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Old 12-02-2015, 08:05 AM   #1
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Dog Bone and EMS Protector

I have a 30 amp TT and am about to purchase a Progressive Industries PT30C 30 Amp Portable Electrical Management System. I've read many posts where in certain campgrounds those are plugging into the 50 amp outlet use a 50 amp to 30 amp dog bone to maximize the 120 voltage due to so many 30 amp hook ups. My question is does the EMS work the same by simply connecting to the dog bone, which is plugged into the camp panel, or do I have this backwards?

This is our first TT and I'm trying to educate myself as much as possible before doing something stupid.

Thanks!
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Old 12-02-2015, 08:33 AM   #2
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It works just fine.

Ps consider buying a 50 amp ems hardwired for your "next" camper that most likely will be 50 amp.
You can install a 50 amp ems in your 30 amp camper.
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Old 12-02-2015, 08:37 AM   #3
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I'm the same as you (first TT and trying to learn) and have the same EMS as you and a dogbone.

You are correct that the dogbone plugs into the panel and the EMS to the dogbone. I've also picked up that the breakers in the panel should always be off when you are plugging anything into or out of the panel sockets.

I think the reason for using the 50A line may not be so much the load on the 30A supply as that the 50A socket in the pedestal, in many cases, is in much better shape than the 30A. It typically gets less use, less wear and tear, arcing marks, etc. than in the 30A socket.

The last park I was at this was true and I decided to use the dogbone as the 30A socket just looked a little sketchy to me.

Hope this helps!

Bob
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Old 12-02-2015, 08:57 AM   #4
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That is great help. Thanks!
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Old 12-02-2015, 09:26 AM   #5
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Jbeal43 & Cavalier,

It's true the 50A socket gets less use and some use the dog bone to take advantage of this. An additional reason is the load on one leg of the electrical supply might have more load as the 20A & 30A sockets only use the one leg.

The 50A socket connects to both legs, but with a 30A camper you only use one leg. If you get a 50A DogBone that splits into two 30A sockets this gives you a solution with a 30A socket on each leg of the electrical service, so when the one legs voltage is too low for the EMS you can plug into the other 30A socket.

So if you go to a camp ground where there is too much load (low voltage) on the 30A or one side of the 50A-> (2x 30A) DogBone you would just plug into the other 30A socket on the 50A -> (2x 30A) DogBone.

Your standard 50A to 30A DogBone is connected to only one leg on the 50A. You might find two brands that connect to different legs of the 50A socket, then you would just switch out the dog bones as needed.

The 50A -> (2x 30A) DogBone gives you the solution with one DogBone.


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Old 12-02-2015, 10:05 AM   #6
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elunquist,

That makes sense to me, but wow those that split into the two 30A sockets are expensive.

Appreciate your input.
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Old 12-02-2015, 10:33 AM   #7
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Yes, thank you Erik.

I see what you are saying about the 50A dogbone split to 2 30A connectors. If and when I need to replace the standard 50A to 30A dogbone I have I'll have a look at one.

Bob
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Old 12-02-2015, 10:45 AM   #8
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Yea they probably don't see the level of sales to bring down the costs.

Another option for the DIY:

1. Cut your shore power cord about 12" to 16" from the 30A male plug head.

2. Install water proof twist lock 30A ends to each cut end of the cord. The cord end from the camper gets the male plug and the other gets the female socket.

3. Buy or fabricate two 50A male plug pigtail's with a 30A female twist lock water proof socket at each end of the 50A pigtail's. Make sure each pigtail's 30A socket is wired to opposite legs of the 50A legs.

Now you have a shore power cord with a 30A twist lock end that can either be connected directly to a generator or to one of three cord ends. One cord end with the original 30A male plug cord end, one new pigtail with a 50A plug connected to one legs on the 50A plug, the third is the same as the second except its connected to the opposite leg of the 50A plug.

I am not sure this would be cheaper than a 50A -> (2x 30A) 'Y' DogBone, but you will have a better water proof setup and don't have to worry about an open live 30A socket on the 50A -> (2x 30A) 'Y' DogBone.




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Old 12-02-2015, 02:22 PM   #9
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our seasonal went to a 50 amp system. we all pretty much had to use the 50 to 30 amp reducer and the EMS works the same.
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Old 12-02-2015, 09:56 PM   #10
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50to30 dogbone

Quote:
Originally Posted by elundquist View Post
Jbeal43 & Cavalier,

It's true the 50A socket gets less use and some use the dog bone to take advantage of this. An additional reason is the load on one leg of the electrical supply might have more load as the 20A & 30A sockets only use the one leg.

The 50A socket connects to both legs, but with a 30A camper you only use one leg. If you get a 50A DogBone that splits into two 30A sockets this gives you a solution with a 30A socket on each leg of the electrical service, so when the one legs voltage is too low for the EMS you can plug into the other 30A socket.

So if you go to a camp ground where there is too much load (low voltage) on the 30A or one side of the 50A-> (2x 30A) DogBone you would just plug into the other 30A socket on the 50A -> (2x 30A) DogBone.

Your standard 50A to 30A DogBone is connected to only one leg on the 50A. You might find two brands that connect to different legs of the 50A socket, then you would just switch out the dog bones as needed.

The 50A -> (2x 30A) DogBone gives you the solution with one DogBone.


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Be careful - when you plug this type of device into a 50A receptacle on the power post, each hot leg is protected by a 50A breaker in the post. Your 30A cord and plug is now protected by a 50A breaker. The 30A main breaker in your TT will interrupt current only in the case of overloads on the TT-side of this 30A breaker. A fault upstream - between the TT 30A main breaker and the cord's plug - can result in a 30A cord carrying more current than it is rated for. Overheated cord, plug and cord terminations, melted insulation, cord burning setting fire to TT.
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Old 12-02-2015, 10:23 PM   #11
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Be careful - when you plug this type of device into a 50A receptacle on the power post, each hot leg is protected by a 50A breaker in the post. Your 30A cord and plug is now protected by a 50A breaker. The 30A main breaker in your TT will interrupt current only in the case of overloads on the TT-side of this 30A breaker. A fault upstream - between the TT 30A main breaker and the cord's plug - can result in a 30A cord carrying more current than it is rated for. Overheated cord, plug and cord terminations, melted insulation, cord burning setting fire to TT.
I think you point makes sense if you're not using an EMS.

But the EMS should protect everything downstream from the output connection of the EMS (e.g. everything you listed), yes? The EMS provides protection for high/low voltage, surge (current), frequency, open ground, open neutral, polarity, and accidental 240V.

Bob
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Old 12-03-2015, 07:29 AM   #12
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Originally Posted by CavalierBob View Post
I think you point makes sense if you're not using an EMS.

But the EMS should protect everything downstream from the output connection of the EMS (e.g. everything you listed), yes? The EMS provides protection for high/low voltage, surge (current), frequency, open ground, open neutral, polarity, and accidental 240V.

Bob
Yep!
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Old 12-03-2015, 09:58 AM   #13
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Dog Bone and EMS Protector

If anyone plugs their RV into a 50A outlet, DogBone or not, should have the RV electrical system rated for 50A service from the shore power plug all the way to the RV panel board.

I think DSQR is talking about the circuit from the point of the pedestal outlet to the main breaker at the RV converter.

The issue would be if there was a fault in the shore power cord and/ or the wiring from the shore power cord to the main breaker.

In my post below on DIY option one should have/use a shore power cord with a wire gauge for 50A and 50A rated twist lock connectors.

DO NOT use the 30A versions!

When I originally typed that post I was thinking of my planed setup where I am using a 50A wire gauge shore power cord.

But later before submitting the post ,without thinking, I went back and edited so it would make since in connecting to the 30A twist lock outlet on my Honda generator. In my planned setup I am going to need another pigtail to connect the shore power cord to the generator!

If you plug your RV into a 50A protected outlet you should make sure the circuit from the RV panel board/ converter to the shore plug end is rated for 50A!

Do not use 30A connectors on a cord if you going to plug into the 50A outlet. If you are going to plug into a 50A outlet make sure the shore power cord is rated for 50A.


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Old 12-03-2015, 10:18 AM   #14
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Originally Posted by elundquist View Post
If anyone plugs their RV into a 50A outlet, DogBone or not, should have the RV electrical system rated for 50A service from the shore power plug all the way to the RV panel board.




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Why?
Your limited to your 30 amp breaker regardless. .
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Old 12-03-2015, 10:38 AM   #15
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Dog Bone and EMS Protector

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Why?
Your limited to your 30 amp breaker regardless. .

The problem is there is a possibility of a fault before the 30A breaker in the RV, where the fault could draw 50A of power on the 30A shore power cord/plug.

The 30A shore plug/ cord is only being protected by the 50A breaker in the pedestal. It's true the 30A EMS/ Breaker will protect the shore power cord from going above 30A based on loads in the RV, but not if there is a fault before the 30A EMS/ breaker in the camper.

Say your plugged into the pedestal and something cuts into the shore power cord shorting between the hot leg and ground, the neutral, or the safety ground. The fault could draw up to 50A before the pedestal breaker trips. This 50A draw could be a problem on a 30A shore power cord/ plug.

The difference between a 50A and 30A shore power cord is the 50A has 4 wires (L1, L2, neutral, & safety ground) and the 30A has 3 wires (L1, neutral, & safety ground). The other difference is in the gauge of the wire.

I am working with a 3 wire cord with a wire gauge that's large enough for 50A, but you can't count on every cord being a wire gauge for 50A!

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Old 12-03-2015, 10:51 AM   #16
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Quote:
Originally Posted by elundquist View Post
If you plug your RV into a 50A protected outlet you should make sure the circuit from the RV panel board/ converter to the shore plug end is rated for 50A!

Do not use 30A connectors on a 50A cord if you going to plug into the 50A outlet. If you are going to plug into a 50A outlet make sure the shore power cord is rated for 50A.
I agree to this in theory only.
Yes you will have a 30 amp shore cord between your rig and the 50 amp post connector that is then protected by a 50 amp breaker but everything inside the rig is limited to 30 amps by your rig's breaker box so the chances of overloading/shorting your 30 amp shore power cord are slim to none unless a bulldozer runs over it or something.

You could take a 50 amp shore power cable and cut the trailer side end off and install a 30 amp trailer side connector but that sure wouldn't be something I'd do.
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Old 12-03-2015, 11:26 AM   #17
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There's four things that scare me...fire, angry wives, mules and electricity. All the talk in this thread is getting my attention.

My impression is that, generally, it's OK for me to use a dog-bone adapter to plug my 30 amp cord into a 50 amp output. The trailer CB would protect the trailer and if it did its job because of, say, a short at the female end of the cord (where it connects to trailer) then it's possible to have an overheat/fire in the actual 30 amp power cable.

In other words...be careful where one places the power cord. Electricity concerns me enough that when I hook up (even to my home 30 amp outlet) the first thing I do is turn off power at the breaker. Then, I attach the cord to the trailer followed by plugging the cord into the receptacle. After that, I activate the breaker.
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Old 12-03-2015, 11:28 AM   #18
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I should clarify...

A 30A shore power cord can be a 8 gauge 3 wire cord or likely be a 10 gauge 3 wire cord.

A 50A shore power cord could be a 8 or 6 gauge 4 wire cord.

To use a 3 wire shore power cord to plug into a 50A circuit you should verify the wire gauge in the cord to make sure it's rated for 50A.

There is no need to use a standard RV 50A 4 wire cord for a 30A 120VAC RV service as you only need 3 wires.

Just verify your wire gauges are large enough for the connection/ load and use connectors rated for the application.






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Old 12-03-2015, 12:26 PM   #19
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Quote:
Originally Posted by emm-dee View Post
There's four things that scare me...fire, angry wives, mules and electricity. All the talk in this thread is getting my attention.

My impression is that, generally, it's OK for me to use a dog-bone adapter to plug my 30 amp cord into a 50 amp output. The trailer CB would protect the trailer and if it did its job because of, say, a short at the female end of the cord (where it connects to trailer) then it's possible to have an overheat/fire in the actual 30 amp power cable.

In other words...be careful where one places the power cord. Electricity concerns me enough that when I hook up (even to my home 30 amp outlet) the first thing I do is turn off power at the breaker. Then, I attach the cord to the trailer followed by plugging the cord into the receptacle. After that, I activate the breaker.

It should be everyone's SOP (standard operating procedure) to cut off the breaker before inserting or removing their RV shore power cord! It prevents arch pitting on the terminals at the pedestal socket and on your shore plug.


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Old 12-03-2015, 12:39 PM   #20
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I don't turn off the breaker before because the surge protector doesn't allow power to enter the RV for 128 seconds. So there is no arching in the plug to worry about.
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