50 amp shore power connector but 30 amp breaker at the panel - what do I need to change?

mckenzie.keith

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I believe you can bring 4 wire 50 amp service onboard & split the hot legs at the plug. But I don't have the standards book to verify
For convenience (and maybe per ABYC) there needs to be a disconnect switch. Otherwise you would need to unplug shore power to work on the electrical system.

Oh, also, the aircon units probably need individual breakers (have to read installation instructions). So a second AC panel would probably be needed regardless. With a main switch and however many branch circuits are required. Maybe it could just be a 30 Amp pane if that is enough for the loads.
 
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longy

Overlord of Anarchy
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Brief unofficial AC wiring schema

Input socket - breakers - galv isolator - main panel input breaker - sub breakers - users

I'm not certain if there is a specified sequence with isolator & first breakers. First breakers are to be very close to input socket
 
Do what Longy suggested on boat. 2ea. 30 amp one for AC, microwave etc and one for the rest. Put two 30amp outlets in your dock pedestal. Two cables good to go. For the most part everyone has 30amp power available. Some will have 50 as well but you really don't want your boat to be the oddball 50amp 110 settup. Or even if you split and take 220 to boat and make dist on vessel, you will still be limited to where you can go. Keep it simple, ac is a luxury out and about.
 

Alaris

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Okay so the boat is 50A 120V.

Isn’t the easiest solution here, since I have #6 wire from the shore power inlet to the panel, to replace the panel breaker with 50A? (Currently 30)

I am only adding one 120V HVAC unit at this time and peak startup draw is 17A. This would require no rewiring, there is room on the panel for another breaker, and if and when I add a genset and/or second HVAC I can go to all the extra expense then to wire it up for 240 or add another 120V panel.

 
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Slick470

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Not necessarily. You need to make sure that everything on the load side of the main breaker is rated for 50A or higher until it is protected by another circuit breaker. This includes the busbars that form the panel.
 

Alaris

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Not necessarily. You need to make sure that everything on the load side of the main breaker is rated for 50A or higher until it is protected by another circuit breaker. This includes the busbars that form the panel.
It appears that the wires from the input are #6 and go directly to the 30A panel breaker. Below are zoomed in diagrams. The entire diagrams are further up the thread.

85739137-24B8-428E-BDCF-FA00F1B1C634.jpeg
C64556AA-92B6-466D-A6F1-122A5F3F77AE.jpeg

C42F7E9A-5610-4788-98D2-EEC9152A228C.jpeg
 

Slick470

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I tried to follow the circuit through your one line drawings, and I agree it looks like it is all #6 after the 30A main breaker (except for the bit below the 30A main with the #4 wire and 40A breaker which doesn't make much sense to me). There is a way to calc the bus bar amperage by measuring the area of the cross section to confirm that too, but if all rated for 50+ amps, I don't see why you couldn't just swap out the breaker.

You'll still want to confirm that everything was installed per the drawings and a PO hasn't changed anything.
 

Alaris

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I tried to follow the circuit through your one line drawings, and I agree it looks like it is all #6 after the 30A main breaker (except for the bit below the 30A main with the #4 wire and 40A breaker which doesn't make much sense to me). There is a way to calc the bus bar amperage by measuring the area of the cross section to confirm that too, but if all rated for 50+ amps, I don't see why you couldn't just swap out the breaker.

You'll still want to confirm that everything was installed per the drawings and a PO hasn't changed anything.
The stuff going down from the main breaker is for a generator which is not equipped. Thanks!
 

longy

Overlord of Anarchy
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It does appear wiring is sized OK, but you must verify panel buss bars are also. Your main breaker is a 3 pole, across hot/neutral/ground, so you'd need:
to fill space properly. 50 amps is a shit load of power - please inspect all wiring, connections, ABYC standards, etc before going down this path. All the way from input socket thru panel. I've survived a few good 30 amp shocks, scary. (sweat is very conductive!)
 

Alaris

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It does appear wiring is sized OK, but you must verify panel buss bars are also. Your main breaker is a 3 pole, across hot/neutral/ground, so you'd need:
to fill space properly. 50 amps is a shit load of power - please inspect all wiring, connections, ABYC standards, etc before going down this path. All the way from input socket thru panel. I've survived a few good 30 amp shocks, scary. (sweat is very conductive!)
Current one is two not three poles:

A34C00A2-6F68-4B46-8A19-DC06431BE65F.jpeg
 

longy

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OK, now you know panel was NOT built to schematic!!!!! So even more important you verify wiring thru new additions. Your schematic clearly shows 3 pole 30 amp breaker
 

Slick470

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it also looks like they used (2) single pole 30A breakers with a homemade handle tie.

It was (and I wouldn't be surprised if it it still is) pretty common with production boats for the wiring shop to make changes on the fly to finish a boat with parts that they have on hand vs what the spec called for. Not always a bad thing, just this is a good example to make sure you check everything over carefully before making changes. Plus it's a older boat with lots of time for PO's to do dumb stuff. I pulled a surprising amount of lamp cord out of my boat when I bought it.
 
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Alaris

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OK, now you know panel was NOT built to schematic!!!!! So even more important you verify wiring thru new additions. Your schematic clearly shows 3 pole 30 amp breaker
Can you explain what the ramifications of this difference are? How are they able to just omit one pole?
 

SimonGH

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Westbrook CT
#1 cause of boat fires... per the ABYC video on youtube.

Now you know the schematic doesn't really match the boat, so now you have to update the drawing to match what you actually have...

Reading through it all, I go back to my wife's favorite challenge - "what's the mission?"

Are you just trying to wire up your boat as simply as possible to match your dock, and you don't really care much if you can't plug in at other marinas?

Or do you often use transient slips and thus it's important to be able to hook up to most other places?

In my neighborhood, you typically have twin 30A and single 50A. You also have to note that 50A can be NEMA SS1-50R Female / SS1-50P Male (3 prong, 125v) or SS2-50R with the extra ground and two hot wires.

Like others have said, having twin 30A 125v is generally the most universal, but you made a comment about not wanting more than one cord...

So if you go with 1 50A cord, then I'd try to get some info on what's on a typical marina hookup (if you intend on going somewhere other than your own dock). it would be an annoyance to have to have a custom cable or adapter to connect other places.

Screen Shot 2022-12-05 at 8.24.56 PM.png

As for the wiring in the boat, as others have said, you can split the 50A 125V or 250V before the breakers. Modern standards say you need breakers within a few feet of the shore inlet connector, which means you probably have to install a small DIN breaker box somewhere, with a galvanic isolator on each branch.
 

Alaris

Super Anarchist
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#1 cause of boat fires... per the ABYC video on youtube.

Now you know the schematic doesn't really match the boat, so now you have to update the drawing to match what you actually have...

Reading through it all, I go back to my wife's favorite challenge - "what's the mission?"

Are you just trying to wire up your boat as simply as possible to match your dock, and you don't really care much if you can't plug in at other marinas?

Or do you often use transient slips and thus it's important to be able to hook up to most other places?

In my neighborhood, you typically have twin 30A and single 50A. You also have to note that 50A can be NEMA SS1-50R Female / SS1-50P Male (3 prong, 125v) or SS2-50R with the extra ground and two hot wires.

Like others have said, having twin 30A 125v is generally the most universal, but you made a comment about not wanting more than one cord...

So if you go with 1 50A cord, then I'd try to get some info on what's on a typical marina hookup (if you intend on going somewhere other than your own dock). it would be an annoyance to have to have a custom cable or adapter to connect other places.

View attachment 557869
As for the wiring in the boat, as others have said, you can split the 50A 125V or 250V before the breakers. Modern standards say you need breakers within a few feet of the shore inlet connector, which means you probably have to install a small DIN breaker box somewhere, with a galvanic isolator on each branch.
The mission is 50A of 125V power.

My dock is being rewired so I can put whatever I want on it. I am installing a SmartPlug 50A 125/250V inlet on the boat. The current plan is to wire the dock for 250V and only use one leg in the boat on the existing wiring to a 50A breaker. Since everyone is saying it’s required now, I guess I’ll add a new breaker near the shore power inlet as well.

I plan to eventually get a 30A adapter to put on the end of my 50A shore power cable in case I decide to travel somewhere that doesn’t have 50A 125/250 service. I do not do a lot of cruising to marinas. It is 99% anchoring.

Way down the road, if I add a second HVAC unit or generator or something I will rewire everything to 125/250V and put in a new panel.
 

SimonGH

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Westbrook CT
Looking at your schematic they switched the ground as well... not really sure you need to do that.
Do you currently have a galvanic isolator on the boat?
 

Alaris

Super Anarchist
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Looking at your schematic they switched the ground as well... not really sure you need to do that.
Do you currently have a galvanic isolator on the boat?
I don’t know. The boat hasn’t been shipped here yet. I can trace the electrical system when it arrives in a month. The receiving yard didn’t have room for it any earlier.
 

longy

Overlord of Anarchy
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San Diego
Can you explain what the ramifications of this difference are? How are they able to just omit one pole?
Your schematic shows a 3 pole breaker interrupting hot, neutral & ground wires. Breaking the ground is not needed and usually not done. A two pole breaker is OK. Is the 40 amp AC breaker shown on schematic actually installed? A galvanic isolator is much more appropriate and works all the time to protect the hull from stray current carried by the ground circuit
 

Alaris

Super Anarchist
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Annapolis
Your schematic shows a 3 pole breaker interrupting hot, neutral & ground wires. Breaking the ground is not needed and usually not done. A two pole breaker is OK. Is the 40 amp AC breaker shown on schematic actually installed? A galvanic isolator is much more appropriate and works all the time to protect the hull from stray current carried by the ground circuit
It’s a 30 amp AC breaker. The 40 amp one shown is for an optional generator which is not equipped.
 

SimonGH

Member
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96
Westbrook CT
Bottom line is you have to check that you have sufficient wire gauge to go from the breaker you want to switch to 50A (from the 30A currently), to the next set of breakers (for each branch circuit).
Eventually when you get the boat, if you can verify that the wire between the 30A breaker and the distribution buses that feed those smaller breakers can handle 50A vs 30A, and the bus itself is ok for 50A, then you're good to swap the breaker and install a galvanic isolator (if you don't already have one).
 

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