Ground. One of the reasons why is that if anything were making a connection between the RV's ground and neutral circuits and the polarity of the extension cord was reversed, or that the polarity of the source power was reversed, the RV would have a HOT SKIN condition or meaning that anything connected to electrical ground via the wiring including the vehicle chassis the siding if metal, door frames, etc. could be on the Hot or dangerous side of the 110-volt. This is aggravated by how well the tires insulate the RV from earth ground. This scenario may seem a little far-fetched but Hot Skin conditions happen and there is still a lot of backwards wiring out there. When planning any electrical switching for your RV always switch the Neutral as well as the Hot or "Hots". In most cases the internal wiring of your properly installed onboard Genset has its Neutral bonded to Ground. This case the source ground "The Genset", and the RV Ground is electrically the same."�

[Hillbilly2]

Sounds like your getting a pretty good grasp on it, One of the differences between a ground and neutral is that a neutral normally carrys current or the unbalanced load (120/240 systems) to where a ground only carries current during a fault. There is a nice thick chapter on grounding and bonding in the code book, it's all for safety.

[SteveG]

Thanks for reminding me about the code book. A friend of mind loaned me his old books: NEC 1993 & 1996. I suspect there have been changes. But there is a section 550 that deals with mobile homes and mobile home parks. This read will probbaly create more questions then answers. But maybe I'll expand the old brain!