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Old 11-06-2017, 12:25 AM   #41
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Originally Posted by diver dave View Post
hmmm, not true for the 1 billion homes on the planet? But true for a few thousand marinas with a similar demand for service?

In all my travels, I have come across 1 house with 3 ph service. We have entire multi-square mile neighborhoods supplied with single phase. Efficiency is high on the list for utility distribution. Few residential areas have even 3 phase available.

so, my fundamental question remains. Who on a dock wants 3 phase??

For single family homes, there is a transformer on a pole, and it serves a few homes. Then there is another transformer on another pole and connected to a different phase of the 3-phases on the poles, and it serves a few other homes. The key is that they are spaced out.

If you look at the wiring in an apartment building or other high-density facility, I think you will find the same 208/120V setup that you have in a marina.

So I maintain that it's about economics and how you best provide power to a high density collection of consumers.

Here's an example. Say you want to deliver power to 12 50A dock pedestals. With 3 phase you need 4 conductors capable of carrying 200A each, and a single 200A 3-phase transformer. Four 50A outlets can be placed on each of three line to line combinations, and each with a neutral connection to support 120V.

With single split phase, you need 9 conductors capable of carrying 200A each, and three 200A single phase transformers. Four 50A outlets can be placed on each of the 200A, 3 wire circuits.
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Old 11-06-2017, 12:36 AM   #42
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In all my travels, I have come across 1 house with 3 ph service. We have entire multi-square mile neighborhoods supplied with single phase. Efficiency is high on the list for utility distribution. Few residential areas have even 3 phase available.
For what it's worth, the power on the street poles is always 3-phase. Up high, you will see either 3 or 4 conductors. That's 3 phase, with or without a ground (usually without). As you get more off the beaten path, those three wires may drop down to two or one. But they are still the legs of a 3 phase system. They have just run one leg down one street and another leg down another street.

It's definitely true that all three of the phases are very seldom brought into the house. I have seen one or two, but it's very rare. And unless you are on a street where the power co only run one or two legs of the 3 phase down that street, you can get 3 phase power in your house if you want it.
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Old 11-06-2017, 07:34 AM   #43
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I have zero doubt this 208 fiasco is caused by economics. Since there is no "rule" or "code" violation, it's free market, buyer beware.
Most of the above points are arguable. I'm not seeing how secondary wiring becomes cheaper depending on the transformer, it doesn't. No matter the source, each post needs a 3 wire (L1,L2,N) for service. Each rated at 50A. It could be a more compelling argument that you need LESS copper at 240 than at 208V, since the current will be less. You are NOT feeding 3 phase to the user, so you don't get any proposed advantage. It's only the primary side we are discussing.

The sum story is that the marinas have a way to make things cheaper, at the cost to the boater. Boaters want 240V, they get 208. It's that simple. Worse yet, many marinas don't seem to be able to describe what voltage they actually supply. They may even advertise 50A 240/120, but give 208/120. Sad.

The right way to do this is run phase A primary down one set of docks, to 240/120 split transformers, Phase B down set 2, phase C down set 3. etc. Mega yachts get 480 3 phase at the huge dock. Done.
More transformers, but each is smaller. And, you only have 1 HV conductor plus N down each dock. Not 3 plus 1.
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Old 11-06-2017, 09:13 AM   #44
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Is there usually / always only one neutral on each side of a power pedestal?

My boat has 50 amp 125 / 250 volt service. Everything in the boat is 120 volt. Occasionally I end up at a slip that has no 50 amp receptacle on the power pedestal. Sometimes the two 30 amp receptacles yield 240 volts, sometimes 208 volts, and sometimes 120 as they are on the same phase. The smart box adapters from either Hubbell or Marinco have a problem with 208 and go into error mode (they're fine on 240 volts). They also error if the two receptacles are on the same phase.

Found an adapter that has two 30 amp males to a 50 amp 125 / 250 female without the smart box. It works very well. My only concern was whether both 30 amp receptacles in the power pedestal shared the same neutral and if they didn't, could that potentially be a problem?

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Old 11-06-2017, 09:21 AM   #45
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Originally Posted by diver dave View Post
I have zero doubt this 208 fiasco is caused by economics. Since there is no "rule" or "code" violation, it's free market, buyer beware.
Most of the above points are arguable. I'm not seeing how secondary wiring becomes cheaper depending on the transformer, it doesn't. No matter the source, each post needs a 3 wire (L1,L2,N) for service. Each rated at 50A. It could be a more compelling argument that you need LESS copper at 240 than at 208V, since the current will be less. You are NOT feeding 3 phase to the user, so you don't get any proposed advantage. It's only the primary side we are discussing.

The sum story is that the marinas have a way to make things cheaper, at the cost to the boater. Boaters want 240V, they get 208. It's that simple. Worse yet, many marinas don't seem to be able to describe what voltage they actually supply. They may even advertise 50A 240/120, but give 208/120. Sad.

The right way to do this is run phase A primary down one set of docks, to 240/120 split transformers, Phase B down set 2, phase C down set 3. etc. Mega yachts get 480 3 phase at the huge dock. Done.
More transformers, but each is smaller. And, you only have 1 HV conductor plus N down each dock. Not 3 plus 1.
I haven't opened up the wiring boxes on a dock to know for sure, but my assumption, using my previous example to illustrate, is that a single bundle of 4 conductors would run down the dock, and each 50A post would be tied into it. So yes, there are still 3 50A conductors to each post, but they are short - on the order of maybe 5 feet. The long run down the dock is the 200A 3-phase bundle of 4.

I think you are assuming that each dock post would be home run wired back to the transformer, and I don't think that is the case. Perhaps The Other Gary knows since this is his business.

You seem to feel cheated by 208 power, yet it is commonplace and has been for 100 years or more. You would be hard presses to find any commercial building or apartment building that isn't set up just like your marina.

I think the real issues here is that in some marinas, out at the end of the power runs, when it's hot and everyone has their HVAC on, there is too much voltage drop. 208V becomes 190V, and you effectively have a brownout, just like in cities when it's unusually hot out and power demand is very high. I expect that dock power demand had gone up quite a bit over the past 30 years, i.e. since many dock power systems were designed and installed, so they are likely loaded more then ever expected. Heck, there are lots of places that only have 30A 120V power, and consider 50A to be mega yacht power.
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Old 11-06-2017, 10:09 AM   #46
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Further:

Many yachts that spend time at marinas also spend time at the owners home. As we noted, no homes have 3 ph, therefore no homes have 208V. This notion that boat owners must now comply with this marina imposed new standard of 208 is ridiculous. And now, the yacht owner needs to buy only 208V equip for the boat, and "make" 208 at home?

Saying that, certain equipment can very easily accomodate both, some can with performance degredations, and some can't. Notably, large motors and large transformers are challenging to design with wide input voltage tolerances. If 208 V is your target nominal, it will arrive, with cable drops, less than that, down to 187 V (-10%) and still be in spec. And, this does not include ship's internal losses. So now, the motor has to accomodate 187 to 265 (240 + 10%). That is alot to ask of a induction motor. A/C units, icemakers, air compressors, etc.
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Old 11-06-2017, 10:18 AM   #47
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You seem to feel cheated by 208 power, yet it is commonplace and has been for 100 years or more. You would be hard presses to find any commercial building or apartment building that isn't set up just like your marina.
I work with 3 phase up to and including 500kV with my work. All the way to 500kV DC in last week's station.
Cheated is close to the right term, but more to the point, is that it appears yacht owners are being abused. The uber rich are running 480 3 phase and don't have this issue. The smaller guys that don't have appliances beyond 120V are unaffected. Its that middle ground of middle sized yachts and workboats, that do have critical systems on 240V that are taking this in the shorts.

And,this apartment thing... Apartment dwellers are handed appliances that are speced to 208V and life is good. They don't even know about the issue. Who in an apartment is buying/running 3hp air compressors?
Boaters are transient beasts, and need to know what is in that yellow cord. They are being surprised.
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Old 11-06-2017, 10:53 AM   #48
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This is from one of our recent installations. It is a single phase 120y/240v installation.
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Old 11-06-2017, 11:14 AM   #49
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This is also from one of our recent installations. It is a 3 phase 277/480v distribution system to the dock mounted transformer/distribution modules then 120/240v to the pedestals.
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Old 11-06-2017, 11:21 AM   #50
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Originally Posted by diver dave View Post
Further:

Many yachts that spend time at marinas also spend time at the owners home. As we noted, no homes have 3 ph, therefore no homes have 208V. This notion that boat owners must now comply with this marina imposed new standard of 208 is ridiculous. And now, the yacht owner needs to buy only 208V equip for the boat, and "make" 208 at home?

Saying that, certain equipment can very easily accomodate both, some can with performance degredations, and some can't. Notably, large motors and large transformers are challenging to design with wide input voltage tolerances. If 208 V is your target nominal, it will arrive, with cable drops, less than that, down to 187 V (-10%) and still be in spec. And, this does not include ship's internal losses. So now, the motor has to accomodate 187 to 265 (240 + 10%). That is alot to ask of a induction motor. A/C units, icemakers, air compressors, etc.
You call it a "marina imposed new standard of 208V", yet it has been around for ages. There is absolutely nothing new about it. You have just tripped over it for the first time. Nobody sneaked into the marina in the middle of the night and rewired it to cheat you out of power.

I think your assessment is correct that it's boats "in the middle" that are potentially impacted. 120V boats see no difference, and 3 ph boats see no difference.

But rather than blaming the marina for the power they have had for who knows how many decades, perhaps you should look at the inadequate design of your boat's electrical system, and ask the builder why they designed it to work with one half of the marinas out there, but not the other half. Lots of boats in the "middle" are designed to use 50A 208/120 and 50A 240/120 interchangeably. Some utilize only the individual 120V legs - no problem. Others ensure that 240V devices are specified for 208-240VAC - no problem. Others use isolation transformers with automatic or manual step up - no problem.

I'd suggest you either improve you boat's electrical system so it can work with a wider range of marina wiring, or restrict your cruising to marinas that have power that meets your boat's limitations. It's really no different than dealing with Marinas that only have 30A 120V power, or that only have 50A 120V power. Do you expect all of them to re-wire to meet your boat's 240/120V needs? And what about marinas that have 50hz power? Should they change?
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Old 11-06-2017, 12:18 PM   #51
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You call it a "marina imposed new standard of 208V", yet it has been around for ages. There is absolutely nothing new about it. You have just tripped over it for the first time. Nobody sneaked into the marina in the middle of the night and rewired it to cheat you out of power.
OK, the problem has been around for years. Still needs fixing. And, longer we wait, even more marinas need fixing.

I think your assessment is correct that it's boats "in the middle" that are potentially impacted. 120V boats see no difference, and 3 ph boats see no difference.

But rather than blaming the marina for the power they have had for who knows how many decades, perhaps you should look at the inadequate design of your boat's electrical system, and ask the builder why they designed it to work with one half of the marinas out there, but not the other half. The marinas are choosing the voltages, therefore the marinas are responsible for the voltages; this is not a utility issue to solve, and boats should not be expected to have a variable input autotransformer at the readyLots of boats in the "middle" are designed to use 50A 208/120 and 50A 240/120 interchangeably. Some utilize only the individual 120V legs - no problem. Others ensure that 240V devices are specified for 208-240VAC - no problem. Others use isolation transformers with automatic or manual step up - no problem.

I'd suggest you either improve you boat's I don't currently have a boat with AC rqmts electrical system so it can work with a wider range of marina wiring, or restrict your cruising to marinas that have power that meets your boat's limitations. It's really no different than dealing with Marinas that only have 30A 120V power, or that only have 50A 120V power. Do you expect all of them to re-wire to meet your boat's 240/120V needs? And what about marinas that have 50hz power? Should they change?
So, far, I'm in the North America bog; I have no idea what euro marinas do, but I'd be very surprised if continental euro and UK are other than 230V 50Hz uniformly. If I was a critical European, I'd think our marinas are run by idiots.
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Old 11-06-2017, 12:36 PM   #52
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This is also from one of our recent installations. It is a 3 phase 277/480v distribution system to the dock mounted transformer/distribution modules then 120/240v to the pedestals.
Thanks for posting!

We need to take note of the marinas that use this type of design. Load Marinanow, and Dockwa with the results.
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Old 11-06-2017, 01:43 PM   #53
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So I'm on a metered pedestal but instead of having a small meter on the pedestal I have a house type meter on shore and I deal directly with the power company for billing. Does that mean that every pedestal on my dock has its own dedicated conductors? Seems pretty inefficient if that's the case, and I don't see how it wouldn't be.
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Old 11-06-2017, 02:24 PM   #54
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A comment was made that a lot of boats are made to take dual voltage 208 and 240. Not saying they are not, but of the medium priced 45 to 60 foot boats that I am familiar with that have larger AC units that require 240 or 208 are prone to this issue. Not sure of which ones you are talking about. I know that Jefferson, Hatteras and Prima were not. Maybe the new ones are, don't know that but mid 80's to early 90s are prone to this issue. I think the 208 was around at that time. So should we all be required to go out and buy different boats are spend thousand of dollars for these marinas. I guess that's what's being said. I just avoid the marinas if I can.
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Old 11-06-2017, 03:36 PM   #55
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So I'm on a metered pedestal but instead of having a small meter on the pedestal I have a house type meter on shore and I deal directly with the power company for billing. Does that mean that every pedestal on my dock has its own dedicated conductors? Seems pretty inefficient if that's the case, and I don't see how it wouldn't be.
some meters have remote current sensors. Without a pix, can't be sure about yours.
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Old 11-06-2017, 04:01 PM   #56
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answer in red.

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Is there usually / always only one neutral on each side of a power pedestal? Most every 120V receptacle that I know of in this country contains a grounded current carrying conductor, commonly called a neutral; true for boats, homes, factories, etc. Not military ships though.

My boat has 50 amp 125 / 250 volt service. Everything in the boat is 120 volt. Occasionally I end up at a slip that has no 50 amp receptacle on the power pedestal. Sometimes the two 30 amp receptacles yield 240 volts, sometimes 208 volts, and sometimes 120 as they are on the same phase. The 208 or 240V should be OK, the same phase is NOT OK.
Your neutral conductor in the shore cable could attempt to carry 2 x 30 or 60Amps at full load
The smart box adapters from either Hubbell or Marinco have a problem with 208 and go into error mode (they're fine on 240 volts). They also error if the two receptacles are on the same phase. sounds like your smart box is more clever than many experts!


Found an adapter that has two 30 amp males to a 50 amp 125 / 250 female without the smart box. It works very well. My only concern was whether both 30 amp receptacles in the power pedestal shared the same neutral and if they didn't, could that potentially be a problem? potentially.
Again, if you are bringing in 2x 30A of 120V at the same phase, the neutral currents add up. Your shore power white wire could run warm.


Ted
edit: If your 50 Amp panel has a triple pole breaker, rated at 50A, then it will trip if neutral current exceeds 50A. Even if each hot line is only supplying 25Amps.
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Old 11-07-2017, 10:32 AM   #57
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I talked to the facilities mgr at port of Seattle yesterday day. He said that in the 60s when the marinas were built they used wye and ran each leg up a different dock. The most you could get in those days was 50a 120v. It wasnt until the 80s that demand for 50a 125/250v started to show up but the need was for 100a 120v not 50a 240v so the just ran another leg of the wye up each dock. Starting in 00s they started to get 208v complaints so they started replacing the wyes with deltas. Now most but not all docks are 50a 120/240v. He also said that the original 60 slip dock still is wye and they put a lot of transients on that dock so they can ignore the power complaints.
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Old 11-07-2017, 01:09 PM   #58
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answer in red.



edit: If your 50 Amp panel has a triple pole breaker, rated at 50A, then it will trip if neutral current exceeds 50A. Even if each hot line is only supplying 25Amps.
Yes, my breaker panel has a 3 pole 50 amp main breaker. Thanks for your response!

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Old 11-07-2017, 02:10 PM   #59
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Not exactly right on the neutral. The breaker will not trip if both hot legs are at full capacity. Any 230 volt loads do not use the neutral wire at all and any 120 volt loads will only load the neutral with the difference between the two legs.
On a 50 amp circuit using 20 amps at 230 and you use 25 amps of power on the black leg at 120 volts and 30 amps of power on the red leg at 120 volt 25 of those amps are cancelled in the neutral and the neutral is only carrying 5 amps.
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Old 11-07-2017, 02:16 PM   #60
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Quote:
On a 50 amp circuit using 20 amps at 230 and you use 20 amps of power on the black leg at 120 volts and 30 amps of power on the red leg at 120 volt
But that's not operating at capacity..
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