power problems

[camprat]

Hi Jimh: May be I help just a little. ON any 120/240 service the two pole breaker is there for the service & services feed overloads & it is a service disconnect too . In your sub-feed power supply (power cords) like rv. You can overload the neutral to. If you loose the neutral on a sub panel or feed to the panel, anything that is on , will go to 240v. IN sub panel the ground & neutral are isolated form each other. What is common in the panel is that both 120 leg us the neutral. So both hot leg will cross-feed through the neutral to what ever on at that time. this give you 120v circuit running at 240V now & lots of smoke. This is why correct wiring is a must with outlet, plug & so on.

[Herk7769]

Originally Posted by camprat

Hi Jimh: May be I help just a little. ON any 120/240 service the two pole breaker is there for the service & services feed overloads & it is a service disconnect too . In your sub-feed power supply (power cords) like rv. You can overload the neutral to. If you loose the neutral on a sub panel or feed to the panel, anything that is on , will go to 240v. IN sub panel the ground & neutral are isolated form each other. What is common in the panel is that both 120 leg us the neutral. So both hot leg will cross-feed through the neutral to what ever on at that time. this give you 120v circuit running at 240V now & lots of smoke. This is why correct wiring is a must with outlet, plug & so on.

I get that the neutral can be overloaded, since it is the same gauge as the hots. What I don't understand is how anything in the camper can go to 240 if the neutral is "lost." Each 120volt leg is on its own circuit.

If you were to lose the neutral/ground in your home breaker box, you would never get 240 on a 120 circuit; the 120 volt circuits would just go dead. The 240 volt appliances would not be affected since they don't use the neutral wire.

Somebody help me here; I am just an out of work pilot who is scratching his head.

[jimh]

i understand abt the neutral and overloading it. that would be the case if u used two 110 v in phase from two different sources. because both 110v legs would use the same nutral. if the two 110v are 180 out of phase, the neutral would only be used if their was an imbalance between the two legs. if u were using exactly the same load on each 110 leg, nothing would flow from the neutral back. (it would flow from one hot thru one load back to the neutral bus then from the neutral bus thru the other load then back to the utility).
the neutral and the ground connect at the same place. the two wires are insurance in case one develops a problem. now once in the home, although the neutral and ground connect to the same place in the breaker box, the ground is used differently at the appliance.

what i am saying is that if, in ur trailer u connect a voltmeter between the two hot legs and get 0, both legs are at the same phase and use the same ground as a return. (you would still have 110 from each hot and ground). this is where u can overload the ground if you come off two sources that are less than 50 amp rated and feed the trailer. the twist is that each of the sources provides its own ground: one will go to the ground lug and the other will go to the neutral of adapted 50 amp socket (one of those boxes with a 50 amp socket that has two 30 amp pig tails coming out to plug into the service. i have one; a box with a 50 amp 4 prong recptical.

if u measure between the two hots and get 220, they are 180 out of phase.

there is nothing in the trailer that uses 220 but this doesn't mean that you don't have 220 coming in.

think abt the service coming from the utility (to ur home), there are 2 wires and a ground. the two wires have 220 between them but most everything in ur home uses 110. now where does that 2nd ground magicly come form...yes there is an earth ground from a rod in the ground that goes to...the neutral bus. if you doubt this, pull the cover off the breaker box either in ur house or in the trailer. the white wire and bare wire goes to the same bus.

the disagrement seems to be between wheather there is 220 coming into the trailer. it can be either but nothing in my 2002 uses 220. its all 110.

110 in ur home or in the trailer is the voltage between the hot leg (either one) and ground. ur home is supplied by a 220volt center taped transformer. the center tap is tied to ground. that gives u 110 from each hot coming into ur home and 220 between the two hots.

if u say a trailer can't run on 220. i would say the applinces can't but with a 50 4 prong service, it can have coming into the breaker box.

[jimh]

Originally Posted by herk7769

I get that the neutral can be overloaded, since it is the same gauge as the hots. What I don't understand is how anything in the camper can go to 240 if the neutral is "lost." Each 120volt leg is on its own circuit.

If you were to lose the neutral/ground in your home breaker box, you would never get 240 on a 120 circuit; the 120 volt circuits would just go dead. The 240 volt appliances would not be affected since they don't use the neutral wire.

Somebody help me here; I am just an out of work pilot who is scratching his head.

what will more likely happen here is that nothing will happen in the trailer but if u are standing, touching, or come in contact with the ground (or a ground outside the trailer) and touch the trailer, u will become that 110 path back to ground..the same can happen with a 30amp service that is only 110 and u loose the return path.
the reason 220 would still work normally (probably woudn't because something would keep it out or balance) is because 220 flows from one hot thru the appliance and back to the other 220 hot. the ground doesn't play a part in this circuit.

[jimh]

i'll give u an example of ground loss to a home. i had one that the wire to earth ground had been cut with an edger probably years before. one day i got a call abt lights getting brighter when the heater came on. i had a convinent 220 recptical and checked the voltage between the two hots...240. when i checked the voltage from each hot to ground, one was 100 and the other was 140. the neutral from the utility had developed a poor connection coming to the house. the utility came out and recrimped the ground and all was well.

if i had gone out and grabbed the cut earth ground, i would have been used to pass current to try and get the neutral back to zero.

my statement in a previous post stating that u would complete the 110 to ground was more example than accuracy. the actual voltage is going to depend on how much voltage mismatch u have at the neutral.

the neutral and ground may attach at different points in some boxs but they aren't isolated from the box and they are not isolated at the home breaker box. do an ohm meter check between the ground and the neutral...u should not get an open.

from what i'm reading, i'm not differing from some of the other post except on the neutral and ground. the only time there is really a difference is when they attach at the appliance.

[Herk7769]

I think I understand now the process of how a 240 ganged breaker (one leg from each phase) will not be able to overload the neutral.

Your explanation gave be a big "Duh" moment as "I knew that"

Even though there are 50 amps "available" on each leg, since one leg is "high" when the other is "low" due to 180 out phasing, it is not possible for there to be 100 amps returning to ground through the neutral.

If the 2 legs of the service connection are "fed" from the same 110 phase coming in to the house through two 50 amp breakers (like across from one another or skipping a blank on the panel) it would certainly be possible to have, potentially, more than 50 amps on the neutral. In this case a properly sized ground (green) wire would hopefully carry the "extra" since they originate and terminate at the same place.

I now get the danger of a missing neutral/ground as well. Since travel trailers have no "earth ground rod" they are all grounded to the frame of the trailer.

If there is no neutral/ground available for whatever reason, how the hot legs are sourced becomes critical.

If both are the same phase, nothing works. However, the real danger is someone "completing the circuit" by touching the frame while standing on the ground. ZAP!

If they are sourced from two different phases (240 total line voltage), it is "smoke city" as there would be 240 volts passing through the converter instead of 110.

(Left plug leg -> left hot breaker -> appliance -> ungrounded neutral buss -> appliance -> right hot breaker -> Right plug leg).

Did I get that right?

[jimh]

i know that "duh" feeling well. i have personally experienced it a lot.

i believe u have the concept. ground or partial ground problems can create all sorts of unsafe or unusual circimstances. i kind of look at electricity like i do propane escaping to the atmosphere: you have to assume that it will find a source of ignition; open or bad ground/neutral, u have to figure the electricity is going to complete the circuit somehow.

[Herk7769]

There was a line in one of the Jurassic Park movies.
"Life will find a way"

[camprat]

Jimh & herk7769 your right to say 120v same phase would read 0v across And you don't have the problem of 240 when losing the neutral, but if you have a two 50amp same leg you can overload the neutral as much as 40-50 amp. But the rv & panel makes are now using the 120/240voltage. this way they can balance the loads & get more out of a 50 amp services. Yes it still for the most part 120v circuits , but they will have 240 coming in to the trailer. I have seen some of the new rig have 240 dryers. And if you think about it 240v is 0 load on the neutral. They where behind on getting the panel size big for more spaces . This is all coming. Your house is mostly 120v circuits, with the high loads 240volt.
What I see is the confusion in the wiring of the isolated neutral & ground & why it like that.They confuse it with the old way of wiring.

Now all being said. I have see single pole 50amp with the newer 120/240 plug, but there use only one hot leg with a single pole main in the RV. This keep the problem of overloading the neutral,cord plugs & outlets from happening. The park RV service 50amp 2-pole will trip if any or both legs overload.

[jimh]

Originally Posted by camprat

Jimh & herk7769 your right to say 120v same phase would read 0v across And you don't have the problem of 240 when losing the neutral, but if you have a two 50amp same leg you can overload the neutral as much as 40-50 amp. But the rv & panel makes are now using the 120/240voltage. this way they can balance the loads & get more out of a 50 amp services. Yes it still for the most part 120v circuits , but they will have 240 coming in to the trailer. I have seen some of the new rig have 240 dryers. And if you think about it 240v is 0 load on the neutral. They where behind on getting the panel size big for more spaces . This is all coming. Your house is mostly 120v circuits, with the high loads 240volt.
What I see is the confusion in the wiring of the isolated neutral & ground & why it like that.They confuse it with the old way of wiring.

Now all being said. I have see single pole 50amp with the newer 120/240 plug, but there use only one hot leg with a single pole main in the RV. This keep the problem of overloading the neutral,cord plugs & outlets from happening. The park RV service 50amp 2-pole will trip if any or both legs overload.

I have to make a correction to my earlier post reguarding the neutral and the ground. i was thinking abt the main. the sub panel is different.
The ground goes to the case of the breaker box in the trailer and stays isolated all the way back to the main panel (the one in the house). the neutral is also isolated from the ground and stays that way all the way back to the main panel. this would probably mean u wouldn't get shocked if u lost the neutral in the trailer but i wouldn't trust that...if it can go wrong, it will.

my problem comes from thinking as a sub panel as being wired just like a main panel. it isn't. i am going to try and post a picture of my panel showing the isolation. an ohm meter confirms that they are isolated.



50 amp adapter using 2 sources. ground passes thru as ground to round pin of 50 amp socket, hot from pig tail one passes to right side of socket, the other to left. neutral passes thru to top spade pin of socket. neutral, each hot, and ground stay isolated all the way back to main box.




50 amp panel in trailer. neutral to left is isolated from case. upper all the bare wires from the circuits, the ground from the service, all attach to the case. the two hots are red and black...what i would expect in a 220 circuit, if the service provided is 220 it will carry thru to the breaker box (trailer) even though nothing on the above uses 220. if ur service is 220 u can run up to 50 amps thru each circuit. if u are adapting, the neutral is going to be ur restriction.
the ground in this photo appears to be #10 to me. i useto be able to look at wire up to #6 and identify it, i don't fool with it enough to do that now.

i appreciate u pointing out my error.

[camprat]

On problem! I was dealing with isolated ground & neutral about ten year in NM before NEC put in place. Now I can't think of any new use where the neutral used as ground beside a main services. The old day you had 220v with neutral, now it 240v with ground, IF you have neutral it the 120v/240. Your new rang , dryer, & trailer cord are 4-prongs . That is why I hate to hear someone post that they are changing a hot tub or a old rang to work as a 50amp 120/240 service. There go the ground, It can kill them. That is why I posted Confused ?

[Herk7769]

I think I will stick with my 30 Amp camper. My poor brain is fried.

[camprat]

If WE just get people thinking About Rv services when it come to the 120-240volt 50 amp. maybe it will keep somebody from smoking his rig, by not knowing or shortcuts. I'm a happy camper

[jimh]

Originally Posted by camprat

If WE just get people thinking About Rv services when it come to the 120-240volt 50 amp. maybe it will keep somebody from smoking his rig, by not knowing or shortcuts. I'm a happy camper

i'm hearing abt arc preventers (or something tt sounds like tt. will trip in case of an arc)? we were at a park near glasier and they showed us a pig tail used to adapt i believe 30 amp to 50 it could have been the other way around but it plugged into a socket for the service at the trailer. the contacts in the socket were melted. the insulation looked ok. they were using it to demonstrate the perils of using adaptors. what i saw looked like poor contacts causing an arc that melted the contacts rather than something wired wrong (the problem develepoed later in the night farther making me believe not a wiring issue). the insulation on the pig tail showed no signs of overheating (weren't discolored, brittle or anything). it wasn't the rver's first time to use the adapter and it appeard to be comercially made.

if there really is an arc fault interupt out there, would it work by installing on the service between the pedistal and the rv? looks like something like that could have sensed the arc and shut down the circuit.
i see discussions abt autoformers here also. i'm under the impression that most everything in the trailer will take a 10% swing without damage.
an autoformer is nothing more than a single wound transformer that has multiple tabs above and below one of the input points. the other side remains at ground and that carries thru to the trailer. apparently they have circuitry within that switches between these taps to give a more uniform output. are they really a nescessary addition to the trailer? what is the worse voltage swing ur encontered?
surge suppresion, i can see the need for that a little more...large loads droping out will cause spikes (like water pressure build up if u have a large flow and shut it down velocity changes to pressure). lightning causes interesting problems...i've had a clock knocked out at home and nothing else touched. i'm trying to figure where u would encounter spikes at a campground unless one is simply plugging in ur rv or the a/c (urs and everyone elses cutting in and out).
i haven't priced anything but can't see a surge supressor costing that much. an autotransformer, looks like it would be expensive because of the size of the windings needed to carry the load. i'd need to see a schematic (or maybe just a wiring diagram) to see how they can take 110 or 220 input and give the desired output. it is easier for me to see using 2 autoformers.
looks like a 50 amp one would be heavy and run warm.
looks like the electronics tied to the output of the converter would have a layer of protection already from the battery (like a large capacitor).