50amp to 30amp adapter and air conditioning

[MichaelB1969]

Originally Posted by twistedtree

It sounds like you will need to get a reverse Y that takes two 30A 120V dock outlets and converts it to a single 50A 120/240 receptacle that you can plug your boat cord into. You will need two 30A receptacles. The only caveat is that you will be limited to 30A of shore power draw, not 50A. And a heads up.... the Reverse Y adapters are expensive. Figure around $700.

Will this work? It's $82 at ECS.

http://www.ecspremier.com/Marine-2-3...167_p_296.html

This is where I bought my 50amp cord and the quality was excellent.

[caltexflanc]

Advise you read up on the Smart Y adapters and decide if spending $400 is worth it vs 82. Sure was for me.

[twistedtree]

Originally Posted by MichaelB1969

Will this work? It's $82 at ECS.

Marine (2) 30A Locking Male Plugs to (1) 50A locking Female "Y" Adapter (8167)

This is where I bought my 50amp cord and the quality was excellent.

Maybe, and if so, it's an awesome price.

The key is whether is has the requisite safety features, and I'm skeptical given the price, but you never know. Good reverse Y adapters are "smart" and sense the presence and phase of the two 30A plugs, and only connect to the 50A side if all is kosher. Without that, you have a "dumb" adapter and two things can happen, neither of which is good.

1) If the 50A side is plugged into a load and you plug in one of the two 30A plugs, you can end up with hot power on the exposed prongs of the other 30A plug. That's pretty dangerous.

2) If the 30A sides are plugged into outlets on the same side of a split phase circuit. The result will be in-phase L1 and L2 on the 50A side. You will have 0 volts for 240V circuits, and can also overload the neutral with 60A where is it rated for 50A.

A dumb adapter can work just fine, but to use it safely requires knowledge and care that is beyond most users abilities.

[MichaelB1969]

Originally Posted by twistedtree

Maybe, and if so, it's an awesome price.

The key is whether is has the requisite safety features, and I'm skeptical given the price, but you never know. Good reverse Y adapters are "smart" and sense the presence and phase of the two 30A plugs, and only connect to the 50A side if all is kosher. Without that, you have a "dumb" adapter and two things can happen, neither of which is good.

1) If the 50A side is plugged into a load and you plug in one of the two 30A plugs, you can end up with hot power on the exposed prongs of the other 30A plug. That's pretty dangerous.

2) If the 30A sides are plugged into outlets on the same side of a split phase circuit. The result will be in-phase L1 and L2 on the 50A side. You will have 0 volts for 240V circuits, and can also overload the neutral with 60A where is it rated for 50A.

A dumb adapter can work just fine, but to use it safely requires knowledge and care that is beyond most users abilities.

Since I am relatively dumb with electrical matters (I'm better with mechanical things), probably better to get a smart adapter!

[twistedtree]

Originally Posted by MichaelB1969

Since I am relatively dumb with electrical matters (I'm better with mechanical things), probably better to get a smart adapter!

I think that's smart unless you are really comfortable with split phase AC power.

What I can't tell is whether the product you referenced is smart or dumb. They are silent on the matter, and that coupled with the low price makes me suspect it's a dumb adapter.

[MichaelB1969]

Originally Posted by twistedtree

I think that's smart unless you are really comfortable with split phase AC power.

What I can't tell is whether the product you referenced is smart or dumb. They are silent on the matter, and that coupled with the low price makes me suspect it's a dumb adapter.

Yeah, I'd imagine that ECS would indicate the fact that it was smart if that was indeed the case. They do make great shore power cords for the price though!

So there is no adapter that converts the old 125 to the newer 125/250?

[twistedtree]

Originally Posted by MichaelB1969

Yeah, I'd imagine that ECS would indicate the fact that it was smart if that was indeed the case. They do make great shore power cords for the price though!

So there is no adapter that converts the old 125 to the newer 125/250?

Not without all the same smart vs dumb issues. The problem is getting from 120V to 240V. To do that you need two 120V outlets that are out of phase with each other, so they can be combined to create 240V. I've never seen a 120V 50A to 120/250 50A smart reverse Y, but that doesn't mean they don't exist.

[dhays]

I don't know about 50a/240v systems. I see a lot of boats that have two 30amp inputs. I assume they are powering two 30 amp panels. They could be powered by a 50amp/240v pedestal with the appropriate splitter. They can also be powered by two 30amp cords.

If having one 50a/240v inlet in your boat becomes a problem, would splitting it into two 30amp inlets be a reasonable alternative?

I really don't know, just trying to learn.

[twistedtree]

Originally Posted by dhays

I don't know about 50a/240v systems. I see a lot of boats that have two 30amp inputs. I assume they are powering two 30 amp panels. They could be powered by a 50amp/240v pedestal with the appropriate splitter. They can also be powered by two 30amp cords.

If having one 50a/240v inlet in your boat becomes a problem, would splitting it into two 30amp inlets be a reasonable alternative?

I really don't know, just trying to learn.

Maybe, but it requires some pretty careful investigation of how the boat is wired, including checks for any modifications that might have been made along the way.

On some boats the two "halves" of the 240V 50A split out into two independent 120V circuits/panels on board, and there are no 240V appliances. In that case, you could feed it with two independent 30A 120V cords, or even two 50A 120V cords. The key is that the boat has no need for 240V. It's just convenient to bring the two 120V circuits on board as a single 240V cord/inlet. There are other subtleties that need to be checked as well, like common neutrals that might get overloaded.

On other boats, and probably most built in the past decade or so with 240V 50A service, the 240V is actively used by things like HVAC, water heaters, etc. In this case, dual incoming 120V cords must somehow be used to reconstruct 240V service on the boat, or none of the 240V devices will work.

To reconstruct 240V service, you can't just pick any two 120V services. They need to be "out of phase" to make 240V. It's not unlike wiring batteries in parallel vs series. Hook them up one way and you still have the same voltage. Hook them up another way and you get double the voltage. The trouble is you can't tell by looking at two outlets whether they are in phase or out of phase. The only way to tell is to measure the voltage between various points on the two. This is what a "smart" adapter does, and only connects everything if all measures up.

I hope that helps, at least conceptually.

[dhays]

Originally Posted by twistedtree

I hope that helps, at least conceptually.

It does, thanks. Very few boats with AC in my area. I haven't met anyone in my area whom I know of that has any 240v appliances. However, that doesn't mean that they don't.

[ranger58sb]

Originally Posted by twistedtree

On some boats the two "halves" of the 240V 50A split out into two independent 120V circuits/panels on board, and there are no 240V appliances. In that case, you could feed it with two independent 30A 120V cords, or even two 50A 120V cords. The key is that the boat has no need for 240V. It's just convenient to bring the two 120V circuits on board as a single 240V cord/inlet.

Ours is like that.

And the loads are sorta balanced between the two circuits, water heater on one, cooktop on the other, etc. In our case, two ACs, one on each 120V circuit.

-Chris