1972 58' YF, useing 2 50a 125v to power boat

[MarioG]

I have 2 shore power cables connected to each starboard 50a 125v recepticals. I can now power all of the 110v service but cannot power the 220v panel (water heater and stove ect). I looked at the 110v/220v schematic and I see two lines coming from the 110v pannel to the 220v panel. I assumed that if I brought aboard 2 50a 125v source of power I would get 220 at the panel. now i'm thinking that the only way to get 220 from shore is through the 50a 125/250v receptical located next to the two 50a 125v receptical. basicly the 220v circuit powers the each 110 panel? am I right or wrong?

 

[SKYCHENEY]

There are only 2 ways to get 220v from 110v cords. One is with an isolation transformer and the other is with 2 110v legs that are at opposite phase. If you have 2 lines but they are from the same phase, you will still only have 110v. If they are 180 degrees opposed, you will get 220v between them.

 

[Pete]

Do you not get zero volts phase to phase when both lines are attached to the same 120 volt phase, 120 volts from any phase to neutral, 240 volts phase to phase if phases are 180 degrees out (single phase/split phase power), and 208 volts phase to phase if phases are 120 degrees out of phase (3 phase power)?

Pete

 

[dwaynec]

Mario, You are correct. You can power the 125V panels from the 250V shore power cord, but you can't power the 250V panel from the 125V cords. If your slip doesn't have the 250V outlet then you are just outa luck. The only adapters that I have been able to find are 30 amp, which means something isn't going to run.

 

[TedZ]

Talking about phases besides being wrong, doesn't help as almost no one carries a scope around to check.

If the marina has done it right - they likely have - you get 240 VAC from two 120 VAC supplies either 50 or 30 amp plugs. If there are four 30 amp supplies, the way i wire them is to put the plugs on the same side from a 240 supply so they will produce 240 between the two hot legs. Others may wire them so opposites work that way.

If your 50 amp plugs do not measure 240 between hot legs, plug into a different outlet or power pole to see if that gets what you want. Obviously, if you plug into a 125/250 outlet you can get both from one supply.

The oven i installed on my 43DC is 240 VAC and i use two 30 amp supplies to power it all of the time.

Ted

 

[Maynard Rupp]

Clear as mud now, eh Mario??

 

[Pete]

Let me try to make the mud semi-transparent. If you are using the two 125v/50a shore power inputs, the only way to get 250 volts on the boat is if you have an isolation transformer, period. With that said, yes you can make a home made adapter that will in SOME cases produce the 250v/50a and in other cases produce ZERO volts. What you get is determined by the wiring that you plug into at the marina. There is no way to build an adapter that will always produce 250v/50a from two 125v/50a shore power outlets at every marina. And, in some cases, the two 125v/50a marina outlets will produce 208v/50a because of the type of power the marina has. That is as clear as I know how to make it.

Pete

 

[TedZ]

Its clear but wrong. Sorry.

You do not need an isolation transformer to get 240 VAC from two 50 or 30 amp cords. I honestly don't know why you think that. If the power pole is wired with a 240 VAC feed and the feed is split to power the individual 30 or 50 amp outlets, obviously you can get the 240 back when combining them.

I installed over 50 high quality power poles this summer and in each and every case they were fed with 240 VAC split into four 30 amp outlets or two 50 amp outlets or two 30 amp and one 50 amp outlet. This is the way they are internally wired...no great accomplichment on my part. Want pictures and wiring diagrams?

Ted

 

[MarioG]

Mario, You are correct. You can power the 125V panels from the 250V shore power cord, but you can't power the 250V panel from the 125V cords. If your slip doesn't have the 250V outlet then you are just outa luck. The only adapters that I have been able to find are 30 amp, which means something isn't going to run.

Thanks you! today I refitted one of my cables with a 50a 125/250v female plug boat side and connected into the 50a 125/250v receptical like Pascal told me to do. I now have the whole boat powered.

Problem solved!

Thanks for all of the replys, in the end, I do learn alot!

 

[Pete]

TedZ, sorry but your response is wrong, as far as your comments about my post. If you have a boat with two 50a/125v shore power cords connected to your boat, have no isolation transformer, then you can not get 250 volt service on your boat, period. Can you mess with the internal wiring on the boat and SOMETIMES get 250 volts, or make a home made external adapter and again SOMETIMES get 250 volts, yes (see my third sentence).

Your installation of new power poles does not change the wiring at other marinas. You need to cruise the southeast and mid Atlantic marinas that have old and unpredictable hookups. Most do not even understand the difference between single/split phase and 3 phase power. Bring up phase balancing and the eyes roll back in the heads.

Perhaps a thoughtful read of my post before commenting could have avoided this exchange for all of us.

Pete

 

[Pascal]

125/50 is old technology, which you rarely see on the east coast. The standard for splips over 40 is 125-250/50

when you get to a marina, you will usually find a 125-250/50.

occasionally, some marinas will only have 125/30 power. In this case, you need to use a Smart Y to connect your 125-250/50 to two 125/30 outlets. The smart Y has circuitry to only activate the Y if both 30 amps plugs are connected and if they are connected to opposing phase. an indicator light will come on.

this is the only safe way to do it and it will give you 30 amps on each leg plus 220 across the legs. enough to power a couple of Air Cons, you stove and most house loads.

last year, on the round trip to Nantucket, i had no problem finding at least one 125-250/50. I remember a couple of times where only one was available but didn't need to run the heat or air; I think i used the smart Ys 3 or 4 times altogther on the round trip where only 30amp could be found, they were always on opposing phases so that i coudl run some 220v loads.

not a major issue in my experience.

Mario, in your case for a permanent slip, the marina should be able / willing to re wire your pedestal with a 125-250/50 outlet.

one last thing... I've seen a few slips with no breakers! make sure your pedestal has a two pole circuit breaker to protect the outlet and the cord.

 

[TedZ]

That is all correct although we run across a lot of marinas that have precious few 50 amp outlets and a lot of 30's. The point is even without smart Y's you can still get your 240 in most instances. The smart Y's are great but VERY expensive for want of providing one wire on board through a switch to be able to get 240 no matter what the marina is supplying.

If you have to have a marina add breakers, make sure they are of the GFI type. Much safer.

Ted

 

[Nonchalant1]

Let me try to make the mud semi-transparent. If you are using the two 125v/50a shore power inputs, the only way to get 250 volts on the boat is if you have an isolation transformer, period.

Pete

I'm not sure that's true. I just use a Marinco "Reverse Y" to get 240V from two 120V lines. It's very common and in use everywhere. It normally uses twin 30A/120V lines to make 240V power. The reverse Y I have is a "smart Y" which will not pass power unless the two 120V lines are from different circuits. You just plug the 120V lines into it and plug your 240V line into the Y. If the marina has real 50A/125V outlets (very uncommon) I have to use adapters to change the cords to the 30A/120V plugs on the reverse Y. Because some of the cords or pigtails are for 30A service, you should manage power to use only 30A X 2 power draw, but you can use the 240V consumers, like your stove.

Doug