Shore power question.

[THyatt123]

Why would the 30 Amp breaker outside on the power pole trip (shore power) but no the main 30amp breaker inside the TT? It’s only happened twice and both times the A/C was full blast.

If we pulled more than 30 amps between the A/C and the other outlets/water heater/fridge, why didn’t the inside breaker pop? Thanks for any info!

2022 Jayco SLX8 26RLS

[Grumpy]

Because that was the weakest link. Breakers do wear out/weaken, especially if turned off and on regularly which is what happens at the power post.

[THyatt123]

Originally Posted by Grumpy

Because that was the weakest link. Breakers do wear out/weaken, especially if turned off and on regularly which is what happens at the power post.

Sounds like a conversation is to be had with the campground. Thank you for such a quick response!

[GEPrice]

Examine your power cable & trailer side cleaning what you can.

[mrmom]

Originally Posted by Grumpy

Because that was the weakest link. Breakers do wear out/weaken, especially if turned off and on regularly which is what happens at the power post.

Agree with above but also say that the breaker inside of your rig should be exercised occasionally as well. Have seen them stick over the years from never being moved.

[craigav]

While a circuit breaker can wear out with time and especially with multiple trips on the breaker, there is still yet another reason why the pedestal 30a breaker often breaks before the 30a main inside the RV.

The reason is that a common breaker works by two different methods, first being magnetic and if a large amount of power flows through the breaker, the breaker trips due to the increased magnetism, the second method and the one of relevance here is the "thermal" trip where as the temp inside the breaker increases due to the load and with time, the breaker will trip due to the thermal (heat) increase inside the breaker.

What happens is that as power flows through the breaker, heat is generated. When that heat is high enough for a long enough time (greater or equal to 80% of the breakers rating) then the breaker will trip. The thermal aspects are sensitive to the ambient temperature that the breaker exists in. So, with two fully functional breakers at the same rating (30a in this case) once you exceed about 24a (80%) with a continuous load then the breaker in the warmest location will break prior to the breaker located in the cooler location (there are curve charts regarding load and time to break). This often means and in particular during the summer months that the pedestal breaker breaks first being in the hot ambient temp vs the breaker inside the RV being in an air conditioned environment in most cases (even if there isn't much air flow in the breaker panel, often that location is cooler than inside the pedestal).

btw, just the opposite would occur in the winter, if you had electric heaters that pulled more than the 24a continuously, with time the interior breaker would trip prior to the breaker located at the pedestal which would be in a colder environment.

Most of what I am saying here is rarely noted, as the condition only occurs when the load is right there at the maximum breaker rating for current and the pedestal breaker is warmer than the RV main breaker. A standard breaker can hold 80% continuous of its rating for 3 hours. 100% non-continuous, and a curve in time between 80 and 100% where more than 80% reduces the time to trip, but is certainly not an instant trip (from minutes into about 3 hours). ~CA

btw, what I am sharing here is not specific to 30a breakers, same would be for all common breakers as well.

[Marcm157]

Originally Posted by craigav

While a circuit breaker can wear out with time and especially with multiple trips on the breaker, there is still yet another reason why the pedestal 30a breaker often breaks before the 30a main inside the RV.

The reason is that a common breaker works by two different methods, first being magnetic and if a large amount of power flows through the breaker, the breaker trips due to the increased magnetism, the second method and the one of relevance here is the "thermal" trip where as the temp inside the breaker increases due to the load and with time, the breaker will trip due to the thermal (heat) increase inside the breaker.

What happens is that as power flows through the breaker, heat is generated. When that heat is high enough for a long enough time (greater or equal to 80% of the breakers rating) then the breaker will trip. The thermal aspects are sensitive to the ambient temperature that the breaker exists in. So, with two fully functional breakers at the same rating (30a in this case) once you exceed about 24a (80%) with a continuous load then the breaker in the warmest location will break prior to the breaker located in the cooler location (there are curve charts regarding load and time to break). This often means and in particular during the summer months that the pedestal breaker breaks first being in the hot ambient temp vs the breaker inside the RV being in an air conditioned environment in most cases (even if there isn't much air flow in the breaker panel, often that location is cooler than inside the pedestal).

btw, just the opposite would occur in the winter, if you had electric heaters that pulled more than the 24a continuously, with time the interior breaker would trip prior to the breaker located at the pedestal which would be in a colder environment.

Most of what I am saying here is rarely noted, as the condition only occurs when the load is right there at the maximum breaker rating for current and the pedestal breaker is warmer than the RV main breaker. A standard breaker can hold 80% continuous of its rating for 3 hours. 100% non-continuous, and a curve in time between 80 and 100% where more than 80% reduces the time to trip, but is certainly not an instant trip (from minutes into about 3 hours). ~CA

btw, what I am sharing here is not specific to 30a breakers, same would be for all common breakers as well.

Very well stated Craig - Thank you! I can't send thanks from my phone....

[THyatt123]

You done learnt me something, lol. I appreciate the thorough explanation. Makes perfect sense.

[JFlightRisk]

Excellent explanation craigav! Thanks, I wasn't aware of the two ways they trip. You get an 'attaboy'!

[THyatt123]

Originally Posted by JFlightRisk

Excellent explanation craigav! Thanks, I wasn't aware of the two ways they trip. You get an 'attaboy'!

Agreed. I will have to admit other forums (not RV related), it feels like people are just waiting to pounce on someone for asking a question. I always appreciate someone genuinely willing to help and share information. 🙏🏻

[JFlightRisk]

Originally Posted by THyatt123

Agreed. I will have to admit other forums (not RV related), it feels like people are just waiting to pounce on someone for asking a question. I always appreciate someone genuinely willing to help and share information. 🙏🏻

Thanks, that's what makes the JOF a family friendly place. All of the moderators here take great pride in what we do, and anti-pouncing was one part of our exhaustive and highly intense training. Ok, that's not entirely accurate, but there was a lot of it. We love what we do.

[SloPoke]

Originally Posted by craigav

While a circuit breaker can wear out with time and especially with multiple trips on the breaker, there is still yet another reason why the pedestal 30a breaker often breaks before the 30a main inside the RV..

Well described,

But OP still should look for any faults in the power cord / connectors / connections to the main RV panel. The power pedestal breaker is protecting everything past the breaker, that could be the pedestal 30A receptacle as well as the entire cable/RV connected to it.

[THyatt123]

Gotcha, I appreciate it!