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 > Electrical Pigtail question

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69gp

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Posted: 07/31/12 12:43pm Link  |  Print  |  Notify Moderator

cjalphonso wrote:

A couple of things about this statement:
" As for your theory that the 50 amp breaker will protect the #10 cord your dead wrong. Every time you exceed the limit of this cord you are heating it up and degrading it. This cord by code is limited to 80%of its rated value. Its rated for 30 amps you should not draw more then 24 amps. Over time if you keep using it this way you will have an issue. That's a fact.

You will never exceed the limit on this cord as the 30A breaker will trip and stop any current draw (unless catastrophic failure and yes it may see 50A until the 50A breaker trips.)
The cord is not limited to 80% of its value, the cord will handle 100% of its value, the 80% is an NEC design requirement, not a limitation on the cord. In fact #10's are rated up to 35A.

Here is a little secret, I use the pigtail all the time...Why? Because it is safer, how?
Well because I know that in the summer when current draw is high and voltage drop is at it's greatest, the 50A receptacle has a minimum of #8 going to it. This reduces voltage drop dramatically, saving my equipment and reducing my risk for a fire from the a/c trying to start.
But don't tell anyone, I don't want the pigtail police coming after me.



You cannot manipulate the NEC to make it work for you. If you want to do something that is not right it's fine by me. The 30 amp breaker in your motor home does not protect the cable going out to the post .

If you are an electrician you would know that the breaker protecting the cable to your motor home is the one that feeds the receptacle on the post.

The following is from the previous post that you may not have seen.


Here is a video of an electrical fire that did not trip a breaker or blow a fuse. A little background first because I do not want people to say its not the same as a RV cord or you need to figure for the impedance of the transformers, its still a electrical fire. This appears to be 13,800 volts feeding 3 pole mounted transformers. The output from the transformers is most likely 480/277. You can see the electrical fire at the bottom of the pole. It's more then likely is rigid steel and the wires are bouncing around and arcing but not tripping the fuses overhead. Just showing that it certain situations freaky things can happen with electricity.

You would never have a catastrophic situation happen like this with your motor home just want you to see the power of electricity.


Steve B
4100 lb 8.872@ 156 MPH naturally aspirated
Square peg in a round hole is the way to go

cjalphonso

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Posted: 07/31/12 01:35pm Link  |  Print  |  Notify Moderator

In no way am I manipulating the code and I never once said the 30A breaker protects the cable going out to the post. What I said was that if the breaker in the RV sees 30A or according to you 24A, the breaker would trip stopping the current draw. Notice I said draw, as the RV would no longer be drawing any amperage from the pedestal. So now that the RV is disconnected via the breaker, the only possible way for the wire to see any current draw is a failure within the wire itself and even if that happened it would only see the 50A and then trip the pedestal.

Ok, I've looked at your video. Your analyses really makes me question your abilities here. The video electrically is completely different from the situation at hand. There is no breaker protecting the wires on the secondary side of the transformers, there rarely is. The breakers you see are on the primary side of the transformers and they don't trip because the transformers never get overloaded. In order for this video to valid to our situation, you would have to remove the 50A pedestal breaker and the 50A breaker in the panel and the main breaker of the panel and the breaker in the main distribution panel.

This is a prime example of why never to hire a contractor to do an engineers job.





69gp

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Posted: 07/31/12 04:20pm Link  |  Print  |  Notify Moderator

cjalphonso wrote:

In no way am I manipulating the code and I never once said the 30A breaker protects the cable going out to the post. What I said was that if the breaker in the RV sees 30A or according to you 24A, the breaker would trip stopping the current draw. Notice I said draw, as the RV would no longer be drawing any amperage from the pedestal. So now that the RV is disconnected via the breaker, the only possible way for the wire to see any current draw is a failure within the wire itself and even if that happened it would only see the 50A and then trip the pedestal.

Ok, I've looked at your video. Your analyses really makes me question your abilities here. The video electrically is completely different from the situation at hand. There is no breaker protecting the wires on the secondary side of the transformers, there rarely is. The breakers you see are on the primary side of the transformers and they don't trip because the transformers never get overloaded. In order for this video to valid to our situation, you would have to remove the 50A pedestal breaker and the 50A breaker in the panel and the main breaker of the panel and the breaker in the main distribution panel.

This is a prime example of why never to hire a contractor to do an engineers job.


I did explain in my post that this is an example not to be associated with an RV. You should read the full post a few pages back.

As for the 30 amp breaker and any other breakers you should not exceed 80% of the breaker rating. This also applies to wire. Examples of max amperage on wires. #14 wire no more then 12 amps, #12 wire no more then 16 amps, #10 wire no more then 24 amps. For breakers 15 amp breaker should not be loaded with more then 12 amps, 20 amp breaker no more then 16 amps and a 30 amp breaker no more then 24 amps.

As for my abilities, I am more then capable of doing any type of electrical construction work.

69gp

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Posted: 07/31/12 08:24pm Link  |  Print  |  Notify Moderator

cjalphonso wrote:

A couple of things about this statement:
" As for your theory that the 50 amp breaker will protect the #10 cord your dead wrong. Every time you exceed the limit of this cord you are heating it up and degrading it. This cord by code is limited to 80%of its rated value. Its rated for 30 amps you should not draw more then 24 amps. Over time if you keep using it this way you will have an issue. That's a fact.

You will never exceed the limit on this cord as the 30A breaker will trip and stop any current draw (unless catastrophic failure and yes it may see 50A until the 50A breaker trips.)
The cord is not limited to 80% of its value, the cord will handle 100% of its value, the 80% is an NEC design requirement, not a limitation on the cord. In fact #10's are rated up to 35A.

Here is a little secret, I use the pigtail all the time...Why? Because it is safer, how?
Well because I know that in the summer when current draw is high and voltage drop is at it's greatest, the 50A receptacle has a minimum of #8 going to it. This reduces voltage drop dramatically, saving my equipment and reducing my risk for a fire from the a/c trying to start.
But don't tell anyone, I don't want the pigtail police coming after me.



Take a look at table 400.5(A)(1) you would need to use column B. Cable is rated at 30 amps. You cannot use the far right column as these are for the most part dealing with electric heat and a few of them are rated for dry locations only.

cjalphonso

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Posted: 08/01/12 06:32am Link  |  Print  |  Notify Moderator

" A little background first because I do not want people to say its not the same as a RV cord or you need to figure for the impedance of the transformers, its still a electrical fire"

This statement specifically says that it is the same situation as the RV cord. This is a false statement and the video is nothing like the situation we are talking about. However, I will say that the video IS the exact situation of every household in America. There is no protection from the pole mounted transformer to your house and if your main panel is inside your house, then you have unprotected conductors running from the meter to your main breaker, which is a much worse situation than what we are talking about here.

Ok, so the cable is rated at 30A rather than 35A. Either way that point is mute as once the breaker inside the RV trips, which it will once it reaches 30A, the flow of current will stop, making it impossible for the conductors to ever see more than 30A unless your have a cord failure. If that's the case, 30A or 50A cord will make no difference, the 50A at the pedestal will trip.

Stop using scare tactic videos and electrical jargon to prove your point. If your point is to impress with words, I'm not impressed.

pianotuna

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Posted: 08/01/12 06:45am Link  |  Print  |  Notify Moderator

Hi,

Roll your own 50 to 30 adapter with a 30 amp circuit breaker.


Regards, Don
Full Time in a Kustom Koach Class C 28'5", 256 watts Unisolar, 875 amp hours in two battery banks 12 volt batteries, Magnum 3000 watt PSW inverter.

69gp

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Posted: 08/01/12 11:01am Link  |  Print  |  Notify Moderator

cjalphonso wrote:

" A little background first because I do not want people to say its not the same as a RV cord or you need to figure for the impedance of the transformers, its still a electrical fire"

This statement specifically says that it is the same situation as the RV cord. This is a false statement and the video is nothing like the situation we are talking about. However, I will say that the video IS the exact situation of every household in America. There is no protection from the pole mounted transformer to your house and if your main panel is inside your house, then you have unprotected conductors running from the meter to your main breaker, which is a much worse situation than what we are talking about here.

Ok, so the cable is rated at 30A rather than 35A. Either way that point is mute as once the breaker inside the RV trips, which it will once it reaches 30A, the flow of current will stop, making it impossible for the conductors to ever see more than 30A unless your have a cord failure. If that's the case, 30A or 50A cord will make no difference, the 50A at the pedestal will trip.

Stop using scare tactic videos and electrical jargon to prove your point. If your point is to impress with words, I'm not impressed.


Hi Curt,

As for the video I state that it is not like a MH. Just shows what electricity can do. As for 30 amp vs 50 it seems as if it is a moot issue, both sides are sticking to their view and not budging.

As for scare tactics that's not what I am doing.

You seem to have some knowledge of the electrical industry how does this sound. I run my RV off the following, 1 set of 4 group 31-batteries that each have a 120 amp hour capacity. These each have a CCA of 1250 amps and cranking amps of 2150 amps. That is 8600 amps that instantaneously available if a positive cable shorts out. Its not likely to happen but if it did it would make one heck of a mess.

cjalphonso

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Posted: 08/01/12 01:26pm Link  |  Print  |  Notify Moderator

Ok truce, I did enjoy tip-toeing through article 551 though. It's been a while since I designed one.
I must ask, why group 31@12v? wouldn't T-105 @ 6v be more bang for the buck?

69gp

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Posted: 08/01/12 02:04pm Link  |  Print  |  Notify Moderator

cjalphonso wrote:

Ok truce, I did enjoy tip-toeing through article 551 though. It's been a while since I designed one.
I must ask, why group 31@12v? wouldn't T-105 @ 6v be more bang for the buck?



I only paid $125.00 each for them. That was for the Interstate Odyssey brand. Last year on a project we were doing I had 4 electric lifts on the job and over one weekend the site was burglarized with the batteries and other equipment stolen. That's 4 batteries per lift for a total of 16. I made a deal with Interstate for a buyout as not only did I have 4 lifts put out of service but there were 5 others. The only good thing is I have insurance for loss of tools.

Steve

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