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-   -   Power from 30a outlet to 50a boat? (http://www.trawlerforum.com/forums/s4/power-30a-outlet-50a-boat-36412.html)

aboatman 01-10-2018 08:18 AM

For a 50 amp boat at a marina it's possible to buy a "Y adapter that allows the boat to have full power by plugging into two shore receptacles (as long as they are on opposite "legs"). And of course if only one is available or they are both on the same leg you still have 30 amps available.

For the home dock, I would look into the cost of rewiring it for 50 amps.

CaptTom 01-10-2018 09:12 AM

Quote:

Originally Posted by FF (Post 625086)
IF a 30 A light weight power hose is used the 240 plug will simply have the red and black wires connected.

This works fine ,,,until you forget the vessel is only getting 30A and you turn on too much load.

The 30A plug will loose a terminal in its black wire., or you could melt the 30A wire.

Wait, if the shore power is 30A, then there's a 30A breaker somewhere ashore. Pull more than that and you trip the breaker, not melt the wire.

It's true that the 30A wiring could be degraded and no longer capable of pulling 30A. But the same can be said for a boat wired for only 30A.

My boat is wired for two, 30A circuits (no 240V appliances.) I pretty much permanently have a 30-30-30 "Y" adapter connected, and plug into a 30A outlet wherever I go, including my home dock. I never felt the need to find a 50A outlet (I do have the cords) or even two 30A. A lot of places I've found only 20A or even 15A, and used that without incident.

There is some consideration required concerning load. I think twice before starting the electric range, and check to be sure the air conditioner and/or electric water heater is turned off, first. But it's not rocket science, and the worst I can do is trip a breaker.

ranger42c 01-10-2018 09:17 AM

Quote:

Originally Posted by ranger42c (Post 625087)
Yeah, I don't have either, hence my basic lack of understanding how they work, or symptoms when/if something doesn't work...

And we have no 240V appliances either, so the simple 30-to-50A adapter works fine for light loads.

I've asked the other owners for a memory refresher, so maybe the guys who told me about it in the first place can help me clarify whatever the heck it was I was trying to remember...


I got my memory refreshed; that'll maybe last for a nano-second or so...

The guys who told me about it said their system has an isolation transformer (not galvanic isolater as I original mis-said). And their chargers are 110V.

They say unless that transformer has a legit 240V (208+) feed, nothing on the other side of the transformer will work, no matter whether a 220V or a 110V appliance (or charger). They described the transformer acting like a gate... that won't open without typical 50A/250V voltage.

And they said they had to use a Smart Y to get there from here, unlike our easy 30-to-50 adapter solution.

All that transformer stuff is second-hand info; I have no direct experience with this...

-Chris

diver dave 01-10-2018 09:38 AM

Quote:

Originally Posted by aboatman (Post 625103)
For a 50 amp boat at a marina it's possible to buy a "Y adapter that allows the boat to have full power by plugging into two shore receptacles (as long as they are on opposite "legs"). And of course if only one is available or they are both on the same leg you still have 30 amps available.

For the home dock, I would look into the cost of rewiring it for 50 amps.

hmmm; are we talking a 50A 120V (3 wire) boat with one inlet connector?
Or, a 50A 4 wire 240/120V boat, or a 2x 50A inlets, or ?

You would be limited to either 30A @ 120V in the first case (with no need for a Y), and 60A @ 120V in the second. The second case doesn't care if in phase or out for the 120V boat loads.

I guess my point is that you can't get a legit 50A from 2 x 30A shore connections thru a single circuit.

AND, a dumb "Y" to parallel two shore outlets into a single circuit is very risky.

diver dave 01-10-2018 09:45 AM

Quote:

Originally Posted by ranger42c (Post 625124)
They say unless that transformer has a legit 240V (208+) feed, nothing on the other side of the transformer will work, no matter whether a 220V or a 110V appliance (or charger).

-Chris

Many, most? isolation transformers have a dual primary. That is, it can be wired for 240 OR 120V input. But, to change takes a small rewire at the transformer. They are not typically "agile", or smart to do either.

https://image.fisheriessupply.com/f_...former_ppm-tif

And, don't get me going on 208:nonono:

ranger42c 01-10-2018 10:00 AM

I don't actually know what an isolation transformer does... or why...

-Chris

diver dave 01-10-2018 11:05 AM

Quote:

Originally Posted by ranger42c (Post 625135)
I don't actually know what an isolation transformer does... or why...

-Chris

That's a leading statement. :)

Two main purposes:
First, to "adjust" the voltage as potentially a step up or step down.
Typically, a euro boat would step up a 120V feed to run the ship on 240V.
A US boat in a non-split phase Euro dock would apply the euro 230V 3 wire at the input and get a 230/115V 4 wire at the boat. So, it makes the US to non-US power feed possible, either way.

Second, they block "stray currents". By making the boat ground reference not connected to the dock ground reference. In enginneering speak, an iso transformer blocks common mode currents. Including, lightning induced Line to ground surges.

An iso transformer also gives the capability to provide a non-grounded (aka neutral) output, but this is not typically done for civilian boats. But, military and certain other vessels that benefit from a more reliable power distribution may do this.

ps: I should use "North America" in lieu of "US" above.

ranger42c 01-10-2018 02:32 PM

Quote:

Originally Posted by diver dave (Post 625144)
Second, they block "stray currents". By making the boat ground reference not connected to the dock ground reference. In enginneering speak, an iso transformer blocks common mode currents. Including, lightning induced Line to ground surges.


Thanks. Maybe this is why the maker started adding transformers in later years... at least in the larger range of boats they produced...

I might benefit from adding one, then, given we've had some electronics glitches that I could conceivably ascribe to nearby known/verified lightning strikes.

Nothing catastrophic on our boat, just a few odds and ends... but a couple boats further inside the dock took some serious damage, two different occasions -- and two different set of glitches on our boat afterwards, not immediately recognized (I hadn't known about the second strike until a few months afterwards).

OTOH, back on OP's topic, that'd apparently make it more difficult to use minimal current supplies with simple adapters...

-Chris

FF 01-13-2018 01:15 PM

"I might benefit from adding one, then, given we've had some electronics glitches that I could conceivably ascribe to nearby known/verified lightning strikes."

You need a GFI for the vessel, not an isolation transformer that solves the problems of sray current from the dock opr other boats.

ranger42c 01-13-2018 02:44 PM

Quote:

Originally Posted by FF (Post 626173)
You need a GFI for the vessel, not an isolation transformer that solves the problems of sray current from the dock opr other boats.


We have several AC outlets with GFCIs... is that what you mean?

-Chris

FF 01-13-2018 03:47 PM

A GFI will help keeping you from being electrocuted if a unit in the boat has a problem.

It may also help not dump electric in the water to get swimmers.

A surge protector is what is required if lightning strikes or side strikes coming aboard in the power hose is the fear.

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aboatman 01-13-2018 06:46 PM

Quote:

Originally Posted by ranger42c (Post 625135)
I don't actually know what an isolation transformer does... or why...

-Chris

Well, it electrically isolates the boat from the dock electricity. There is no direct connection. The magnetic field from the primary winding (shore power) induces a current in the secondary winding (the boat). It might help to look up "transformer" on the Internet.

Depending on the transformer it can also raise or lower the voltage or keep it the same.

Bay Pelican 01-14-2018 03:54 AM

You might consider an isolation transformer as an electrically powered generator. As such it uses shore power to generate a separate (isolated) power source on the boat.

Two examples, the shore power is 240 v European, unusable on most North American boats, but my isolation transformer can operate on 240 v European and generate 240 v North American (can't change the hertz however).

A North American marina's power supply is too small for its needs so it is sending out 208 v and not 240 v to its shore power posts. The isolation transformer with the boost feature can use the 208 v power and output 240 power (although smaller amps).

ranger42c 01-14-2018 06:40 AM

Quote:

Originally Posted by FF (Post 626222)
A GFI will help keeping you from being electrocuted if a unit in the boat has a problem.

It may also help not dump electric in the water to get swimmers.

A surge protector is what is required if lightning strikes or side strikes coming aboard in the power hose is the fear.


Good, got that, but those seem to be all about AC; the glitches I noticed were in a couple of the DC electronics products...



Quote:

Originally Posted by aboatman (Post 626264)
Well, it electrically isolates the boat from the dock electricity. There is no direct connection.


Quote:

Originally Posted by Bay Pelican (Post 626340)
You might consider an isolation transformer as an electrically powered generator. As such it uses shore power to generate a separate (isolated) power source on the boat.

Two examples, the shore power is 240 v European, unusable on most North American boats, but my isolation transformer can operate on 240 v European and generate 240 v North American (can't change the hertz however).

A North American marina's power supply is too small for its needs so it is sending out 208 v and not 240 v to its shore power posts. The isolation transformer with the boost feature can use the 208 v power and output 240 power (although smaller amps).


Got it, thanks, guys.

I think this is leading to "nifty to have" but not earth-shattering without. I can put it into my "maybe someday" list -- along with the bow thruster :) -- to see if it ever bubbles up to the top of my wallet.

-Chris

FF 01-14-2018 06:49 AM

"Wait, if the shore power is 30A, then there's a 30A breaker somewhere ashore. Pull more than that and you trip the breaker, not melt the wire."

Loads of current is used during the heating season.The usual time for burnt plugs.

CB are temp and load sensitive so a heating load on a 30A CB on a freezing dock may not pop till 35A or 40A is reached.

If the boat is wired for 50A 240V the breakers inside the warm boat wont pop till the 50A limit is past for a while.

kartracer 01-14-2018 09:14 AM

Once you find what you are going to use look on Ebay or Craigslist, I see them all the time.


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