Surge Protector Question

[Luv2Ski]

Ummm... if the OP has a 30 amp plug and cord on his trailer, then it IS safe to plug an adaptor into 50 amp (as long as it is not some home-brew adaptor). The trailer max is the trailer max. It will only pull 30 amps with everything running.
It's like putting in a 10 watt bulb into a lamp socket that can power a 150 w bulb.......

Well not exactly. Consider this circuit using the example you gave:

A 10w 120v bulb will only draw 83 milliamps. Let's say it's fused with a 0.125A fast fuse at the bulb end and 24 gauge solid copper wiring rated at 3A max is used to connect it all to a 120v 15A wall socket. One could argue that the 10w bulb is only going to draw a negligible 0.083A current and therefore using such small diameter wire rated at 3 amps is safe. Besides it's fused next to the bulb using a 0.125A fuse so no worries, right? If the bulb was to internally short, the fuse would blow long before the 24 gauge wire could overheat.

But what if a short develops between the 120v 15A socket and the fuse? That little 24 gauge wire will turn white hot as the full 15A flows through it. However, if the fuse was moved from the bulb end back to the 120v 15A socket end, then the bulb AND the 24 gauge wiring would be protected. That's the issue here. The issue isn't about what the 30A breaker does. It's about where it is.

The wiring that goes between the pedestal and the RV's 30A breaker is at risk. The wiring is mostly 10 gauge and therefore not rated for 50A. If it were to short out, it would get up to 50A from the pedestal. Amperages between 30 amps and 50 amps are especially concerning. If the short was a weak short, perhaps 48 amps of current could flow continuously without tripping the pedestal breaker while overheating the 10 gauge wiring.

This is why Christmas tree lights with their thin wires must have a fuse in the plug end to get a UL listing. The fix here would be be the same. Put a 30A self resetting circuit breaker (or just a 30A fuse) in the head of the 50A to 30A adapter.

[alexxx84962]

Thanks for info guys. That's tight.
Without any doubt, protecting electrical grids and electronic devices from voltage surges should be considered of primary importance. To do that right, you can get a surge protector and secure all your household appliances from outlet rises and drops. The operating principle of surge protectors is rather simple. They take in excessive power from the outlets and divert it to the ground wire, preventing damage to connected appliances.

[Najataagihe]

You can plug into any amperage outlet you like, as long as you use your RV's power cord and the proper adapter.

Electricity does not PUSH itself from the power source, it is PULLED from whatever uses it.


An RB2600 can only pull 30 amps, regardless of whether pedestal has 15, 20, 30, 50, 100, 1000 amp service or whatever.

30 amps is MAX.


The pedestal may have the CAPACITY to provide a bajillion amps, but that trailer can only draw 30.

Likewise, a 15-amp circuit is only going to provide 15 amps, so if you try to pull more than that, it's breaker will trip and not let you overheat the wire to the outlet.


As far as using a 50-amp pedestal, you are only using ONE LEG of the TWO LEGS used to get a 50-amp capacity.

To get those 50 amps, you combine TWO 30-amp 120V circuits to get a total capacity of 60 amps, but you install a 50-amp breaker on it to prevent campers from drawing more current than their systems can handle.


Part of the function of a 50-amp to 30-amp dogbone is to isolate one of the 30-amp legs of the 50-amp circuit.

If you will notice, the 50-amp plug on the dogbone has four blades - two hot legs of 120V, one neutral and one ground.

The 30-amp end of the dogbone only has three holes - one hot leg of 120V, one neutral and one ground.

You are NEVER going to draw 50 amps through that dogbone.


Those of you worried that you might pull more than 30 amps due to a short, rest assured.

The 50-amp breaker is actually two breakers tied together, one for each hot leg.

If EITHER trips, they BOTH trip, so your short will trip the breaker when it exceeds the capacity of the breaker on the leg you are using.

It CAN NOT pull juice from the other leg and melt your cable.


The big problem is someone using too small an extension cord, instead of the supply cable that came with their RV.

If you pull more amperage than the wire can handle, it WILL overheat, possibly melting the insulation and starting a fire.

To prevent this sort of tragedy, do not plug an extension cord into a circuit with a breaker rated higher than the cord can handle, UNLESS you take pains to make sure the amount of current you are pulling NEVER exceeds the capacity of the cord.


For the 50-amp folks, there is a Y-adapter that allows you to tap both the 30-amp and 15-amp outlets in an older pedestal that doesn't provide 50 amps.

It only gives you 45 amps, but that is not usually a big deal, as few people run everything in the RV at the same time.


One caveat if you use one of these things.

In some of the really old parks, there is only one 30 amp circuit at the pedestal.


The 15-amp circuit is wired in parallel to the 30-amp circuit with a 15-amp breaker between the circuit and the outlet.

With these setups, you will only get 30-amps, no matter if you DO have a Y-adapter and BOTH legs of your RV cable are going to be tied to the same circuit.

You would do better to use a 30-amp to 50-amp dogbone and be done with it.


A LOT of engineers have put a LOT of thought into sizing wire and breakers, computing circuit loads and developing procedures to allow folks to use electricity safely without having to use a lot of thought.

Use the proper equipment following the directions provided and you will not endanger yourself, your family or your equipment.


It is when someone tries to redesign an electrical system without knowing what they are doing that tragedy strikes.

Don't be a statistic.


Happy (and safe) travels!


8)

[TheSpareTire]

I have some questions on this:

You can plug into any amperage outlet you like, as long as you use your RV's power cord and the proper adapter.

Electricity does not PUSH itself from the power source, it is PULLED from whatever uses it.

What about folks that use generators and/or driveway surf? If they use a 30->15amp dogbone so they can use their extension code to reach their 50amp shore cord. Wouldn't that present a issue where the extension cord could be overloaded with more amps then it was designed to carry?

As far as using a 50-amp pedestal, you are only using ONE LEG of the TWO LEGS used to get a 50-amp capacity.

To get those 50 amps, you combine TWO 30-amp 120V circuits to get a total capacity of 60 amps, but you install a 50-amp breaker on it to prevent campers from drawing more current than their systems can handle.

I believe you mean on 50amp shore pedestal service you are provided with two independant 120v 50amp legs. Each leg is supplying half the coaches breaker box for a total of 100amps? A 30amp shore cord should only have one 120v 30amp leg, correct?

Part of the function of a 50-amp to 30-amp dogbone is to isolate one of the 30-amp legs of the 50-amp circuit.

I may be wrong but wouldn't that be split single 120v 30 amp service across both legs of the 50amp circuit? So our coach only has a total of 30amps vs the normal 100amps it could potentially draw.

Those of you worried that you might pull more than 30 amps due to a short, rest assured.

The 50-amp breaker is actually two breakers tied together, one for each hot leg.

If EITHER trips, they BOTH trip, so your short will trip the breaker when it exceeds the capacity of the breaker on the leg you are using.

It CAN NOT pull juice from the other leg and melt your cable.

Just glance at the pedestal before you connect 30amp cords. I have totally been in parks that put a 50amp breaker into the spot for the 30amp service. Normally we think about the plug and not breaker as the differentiation between services.

[warsw1]

You can plug into any amperage outlet you like, as long as you use your RV's power cord and the proper adapter.

Electricity does not PUSH itself from the power source, it is PULLED from whatever uses it.


An RB2600 can only pull 30 amps, regardless of whether pedestal has 15, 20, 30, 50, 100, 1000 amp service or whatever.

30 amps is MAX.


The pedestal may have the CAPACITY to provide a bajillion amps, but that trailer can only draw 30.

Likewise, a 15-amp circuit is only going to provide 15 amps, so if you try to pull more than that, it's breaker will trip and not let you overheat the wire to the outlet.


As far as using a 50-amp pedestal, you are only using ONE LEG of the TWO LEGS used to get a 50-amp capacity.

To get those 50 amps, you combine TWO 30-amp 120V circuits to get a total capacity of 60 amps, but you install a 50-amp breaker on it to prevent campers from drawing more current than their systems can handle.


Part of the function of a 50-amp to 30-amp dogbone is to isolate one of the 30-amp legs of the 50-amp circuit.

If you will notice, the 50-amp plug on the dogbone has four blades - two hot legs of 120V, one neutral and one ground.

The 30-amp end of the dogbone only has three holes - one hot leg of 120V, one neutral and one ground.

You are NEVER going to draw 50 amps through that dogbone.


Those of you worried that you might pull more than 30 amps due to a short, rest assured.

The 50-amp breaker is actually two breakers tied together, one for each hot leg.

If EITHER trips, they BOTH trip, so your short will trip the breaker when it exceeds the capacity of the breaker on the leg you are using.

It CAN NOT pull juice from the other leg and melt your cable.


The big problem is someone using too small an extension cord, instead of the supply cable that came with their RV.

If you pull more amperage than the wire can handle, it WILL overheat, possibly melting the insulation and starting a fire.

To prevent this sort of tragedy, do not plug an extension cord into a circuit with a breaker rated higher than the cord can handle, UNLESS you take pains to make sure the amount of current you are pulling NEVER exceeds the capacity of the cord.


For the 50-amp folks, there is a Y-adapter that allows you to tap both the 30-amp and 15-amp outlets in an older pedestal that doesn't provide 50 amps.

It only gives you 45 amps, but that is not usually a big deal, as few people run everything in the RV at the same time.


One caveat if you use one of these things.

In some of the really old parks, there is only one 30 amp circuit at the pedestal.


The 15-amp circuit is wired in parallel to the 30-amp circuit with a 15-amp breaker between the circuit and the outlet.

With these setups, you will only get 30-amps, no matter if you DO have a Y-adapter and BOTH legs of your RV cable are going to be tied to the same circuit.

You would do better to use a 30-amp to 50-amp dogbone and be done with it.


A LOT of engineers have put a LOT of thought into sizing wire and breakers, computing circuit loads and developing procedures to allow folks to use electricity safely without having to use a lot of thought.

Use the proper equipment following the directions provided and you will not endanger yourself, your family or your equipment.


It is when someone tries to redesign an electrical system without knowing what they are doing that tragedy strikes.

Don't be a statistic.


Happy (and safe) travels!


8)

Najataagihe, You need to reread what Luv2Ski had said. What he has said is positively true. What you are saying is wrong. A breaker will only protect what is down stream of the breaker. It will not protect what is feeding it from up stream. That is why you need the proper sized breaker at the source if you want to also protect the 30 amp cord that feeds your 30 amp RV.

[klenger]

I believe you mean on 50 amp shore pedestal service you are provided with two independent 120v 50amp legs. Each leg is supplying half the coaches breaker box for a total of 100 amps? A 30 amp shore cord should only have one 120v 30 amp leg, correct?

This is correct. 50 amp service is supplied by two 50 amp legs 180 deg out of phase for a total of 100 amps. 30 amp service is one 30 amp leg for a total of ... 30 amps. So in fact, 50 amp service is more than 3 times the power of 30 amp service.

I can't say for sure, and power pedestals can be wired multiple ways, but I expect that most 50/30/20 amp pedestals are wired with one 50 amp leg and the 30 amp receptacle on one phase and the other 50 amp leg and the 20 amp receptacle on the other phase in an attempt to balance the loads.

One more point, the 30 amp / 20 amp combiner adapters rarely work in the real world because the 20 amp outlet is on a GFCI, which is not happy with the 30 amp let that is not on the GFCI. I tried one, and ended up sending it back for that reason.

[Najataagihe]

I have some questions on this:


What about folks that use generators and/or driveway surf? If they use a 30->15amp dogbone so they can use their extension code to reach their 50amp shore cord. Wouldn't that present a issue where the extension cord could be overloaded with more amps then it was designed to carry?

Yes, because you have built a 15-amp capacity circuit.

Thus, the sentence about making sure that IF you plug an extension cord into a circuit with a breaker rated higher than the cord, you MUST make sure the current draw does not exceed the capacity of the cord.

Otherwise, you have just turned your extension cord into a fusible link - and not a well-designed one!

I believe you mean on 50amp shore pedestal service you are provided with two independant 120v 50amp legs. Each leg is supplying half the coaches breaker box for a total of 100amps? A 30amp shore cord should only have one 120v 30amp leg, correct?

You're right.

I typed 30, instead of 50.

NOT good, on my part.

I may be wrong but wouldn't that be split single 120v 30 amp service across both legs of the 50amp circuit? So our coach only has a total of 30amps vs the normal 100amps it could potentially draw.

No.

The 30-amp circuit is only hooked to one of the legs from the 50-amp outlet.

The other leg is not even connected, if you use the proper adapter.


If you have a dead short in the supply cable, itself, it could potentially draw 50 amps, not 100.

Just glance at the pedestal before you connect 30amp cords. I have totally been in parks that put a 50amp breaker into the spot for the 30amp service. Normally we think about the plug and not breaker as the differentiation between services.

AMEN to that!



8)

[Najataagihe]

Najataagihe, You need to reread what Luv2Ski had said. What he has said is positively true. What you are saying is wrong. A breaker will only protect what is down stream of the breaker. It will not protect what is feeding it from up stream. That is why you need the proper sized breaker at the source if you want to also protect the 30 amp cord that feeds your 30 amp RV.

I'm confused.

When did I say otherwise?


It's really quite simple - ANY circuit can only carry as much current as its smallest conductor.

To protect it, your current protection MUST be rated lower than the conductor's capacity.

[TheSpareTire]

50 amp service is supplied by two 50 amp legs 180 deg out of phase for a total of 100 amps.

RV 50amp legs are not necessarily split phase, its two independant 120volt legs at 50amps. Think of the coaches panel as really two independent panels each getting 120 volt 50amp service. Most parks like klenger points out try to balance the load on each 50amp leg. This is why you can use portal generator or dog bone from a single 30amp pedestal on both legs.

I know this semantics. I not picking on anyone but future people searching I want to make sure we ultimately provide the most accurate information.

Be careful before you plug your Tesla in thinking it's true 240 split phase ;-)

[Cate&Rob]

A 50A male to 30A female adapter should only be used if you have a 30A breaker in the trailer panel. The trailer breaker will pop if you try to draw more than 30A through the 30A cord. Where this gets dangerous is when another 30A male to 50A twistlock adapter is used and the trailer has a 50A service. This configuration can draw 50A through a cord rated for 30A.

A 50A service is supplied to the trailer as two 120VAC 50A feeds. But . . . these must be opposite phases from a 240VAC feed. If both sides were fed from two 50A breakers on the same 120VAC feed, the single neutral wire would be overloaded.

Rob