Sequence for Switching from Shore to Ship (Genny)

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.

I would never combine (both) AC sources, unless they had a synchronization system, which is unlikely. With the two sources out of phase something is likely to be unhappy and possibly burn out / blow fuses. My procedure would be to disconnect from shore power then switch to the generator / ship.

Seadog are you switching to generator (Ship) before or after you have started the Genny?

I usually have the generator running before switching the ship to it. That way if the generator is putting out low voltage and or frequency during start up it will not affect any of the ship's electronics.

Warm the generator up for several minutes. Turn off any high load items like air conditioners, etc. Move selector switch from shore to generator, load up the generator by turning back on air conditioners, etc Turn the shore power pedestal switches off, remove power cords and cap off the power inlet plugs on the boat.
When removing the electric load from the generator let it run unloaded for at least five minutes or more to cool down the electrical end of the generator before stopping it.

Very unlikely you have a Shore, Both, Gen switch unless it is for battery banks (12V) on small vessels such as yours.


As mentioned, the chances you have the electrical system that could synchronize both is not likely.


There may be a shore, off, gen switch but not a both.

Start generator (to warm up and look for water in exhaust)... boatside main AC breaker to OFF... ship/shore switch to off... turn off power at pedestal breaker... ship/shore switch to ship... turn on main boatside breaker

psneeld - it definitely is Shore Both Ship and it looks original. Since the boat is 45 years old it may be that the boat originally didn't have a generator. There is a separate Ac/Dc switch.

Is there two shore inlets? This may be the "both" it is referencing.

My boat has 2-50 amp shore cables labeled shore 1 and shore 2. Switch is shore 1, shore 2, both (1 and 2), OFF, and Gen.

Same sequence as HiDHo above...^^^^

BOTH??? Wow is that wrong! Can you say KA-BLAM!!!
Hopefully everything goes dead in the Both position and it is just mis-labeled instead of OFF. Just to be safe, make sure the generator output BREAKER is OFF before switching.

psneeld said:

Very unlikely you have a Shore, Both, Gen switch unless it is for battery banks (12V) on small vessels such as yours.


As mentioned, the chances you have the electrical system that could synchronize both is not likely.


There may be a shore, off, gen switch but not a both.

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Agree that it is very unlikely the OP has a BOTH position. Mine is ShorePower Aft/S'power Fwd (two inlets, only 1 can be selected at a time), Off and Ship. When wanting to use the genset, I switch to Off (usually already selected if we've left the dock); check that all AC breakers including charger are off, start genset and let it warm up briefly, then select Ship, then progressively turn on each relevant AC breaker starting with the charger.

It is always possible that a previous owner mis-used a standard battery joining switch for the AC connection.

That would be a real wiring trick.


If that's the case and it works when it is switched..... that's a huge problem.


It could only switch one out of 3 wires and that would mean the others would have to be directly connected with no interlock.

HiDHo said:

Warm the generator up for several minutes. Turn off any high load items like air conditioners, etc. Move selector switch from shore to generator, load up the generator by turning back on air conditioners, etc Turn the shore power pedestal switches off, remove power cords and cap off the power inlet plugs on the boat.
When removing the electric load from the generator let it run unloaded for at least five minutes or more to cool down the electrical end of the generator before stopping it.

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HiDHo has it exactly right.


If you have the shore/genset breakers lockout slide then turn the shore breaker off, push the slide over then turn the genset breaker on, always after warming it up and cooling it down after using it.



David

I’ve never heard of a “both” switch like this, but my guess would be that “both” has shore powering some loads, and the gen powering others (probably air con). It’s probably to allow air con use when the shore power can’t otherwise handle it.

twistedtree said:

I’ve never heard of a “both” switch like this, but my guess would be that “both” has shore powering some loads, and the gen powering others (probably air con). It’s probably to allow air con use when the shore power can’t otherwise handle it.

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Having a hard time thinking why someone would use a switch if the panel isn't split or separate somehow...and then a "both" position still boggles the mind.

If indeed you do have a both switch for the generator and shore power get rid of it. In both position you can backfeed into the shore which can be dangerous. You could potentially electrocute someone if they think the electricity is turned off on the shore and are working on the wiring and you start your generator in both position and feed electricity into the shore wiring. There should be no way for your generator to hook to the shore wiring, either your boat should be on shore power or on the generator, never both.

I would highly recommend that you get a qualified marine electrician to look at your system.

Conrad said:

I would highly recommend that you get a qualified marine electrician to look at your system.

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+1

Somehow this boat has survived for 45 years with the current configuration so I seriously doubt the BOTH position is true.
Turn off all large loads like the air conditioners first.
As others said, let the genny warm up before applying full load. My manual says wait until coolant temp above 150F. I try to always switch the transfer switches unloaded. The contacts will last longer that way. Once over on the genny then load it up one load at a time.
OTOH, I've watched people start their gen then throw the transfer switches immediately to GEN with no thought whatsoever of slowly loading it. Not my style!

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

Sounds good, I did not think it would have been a both position because that could be highly dangerous. Glad it is correct.

HiDHo said:

Warm the generator up for several minutes. Turn off any high load items like air conditioners, etc. Move selector switch from shore to generator, load up the generator by turning back on air conditioners, etc

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I know this may be hard to quantify, but how long should the genset run before putting a load on it? I start it up with the AC selector on one of the shore power inlets. I don't allow the genset to run all that long, generally just enough for the oil to circulate and the water to flow. This is typically only about 30 seconds. Then I start to load up the genset first with the charger (the primary reason I run the genset) and any other AC loads to get the genset well loaded.


So should I let it run long enough to raise the oil temp? How long is long enough.


A related question, what is a good way to determine how much the genset is loaded, by the amps that it is putting out?

If your genset is in the engine room and you are starting it while the engine room is still hot from a passage, the genset itself will already be warm to some extent. In this circumstance, I don't think you need to run it for too long at all before applying a load. Obviously, if you are in very cold conditions and the engine room itself is cold, letting the genset engine warm up to, say, 50% of its operating temp would make sense before applying load.

Do you have any metering at your helm or with the genset control panel that shows the amp output of the genset as loads are applied? Good idea to fit an ammeter if you do not have one. My metering (digital) shows volts, hertz, amps, run hours, genset start battery volts, etc.. Wouldn't be without it

Aquabelle said:

If your genset is in the engine room and you are starting it while the engine room is still hot from a passage, the genset itself will already be warm to some extent. In this circumstance, I don't think you need to run it for too long at all before applying a load. Obviously, if you are in very cold conditions and the engine room itself is cold, letting the genset engine warm up to, say, 50% of its operating temp would make sense before applying load.

Do you have any metering at your helm or with the genset control panel that shows the amp output of the genset as loads are applied? Good idea to fit an ammeter if you do not have one. My metering (digital) shows volts, hertz, amps, run hours, genset start battery volts, etc.. Wouldn't be without it

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Good point about the genset being in the ER. Most of the time, my genset gets run for about an hour in the evening (less so now with my solar) and definitely an hour in the morning. In the morning, the ER is generally cool.


I do have a meter that shows voltage, amps, and Hz. I generally keep it on amps. Being 6kw genset, I figure the max amps at 120v would be 50? Knowing that the genset shouldn't be run under light load for too long, I guess I'm wondering what amp draw would be appropriate? So far, I've tried keep the load at least 30amps where possible. That is just a WAG however, and I'm wondering if anyone else has better informed ideas?


Before shut down, I reduce the load and finally cut out all the loads before I shut it down, then turn the power selector back to a shore power inlet.

It's not rocket science to sync a generator and shore power or two generators. Between the 2 hot legs of the source is a socket and light bulb duplicated on shore power or the other generator. The bulbs flash, when they flash off together, you throw the switch. This was common on ships in the 1920s and I saw it still in use on a ship in the 1950s. I've been using the method since I was shown without issues, but only for switching the load, not continuous connection. For that you need voltage control and other safeties. Without voltage control, one generator will try to run the other as a motor.

Here's my shore power to generator switch. I don't know if it's common or not. I have a twin 30A shore power config. This is my first boat with a generator. YES, IT'S GAS. Please refrain from the "You're gonna kill yourself or someone else" malarkey. The anti-gasoline rhetoric is really getting old on Trawler Forum.

That's an interesting set-up and makes sense...but what does TRANSFER mean/do?

Aquabelle said:

That's an interesting set-up and makes sense...but what does TRANSFER mean/do?

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Well, to use the generator I have to switch both of the shore power fuses and then put on the generator transfer fuse.

SeaBreeze said:

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.

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Start the generator. Open the shore power pedestal breakers. Open the shore power breakers on the boat. You now have a "dead" boat. Shut loff the A/Cs, hot water heater and other heavy loads. Bring the generator on line, starting the A/C loads one at a time. To go back to shore power, again, start with a dead boat. Bring shore power back onto the boat and begin reloaded shore power.

Just curious, how have you been doing it now?

Years ago, there used to be recreational type boats with 2 generators and they would sync the 2 together when necessary. It is my understanding, that never worked out well so the practice was abandoned.