Outlet A/B Switch

So I have 2 outlets buried in galley cabinetry (dont ask). One is inverter powered and one is not (do not know why). At the dock microwave and fridge are plugged into the non-inverted plug and when not docked I plug them into the inverted plug.

Not a very convenient process given the outlets location. Searched around for a simple solution and did not find anything. Is there a simple A/B switch set-up available or than can be assembled to fit the bill?

Thanks in advance.

Osprey69 said:

One is inverter powered and one is not (do not know why). At the dock microwave and fridge are plugged into the non-inverted plug and when not docked I plug them into the inverted plug.

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What would be the impact if you leave them always plugged into the inverted outlet?

-Chris

PO may have had appliances that they did not want run through inverter.

I have shore only plugs for electric heaters. Do not want inverter to power heater by accident for instance.

Yes an AB switch is possible.

I agree that's not a convenient setup, but I don't think an "AB switch" is the ideal solution. You would have to switch all three conductors to avoid problems and code violations.

I suggest having a qualified marine electrician examine your boat's wiring and see if both circuits can be combined and switched with an automatic transfer switch so the outlets will be hot regardless of whether you are connected to shore power or running on the inverter.

This is how I configured my boat when I installed an inverter.

The guy who set my inverter up attached it to my only AC panel (pre-existing), but cut the connection at that panel that connects all circuits (sorry, not being electrically trained my explanation may not use all the correct terms) together, leaving the water heater and charger connections separate from the rest. This way all of the outlets are live whenever either shore power is connected or the inverter is turned on, but the water heater and charger circuits are energized only by shore power.

I also have water heater and some outlets only on shore. The buss bar for hot and neutral are isolated, either from shore or from inverter. The ground buss remains joined.
The LED lights must be attached to the buss that the breaker is attached

koliver said:

The guy who set my inverter up attached it to my only AC panel (pre-existing), but cut the connection at that panel that connects all circuits (sorry, not being electrically trained my explanation may not use all the correct terms) together, leaving the water heater and charger connections separate from the rest. This way all of the outlets are live whenever either shore power is connected or the inverter is turned on, but the water heater and charger circuits are energized only by shore power.

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All the 120 volt outlets on my boat are on a single circuit (it's a relatively small boat) so it was a simple matter to connect the inverter to that circuit. The transfer switch automatically connects the inverter to that circuit when shore power is disconnected.

Some of the cheepo shore power cords have molded on ends,

When they fail and folks investigate the price of quality ends (Hubbel) the dump the cord and buy a new one.

Some of these cords are 6-3 , so if you cut a piece out of the center it might be fine..Some use tinned wire , some don't.

OP fails to mention what type of inverter he has. This info might explain why things were done a certain way. Knowing the inverter would also help us know what options are available to the OP. The most convenient method would be to install a pass through inverter. This allows shore power to pass through when available and inverting when shore power is not present.

Thanks for the input. The inverter has dedicated outlets to avoid usage by high amp appliances (toaster oven etc). It is a brand new inverter install (shore power pass thru etc), but some outlets are just not on its circuit.

The A/B switch is to avoid over-exercising the batteries when not needed (dockside) while having the fridge being able to run all day without the generator running when anchored. It seems like sourcing the two outlets with pre-made high quality components cords to a A/B switch for the appliances to source from would be possible without re-inventing the wheel or over-engineering.

Perhaps not.

tiltrider1 said:

The most convenient method would be to install a pass through inverter. This allows shore power to pass through when available and inverting when shore power is not present.

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I assume the pass through you’re referring to does not isolate the incoming power like a charger or an isolation transformer would

Osprey69 said:

... It is a brand new inverter install (shore power pass thru etc)...

The A/B switch is to avoid over-exercising the batteries when not needed (dockside)...

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Not sure if we're talking the same terminology here. To me, pass-through means that the inverter passes shore power through to the attached circuits when it's available, and supplies power from the batteries only when it's not.

In this case, just leaving something plugged into the inverter-supplied outlet will achieve what I think you want.

Or am I totally misunderstanding the question?

To elaborate on some of the comments here, transferring power gets tricky with the new GFCI and AFCI breakers being installed in marinas these days.

The problem is the safety ground. The ground and neutral can only be bonded at the source. The source can be the inverter, or the shore power breaker. So you need to switch not only hot and neutral, but also ground. Newer inverters do this. Old boat wiring may need to be tweaked to accommodate this requirement. Also, old inverters may not switch quickly enough, and will trip the breaker when first plugged in.

Mako said:

I assume the pass through you’re referring to does not isolate the incoming power like a charger or an isolation transformer would

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Pass through means the inverter passes the shore power through when available. If shore power is lost it switches to inverter mode and creates AC from your DC. Chargers do not isolate. Isolation transformers are the only device that truly separate shore power from boat power.

It’s very common to split an AC panel between inverter and non inverter loads. This can be done two different ways. Run everything through the inverter and then put in relays to drop out high power circuits such as hot water heater, heaters, stove,etc. The other way is to split the panel with the high power circuits wired directly to shore power and the rest going through a pass through inverter.

I would leave it just the way it is.



Why introduce needless complexity?

"I would leave it just the way it is."

YES! it handles the neutral to ground properly .

Move the boxes to an easier to access location.

FF said:

"I would leave it just the way it is."

YES! it handles the neutral to ground properly .

Move the boxes to an easier to access location.

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If the boxes were easily accessible, or easily moved, I would not have asked the question.

Upon further research I will hard-wire in one of these for the automatic transition for the two appliances.

https://www.amazon.com/gp/product/B004S5Y158/ref=ox_sc_act_title_1?smid=ATVPDKIKX0DER&psc=1

Thanks for the replies.

Wait, what???

Does your new inverter support pass-through or not?

It seems most of us here thought you already had what you wanted; an outlet which is powered by shore power when available (passing through the inverter) or battery when not (powered BY the inverter.)

What did we misunderstand? I'm curious because I see all kinds of electrical setups on deliveries, and I want to be prepared if I ever run into a situation like yours.

Osprey69 said:

If the boxes were easily accessible, or easily moved, I would not have asked the question.

Upon further research I will hard-wire in one of these for the automatic transition for the two appliances.

https://www.amazon.com/gp/product/B004S5Y158/ref=ox_sc_act_title_1?smid=ATVPDKIKX0DER&psc=1

Thanks for the replies.

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So I have been watching this closely as I would like to do the same. The difference is my inverter is old (15 years) so likely does not support pass through. Will this permit me to power a few outlets to run on both shore and inverted power (I think yes). Seems like a simple fix at a reasonable cost. Thanks

Rob

CaptTom said:

Wait, what???

Does your new inverter support pass-through or not?

It seems most of us here thought you already had what you wanted; an outlet which is powered by shore power when available (passing through the inverter) or battery when not (powered BY the inverter.)

What did we misunderstand? I'm curious because I see all kinds of electrical setups on deliveries, and I want to be prepared if I ever run into a situation like yours.

Click to expand...

Yes, but apparently not all outlets (I have only identified this one) are supported by the inverter. So I am using the non-inverter supported outlet for the microwave/refrig when dockside/generator powered and the other inverter outlet for when not.

Perhaps I should have mentioned that this whole exercise is being driven by my thinking the that less cycles the batteries are drawn down and charged by high amp items like the fridge and microwave the longer they will last.

@Osprey, don’t mean to over complicate your life, but that is a strange electrical setup which is what happens to all boats as the years go by with various meatball owner.

Perhaps it’s time to think about restoring / updating your system. Fun winter project.

Osprey69 said:

Yes, but apparently not all outlets (I have only identified this one) are supported by the inverter. So I am using the non-inverter supported outlet for the microwave/refrig when dockside/generator powered and the other inverter outlet for when not.

Perhaps I should have mentioned that this whole exercise is being driven by my thinking the that less cycles the batteries are drawn down and charged by high amp items like the fridge and microwave the longer they will last.

Click to expand...

The inverter/charger we had in the last boat didn't use battery when we were on shorepower. The inverter was wried into the panel to service all outlets (including the one for the microwave), but that's where the automatic transfer came into play...

-Chris

Osprey69 said:

Yes, but apparently not all outlets (I have only identified this one) are supported by the inverter. So I am using the non-inverter supported outlet for the microwave/refrig when dockside/generator powered and the other inverter outlet for when not.

Perhaps I should have mentioned that this whole exercise is being driven by my thinking the that less cycles the batteries are drawn down and charged by high amp items like the fridge and microwave the longer they will last.

Click to expand...

Stop thinking like that and plan to enjoy the boat. How will you know in 5 years if the batteries lasted longer by being frugal. If the batteries die because they were used then you have enjoyed that time along the way. If they die because of old age, then not so much.

Osprey69 said:

Yes, but apparently not all outlets (I have only identified this one) are supported by the inverter. So I am using the non-inverter supported outlet for the microwave/refrig when dockside/generator powered and the other inverter outlet for when not.

Perhaps I should have mentioned that this whole exercise is being driven by my thinking the that less cycles the batteries are drawn down and charged by high amp items like the fridge and microwave the longer they will last.

Click to expand...

If the inverter supports pass through, it won't be exercising the batteries when on dock power. If you can take a picture of the inverter, we could probably identify it right away and confirm whether it does pass through.

The automatic switch device you bought is interesting, I'd be curious whether the ground is switched internally. I suspect this device could lead to problems with ground fault detecting power pedestals.

It all depends on how much $$ you want to spend.

I do like the way my boat from a past owner set it up. They installed a 3000w pass thru inverter/charger with auto switching if the inverter is enabled. All outlets and everything other than reverse cycle heat/AC is connected to it. Which gives me 25amps A.C. and a 230amps D.C. load on the batteries. Which I never use it that high anyways. Point is, with the engine running I can power anything keeping in mind the full load on the batteries. Without the engine running, I an more careful on how I use it.

This really depends on how you use your boat. At times underway I want a cup of coffee. For the 800watt coffee maker I use the inverter and at times I start the genset just to run it. Engines like to be used!

Its is an easy setup to handle! I just need the admiral to understand what can or can not be used and when.

DOH!

I missed the boat on that one (pun intended).

Yup, no battery intervention with pass through. New inverter so definitely a pass-through.

Nothing like a public shaming...

Thanks for the course adjustment.

Osprey69 said:

DOH!

I missed the boat on that one (pun intended).

Yup, no battery intervention with pass through. New inverter so definitely a pass-through.

Nothing like a public shaming...

Thanks for the course adjustment.

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I meant no disrespect! Or public shaming as you put it. Sorry you fell that way.

I just like the way a past owner set it up and if the idea helps you, thats great! If not, no loss but the thought was thrown out and may help someone else.

Osprey69 said:

DOH!

I missed the boat on that one (pun intended).

Yup, no battery intervention with pass through. New inverter so definitely a pass-through.

Nothing like a public shaming...

Thanks for the course adjustment.

Click to expand...

You are definitely much better off knowing now, I suspect that many owners of inverter equipped boats don't have a full grasp exactly how they operate, especially in the case of factory installations or prior owner installs. A good surveyor can be valuable in this respect for figuring out such systems.

My boat came with what I consider the worst possible inverter/charger configuration. The entire AC panel was fed through it including the air conditioning and water heater, the house battery bank and the inverter took a beating any time the shore power went out. Neither the battery bank nor the inverter were adequately sized to support this configuration. I've since reconfigured the entire system to a split configuration as well as replacing the batteries and the inverter/charger.

Iggy said:

I meant no disrespect! Or public shaming as you put it. Sorry you fell that way.

I just like the way a past owner set it up and if the idea helps you, thats great! If not, no loss but the thought was thrown out and may help someone else.

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Iggy...no worries. That comment was not directed at you. I know you meant no disrespect. Just a bit of tongue in cheek humor.

Osprey69 said:

Iggy...no worries. That comment was not directed at you. I know you meant no disrespect. Just a bit of tongue in cheek humor.

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Thanks, I do at times talk out of turn not meaning to. Writing is not my best quality