50A site with 30A TT

[CedarCreekWoody]

Originally Posted by tkarper14

No it is not accurate. The power cord is protected by the 30 amp breaker in the trailer.

Here we go again. A cord rated for 30 amps could overheat and catch fire BEFORE it drew 50 amps of current to trip the breaker on the pedestal. That is the concern.

[tkarper14]

Originally Posted by DouglasReid

I was wondering when someone would post this information. The breaker is there to protect the electrical wiring. If you put a 30 amp cord on a 50 amp circuit without a fuse or circuit breaker there is virtually NO Protection!

This will be my last post which is meant to calm the fear that many create when making statements like this. When you plug a 30 amp RV into a 50 amp receptacle, you no longer have a 50 amp circuit. It is now a 30 amp circuit which is determined by the weakest link. This weakest link is located in the RV main service panel. It provides the protection needed for the power cord.

I would bet peanuts to dollars that somewhere between your 50 amp pedestal and the Hoover Dam that there is another breaker that is at least a 200 amp breaker. Does that mean you have 200 or more amps available? No. You only have available the weakest link, which would be 50 amps. Once the 30 amp breaker is installed, it now becomes the weakest link so you only have 30 amps available. As Mr Havercamp stated. This is no different than your supply lines going into you house.

[KyDan]

OK- all opinions are appreciated but let's not argue please!!

In a perfect world everyone would have the exact perfectly sized power available at their
perfect camp site.

I think the OPs question was answered very early on.
I want to stress to the OP usually sites that say 50 amp actually have both
30 and 50 amp sockets. So an adapter is good to have but you might not need it!

Lots of people use adapters from time to time. Lots as in thousands.
I'm way more worried about someone driving under the influence or distracted taking us out than a power cord fire due to use of an adapter.

My 2¢
Please feel free to state your opinion and move on.... remember it's not
your job to change everyone else's mind

[elind]

The 30 amp cord goes directly into the 30 amp RV breaker box. Unless you divide power off of the cord, before the breaker box, the 30 amp breaker controls the max amp draw on the cord.

edit: If the cord has a malfunction the 50 breaker will shut it down.

[Sterlingsilver]

All protection is upstream. Before you get to the camper's breaker, your only protection is the 50 amp pylon breaker. If you want to play with opinions as your rules for safety, you could ask why any campground would bother with 30 amp breakers if 50 amp was safe. You ask why anyone would even make any sort of breaker if Hoover Dam was all we need. I have never had to move because my regular campground will have none of that. Run a 50 amp RV off a 30 amp pylon, with an adapter, that's as safe as it gets. The reverse is hazardous.

[Flybob]

It appears that there is some confusion as to what is being protected by what.

A circuit breaker is designed to sense current flowing through it and if it is higher than the limit of the breaker trip and open the circuit to protect things downstream from the breaker. In the case of a 30A system in a TT connected to a 50A breaker in the pedestal via an adapter.
1. If there is a short in the TT or the appliances draw more than 30A total the breaker in the TT will trip and open the circuit. So yes the 30A breaker will protect you in this case.
2. If there is a dead short in the power cable between pedestal and the TT the 50A breaker in the pedestal will protect the power cable and the TT.
3. The problem comes when you have a high current failure before the 30A breaker in TT ( in the power cord itself or the connection where the power cord enters the TT) that is not high enough to trip the 50A breaker say 45A. In this case the power cord could overheat and catch fire. Remember the 30A breaker in the TT is not seeing this high current and therefore will not react. This type of failure is not totally uncommon and can result from damaged power cords (chewed by animals) or from the pigtail end of the power cord coming lose ( improperly tightened screw) and making a high resistance contact with the chassis or other wiring.

[CedarCreekWoody]

Flybob got it right.

[mikeysotp]

Huh, I don't know a damned thing about electricity but I was thinking exactly what Flybob said. And I didn't even stay in a Holiday Inn Express last night!

[Asrabbit]

I think about it like this: If you had a 20 amp breaker in your home, you need 12 gauge wire over the course of the entire run to be protected. If a run had 14 gauge wire on it, and you had a 20 amp breaker, you have a dangerous situation, as something can draw more amps that a 14 gauge wire can accommodate. In that case, if you had a microwave, coffee pot, hairdryer, etc, all running at the same time so that you were drawing 18 amps, the 20 amp breaker would not trip. But, you have gone past what a 14 gauge wire can accommodate. So, nothing is really wrong with what is going on, (there are no shorts or wire that has a nick in it), but you could melt you 14 gauge wire. That is why you cannot change out a 15 amp breaker with a 20. Because likely the 15 amp is run with 14 gauge wire. A 20 amp breaker should have a minimum of 12 gauge wire. You can always go bigger, meaning use a 15 amp breaker with 12 gauge wire, but you can never go smaller, using a 20 amp breaker with 14 gauge wire.

It is fair to say it is not likely that anything will happen to the power cord to the camper that would cause an issue, but it could. As it has been said, if a connection became loosened up on the way to the RV park, even though you never exceeded 30 amps on the circuit inside your camper, (at lest from your panel onward), you may well have an issue that will cause you a problem as that connection is 6 inches inside your camper.

Bottom line, I would want to some how be protected. I would never want to hook up a 16 gauge extension cord to the 30 amp plug, (really, I would not want to do that on a 20 amp plug, although it is common to see as a 12 gauge extension cord is expensive).

[Iwannacamp]

Originally Posted by Asrabbit

I think about it like this: If you had a 20 amp breaker in your home, you need 12 gauge wire over the course of the entire run to be protected. If a run had 14 gauge wire on it, and you had a 20 amp breaker, you have a dangerous situation, as something can draw more amps that a 14 gauge wire can accommodate. In that case, if you had a microwave, coffee pot, hairdryer, etc, all running at the same time so that you were drawing 18 amps, the 20 amp breaker would not trip. But, you have gone past what a 14 gauge wire can accommodate. So, nothing is really wrong with what is going on, (there are no shorts or wire that has a nick in it), but you could melt you 14 gauge wire. That is why you cannot change out a 15 amp breaker with a 20. Because likely the 15 amp is run with 14 gauge wire. A 20 amp breaker should have a minimum of 12 gauge wire. You can always go bigger, meaning use a 15 amp breaker with 12 gauge wire, but you can never go smaller, using a 20 amp breaker with 14 gauge wire.


It is fair to say it is not likely that anything will happen to the power cord to the camper that would cause an issue, but it could. As it has been said, if a connection became loosened up on the way to the RV park, even though you never exceeded 30 amps on the circuit inside your camper, (at lest from your panel onward), you may well have an issue that will cause you a problem as that connection is 6 inches inside your camper.

Bottom line, I would want to some how be protected. I would never want to hook up a 16 gauge extension cord to the 30 amp plug, (really, I would not want to do that on a 20 amp plug, although it is common to see as a 12 gauge extension cord is expensive).

Hmmmm. I wanted to argue with a couple things here(even though it sounds like you know) about 15/20 amps vs: 12/14 ga wire.... then I looked it up.

Next deal... I would not fret so much on wire to pedestal but I WOULD fret the connection at the pedestal... hence the wire smoking issues. IMO

As I stated before... one could make a box that would protect the RV on 50 RV connected to a 30 pedestal. I guess I need one of those too. If you have the pigtail adapter then you could cut it and add a breaker box... now one has to be smart enough to wire it.

[Asrabbit]

I am not sure about the proper gauge for 50 amp service. I would guess 8 or 6. If you had a short piece of the correct size wire going to a small breaker box with a 30 amp breaker and then a 30 amp plug that would work as an adoptor. However who is going to do that?

I don't know why a 50 to 30 amp adapter is made but you would think it would come with some fine print stating the proper size wiring must be used.

[CedarCreekWoody]

The risk is there, but it is small. It is also very common. In your home your outlets are fed with 15 or 20 amp breakers but the cords going to lamps or appliances are rarely of a heavy enough Guage to carry that amperage. That is why they occasionally catch fire after shorting out.

I have a 50 to 30 amp dog bone adapter but I've never had to use it. If I do need it I won't worry a lot about it.

[Asrabbit]

You are correct. For the most part, a lamp on a 20 amp breaker is not using 12 gauge wire, (likely 16 or 18). So, it is very much falls along the same line of what we are talking about here. There is some risk involved, but people take that risk everyday.

[B and B]

There is nothing to worry about. The Fear mongering in this thread is not helpful to the OP.

The 50 to 30 amp dogbone will work just fine for your application. Inspect your power cable for abrasions or heated (discoloured pins) on the plug end. Be careful and you are just fine.

I have seen more issues with loose connections on the twist lock shore power connection than a cord that melts due to usage at 30 amps.

[tkarper14]

Here is the problem with Flybob's third point. You can not have 45 amps flowing through the power cord without the 30 amp breaker also seeing 45 amps.

From the 50 amp breaker to the individual 15 amp breakers is a series circuit within a series/parallel circuit. The current is the same ANYWHERE in that portion of the cicuit. The only place the current will be decreased is in the parallel branches. This happens at the individual breakers, which is after the 30 amp breaker. Then the sum of the individual branches is equal to the total current at the point they branch from.

Therefore, if you had 4 circuits drawing 10 amps each, the total current would be 40 amps. The 30 amp breaker would trip.

I am not trying to change anyone's opinion. Everyone has one and they all stink. And yes, the OP got his answer after the first reply and this should be a dead post. But then we have some throwing their credentials out there spreading paranoia. So I ask again, why can you not buy 50 to 30 amp adapters with built in protection?

[Tapex]

Originally Posted by mikeysotp

Huh, I don't know a damned thing about electricity but I was thinking exactly what Flybob said. And I didn't even stay in a Holiday Inn Express last night!

Same here for me, I'm trying to learn!

[gectisme]

Originally Posted by tkarper14

Here is the problem with Flybob's third point. You can not have 45 amps flowing through the power cord without the 30 amp breaker also seeing 45 amps.

From the 50 amp breaker to the individual 15 amp breakers is a series circuit within a series/parallel circuit. The current is the same ANYWHERE in that portion of the cicuit. The only place the current will be decreased is in the parallel branches. This happens at the individual breakers, which is after the 30 amp breaker. Then the sum of the individual branches is equal to the total current at the point they branch from.

Therefore, if you had 4 circuits drawing 10 amps each, the total current would be 40 amps. The 30 amp breaker would trip.

I am not trying to change anyone's opinion. Everyone has one and they all stink. And yes, the OP got his answer after the first reply and this should be a dead post. But then we have some throwing their credentials out there spreading paranoia. So I ask again, why can you not buy 50 to 30 amp adapters with built in protection?

Your logic misses Flybobs 3rd point - if the short happens before the RV 30amp breaker. In your terms that would be putting another parallel circuit on the line but in this case it would before the RV 30amp breaker so only the 50amp pole breaker would see it. I could draw a print of the circuit if that helps.

[tkarper14]

Then the 50 amp breaker would trip.

[gectisme]

Originally Posted by tkarper14

Then the 50 amp breaker would trip.

Only if the current were enough to trip it. What happens if the current is under that but much higher than the 30 Amps the cord is rated at? And also the plug and internal wiring inside the RV, before the RV 30 Amp breaker that is rated at 30 Amps.

I think at this point were beating a dead horse, at least I am, it is as everything in life, your choice your risks. I myself would not be too worried but I just wanted to point out to someone who might read your statement and believe it is correct. And of course I could be incorrect but my electrical background in college tells me otherwise, (that was a long time ago so who knows ).

[CedarCreekWoody]

Originally Posted by gectisme

Only if the current were enough to trip it. What happens if the current is under that but much higher than the 30 Amps the cord is rated at? And also the plug and internal wiring inside the RV, before the RV 30 Amp breaker that is rated at 30 Amps.

I think at this point were beating a dead horse, at least I am, it is as everything in life, your choice your risks. I myself would not be too worried but I just wanted to point out to someone who might read your statement and believe it is correct. And of course I could be incorrect but my electrical background in college tells me otherwise, (that was a long time ago so who knows ).

Once again, an accurate assessment.

Now it is time to move on...