50A trailer, 30A cord, 50A pedestal

[ependydad]

Originally Posted by LegacyFB38

A small, custom adaptor with a 30 amp breaker plugged into the 50A pedestal sounds like a viable solution.

Wouldn't it be safer to put the adapter at the camper vs. the pedestal?

If it's at the camper, it'll shut down power before it tries sucking it through the cord.

If it's at the pedestal, the cord is already carrying > 30amps.

But, I guess the time to trip the breaker is minimal and shouldn't be a problem. So the position is more likely theoretical than anything.

[dbledan]

Just a thought and not sure if it would cover you but would putting a 30A surge suppressor resolve the concern of drawing more than 30A and melting the cord? I am not sure if these have breakers in them or not.

A EMS would also tell you the draw and I assume it would not allow you to pull more than 30A if it was a 30A EMS.

Anyone know for sure if the surge guards have a breaker in them? Seems simple.

[LegacyFB38]

Originally Posted by ependydad

Wouldn't it be safer to put the adapter at the camper vs. the pedestal?

If it's at the camper, it'll shut down power before it tries sucking it through the cord.

In my mind, placing the custom breaker/adapter closest to the source (e.g. pedestal) is safest. That way, if any thing caused greater than 30A draw (cord damage for example) everything after the breaker will be protected by the breaker.

[LegacyFB38]

Originally Posted by dbledan

...Anyone know for sure if the surge guards have a breaker in them? Seems simple.

Good question.

I know little about the EMS (this will be new to me in our new coach). Here is a section I copied from a manual:

"Midi-PCS automatically senses 0VAC between L1 and L2, and 120VAC between L1 and
Neutral, to determine 30A Service. The I/O Module has a current sensor which monitors total
RV current. When the current exceeds the 30-amp limit, the Midi-PCS will limit current by
shedding appliances that it controls. Once the RV current has dropped, the procedure will be
reversed and power will be restored to the shed appliance."


Interesting! It will not be trivial to wire up the circuits to be shed, and I think there is a limit as to the number of circuits available. Lastly, the EMS is not an actual circuit breaker...my gut is that it should not be used as a surrogate circuit breaker, but as an accessory to a RV currently wired with appropriate circuit breakers.

[Evereddie]

I don't have 50 amp camper but from what I have read here on this forum 50 amp setups only put the second air conditioner on the second leg? Do they really divide up the loads to be equal on both legs like appears to be the discussion here?

[CHICKDOE]

yes, the loads on a 50 amp panel are split between the two hot legs. of course it is not perfect and not all loads will be on at the same time. typically the heavy loads (the two air conditioners) are split between the two hot legs.

[doc73]

Yes mine are split mostly.. We added the second ac so it is now balanced.

[jessa82]

Originally Posted by doc73

you did... my apologies. I saw 30amp and my head just ignored the whole double part... but yes he'd be able to pull 60amps total (30 from each "leg") so still overloaded.

A 30 amp cord is rated for 30 amps on each leg.

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[jessa82]

Originally Posted by jessa82

A 30 amp cord is rated for 30 amps on each leg.

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My apologies. I just looked up wiring for a 30 amp RV and it's not each leg as there is only one, although on a 50 amp it is 50 on each leg.

I am an electrician and have noticed that most people don't realize the amp rating refers to each leg. So if you have a 100 amp 240-volt service on your home, you actually have 2 legs that are each rated up to 100 amps.

[CHICKDOE]

the original issue has pretty well been beaten to death. do not use a 30 amp cord with only 50 amp breakers in the circuit. there were also comments about making your own little junction box and putting a 30 amp breaker in it. that would work, the breaker would limit circuit flow to 30 amps. then there was a discussion about whether this 30 amp breaker should be at the pedestal or in the trailer. it doesn't matter. the amps flowing in a circuit (cord) like this will be the same at each point in the circuit. wherever the circuit breaker is located it will see the amps flowing in the circuit and if they exceed the rating of the circuit breaker, it will trip. thus the circuit is protected from an overload regardless of where the circuit breaker is located.


I am not an electrician but I have to take exception to the last comment about a 100 amp 240 volt circuit. my understanding is that this would have a 100 amp double pole breaker in the circuit on both of the hot leads. the breaker will trip should either hot lead exceed 100 amps. the circuit flow is down one hot lead and up the other. this circuit provides up to 100 amps. this is the way electric stoves and dryers are wired (at 30 amps). the older ones do not have a neutral wire. newer circuits for these devices do provide a neutral wire but the power flow is still down one leg and up the other. its when we get to the 50 amp rv world that we actually use the neutral wire to carry power as a split phase circuit.

[doc73]

Originally Posted by jessa82

My apologies. I just looked up wiring for a 30 amp RV and it's not each leg as there is only one, although on a 50 amp it is 50 on each leg.

I am an electrician and have noticed that most people don't realize the amp rating refers to each leg. So if you have a 100 amp 240-volt service on your home, you actually have 2 legs that are each rated up to 100 amps.

Way off topic here but it's funny you said this.. I do not call you out for shame but even owning an rv you were not sure how to wire an rv plug (no disrespect to you). It should be a good psa to really MAKE SURE your electrician is aware of the proper wiring. This time a year it seems at least once or twice a month someone blows up their rv electronics from a 12030amp service wired at 240.

[5picker]

Originally Posted by CHICKDOE

the original issue has pretty well been beaten to death. do not use a 30 amp cord with only 50 amp breakers in the circuit. there were also comments about making your own little junction box and putting a 30 amp breaker in it. that would work, the breaker would limit circuit flow to 30 amps. then there was a discussion about whether this 30 amp breaker should be at the pedestal or in the trailer. it doesn't matter. the amps flowing in a circuit (cord) like this will be the same at each point in the circuit. wherever the circuit breaker is located it will see the amps flowing in the circuit and if they exceed the rating of the circuit breaker, it will trip. thus the circuit is protected from an overload regardless of where the circuit breaker is located.


I am not an electrician but I have to take exception to the last comment about a 100 amp 240 volt circuit. my understanding is that this would have a 100 amp double pole breaker in the circuit on both of the hot leads. the breaker will trip should either hot lead exceed 100 amps. the circuit flow is down one hot lead and up the other. this circuit provides up to 100 amps. this is the way electric stoves and dryers are wired (at 30 amps). the older ones do not have a neutral wire. newer circuits for these devices do provide a neutral wire but the power flow is still down one leg and up the other. its when we get to the 50 amp rv world that we actually use the neutral wire to carry power as a split phase circuit.

Actually... house service wiring and 50 amp R/V service wiring are exactly the same. Split phase.

Your point about the amount of amperage on each leg is spot on.
Same holds true for R/V wiring.
I see so many (especially on this forum) touting that a 50a R/V service provides you 100a of current... yes and no.

It provides 100a of COMBINED current between the two legs but anything over 50a on EITHER leg will trip the breaker. So, no, you can't hook up something that draws more than 50a.

[DanKellar]

OK, electricity is like magic to me, and this is the second time I've heard about "legs." I was at a campground very early this season with my brand new Flagstaff 832FLBS. Some of the power stuff worked, and some didn't. I talked to the dealer who walked me through a trouble-shooting routine with no success. I scheduled an appointment to bring the rig in for service. Huge pain, but... I casually mentioned to the camp office that I might pull the rig off the site for a couple of days, and explained my problem. About an hour later the campground host knocked at my door, and asked me to hold off pulling the rig out. He had called an electrician who was scheduled to come in and check a couple of electrical poles. By the end of the day, I had all my stuff working. Seems there was a short in the ground somewhere that allowed me to get only one "leg" of my power???

[youroo]

Originally Posted by DanKellar

OK, electricity is like magic to me, and this is the second time I've heard about "legs." I was at a campground very early this season with my brand new Flagstaff 832FLBS. Some of the power stuff worked, and some didn't. I talked to the dealer who walked me through a trouble-shooting routine with no success. I scheduled an appointment to bring the rig in for service. Huge pain, but... I casually mentioned to the camp office that I might pull the rig off the site for a couple of days, and explained my problem. About an hour later the campground host knocked at my door, and asked me to hold off pulling the rig out. He had called an electrician who was scheduled to come in and check a couple of electrical poles. By the end of the day, I had all my stuff working. Seems there was a short in the ground somewhere that allowed me to get only one "leg" of my power???

Was it the Campground or Your ground? Youroo!!

[CHICKDOE]

to dan kellar: i'll try to make a real fast explanation for you. look at your electrical receptacles at home. they will have three slots. the two slits are where the power comes out of receptacle from the power and flows to whatever device is plugged into it and the other is where it flows from the device back into the receptacle to goes back to the power source. the first slit is the source of the power and is called the hot lead (or leg) and the second is called the neutral. (i'll ignore polarity and the fact that ac power reverses its flow). the little u shaped connector is for a ground wire which is a safety device and should not have any power flowing on it in normal operation. a 30 amp rv is wired using these same three connections. a hot lead to supply power, a neutral to let power return, and a ground. the connectors are larger and the wiring is larger to support more power, but conceptually they are the same as what you have at home.


you seem to have a 50 amp trailer. if you look at the power connector it has four connectors. three of them are the same as your home, a hot leg to provide power, a neutral to let it return, and a ground. the fourth connector is another separate hot leg to provide more power. you can think of it as another separate power source. one hot lead is called L1 and the other is called L2. each can supply power to the trailer. the power returns from the trailer via the common neutral wire and the common ground is a safety device that supports both hot leads. (this explanation is not technically correct as the neutral only carries imbalanced power back to the source, but for this layman's explanation you can think of 50 amps being two separate power supply legs sharing a common neutral return and a common safety ground). the one key thing about this type of supply circuit is that you absolutely do not want the two power supply legs (L1 & L2) to every touch each other anywhere. so when these get to your power panel one power source (L1) is connected to supply power to 1/2 of the branch circuits in the panel and the other power source (L2) is connected to supply the other 1/2 of the branch circuits. if you look at the circuit breakers on the pedestal and the main one in our power panel, they are double breakers with each side of the breaker protecting only one of the power legs. they have a bar or some form of mechanical connection between them such that if one breaker sees an overload on it's power leg, it trips and opens that leg and the mechanical connection between the two breakers causes the other breaker to open also. thus you will disconnect both power source legs even though the overload condition may have only been sensed on one power leg.


hope this helps a bit. again this is a layman's explanation. it is missing a few considerations that the electrical gurus would take exception to.


may I make another comment / suggestion? from what you described several of you circuits were not working (not receiving power from the power supply leg -either L1 or L2). as a result all of the branch circuits that that power leg supplied were inoperable. but note that the other power leg was supplying power and all of the branch circuits that it supplied were operating. also not that no circuit breaker tripped and the power on the one leg that was working was not over the breaker limit.


I would suggest that you consider some form of electrical management system (ems) that you install into the power supply line coming into the trailer. it can be in the trailer or a portable model that you plug input side of the ems into the pedestal receptacle and you plug the trailer power supply cord into the output side of the ems. most of these devices have indicators on them to show the status of the power supply. for example, ours shows the actual voltage and amperage flowing on each of the power supply legs. if you had one connected it would have showed you normal voltage and amperage flowing on one leg and no voltage and no amperage flowing on the other. this would have let you contact the park and explain to them that you were not getting power on one leg. these devices to other things but the indication of actual voltage and amperage on the legs is very helpful.


I know this is longwinded but the intent is to let you understand just enough about the power legs so that you can relate and understand why part of your trailer was not working and how you can more easily diagnose the problem should it happen again. it has happened to us also.

[JohnD10]

Originally Posted by pete100

My trailer came prepped for a second A/C and is wired for 50A. I’m never going to add a second A/C and at my age don’t like manhandling the 37’ 27 lb. cable.

I haven't read all the way through this...

However, I'm sure you could buy a shorter 50-amp power cord.

This would be the best solution...

[cavie]

Originally Posted by DanKellar

OK, electricity is like magic to me, and this is the second time I've heard about "legs." I was at a campground very early this season with my brand new Flagstaff 832FLBS. Some of the power stuff worked, and some didn't. I talked to the dealer who walked me through a trouble-shooting routine with no success. I scheduled an appointment to bring the rig in for service. Huge pain, but... I casually mentioned to the camp office that I might pull the rig off the site for a couple of days, and explained my problem. About an hour later the campground host knocked at my door, and asked me to hold off pulling the rig out. He had called an electrician who was scheduled to come in and check a couple of electrical poles. By the end of the day, I had all my stuff working. Seems there was a short in the ground somewhere that allowed me to get only one "leg" of my power???

Yep, that happens a lot. In my camp, the owners have 4 lots down the hill. They have no electricity there because the neutral is broken somewhere between me and their camp.

[DouglasReid]

Originally Posted by CHICKDOE

to dan kellar: i'll try to make a real fast explanation for you. look at your electrical receptacles at home. they will have three slots. the two slits are where the power comes out of receptacle from the power and flows to whatever device is plugged into it and the other is where it flows from the device back into the receptacle to goes back to the power source. the first slit is the source of the power and is called the hot lead (or leg) and the second is called the neutral. (i'll ignore polarity and the fact that ac power reverses its flow). the little u shaped connector is for a ground wire which is a safety device and should not have any power flowing on it in normal operation. a 30 amp rv is wired using these same three connections. a hot lead to supply power, a neutral to let power return, and a ground. the connectors are larger and the wiring is larger to support more power, but conceptually they are the same as what you have at home.


you seem to have a 50 amp trailer. if you look at the power connector it has four connectors. three of them are the same as your home, a hot leg to provide power, a neutral to let it return, and a ground. the fourth connector is another separate hot leg to provide more power. you can think of it as another separate power source. one hot lead is called L1 and the other is called L2. each can supply power to the trailer. the power returns from the trailer via the common neutral wire and the common ground is a safety device that supports both hot leads. (this explanation is not technically correct as the neutral only carries imbalanced power back to the source, but for this layman's explanation you can think of 50 amps being two separate power supply legs sharing a common neutral return and a common safety ground). the one key thing about this type of supply circuit is that you absolutely do not want the two power supply legs (L1 & L2) to every touch each other anywhere. so when these get to your power panel one power source (L1) is connected to supply power to 1/2 of the branch circuits in the panel and the other power source (L2) is connected to supply the other 1/2 of the branch circuits. if you look at the circuit breakers on the pedestal and the main one in our power panel, they are double breakers with each side of the breaker protecting only one of the power legs. they have a bar or some form of mechanical connection between them such that if one breaker sees an overload on it's power leg, it trips and opens that leg and the mechanical connection between the two breakers causes the other breaker to open also. thus you will disconnect both power source legs even though the overload condition may have only been sensed on one power leg.


hope this helps a bit. again this is a layman's explanation. it is missing a few considerations that the electrical gurus would take exception to.


may I make another comment / suggestion? from what you described several of you circuits were not working (not receiving power from the power supply leg -either L1 or L2). as a result all of the branch circuits that that power leg supplied were inoperable. but note that the other power leg was supplying power and all of the branch circuits that it supplied were operating. also not that no circuit breaker tripped and the power on the one leg that was working was not over the breaker limit.


I would suggest that you consider some form of electrical management system (ems) that you install into the power supply line coming into the trailer. it can be in the trailer or a portable model that you plug input side of the ems into the pedestal receptacle and you plug the trailer power supply cord into the output side of the ems. most of these devices have indicators on them to show the status of the power supply. for example, ours shows the actual voltage and amperage flowing on each of the power supply legs. if you had one connected it would have showed you normal voltage and amperage flowing on one leg and no voltage and no amperage flowing on the other. this would have let you contact the park and explain to them that you were not getting power on one leg. these devices to other things but the indication of actual voltage and amperage on the legs is very helpful.


I know this is longwinded but the intent is to let you understand just enough about the power legs so that you can relate and understand why part of your trailer was not working and how you can more easily diagnose the problem should it happen again. it has happened to us also.

X2^^ and a VERY good solution. Even a simple Surge Protector, when plugged in will show if both hot legs are powered up at the pedestal. Then turn the power at the pedestal off.

Then you can plug in your shore power cable to help prevent problems and turn the breaker back on. This sequence will help prevent electrical issues.

[NMWildcat]

*head shaking*. It truly astounds me the problems folks cause themselves, and the suggested fixes that compound it. KISS!!!

[CedarCreekWoody]

Originally Posted by NMWildcat

*head shaking*. It truly astounds me the problems folks cause themselves, and the suggested fixes that compound it. KISS!!!

Well stated!