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Old 01-15-2022, 09:38 AM   #1
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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.
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Old 01-15-2022, 10:55 AM   #2
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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.

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

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Old 01-15-2022, 11:07 AM   #3
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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.
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Old 01-15-2022, 11:18 AM   #4
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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.
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Old 01-15-2022, 11:42 AM   #5
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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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Old 01-15-2022, 12:27 PM   #6
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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
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Old 01-15-2022, 12:31 PM   #7
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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.
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.
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Old 01-16-2022, 08:29 AM   #8
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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.
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Old 01-16-2022, 12:19 PM   #9
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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.
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Old 01-16-2022, 07:46 PM   #10
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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.
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Old 01-17-2022, 07:08 AM   #11
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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.

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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Old 01-17-2022, 09:22 AM   #12
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... 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)...
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.
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Old 01-17-2022, 11:45 AM   #13
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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
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.
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Old 01-17-2022, 11:53 AM   #14
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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.
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Old 01-17-2022, 01:06 PM   #15
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I would leave it just the way it is.



Why introduce needless complexity?
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Old 01-18-2022, 07:33 AM   #16
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"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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Old 01-18-2022, 01:37 PM   #17
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"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.
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/B0...KIKX0DER&psc=1

Thanks for the replies.
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Old 01-18-2022, 09:18 PM   #18
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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.
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Old 01-18-2022, 09:42 PM   #19
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Originally Posted by Osprey69 View Post
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/B0...KIKX0DER&psc=1

Thanks for the replies.
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
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Old 01-19-2022, 07:23 AM   #20
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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.
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.
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