electrical circuit question

Put an amp meter on it and show me 100 amps, not gonna happen. You have a 50 amp service, it is not cumulative. Although I am impressed that a Texan can do simple math

kulas44 said:

Put an amp meter on it and show me 100 amps, not gonna happen. You have a 50 amp service, it is not cumulative. Although I am impressed that a Texan can do simple math

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I told you I have two 50 amp phases. (50amp125/250) With two amp meters I can show you 100 amps. You have to add them together. Maybe thats why you can't get to 100. You have to add.

kulas44 said:

Put an amp meter on it and show me 100 amps, not gonna happen. You have a 50 amp service, it is not cumulative. Although I am impressed that a Texan can do simple math

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psneeld said:

I'm not sure why you guys think things melt at rated capacity.....

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I guess cause I've seen it first hand so many times. Unless ever connection, plug and deceptively is in very good condition at every location you connect to, your cord ends and recepticals are not going to be happy running at full capacity hour after hour, day after day. Then you have start up loads.

henryj2 said:

Our 44' trawler has 3 electrical inlets for shore power: 30 amp, 50 amp, a/c. We have only used 30 amp which sometimes leaves us a little short and the main circuit snaps off. We have been told that if we get the bigger cord and kick up to use the 50 amp inlet we will have more available juice but it will not operate the a/c. We have also been told that the only way we can run a/c from shore power is by using a 50 amp source (available at our marina) and getting a splitter and an additional 30 amp cord and run one cord from the splitter to the 30 amp inlet and the other to the a/c inlet. We are told this will allow us to run the a/c but it will be a separate circuit and will add no more available power for the rest of the vessel. Would appreciate any thoughts.

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As so often happens on boating forums, people have taken your question and turned it into an irrelevant argument among themselves.

Like a couple posters mentioned, this setup, if it really works as you describe, is "less than optimal" at best. Your best bet is to find someone who understands boat wiring and have him or her examine your boat in person and determine the best way to power all your appliances efficiently and at the least cost. Many marinas charge for electricity based on amperage or the number of power cords.

I would think it's a pretty big or complicated boat that couldn't be powered by one 50 amp shorepower service.

Depends if it's 50A 125 or 50A 125/250....especially if the stove is electric

A water heater, air Conditioner, hair dryer can be almost 40 amps....someone using a large and small burner cooking breakfast on an electric stove can use another 15 amps easy...there's always a few parasitic chargers on a boat plus the main charger that may kick on at 5-10 amps...so 50 amps is easy to hit....having another 50 in reserve from a 50A 125/250 cord split into 2 busses is nice to have.

My friends Viking 55 had 2 - 50A 125/250 inlets and with an all electric boat and 6 people aboard or so...much like any house these days....even a 200 amp house service is there for a little cushion.

As a former electric company employee/lineman/wireman/forman/ of 15 years then lead electrician for an oil field electrical contractor I am possibly qualified on this subject. Most folks think they can "add" there electric service. It is still only and exactly what the breaker allows. If I have 2 air compressors each putting out 120 psi (the potential) then add them together do I get 240 psi.? No,,, but I can run a larger cfm load. I still have 120 psi. Same with electric service. Some large boats have 50 amp 3 phase service. The do not consider it to be a 150 amp service. Generally the captain of these boats actually does know his stuff.

kulas44 said:

As a former electric company employee/lineman/wireman/forman/ of 15 years then lead electrician for an oil field electrical contractor I am possibly qualified on this subject. Most folks think they can "add" there electric service. It is still only and exactly what the breaker allows. If I have 2 air compressors each putting out 120 psi (the potential) then add them together do I get 240 psi.? No,,, but I can run a larger cfm load. I still have 120 psi. Same with electric service. Some large boats have 50 amp 3 phase service. The do not consider it to be a 150 amp service. Generally the captain of these boats actually does know his stuff.

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I may be wasting effort here but; In your air compressor example psi is voltage and CFM is amperage.

I have 2 50 amp 125 breakers. They do add and therefore I have 100 amps at 125. Many boats are like this.

In your 3 phase example you would have 150 amps if each phase were provided with a neutral. You would have three services of 50 amps each.

Actually the larger boats have 100a three phase service.

And it's the engineer on board that knows his stuff in that case. Not necessarily the captain.

I have 1 50 amp 120 volt cord going to two 30 amp breakers onboard. That's max for that 50 amp service and 50 amp cable. Run another cable from your neighbors box and you will have 100 amps available. I am not an electrician and will never be an electrician but that's what I did to enable a welder to work. The smiley means you can't jump all over me right?

dimer2 said:

I have 1 50 amp 120 volt cord going to two 30 amp breakers onboard. That's max for that 50 amp service and 50 amp cable. Run another cable from your neighbors box and you will have 100 amps available. I am not an electrician and will never be an electrician but that's what I did to enable a welder to work. The smiley means you can't jump all over me right?

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I read somewhere that a man gotta do what a man gotta do then he goes fishing. If you pay the welder he will figure a way.

psneeld said:

Depends if it's 50A 125 or 50A 125/250....especially if the stove is electric

A water heater, air Conditioner, hair dryer can be almost 40 amps....someone using a large and small burner cooking breakfast on an electric stove can use another 15 amps easy...there's always a few parasitic chargers on a boat plus the main charger that may kick on at 5-10 amps...so 50 amps is easy to hit....having another 50 in reserve from a 50A 125/250 cord split into 2 busses is nice to have.............

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Yea, throw in some power tools,, electric heaters, etc. and you can use a lot of power. Most folks with boats get by with a single 50 amp input or even 30 amp. Ships, of course, are another matter altogether.

Many marinas and most transient marinas charge by the power cord and its capacity so if you have two 50 amp cords you will pay double what someone with a single 50 amp cord will pay. Sometimes it's worth it to manage your power consumption. Don't use a hair drier at the same time you're cooking breakfast and cutting lumber for a new deck.

Seems to me that this discussion has gone completely off track. The only way the OP is going to figure out how his boat wiring works is to either grab the bull by the horns and dig into it, trace wires, unplug stuff to see what quits working, get a clamp on amp meter to help trace wires, etc. Or find someone to do it for him, and good luck with that. This is not something that can be solved on a forum.

Bob

OK..so all I was saying is that a boat doesn't have to be large or complicated to eat up well more than 50A...and even a 100 is just a comfortable margin for surges/occasion.

Not too hard to understand....

An because I have never paid for metered consumption...just either a seasonal rate or transient rate...I could care less until I find myself in that situation. But I have said on several occasions working towards electrical independence the way things are going isn't a bad idea.

I'm not sure why Kulas44 doesn't see that 50A 125/250 provides 2 50 amp legs ( that's the way they are breakered on the poles and in the boat..even if only 1 toggle they break the red and black...each leg is breakered at 50 amps....very similar and using the same wiring that a house uses...hard to believe he doesn't see it)

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.

Are you saying you can't draw 50 amps , 120V per leg (loosely called phase)?

actually rereading your post...please explain how you think a marina power post is wired....

the ones I'm familiar with are just like a house...2 hot legs, each breakered for whatever the main panel is....then sub-paneled out to each power post....which has 2 hot legs, a neutral and a ground that is divided up to all the outlets on the post and breakered according to outlet. At a 50, 120/250 outlet, 2 50A CBs protect 2 legs, each 110 out of phase to provide 50 amps down each leg to the boat.

If the boat is wired with 2 separate busses, each bus can be subbed to provide 50 amps thus the boat can pull 12500 watts....6250 per bus (50x125).

That's my understanding of it and I apologize and need to hit the books again if I'm incorrect...but then again so is my marina so I'll be contacting my lawyer first...

obthomas said:

50 amps is 50 amps.......unless you have two of them. 50 plus 50 is 100.

I have a 50 amp 125/250 service cord and its two 50 amp split phase leads give me 100 amps on my 40 foot boat. I will take you downtown Miami and give you an hour to draw a crowd and kiss your you know what if I don't have a 100 amps.

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As a fellow Texan, 13 years in Friendswood even, Telco field guy in Seabrook I have to disagree.

Watts are watts are watts. Not amps are amps are amps. 50 amps @ 120 volts is 25 amps at 220, 12.5 amps at 440. It works backwards too, 50 amps @120=12 volts @ 500amps. All in Ohms Law
E=IR

No matter what the voltage is, no matter what the amps are the formula is P=EI. Watts converted to various voltages, amps will always show the ratio. Truly wack a mole. Push down amps voltage rises and visa versa.

Mule said:

As a fellow Texan, 13 years in Friendswood even, Telco field guy in Seabrook I have to disagree.

Watts are watts are watts. Not amps are amps are amps. 50 amps @ 120 volts is 25 amps at 220, 12.5 amps at 440. It works backwards too, 50 amps @120=12 volts @ 500amps. All in Ohms Law
E=IR

No matter what the voltage is, no matter what the amps are the formula is P=EI. Watts converted to various voltages, amps will always show the ratio. Truly wack a mole. Push down amps voltage rises and visa versa.

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Alright, lets work backwards. 50 amps @ 125/250 is what I have dockside.
That means 50 amps @ 250. At 125 you get to double the amps. I could repeat the conversion to WATTS and back to amps but you already did that I could also discuss ohm's law but you did that too. The end result is still the same. I have a total of 100 amps @ 125 to use in my boat.

obthomas said:

Alright, lets work backwards. 50 amps @ 125/250 is what I have dockside.
That means 50 amps @ 250. At 125 you get to double the amps. I could repeat the conversion to WATTS and back to amps but you already did that I could also discuss ohm's law but you did that too. The end result is still the same. I have a total of 100 amps @ 125 to use in my boat.

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...certainly the way it's designed....

look at any marine panel with 2 busses like the one I attatched (if the pdf worked)...why do 2 separate busses if all you would get is 50A?....and how would the red and black wires know how much each one should carry...

Ask your marina what size service you have. If you can call your semi planing twin 350 hp motor yacht a trawler I guess its not much of a stretch to call your 50 amp 125/250 service 100 amps. Just because the builder didnt call it a trawler is of no consequence, just like your service provider doesnt call your dockside 50 amp service a 100 amp. You can call it whatever you want to. Why not "two phase 100 amp". Other than there is no such thing as two phase power I dont see a problem with it. I do enjoy the debate, and yes this thread has really drifted. I hope the OP gets his boat figured out.

50a 125/250 shore cord has two hots, its breaker has two 50a poles. If you run 250v loads, max is 50a. If you break it into two 125v loads, each one can load up to 50a.

So if boat is full of nothing but 125v loads, you can have a total of 100a of load. 50a on one panel, 50a on the other. If running 250v loads, you only get 50a. Watts are the same in either case.

Looks like we are all right......

Reminds me of that ins. commercial. "thats not the way it works, that's not how any of this works" While the other old gal is posting pics to her "wall". I do realize how folks think I just dont get it. If anyone can show me, on an amperage meter, any amperage over 50 on a 50 amp circuit I will eat my hat. If the CB is working correctly it will trip at anything over 50 amps. Hence the term "50 AMP SERVICE".

kulas44 said:

Ask your marina what size service you have. If you can call your semi planing twin 350 hp motor yacht a trawler I guess its not much of a stretch to call your 50 amp 125/250 service 100 amps. Just because the builder didnt call it a trawler is of no consequence, just like your service provider doesnt call your dockside 50 amp service a 100 amp. You can call it whatever you want to. Why not "two phase 100 amp". Other than there is no such thing as two phase power I dont see a problem with it. I do enjoy the debate, and yes this thread has really drifted. I hope the OP gets his boat figured out.

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O.K. Once and for all time I will call my dockside service 50 amp 125/250.

hehe hehe but I will still kiss your @$$ If I don't have 100 amps.

Sure that's what it is called...have at it...semantics are great to confuse the issue. I know what you are discussing...do you know what we are?

The rest of us are enjoying 100 amps of 125V power....again no matter what you call the service.

I've been drug down enough to that level...how about everyone else????

I hope we helped the OP in some way...if nothing else to understand what's available depending on what's going on in his panels.

So, no one here can SHOW me any amperage over 50 on a 50 amp circuit. Is this correct ?

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

kulas44 said:

So, no one here can SHOW me any amperage over 50 on a 50 amp circuit. Is this correct ?

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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.....

kulas44 said:

So, no one here can SHOW me any amperage over 50 on a 50 amp circuit. Is this correct ?

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I have two of those circuits. Which one do you want to see 50 amps on.

Mule said:

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

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:lol: