On Monday, March 24, 2014 4:41:27 PM UTC-4, Mr. Luddite wrote:
On 3/24/2014 4:15 PM, wrote:

On Monday, March 24, 2014 3:41:13 PM UTC-4, Mr. Luddite wrote:

On 3/24/2014 3:26 PM, wrote:



On Saturday, March 22, 2014 1:33:11 PM UTC-4, da...@righthere... wrote:



On Tue, 18 Mar 2014 08:01:29 -0400, "Mr. Luddite" wrote:















On 3/18/2014 7:42 AM, KC wrote:







On 3/18/2014 3:34 AM, Mr. Luddite wrote:







On 3/18/2014 12:22 AM, KC wrote:







On 3/17/2014 7:57 PM, Mr. Luddite wrote:







On 3/17/2014 7:14 PM, wrote:







On Mon, 17 Mar 2014 18:19:42 -0400, KC wrote:















On 3/17/2014 6:01 PM, david@righthere... wrote:







I've been on 30A 120V power at the dock for years and would now like







to upgrade







to 50A 220V, or what they refer to as 50A 250V at the marina office.







I haven't







put a meter on it yet but so far suspect it's closer to 220 than







250. The socket







on the pedestal is like the one pictured he















http://www.catagle.com/68-153/CWD_Ar...uyersGuide.htm















They say it's 3-pole 4-wire. I'm guessing X and Y are the two hot







legs and W is







the neutral. Between X or Y and W would be 120V+/- and between X and







Y is the







220/250V. Right? How does the ground tie into it though? With only 3







poles do we







run a separate wire from the boat to the pedestal, and if so how do







we tie in?















Also can anyone suggest the cheapest place to get a plug like that?







So far the







best price I've found is $68.18 he















http://www.ktool.net/servlet/the-581...-63CR65/Detail















































Thank you for any help!







David























The plug is 10-20 bucks at home depot or lowes, Scottys whatever you







have. It's a dryer plug basically... As to the wiring, I forget but I







have a book I always use when I do the wiring.. It was about 20







bucks at







home depot, I have had it for as long as I have owned a house....















Not true at all, sorry.















This is a non-NEMA twist lock 50a plug, that is corrosion resistant.















A dryer plug is a NEMA 14-30 straight blade that would go south pretty







quickly on a pier.































Yup. I think Scotty should stick to building websites and not wiring







boats.































Why, cause I took a quick look and made a mistake? I have done a lot of







wiring in my time including my whole house to code in Essex from moving







in with full Knob and Tube... I have done barns, and wells. When you







have a 100 year old house you tend to pick up stuff. You should see me







sweat a pipe.... even if I don't know all the right terminology. Either







way, that's why I always keep my electrical book with me to check my own







work as I go....























Scott, the OP didn't say if he was re-wiring his *boat* for a 50 amp,







240v marine split service. He might be just trying to use one leg of it







to supply 50 amps to his existing 30 amp, 120v boat panel. If so, he's







taking a big risk because it's not just the plug in question. The







primary feed wires in the boat that run from the power inlet to the







power panel needs to be changed at a minimum. Plus, if the existing







power panel has a 30 amp main, supplying it with 50 amps isn't going to







do him any good. If he changes that to a 50 amp breaker without doing







any changes to the wiring, he could overheat the primary feed wiring in







the boat, causing a fire.















My comment was more than pointing out that a split, 50 amp marine







service plug is not a dryer plug.















I did what I think he is trying to accomplish on the Grand Banks we had.







It had a standard, 30 amp, 120v service. I wanted to add two







air-conditioning units to the boat. Rather than change everything over







to a 50 amp, 240v split service I simply added another 30 amp, 120v







marine inlet connector, wiring (marine type) and a small, dedicated







breaker box with two 15 amp breakers in it, one for each of the AC units.















After talking to a guy at West Marine that's the type of thing I'll do too if I







follow through with it. I might add a couple of extra outlets too, in case I







want to run an extra heater in the winter without tripping the main as I do from







time to time.















I will want to have 240V available though. I did stage lighting for years and







have been given some old moving lights that need repair and the place I work







doesn't want to put the money into them. They are old Martin Mac 500s and 600s







and they only work on 240V (+/-) power. So what I mainly want the 240 for is so







I can work on them and try to get some of them going again. My question is: If







the marina hooks up another 30 amp sevice, will it be out of phase with the







original one or could it be in phase? It wouldn't do me any good if it's in







phase, so would I need to specify or would it be out of phase and I don't need







to bother them about that detail, do you know?















I don't know a lot about many things and nothing about some things







however electrical power distribution and wiring happens to be one thing







I *do* know something about. I'd hate to see someone hurt or killed







because they received bad input.















Now, I have a question for you. Let's say your house has a 200 amp







service. Your main breaker is a double pole, 200 amp per pole breaker.







There's 240vac between the two "hot" legs and 120vac between either of







them and neutral. Each hot leg from the utility pole is sized for 200







amps for each side of the service, yet the neutral is also only sized







for 200 amps. Why isn't it sized for 400 amps, the sum of both sides of







the total service?















See if the answer is in your "electrical" book.















Is this a job you are gonna' do yourself? snerk























No, it's not a job. It's a question. Can you answer it with all your







experience wiring homes, barns and whatever?















Look, any handyman can do basic wiring in their house. It's not rocket







science. But knowing something about current capacities, codes and







particularly how the power in a house, commercial building or a *boat*







is distributed requires more than a handy dandy DIY book from the Home







Depot.















I am not an electrician. I am an electrical engineer. If I wanted a







new power service installed in my house or was doing a major upgrade to







the existing service, I'd hire a licensed, master electrician to do the







job.















BTW, the answer to the question I asked is because the two "hot" legs







are 180 degrees out of phase relative to each other, so the net current







flowing through the neutral leg adds algebraically. The current through







the neutral leg can never exceed 200 amperes.















Thanks for sharing that. I still have the question of whether the the two 30 amp







120s would necessarily be out of phase though, even though what you wrote leads







me to believe they probably would be.







The "phase" of conventional residential is debated a bit as some don't think it is two phase and some do.







The important thing for you is that 240v service will have 2 hots, 1 neutral, and 1 ground. Between either of the hots and the neutral you will see 120vac. The same 120vac you are using now. Between the two hots you will see 240vac.







Your biggest problem is that your current panel inside the boat most likely only accomodates 1 hot, 1 neutral, and 1 ground. If that is true you really need a new panel to safely use the 240vac 50amp service. The regular service breakers you have for outlets and lights are typically distributed evenly between the two hots. Any 240vac connections like heat will use a ganged breaker connecting to both hots.







Now you likely do not have to take advantage of the new power at the dock if you don't want to. Simply ignore one of the two new hots. Connect one hot, one neutral, and one ground to your existing setup. Presuming you have a 30amp main for the one hot. Or you make sure everything between the panel and the shore can handle 50 amps.







Do you have a "main" breaker inside that turns off everything? If so, how many amps is it?







It is very unlikely that you have 3-phase service btw. That's commercial.















I've heard electricians refer to a residential service to your home as a



"split phase" service. I agree there is some confusion as to calling it



"two phase" however, as you correctly state, it does have two hot legs



that are 180 degrees out of phase with each other. In my mind that



means there are two, out of phase hot legs. A 3 phase commercial



service would have three hot legs that are 120 degrees out of phase with



each other.







I agree that the OP's actual service to his boat at the pedistal is not



3 phase however the distributed service to the marina could very



likely be a commercial, 3 phase service. It could also be a split phase



like a residential service however depending on the marina size.



Regardless, if the OP wants to get something close to 220vac for testing



his stage lights, he's going to need two hot legs.



The possibility of 3 phase commercial service somewhere in the marina is immaterial.

In this case bringing it up only creates the possibility of confusing

the op.

His 240v 50amp service at the dock will be the same as is found in US

residential homes.



So? I don't understand how that changes anything. He still needs a

second hot leg, either from a distributed 3 phase system or a split

phase system. He acknowledged that he's not trying to change the

service in his boat from a 120vac, 30 amp service to a 250vac, 50 amp

service. He just wants 208vac, 220vac or 240vac to test some stage

lighting. Understanding how that service is delivered is important to

his intended purpose, don't you think, especially if he is not an

electrician as I suspect?



I stand by my previous comments, including my suggestion to employ the

help of a licensed electrician if he is not familiar or sure how it is done.

No, he doesn't need to understand anything about how his service is delivered! He just needs to understand that he has 2 hots and 1 neutral. If he wants 120 he uses one hot and the neutral. If he wants 240 he uses the 2 hots. He should always use the ground as ground if what ever he is connecting has a ground lead. That's it, end of story. He does not need to know any more than that.

On Mon, 24 Mar 2014 14:29:15 -0700 (PDT), wrote:

I stand by my previous comments, including my suggestion to employ the

help of a licensed electrician if he is not familiar or sure how it is done.

No, he doesn't need to understand anything about how his service is delivered! He just needs
to understand that he has 2 hots and 1 neutral. If he wants 120 he uses one hot and the neutral.
If he wants 240 he uses the 2 hots. He should always use the ground as ground if what ever he
is connecting has a ground lead. That's it, end of story. He does not need to know any more than that.

===

Conceptually you are right of course. My concern is with the
implementation. A person who is not familiar with wiring up shore
power plugs and cables can easily create an unsafe condition.

On 3/24/2014 5:29 PM, wrote:
On Monday, March 24, 2014 4:41:27 PM UTC-4, Mr. Luddite wrote:
On 3/24/2014 4:15 PM, wrote:

On Monday, March 24, 2014 3:41:13 PM UTC-4, Mr. Luddite wrote:

On 3/24/2014 3:26 PM, wrote:



On Saturday, March 22, 2014 1:33:11 PM UTC-4, da...@righthere... wrote:



On Tue, 18 Mar 2014 08:01:29 -0400, "Mr. Luddite" wrote:















On 3/18/2014 7:42 AM, KC wrote:







On 3/18/2014 3:34 AM, Mr. Luddite wrote:







On 3/18/2014 12:22 AM, KC wrote:







On 3/17/2014 7:57 PM, Mr. Luddite wrote:







On 3/17/2014 7:14 PM, wrote:







On Mon, 17 Mar 2014 18:19:42 -0400, KC wrote:















On 3/17/2014 6:01 PM, david@righthere... wrote:







I've been on 30A 120V power at the dock for years and would now like







to upgrade







to 50A 220V, or what they refer to as 50A 250V at the marina office.







I haven't







put a meter on it yet but so far suspect it's closer to 220 than







250. The socket







on the pedestal is like the one pictured he















http://www.catagle.com/68-153/CWD_Ar...uyersGuide.htm















They say it's 3-pole 4-wire. I'm guessing X and Y are the two hot







legs and W is







the neutral. Between X or Y and W would be 120V+/- and between X and







Y is the







220/250V. Right? How does the ground tie into it though? With only 3







poles do we







run a separate wire from the boat to the pedestal, and if so how do







we tie in?















Also can anyone suggest the cheapest place to get a plug like that?







So far the







best price I've found is $68.18 he















http://www.ktool.net/servlet/the-581...-63CR65/Detail















































Thank you for any help!







David























The plug is 10-20 bucks at home depot or lowes, Scottys whatever you







have. It's a dryer plug basically... As to the wiring, I forget but I







have a book I always use when I do the wiring.. It was about 20







bucks at







home depot, I have had it for as long as I have owned a house...















Not true at all, sorry.















This is a non-NEMA twist lock 50a plug, that is corrosion resistant.















A dryer plug is a NEMA 14-30 straight blade that would go south pretty







quickly on a pier.































Yup. I think Scotty should stick to building websites and not wiring







boats.































Why, cause I took a quick look and made a mistake? I have done a lot of







wiring in my time including my whole house to code in Essex from moving







in with full Knob and Tube... I have done barns, and wells. When you







have a 100 year old house you tend to pick up stuff. You should see me







sweat a pipe.... even if I don't know all the right terminology. Either







way, that's why I always keep my electrical book with me to check my own







work as I go....























Scott, the OP didn't say if he was re-wiring his *boat* for a 50 amp,







240v marine split service. He might be just trying to use one leg of it







to supply 50 amps to his existing 30 amp, 120v boat panel. If so, he's







taking a big risk because it's not just the plug in question. The







primary feed wires in the boat that run from the power inlet to the







power panel needs to be changed at a minimum. Plus, if the existing







power panel has a 30 amp main, supplying it with 50 amps isn't going to







do him any good. If he changes that to a 50 amp breaker without doing







any changes to the wiring, he could overheat the primary feed wiring in







the boat, causing a fire.















My comment was more than pointing out that a split, 50 amp marine







service plug is not a dryer plug.















I did what I think he is trying to accomplish on the Grand Banks we had.







It had a standard, 30 amp, 120v service. I wanted to add two







air-conditioning units to the boat. Rather than change everything over







to a 50 amp, 240v split service I simply added another 30 amp, 120v







marine inlet connector, wiring (marine type) and a small, dedicated







breaker box with two 15 amp breakers in it, one for each of the AC units.















After talking to a guy at West Marine that's the type of thing I'll do too if I







follow through with it. I might add a couple of extra outlets too, in case I







want to run an extra heater in the winter without tripping the main as I do from







time to time.















I will want to have 240V available though. I did stage lighting for years and







have been given some old moving lights that need repair and the place I work







doesn't want to put the money into them. They are old Martin Mac 500s and 600s







and they only work on 240V (+/-) power. So what I mainly want the 240 for is so







I can work on them and try to get some of them going again. My question is: If







the marina hooks up another 30 amp sevice, will it be out of phase with the







original one or could it be in phase? It wouldn't do me any good if it's in







phase, so would I need to specify or would it be out of phase and I don't need







to bother them about that detail, do you know?















I don't know a lot about many things and nothing about some things







however electrical power distribution and wiring happens to be one thing







I *do* know something about. I'd hate to see someone hurt or killed







because they received bad input.















Now, I have a question for you. Let's say your house has a 200 amp







service. Your main breaker is a double pole, 200 amp per pole breaker.







There's 240vac between the two "hot" legs and 120vac between either of







them and neutral. Each hot leg from the utility pole is sized for 200







amps for each side of the service, yet the neutral is also only sized







for 200 amps. Why isn't it sized for 400 amps, the sum of both sides of







the total service?















See if the answer is in your "electrical" book.















Is this a job you are gonna' do yourself? snerk























No, it's not a job. It's a question. Can you answer it with all your







experience wiring homes, barns and whatever?















Look, any handyman can do basic wiring in their house. It's not rocket







science. But knowing something about current capacities, codes and







particularly how the power in a house, commercial building or a *boat*







is distributed requires more than a handy dandy DIY book from the Home







Depot.















I am not an electrician. I am an electrical engineer. If I wanted a







new power service installed in my house or was doing a major upgrade to







the existing service, I'd hire a licensed, master electrician to do the







job.















BTW, the answer to the question I asked is because the two "hot" legs







are 180 degrees out of phase relative to each other, so the net current







flowing through the neutral leg adds algebraically. The current through







the neutral leg can never exceed 200 amperes.















Thanks for sharing that. I still have the question of whether the the two 30 amp







120s would necessarily be out of phase though, even though what you wrote leads







me to believe they probably would be.







The "phase" of conventional residential is debated a bit as some don't think it is two phase and some do.







The important thing for you is that 240v service will have 2 hots, 1 neutral, and 1 ground. Between either of the hots and the neutral you will see 120vac. The same 120vac you are using now. Between the two hots you will see 240vac.







Your biggest problem is that your current panel inside the boat most likely only accomodates 1 hot, 1 neutral, and 1 ground. If that is true you really need a new panel to safely use the 240vac 50amp service. The regular service breakers you have for outlets and lights are typically distributed evenly between the two hots. Any 240vac connections like heat will use a ganged breaker connecting to both hots.







Now you likely do not have to take advantage of the new power at the dock if you don't want to. Simply ignore one of the two new hots. Connect one hot, one neutral, and one ground to your existing setup. Presuming you have a 30amp main for the one hot. Or you make sure everything between the panel and the shore can handle 50 amps.







Do you have a "main" breaker inside that turns off everything? If so, how many amps is it?







It is very unlikely that you have 3-phase service btw. That's commercial.















I've heard electricians refer to a residential service to your home as a



"split phase" service. I agree there is some confusion as to calling it



"two phase" however, as you correctly state, it does have two hot legs



that are 180 degrees out of phase with each other. In my mind that



means there are two, out of phase hot legs. A 3 phase commercial



service would have three hot legs that are 120 degrees out of phase with



each other.







I agree that the OP's actual service to his boat at the pedistal is not



3 phase however the distributed service to the marina could very



likely be a commercial, 3 phase service. It could also be a split phase



like a residential service however depending on the marina size.



Regardless, if the OP wants to get something close to 220vac for testing



his stage lights, he's going to need two hot legs.



The possibility of 3 phase commercial service somewhere in the marina is immaterial.

In this case bringing it up only creates the possibility of confusing

the op.

His 240v 50amp service at the dock will be the same as is found in US

residential homes.



So? I don't understand how that changes anything. He still needs a

second hot leg, either from a distributed 3 phase system or a split

phase system. He acknowledged that he's not trying to change the

service in his boat from a 120vac, 30 amp service to a 250vac, 50 amp

service. He just wants 208vac, 220vac or 240vac to test some stage

lighting. Understanding how that service is delivered is important to

his intended purpose, don't you think, especially if he is not an

electrician as I suspect?



I stand by my previous comments, including my suggestion to employ the

help of a licensed electrician if he is not familiar or sure how it is done.

No, he doesn't need to understand anything about how his service is delivered!

He just needs to understand that he has 2 hots and 1 neutral. If he
wants 120 he uses one hot and the neutral. If he wants 240 he uses the
2 hots. He should always use the ground as ground if what ever he is
connecting has a ground lead. That's it, end of story. He does not
need to know any more than that.



I am not disagreeing with you. I simply suggested that if he is not
familiar with how power is distributed at a marina that he should
consider hiring a licensed electrician to help him. If you want to
walk him through how to rewire his boat and service and be responsible
for whatever the outcome is, have at it. Not me.

On Monday, March 24, 2014 3:12:15 PM UTC-7, Mr. Luddite wrote:


I stand by my previous comments, including my suggestion to employ the



help of a licensed electrician if he is not familiar or sure how it is done.



I am not disagreeing with you. I simply suggested that if he is not

familiar with how power is distributed at a marina that he should

consider hiring a licensed electrician to help him. If you want to

walk him through how to rewire his boat and service and be responsible

for whatever the outcome is, have at it. Not me.

exactly. AND...what does the marina say about this? If I was the owner of the marina I'd definitely want it done right for liability protection.

On 3/24/2014 5:40 PM, wrote:
On Mon, 24 Mar 2014 16:53:46 -0400, "Mr. Luddite"
wrote:

I understand and I didn't say it was accurate. However, as the other
poster pointed out there is sometimes some confusion as to what a home
service is called since you *do* have two hot legs 180 degrees out of
phase. The "split phase" isn't a reference to how a motor is wound in
this case. It's a reference to the center tapped, 240v service
producing two hot legs 180 degrees out of phase referenced to neutral.

The terminology used to describe it has been a subject of debate for years.




That is why code officials are trying to straighten it out every
chance they get ;-)


I am not an electrician. I've found over the years that terminology
used in the NFPA codes sometimes differ somewhat from what we use in
engineering even though we are talking the same thing. I also sometimes
found that some industrial applications are not defined or even covered
in the code book. If an issue arose that was questionable I had a EE PE
check it over and stamp the final power and control system drawings.

Last winter I got involved in a project building a performance venue
stage and it's wiring. The building had a dedicated 3 phase power
distribution panel that had previously been used for when the building
had been a large machine shop. I used it to distribute several 120vac,
20 amp feeds to the stage, overhead stage lights, PA system, house
lights, etc., but because I am not up to speed on current code
requirements for things like ground fault protection devices and another
new one that I can't remember the name of, I asked a friend who has been
a licensed master electrician for 26 years to review what my plans were
to make sure I didn't violate any codes and to ensure it was safe to use.

As far as residential house power is concerned, to me it is single phase
(at whatever high voltage is used locally) up to the primary of the
transformer. The secondary has two "hot" legs from the center tapped
transformer that are 180 degrees out of phase with each other referenced
to neutral or ground. In my world that is two phases, "zero" and "180"
relative to neutral or ground. :-)

On Tuesday, March 18, 2014 8:39:35 AM UTC-4, Mr. Luddite wrote:
On 3/18/2014 8:24 AM, KC wrote:

On 3/18/2014 8:09 AM, Boating All Out wrote:

In article ,

says...





I hopefully feel better for the original poster who asked the question.

People like you who shoot your mouth off about things you know

nothing

about can be dangerous to one's health and safety.



He admitted To Wayne he gave a wrong answer, and shouldn't have.

No need to keep insulting him.





Some folks come here for their victories.. Dick needs to know it all,

thus his calling bs on me for saying I use filters then suggesting I go

through third parties.. Huh?? Anyway, I am learning as much about

growing older here from him, as I am from harry....





Sorry Scott, but you respond to Harry's posts on a regular and daily

basis. I didn't question the fact that you have him filtered. I

simply stated that you still respond to his posts based on what you see

quoted in other people's posts.



Why are you so intent on making a regular fool of yourself?



Sorry Scott, but you respond to Harry's posts on a regular and daily
basis.

So do you.

Why are you so intent on making a regular fool of yourself?

Why are you?

BTW...I know which Scott he's talking to.

On 3/24/2014 6:22 PM, Tim wrote:
On Monday, March 24, 2014 3:12:15 PM UTC-7, Mr. Luddite wrote:


I stand by my previous comments, including my suggestion to employ the



help of a licensed electrician if he is not familiar or sure how it is done.



I am not disagreeing with you. I simply suggested that if he is not

familiar with how power is distributed at a marina that he should

consider hiring a licensed electrician to help him. If you want to

walk him through how to rewire his boat and service and be responsible

for whatever the outcome is, have at it. Not me.



exactly. AND...what does the marina say about this? If I was the owner of
the marina I'd definitely want it done right for liability protection.

Good point. I've had long term leased slips at four different marinas
over the years. They didn't care if you were Thomas A. Edison or George
Westinghouse. If you wanted to change or upgrade the power service at
the pedestal to your boat you hired an electrician or they hired one for
you.

wrote:
On Monday, March 24, 2014 4:41:27 PM UTC-4, Mr. Luddite wrote:
On 3/24/2014 4:15 PM, wrote:

On Monday, March 24, 2014 3:41:13 PM UTC-4, Mr. Luddite wrote:

On 3/24/2014 3:26 PM, wrote:



On Saturday, March 22, 2014 1:33:11 PM UTC-4, da...@righthere... wrote:



On Tue, 18 Mar 2014 08:01:29 -0400, "Mr. Luddite" wrote:















On 3/18/2014 7:42 AM, KC wrote:







On 3/18/2014 3:34 AM, Mr. Luddite wrote:







On 3/18/2014 12:22 AM, KC wrote:







On 3/17/2014 7:57 PM, Mr. Luddite wrote:







On 3/17/2014 7:14 PM, wrote:







On Mon, 17 Mar 2014 18:19:42 -0400, KC wrote:















On 3/17/2014 6:01 PM, david@righthere... wrote:







I've been on 30A 120V power at the dock for years and would now like







to upgrade







to 50A 220V, or what they refer to as 50A 250V at the marina office.







I haven't







put a meter on it yet but so far suspect it's closer to 220 than







250. The socket







on the pedestal is like the one pictured he















http://www.catagle.com/68-153/CWD_Ar...uyersGuide.htm















They say it's 3-pole 4-wire. I'm guessing X and Y are the two hot







legs and W is







the neutral. Between X or Y and W would be 120V+/- and between X and







Y is the







220/250V. Right? How does the ground tie into it though? With only 3







poles do we







run a separate wire from the boat to the pedestal, and if so how do







we tie in?















Also can anyone suggest the cheapest place to get a plug like that?







So far the







best price I've found is $68.18 he















http://www.ktool.net/servlet/the-581...-63CR65/Detail















































Thank you for any help!







David























The plug is 10-20 bucks at home depot or lowes, Scottys whatever you







have. It's a dryer plug basically... As to the wiring, I forget but I







have a book I always use when I do the wiring.. It was about 20







bucks at







home depot, I have had it for as long as I have owned a house...















Not true at all, sorry.















This is a non-NEMA twist lock 50a plug, that is corrosion resistant.















A dryer plug is a NEMA 14-30 straight blade that would go south pretty







quickly on a pier.































Yup. I think Scotty should stick to building websites and not wiring







boats.































Why, cause I took a quick look and made a mistake? I have done a lot of







wiring in my time including my whole house to code in Essex from moving







in with full Knob and Tube... I have done barns, and wells. When you







have a 100 year old house you tend to pick up stuff. You should see me







sweat a pipe.... even if I don't know all the right terminology. Either







way, that's why I always keep my electrical book with me to check my own







work as I go....























Scott, the OP didn't say if he was re-wiring his *boat* for a 50 amp,







240v marine split service. He might be just trying to use one leg of it







to supply 50 amps to his existing 30 amp, 120v boat panel. If so, he's







taking a big risk because it's not just the plug in question. The







primary feed wires in the boat that run from the power inlet to the







power panel needs to be changed at a minimum. Plus, if the existing







power panel has a 30 amp main, supplying it with 50 amps isn't going to







do him any good. If he changes that to a 50 amp breaker without doing







any changes to the wiring, he could overheat the primary feed wiring in







the boat, causing a fire.















My comment was more than pointing out that a split, 50 amp marine







service plug is not a dryer plug.















I did what I think he is trying to accomplish on the Grand Banks we had.







It had a standard, 30 amp, 120v service. I wanted to add two







air-conditioning units to the boat. Rather than change everything over







to a 50 amp, 240v split service I simply added another 30 amp, 120v







marine inlet connector, wiring (marine type) and a small, dedicated







breaker box with two 15 amp breakers in it, one for each of the AC units.















After talking to a guy at West Marine that's the type of thing I'll do too if I







follow through with it. I might add a couple of extra outlets too, in case I







want to run an extra heater in the winter without tripping the main as I do from







time to time.















I will want to have 240V available though. I did stage lighting for years and







have been given some old moving lights that need repair and the place I work







doesn't want to put the money into them. They are old Martin Mac 500s and 600s







and they only work on 240V (+/-) power. So what I mainly want the 240 for is so







I can work on them and try to get some of them going again. My question is: If







the marina hooks up another 30 amp sevice, will it be out of phase with the







original one or could it be in phase? It wouldn't do me any good if it's in







phase, so would I need to specify or would it be out of phase and I don't need







to bother them about that detail, do you know?















I don't know a lot about many things and nothing about some things







however electrical power distribution and wiring happens to be one thing







I *do* know something about. I'd hate to see someone hurt or killed







because they received bad input.















Now, I have a question for you. Let's say your house has a 200 amp







service. Your main breaker is a double pole, 200 amp per pole breaker.







There's 240vac between the two "hot" legs and 120vac between either of







them and neutral. Each hot leg from the utility pole is sized for 200







amps for each side of the service, yet the neutral is also only sized







for 200 amps. Why isn't it sized for 400 amps, the sum of both sides of







the total service?















See if the answer is in your "electrical" book.















Is this a job you are gonna' do yourself? snerk























No, it's not a job. It's a question. Can you answer it with all your







experience wiring homes, barns and whatever?















Look, any handyman can do basic wiring in their house. It's not rocket







science. But knowing something about current capacities, codes and







particularly how the power in a house, commercial building or a *boat*







is distributed requires more than a handy dandy DIY book from the Home







Depot.















I am not an electrician. I am an electrical engineer. If I wanted a







new power service installed in my house or was doing a major upgrade to







the existing service, I'd hire a licensed, master electrician to do the







job.















BTW, the answer to the question I asked is because the two "hot" legs







are 180 degrees out of phase relative to each other, so the net current







flowing through the neutral leg adds algebraically. The current through







the neutral leg can never exceed 200 amperes.















Thanks for sharing that. I still have the question of whether the the two 30 amp







120s would necessarily be out of phase though, even though what you wrote leads







me to believe they probably would be.







The "phase" of conventional residential is debated a bit as some
don't think it is two phase and some do.







The important thing for you is that 240v service will have 2 hots, 1
neutral, and 1 ground. Between either of the hots and the neutral
you will see 120vac. The same 120vac you are using now. Between the
two hots you will see 240vac.







Your biggest problem is that your current panel inside the boat most
likely only accomodates 1 hot, 1 neutral, and 1 ground. If that is
true you really need a new panel to safely use the 240vac 50amp
service. The regular service breakers you have for outlets and
lights are typically distributed evenly between the two hots. Any
240vac connections like heat will use a ganged breaker connecting to both hots.







Now you likely do not have to take advantage of the new power at the
dock if you don't want to. Simply ignore one of the two new hots.
Connect one hot, one neutral, and one ground to your existing setup.
Presuming you have a 30amp main for the one hot. Or you make sure
everything between the panel and the shore can handle 50 amps.







Do you have a "main" breaker inside that turns off everything? If
so, how many amps is it?







It is very unlikely that you have 3-phase service btw. That's commercial.















I've heard electricians refer to a residential service to your home as a



"split phase" service. I agree there is some confusion as to calling it



"two phase" however, as you correctly state, it does have two hot legs



that are 180 degrees out of phase with each other. In my mind that



means there are two, out of phase hot legs. A 3 phase commercial



service would have three hot legs that are 120 degrees out of phase with



each other.







I agree that the OP's actual service to his boat at the pedistal is not



3 phase however the distributed service to the marina could very



likely be a commercial, 3 phase service. It could also be a split phase



like a residential service however depending on the marina size.



Regardless, if the OP wants to get something close to 220vac for testing



his stage lights, he's going to need two hot legs.



The possibility of 3 phase commercial service somewhere in the marina is immaterial.

In this case bringing it up only creates the possibility of confusing

the op.

His 240v 50amp service at the dock will be the same as is found in US

residential homes.



So? I don't understand how that changes anything. He still needs a

second hot leg, either from a distributed 3 phase system or a split

phase system. He acknowledged that he's not trying to change the

service in his boat from a 120vac, 30 amp service to a 250vac, 50 amp

service. He just wants 208vac, 220vac or 240vac to test some stage

lighting. Understanding how that service is delivered is important to

his intended purpose, don't you think, especially if he is not an

electrician as I suspect?



I stand by my previous comments, including my suggestion to employ the

help of a licensed electrician if he is not familiar or sure how it is done.

No, he doesn't need to understand anything about how his service is
delivered! He just needs to understand that he has 2 hots and 1 neutral.
If he wants 120 he uses one hot and the neutral. If he wants 240 he
uses the 2 hots. He should always use the ground as ground if what ever
he is connecting has a ground lead. That's it, end of story. He does
not need to know any more than that.

And the ground and neutral are supposed to be connected at the pole. If
not you will get a floating ground looking condition, and some equipment
will not work correctly. We had 12v between grd and neutral on on a older
disk drive and would not always spin up.and I think 220 and 240 are really
the same. 120vac used to be called 110vac. Most of the power companies
went to the higher voltage for efficiency. PG&E was one of the first and
light bulbs lasted a shorter time, until they brought out lights designed
for 120vac. They work fine on 110 also.