electrical circuit question

"thats not how it works, thats not how any of this works" .

Mule said:

Pucker up, bet you are gonna find 25 amps each leg.

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If that were true...why would a 4 wire 50A 125/250 4 wire power cord use much heavier wire than a 30 amp cord carrying more amperage? (50A - 6 Ga, 30A - 10 ga)

Why would it be considered a major power upgrade over 2-30 amp cords?

Need I go on?

Ok boys, try this. Take your amp meter (you do have one dont you ?) and put it on the red wire, lets say it reads 15 amps. Then put it on the black wire, lets say it reads 20 amps. Then put the black AND red in the meter, it will read 5 amps. When you actually understand why you will have grasped the concept and will have had an "aha" moment. Until then ignorance is bliss.

kulas44 said:

Ok boys, try this. Take your amp meter (you do have one dont you ?) and put it on the red wire, lets say it reads 15 amps. Then put it on the black wire, lets say it reads 20 amps. Then put the black AND red in the meter, it will read 5 amps. When you actually understand why you will have grasped the concept and will have had an "aha" moment. Until then ignorance is bliss.

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again cute...

But if I have a 50A 125/250 service split into 2 busses served by 50A CBs....

Can I run 3 space heaters on buss A drawing 39 or so amps...and on buss B run a water heater drawing 13 amps and 2 stove burners drawing another 20 amps?

kulas44 said:

Ok boys, try this. Take your amp meter (you do have one dont you ?) and put it on the red wire, lets say it reads 15 amps. Then put it on the black wire, lets say it reads 20 amps. Then put the black AND red in the meter, it will read 5 amps. When you actually understand why you will have grasped the concept and will have had an "aha" moment. Until then ignorance is bliss.

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how about we do this instead:

lets hook up my washer/dryer 30 amps and my toaster 20 amps up to the red and white wires. Lets hook up my forward air conditioner 25 amps and my rear air conditioner 25 amps up to the black and white wires. I'm now able to loop my ammeter around the red and read 50 amps and then loop it around the black wire and read 50 amps and the last proof I need is I am running 100 amps of load.

The more I read this back and forth, the more I was getting confused. Then I read this:
This 50-amp service has 4 wires with two 120-volt HOT feeds. It is a misconception that this 50-amp RV service is something special. This service is a STANDARD 120/240 50-amp 3 pole with 4 prongs used for numerous applications.
From this common service we can draw 120 or 240 volts. Each leg is 50 amps @ 120 volts. 50-amp X 120-volt = 6000 watts. But since there are 2 HOT 120-volt legs at 6000 + 6000 = 12,000 watts to use in the RV or 50-amp X 240-volt = 12,000 watts when used as a 240-volt service. Almost ALL 50-amp wired RV's use both sides of the service separately as 120 volt on each leg. Only a few mostly high-end coaches utilize the 240-volt from this same service.
The 50-amp 3-pole 4-wire service is superior to the 30-amp service because of the total amperage available.
30-amp 120-volt service = 3,600 watts
50-amp 120/240-volt service = 12,000 watts


If this is true you are both right. Each leg can provide 50 amps individually or they can both be combined into a single 240 volt AC feed and provide 50 amps. The reason for the 240 is to lower the wire gauge required. I claim no special knowledge on this. I was a forestry major.



Tom

psneeld said:

No one is disputing the name...but If I put a amp meter on the red wire and add it to the black wite...50+50=100...so you tell me...it seems like you won't be happy until or you really don't see that each wire can carry 50 amps to 2 separate busses.

Yes we get the name game.... but not the misunderstanding.....

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50A 125/250>>> One 4 conductor cable with one ganged 50A breaker. The 50A from the black is the same 50A current going through the red at any particular instant. Some will go out the common neutral (White) depending on how the loads are set up but what goes out the neutral is not going out the red.
Black current = White + Red.
Red current = White + Black.
100 amps through the neutral = smoke

100A 125v is two 50A 3 conductor cables with two separate 50A breakers on board and the neutrals only connected on the shore post end so that you cannot put more than 50A down the neutral.

You still cannot measure 100 amps anywhere. All of this goes back to the very basics of alternating current theory. Either you get it or you dont. When you can walk through a 138000 volt substation and know the phase angle and rotation and calculate for phase shift thru the step regulators and the required capacitance for a decent power factor to get the power to the end user (large 3 phase motors that do not run backwards) then you can tell me I dont know what I'm talking about. I do know where you guys are coming from, I once had an electrical engineer tell me to lower the voltage so we would sell more electricity. He didnt grasp the concept either, ever, as far as I know.

tpbrady said:

The more I read this back and forth, the more I was getting confused. Then I read this:

The 50-amp 120/240-volt 3 pole 4 wire grounding Service​

This 50-amp service has 4 wires with two 120-volt HOT feeds. It is a misconception that this 50-amp RV service is something special. This service is a STANDARD 120/240 50-amp 3 pole with 4 prongs used for numerous applications.
From this common service we can draw 120 or 240 volts. Each leg is 50 amps @ 120 volts. 50-amp X 120-volt = 6000 watts. But since there are 2 HOT 120-volt legs at 6000 + 6000 = 12,000 watts to use in the RV or 50-amp X 240-volt = 12,000 watts when used as a 240-volt service. Almost ALL 50-amp wired RV's use both sides of the service separately as 120 volt on each leg. Only a few mostly high-end coaches utilize the 240-volt from this same service.
The 50-amp 3-pole 4-wire service is superior to the 30-amp service because of the total amperage available.
30-amp 120-volt service = 3,600 watts
50-amp 120/240-volt service = 12,000 watts


If this is true you are both right. Each leg can provide 50 amps individually or they can both be combined into a single 240 volt AC feed and provide 50 amps. The reason for the 240 is to lower the wire gauge required. I claim no special knowledge on this. I was a forestry major.



Tom

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I have been searching for the same explanation for a marine application...because it's essentially the same...but alas...it's not as popular in marine circles to discuss it as RV circles.

Same idea only a different hobby.

Sure the "tech" of what is read on meters and what the "theory" discussed lends itself to wordy explanations...

But the truth is that a 4 wire 50A 125/250V power cord split into 2-125V busses aboard a boat will power 2X as many appliances as a 3 wire 50A 125V shore power cord.

That's what the people who have them are actually using and living with...so please explain in less than EE terms...why that's so.

I don't need to visit a power station to know how many appliances are running on my boat or know basic house/marine wiring...I can bloat my knowledge base too..but it has nothing to do with simple explanations.

And I don't give a rat's behind who believes me or not...but for all newbies contemplating electrical services aboard their boats...I surely hope you eventually get the straight poop on what service will provide you the electric to meet you needs.

High Wire said:

50A 125/250>>> One 4 conductor cable with one ganged 50A breaker. The 50A from the black is the same 50A current going through the red at any particular instant. Some will go out the common neutral (White) depending on how the loads are set up but what goes out the neutral is not going out the red.
Black current = White + Red.
Red current = White + Black.
100 amps through the neutral = smoke

100A 125v is two 50A 3 conductor cables with two separate 50A breakers on board and the neutrals only connected on the shore post end so that you cannot put more than 50A down the neutral.

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If L1 and L2 are 180deg out of phase, the amps in the neutral will be the difference between L1 and L2 amps, not the sum. So no smoke.

Now if L1 and L2 are in phase, then yes N gets the sum. That would take a bit of a fubar on the dock to get that.

kulas44 said:

You still cannot measure 100 amps anywhere. All of this goes back to the very basics of alternating current theory. Either you get it or you dont. When you can walk through a 138000 volt substation and know the phase angle and rotation and calculate for phase shift thru the step regulators and the required capacitance for a decent power factor to get the power to the end user (large 3 phase motors that do not run backwards) then you can tell me I dont know what I'm talking about. I do know where you guys are coming from, I once had an electrical engineer tell me to lower the voltage so we would sell more electricity. He didnt grasp the concept either, ever, as far as I know.

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Correct, you will not measure over 50a in any one conductor. But you will have two conductors capable of 50a each. For a total capability of 100a at 125v. Do you disagree with this???

But it could be done, theoretically. 2 50 amp breakers on the same leg does equal 100 amps. It would require much larger wire, at least #2 to carry that much load. And the neutral would also need to be larger. You could wire your dual 50 amp breakers in the dock service to one leg and use the red and black wires as one hot lead and the green and white as one neutral lead. I cannot imagine why you would want to, other than to show me you can measure over 50 amps. As far as the power station, Its like understanding a diesel engine, once you actually understand whats going on and why the size is irrelavent.

100A's through one 50A 125/250 cord????

Ski in NC said:

Correct, you will not measure over 50a in any one conductor. But you will have two conductors capable of 50a each. For a total capability of 100a at 125v. Do you disagree with this???

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I think he does....

Yes, I do dissagree. Its kinda like having a nice conversation with a fellow hot rodder about engine modifications, cams, forged or eurectic pistons, etc. And then he says he gained 20 horsepower by putting on a K&N air filter. I usually just walk away shaking my head.

The double-pole (250V) pedestal breaker has a 50 on it. Done deal. You can draw 50A from several loads at 125V from either side of neutral OR 50A across both hot leads at 250V OR any combination of the two. But no matter what happens, if you try and pull more than 50A from it (surges not withstanding), she's gonna blow. Period.

AC Wiring | Boat Wiring Advice - Marine Electrical Tips and Tricks - Part 4



Bruce,
All your y adapter does is combine the white (neutrals) and green (ground) wires internally. You can certainly eliminate the adapter in your system and replace it with a 125/250v 50A Inlet.
Green wire
The green wires should already be combined on your AC distribution panel. If this is the case, you can certainly eliminate one of the green wires between your distribution panel and your inlet.
White wire
The whites can be combined at your AC distribution panel or at the inlet. Most inlets are not designed to accept 2 wires and a poor connection could cause severe problems. You should connect the Neutrals on the line side (inlet) of your 50 amp breakers. This allow the two systems to still operate properly as 2 separate 50 amp systems.

kulas44 said:

Yes you are correct, sometimes I forget the smiley. But when it comes to electric service you only have the size of the breaker. The utility provider says its 50 amps with a pair of 50 amp breakers. They do not add it up and call it 100 amps. Its not 150 amps in 3 phase. ITS 50 AMPS. Unless of course its 30 amps Then its just 30 amps not 30 x 2. Its 2 30 amp circuits. Nowhere will an amp meter read over the amperage of whatever a correctly rated and operating breaker will handle. The only way to get 100 amps from a 125/250v circuit is with a transformer to convert from 250 volts to 125 volts. The resulting output will be "adding" and using both legs of the 50 amp breaker available. That still does not make your service a 100 amp service, still just 50.

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This must be a semantic difference of some sort. With 50A 120/240V service, can't you power two 50A 120V load? I think the answer is yes. That's the cumulative 100A of 120V loads that people are talking about.

kulas44 said:

Yes, I do dissagree. Its kinda like having a nice conversation with a fellow hot rodder about engine modifications, cams, forged or eurectic pistons, etc. And then he says he gained 20 horsepower by putting on a K&N air filter. I usually just walk away shaking my head.

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No No No this conversation has been like rolling in the mud with a hog. Pretty soon I realize it not the conversation its really that a couple of you just like to roll in the mud.

As one of the guys on Shark Tank would say "I'm Out".

I guess this means I dont get that kiss

From Marinco, they make Y connectors:

Let's change it up a little.

What if my over sized Rocna and all chain rode made my shore-cords handle more amperage??

N4712 said:

Let's change it up a little.

What if my over sized Rocna and all chain rode made my shore-cords handle more amperage??

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Oliver…go wash your mouth out…youz are troublemaking…

Peter B said:

Oliver…go wash your mouth out…youz are troublemaking…

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:lol::lol:

Do you connect the ground to the chain for that to work?

dhmeissner said:

From Marinco, they make Y connectors:

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Thank you!!!! Note the cutout from the last para....

Nowhere does it say you have 100 amps. Unless you think the words "2 pools of 50" actually means 100. If it meant 100 it would say 100. Still bliss on your part.

tpbrady said:

Do you connect the ground to the chain for that to work?

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Yes, but I'm wondering if I should hook the engine ground and neutral to it? What kind of zincs do I need?

OK folks....

.... you decide which semantics you want to install on your boat...something that a marine shore power cord manufacturer explains carefully what to use so you get what you want...enough power to run 12000 watts worth of equipment...

or the other....

The Marinco article says it all....no matter what language you speak.