Sequence for Switching from Shore to Ship (Genny)

[HiDHo]

A Rotary switch is the safest installation although very pricey.

 

[SeaBreeze]

I have a rotary selector switch. My current procedure is to start the generator, turn off AC devices, disconnect the AC 30 amp main breaker, turn selector switch from Shore to Ship, engage the 30 amp main breaker, then bring up AC devices one by one. This thread is a good reminder to be slow about the process, and to let the generator run unloaded to cool down after use.

 

[OldDan1943]

A Rotary switch is the safest installation although very pricey.

I am guessing that all boats are like mine. There are lock-out breakers so one cannot engage one source without first disengaging the first source.

Of course, I also enjoy speaking with 'great authority' and discover, once again, I am totally wrong. SMILE

 

[Deano]

If the gen set is warmed up and a/c units are caught up I switch right over and avoid starting amps on the a/c motors. No issues in four years.

 

[rgano]

If the gen set is warmed up and a/c units are caught up I switch right over and avoid starting amps on the a/c motors. No issues in four years.

I am too careful to do that. I shut all equipment down and restart when shifting power source. The a/c units' motors are not stressed because they both have Micro-Air soft starter micro-processors installed. Never hear the 3.5 KW genny load up when either the 10KBtu or 13.5 KBtu units cycle on.

 

[J0k3r]

What is the proper sequence for switching from shore power to Genny? I have a selector switch with three positions: Shore - Both - Ship This on a 1974 vintage boat with diesel genny.

If you actually have a BOTH option and that position is selected while the shore power is connected and the generator is on, you will be feeding out of phase voltage back onto the dock. So, your boat will not be the only one affected by this. There should be no both option for AC on a switch unless it is part of a system designed to handle this properly.

 

[psneeld]

I can not understand why a rotary switch is safer.


I removed mine when I got new panels that had built in main breakers with a lockout.


Seem equally safe to me. The plastic innards could have broken at any point and I would have been stuck without an expensive backup that aren't on a lot of local shelves like breakers.

 

[psneeld]

If you actually have a BOTH option and that position is selected while the shore power is connected and the generator is on, you will be feeding out of phase voltage back onto the dock. So, your boat will not be the only one affected by this. There should be no both option for AC on a switch unless it is part of a system designed to handle this properly.

See post #21


OP posted....


"I just checked - it is Shore-Off-Ship... Whew! I will follow HiDHo's procedure. Great information. Thanks!!"

 

[johnrupp]

I am too careful to do that. I shut all equipment down and restart when shifting power source. The a/c units' motors are not stressed because they both have Micro-Air soft starter micro-processors installed. Never hear the 3.5 KW genny load up when either the 10KBtu or 13.5 KBtu units cycle on.

What model generator do have? That’s impressive a 3.5 KW will start both units.

 

[mdstrum]

Small side note...TURN OFF THE BREAKER FOR THE SHORE POWER AT THE DOCK PEDESTAL, then discount the power breaker in your boat, then remove the shore power cord...and as all have said start gen, let it warm up, and slow load it up.

To many people leave the shore power energized and laying on a dock to get wet or kicked in water fry someone

 

[OldDan1943]

Small side note...TURN OFF THE BREAKER FOR THE SHORE POWER AT THE DOCK PEDESTAL, then discount the power breaker in your boat, then remove the shore power cord...and as all have said start gen, let it warm up, and slow load it up.

To many people leave the shore power energized and laying on a dock to get wet or kicked in water fry someone

 

[rgano]

What model generator do have? That’s impressive a 3.5 KW will start both units.

It's a 160-pound Nextgen 3.5 KW, one lunger. Since running amps are about 1/5 or less the startup amps, getting around that hefty startup amperage with a micro-processor makes it a snap to run 23.5 Kbtu worth of air conditioning.

 

[EdtheC]

Shore-Battery-Ship

Could it have been originally to have a battery charger wired to the BOTH position so that it would operate in that position?

 

[psneeld]

Could it have been originally to have a battery charger wired to the BOTH position so that it would operate in that position?

See post #21


OP posted....


"I just checked - it is Shore-Off-Ship... Whew! I will follow HiDHo's procedure. Great information. Thanks!!"

 

[ProMaritime]

If we are talking AC power here replace that switch if it will really do what it says (Both). Paralleling two source of AC power requires a complicated and expensive piece of equipment I've only seen on large multi-engine jet airplanes.

You must be confused about what this switch actuallyy does or the boat would have burned to the ground long ago.

 

[psneeld]

Post 21 tells all.....

 

[OldDan1943]

If we are talking AC power here replace that switch if it will really do what it says (Both). Paralleling two source of AC power requires a complicated and expensive piece of equipment I've only seen on large multi-engine jet airplanes.

You must be confused about what this switch actuallyy does or the boat would have burned to the ground long ago.

Navy ships and nuc subs used this manual method of putting generators on line and shifting from shore power to ship's power.
I have no idea if they still use this method.

 

[ProMaritime]

Not a nautical comment but on the Boeing 727 (3 generators) and 707 (4 generators) and the Douglas DC-10 (3 generators)in order to parallel AC generator outputs require very close tolerances between volts, Hz and phase of each generator or the paralleling system wouldn't accept the transfer. Standard transport airplane power is 120v, 400Hz 3-phase AC

New twin-engine airplanes usually operate with the left and right busses isolated but are equipped with bus-tie switching (manual or automatic) to power both buses if need be. Extended range (ETOPS) twin-engine airplanes also must have an APU that will operate at all altitudes which can pick up the power for a failed bus if due to an engine failure.

Most marine electrical switch and panel manufactures, like Blue Sea, have a sliding lock-out mechanism that will not allow shore AC to be combined with getset AC.

 

[Sharpseadog]

Not a nautical comment but on the Boeing 727 (3 generators) and 707 (4 generators) and the Douglas DC-10 (3 generators)in order to parallel AC generator outputs require very close tolerances between volts, Hz and phase of each generator or the paralleling system wouldn't accept the transfer. Standard transport airplane power is 120v, 400Hz 3-phase AC

New twin-engine airplanes usually operate with the left and right busses isolated but are equipped with bus-tie switching (manual or automatic) to power both buses if need be. Extended range (ETOPS) twin-engine airplanes also must have an APU that will operate at all altitudes which can pick up the power for a failed bus if due to an engine failure.

Most marine electrical switch and panel manufactures, like Blue Sea, have a sliding lock-out mechanism that will not allow shore AC to be combined with getset AC.

Disconnect shorepower first. Start and shut down Gen set with no load on it. If you don't do this you place huge demand on gen set capacitor, and may destroy it. I had this happen on my Next-gen 3.5 kw. If you can't find replacement capacitor, look for equal or higher capacity "starting capacitor" at commercial HVAC companies. Next-gen sent me a free replacement, but the larger capacity unit is working very well, so I keep that as a spare. [emoji924][emoji196]