SailNet Community banner
1 - 3 of 3 Posts

·
Registered
Joined
·
23 Posts
Discussion Starter · #1 ·
I'm looking at getting a 50A to twin 30A "Y" adapter but not sure which to get. The 50A end is either a 125V or 125/250V plug. My boat has twin 30A 125V plugs. I don't have access to the pedestal at my boat slip to check but also want to know what is more common out there? What type of plug am I likely to encounter at marinas?
 

·
Registered
Joined
·
23 Posts
Discussion Starter · #3 · (Edited)
One of the other questions I had around these adapters was how they were wired, especially the 125/250V version since it is a four wire adapter. In doing a little bit of research I learned a few things that I thought I'd pass along. I apologize in advance if this is already common knowledge.

The pedestal at the dock is typically wired for 240V with an x, y, neutral and ground. This is the four wire system. Much the same as house wiring on land although on land the two hot terminal are designated L1 and L2. From x or y to neutral is 125V. From x to y is 250V. The 50A 125V version of this "Y" adapter connects the hot terminal to x or y and delivers a total of up to 50 amps at 125V to the two 30A "Y" receptacles. Anything more than a total of 50A will trip the breaker on the pedestal. In other words, both 30A receptacles share the same hot terminal either x or y.

On the 50A 125/250V version of this adapter, each of the two 30A receptacles connects to a separate hot terminal, either x or y. Both x and y are used and therefore a full 50A can be supplied to BOTH 30A receptacles. The current has to be limited to 30A by the breakers on the boat. This can be good and bad. Good in that you get the full 30A for both boat circuits for a total of 60A. Bad in that it can in theory deliver 100A before the breaker on the pedestal trips so the connections and breakers on the boat side need to be in good order so you don't start your boat on fire (see Maine Sails excellent write up on these NEMA connectors).

Just thought I'd pass it along.
 
1 - 3 of 3 Posts
Top