T&T: Shore power Question

[Peter Bennett]

Wednesday, October 24, 2007, 6:34:47 PM, Dan wrote:

DW> The thread about the 50 amp 125 vs 50 amp 240 has raised some question about
DW> the wiring in the boat I am. This boat has 3 shore power sockets, one 50 amp
DW> 120, one 30 amp 120 on the starboard side and another 50 amp 120 on the port
DW> side.  My question has to do with how these should be connected at the
DW> panel.  If they are connected in parallel at the panel then all sockets
DW> become hot  when any single socket is used which in my opinion raises a big
DW> safety issue because if someone takes the cover off the unused socket it
DW> exposes 120 volts for easy contact.  I believe the boat I am working on
DW> originally used a selector switch so that only one of the sources could be
DW> used at a time and the other would be disconnected so that it was not hot.
DW> The second 50 amp socket was added later and wired in parallel to the other
DW> 50 amp entrance and the 30 amp was also wired such that it was always
DW> connected unless its separate breaker was thrown.  It seams to me that my
DW> best option is to rewire back to the original configuration and abandon the
DW> starboard 50 amp socket or allow switching between the 50 amp sockets and
DW> abandon the 30 amp socket which is no big deal since an adapter can be used
DW> to connect to a 30 amp shore power service.

DW> Am I looking at this right?  Are there options that would allow safely
DW> keeping all three sockets without adding a very expensive switch that would
DW> allow selecting any of the 3 sources?

DW> The issue of creating a hot socket can also be a problem for those that are
DW> using an inverter without a selector switch of some kind.

DW> Dan Winchester
DW> <www.dwinchester.com>
DW> Portland, Oregon

By electrical code rules and ABYC recommendations, it MUST NOT be
possible for two or more AC sources to be connected together.

Therefore, if you want to keep all the AC inlets, you must have a
selector switch or mechanically-interlocked circuit breakers to ensure
that only one inlet can be connected to the on-board AC system at a
time (and the other inlets are disconnected).

If you are willing to abandon the port-side 50A inlet, and use an
adaptor to use a 30 amp outlet, you could simply wire the starboard 50
amp inlet directly to the on-board AC system, and also abandon or
remove the 30 amp inlet and port 50 A inlet. (Removing the unused
inlets would probably be best, to avoid confusion.)

-- 
Peter Bennett, VE7CEI    Vancouver, B.C., Canada
Ennos 31 "Honeycomb"
GPS and NMEA info: http://vancouver-webpages.com/peter 
Vancouver Power Squadron: http://vancouver.powersquadron.ca