Need a crash course on 100 amp US shorepower

How about getting someone from Ward’s involved?

Well, a 480v 100 amp outlet will give more than twice the power as a 208v 100 amp outlet. Maybe they think the big boats will use 480 to get more power. Dunno.

Ive got Atlas. I regularly plug into 4 pin and 5 pin setups. Atlas handles 480v without an issue. Converts it to single phase, and sends it to my buck boost which dials the voltage up to 240 per leg, or pretty close if low. I think incoming 208 gets up to perhaps 236. It's about 18v under load for the boost at max. But that's not the Atlas.......

So, what's the question?

I don't really understand how or why you'd have a 3 phase setup with 208 per leg, but essentially it's delivering 208 via three different phased sources. The lower voltage merely limits the available amps from the supply. Obviously 480v per leg would deliver more available amps for consumption.

Atlas simply takes the incoming phases and converts them to a single phase, 2 leg output. SO in seeing the 208 as opposed to 480, the Atlas is only going to be able to provide 208 per leg as opposed to 240 per leg. Your buck boost transformer aboard can lift you back towards 240, but you'll obviously consume a lot more amps to make up for that voltage boost. Atlas doesn't really care if the incoming is 208 per leg, 240 per leg, or 480 per leg. It will simply give you two legs of single phase with the available voltage.

Interesting question re two cords at different voltage. But would seem to not matter. If you can get one cord into 480, I wouldn’t think you’d need the other as you’d have twice the amps available to you on 480 versus 208. On 208 you’re not only short amps, but you’re spending amps to get the voltage up.

Four pins is single phase. Five pins is three phase. Does that answer the open items?

Yes, my cords are 5 pin as well. Most often I use the 5-4 adapter where we find single phase 100 amps on a dock.

Again, and sorry, I’m tired, your 208 ends up 190 under load, so you’re consuming a lot of your available amps to get that voltage back up to 240. Amps are already limited via the 208.

What’s upstream? I’m guessing the Marina is simply converting local line voltage on 3 phases to 208 output. I don’t know why marinas do this. Makes no sense to me. Getting the right transformer doesn’t cost more money.

In my regular Marina in Florida I added a buck boost to the switch room for my circuit. I boosted the 208 coming from my breaker through the transformer to get 240 at the source. Lost some voltage with the long run, but I was now starting with 232 volts as opposed to 202. That added voltage made a huge difference.

The 208 three phase power the dock has is 120v on each of the 3 legs and 208 v across any two hot legs.
480v 3 phase has approximately 2.5 times as much power as 208 v 3 phase. We run hundreds of 120/ 240 volt single phase ac units on 3 phase 208. Units don't care.
4 pin and 5 pin plugs differ in that 4 pin has no neutral. Get an ohm meter and measure and mark the female plugs on power pedestals with thier respective L1, L2, L3, N, G. With a sharpie. You won't know rotation unless you buy the proper meter but boat doesn't care because of atlas.
Atlas would need two transformers to boost, drop 208 and 480 simultaneously. Don't think it does but would find out definitively before plugging in.
Just run entire boat from 480 3 phase feed.

Yes 2.5 times as much power as a 208 3 phase. Get the adapter and your all good.

That's good news.

We struggle to keep from popping one 100amp single phase. We have a significant inverter bank which I would think would take some load off the shorepower but hasn’t yet. Maybe I can get one chiller on that bank. Something I want to look into when back in soflo

I recall the 4 pin is used as a single phase.
Ground, Neutral, Top Vac, Bottom Vac (green, white, red, black).
The 208Vac you are reading is the normal (Y Transformer) output in place of the 230 usually found (top Vac to bottom Vac).
You will also find a full 115Vac on two leads, in this outlet also (top or bottom to neutral).

Most equipment should work on 208Vac.
Just remember, when you boost up the voltage, you loose Amps and may over draw (trip) service breakers.

5 pin is usually 3 phase. Extra blue wire. Still 115Vac to neutral and 208Vac to the red and black leads.

Your 5 to 4 pin converters just use the white, green and any two of the 208Vac leads from the 5 pin service.

I have made adapters for dockside 100A-4 pin to twin 50A boat service that worked very well.
I have made adapters for dockside 100A-5 pin to single and dual 100A boat service that worked very well also.

At the St Augustine dock, the larger slips are only 100A-5 pin, 3 phase.
Sadly these services are at the end of a very long dock, a long ways from the Y transformers.
All the boats along the dock are drawing from the transformers also.
One of our customers had a large Hatteras that had dual 100A-4 pin lines. With all the A/Cs running, that second power cord was needed.
I designed a box that had a single 5 pin dock connect and 3 x 4 pin output connects for the boat. Watching the on board volt meters, you could rotate the 2 ships power cords to the strongest of the 3 leads from this box.

Ralph are you sure its not losing the neutral?? Refrigerated shipping containers use 4 pin 480v with no neutral.