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

Alaris

Super Anarchist
1,851
667
Annapolis
If the starting draw is 17A, does the data sheet for the HVAC list a max breaker size or MOCP? A 20A may be ok, but depending on the unit, you may have nuisance tripping if it's too close.
No it does not. I have asked the manufacturer.
 

Slick470

Super Anarchist
2,056
323
Virginia
If running is 11A then 20A should be fine. For motor loads you size a circuit breaker between 175% and 250% of the FLA assuming full voltage (across the line) starting. A 20A is right around 180%. If it is soft start, even better. 30A would be over 250% and might not protect the unit or wiring properly and would violate NEC. If you are concerned about nuisance tripping, you could split the difference with a 25A.
 

Alaris

Super Anarchist
1,851
667
Annapolis
If running is 11A then 20A should be fine. For motor loads you size a circuit breaker between 175% and 250% of the FLA assuming full voltage (across the line) starting. A 20A is right around 180%. If it is soft start, even better. 30A would be over 250% and might not protect the unit or wiring properly and would violate NEC. If you are concerned about nuisance tripping, you could split the difference with a 25A.
Hmm… okay I think I understand what needs to happen. The pump is 20W 110V. So the A/C unit and the pump would need to be on the two breakers in the box (Blue Sea 3118). And the main load can just go directly to the 30A existing panel.
 

221J

Member
199
74
CT
What do they actually do? The articles I’ve read talk about electrocuting someone in the water. Give me a break. No one swims near this pier.
When you plug into shore power they prevent your boat from eating away nearby boats anodes. You are a bad neighbor without one. You could be eroding another boat's prop.
 

Alaris

Super Anarchist
1,851
667
Annapolis
I think I can work an ELCI into my system as described above in a way that will be only minimally more expensive. And I’ll add a galvanic isolator just to get you all to leave me alone.
 
Last edited:

Slick470

Super Anarchist
2,056
323
Virginia
Hmm… okay I think I understand what needs to happen. The pump is 20W 110V. So the A/C unit and the pump would need to be on the two breakers in the box (Blue Sea 3118). And the main load can just go directly to the 30A existing panel.
20W at 110 is tiny. 0.18A. That could go off spare on the main panel if you have one and then you can keep it per your sketch.
 

Slick470

Super Anarchist
2,056
323
Virginia
Thinking about that a bit more, is the pump supposed to be powered from the A/C? That would make the most sense to me given you don't want to run one without the other.

if that is the case, you still should be ok with a 20A.
 

mckenzie.keith

Aspiring Anarchist
856
286
Santa Cruz
Okay I’ve thought more about this and I don’t think I need both 240 legs because that’s 100A of 120 which is way more than I need. Instead, I would use Blue Seas 3118 breaker and box (https://www.bluesea.com/products/31...C___50A_ELCI_Main_-_2_blank_circuit_positions) which has two extra breaker positions. Does this make sense? Sorry about the drawing. I left off the wiring for the reverse polarity indicator. The diagram for the box is here: https://d2pyqm2yd3fw2i.cloudfront.net/files/resources/instructions/980009850.pdf

I am not sure how the ELCI breaker would connect to the other two breakers so that part of the drawing is probably wrong.

Also I suppose the HVAC breaker could be 30A as well, I don’t know what the correct breaker size is for a startup draw of 17A.

View attachment 558077
It is probably OK to use a 30 A breaker to the HVAC (as long as the wire can handle 30 A). If you add up all the breakers on a panel, they are often > the main breaker, at least in domestic AC systems. I am not up on ABYC, etc.
 

Alaris

Super Anarchist
1,851
667
Annapolis
Okay, this breaker box has a 50A 125V ELCI. Plenty for my needs. And it has two extra breaker slots. What’s not clear to me from the drawing is, can you wire this so the breakers are protected by the ELCI, since I don’t see a bus, or are they standalone?

Pardon my ignorance, I am going to talk to an electrician before I install anything, but I’d rather not start paying them until I’m pretty sure of what I want to do.

36580370-5804-46BF-8835-46E16F27AD4B.png
 

Slick470

Super Anarchist
2,056
323
Virginia
That appears to be a generic drawing for that series product showing a feed thru main arrangement and not what you are trying to do. My best guess is the grey rectangles below the main represents the bus bar for the additional circuit breaker positions. I agree that the website and product data isn't very clear. However, they are calling it a surface mounted panelboard with main and 2 blank circuit positions. Based off of that I would assume the main would feed the bus and any circuit positions.
 

See Level

Working to overcome my inner peace
No buss bars in the box. The 2 blanks are for 125/240v wiring and other panel use applications. everything on the load side is elci protected, you could possibly add branch breakers and connect to main breaker load side within the box and have them elci protected but there's not a lot of room in the box for extra wiring.
Best would use separate breaker or at main panel.
 

Alaris

Super Anarchist
1,851
667
Annapolis
No buss bars in the box. The 2 blanks are for 125/240v wiring. everything on the load side is elci protected, you could possibly add branch breakers and connect to main breaker load side within the box and have them elci protected but there's not a lot of room in the box for extra wiring.
Best would use separate breaker or at main panel.
I don’t understand why having unprotected breaker spots would be a selling point. Seems like they just had a box with extra space in it after installing the breaker.
 

Slick470

Super Anarchist
2,056
323
Virginia
I found a picture of the back of the 3119 box. So, yeah, no bus bars. Not sure why they give you the option of additional circuit positions.

1670366479108.png
 

See Level

Working to overcome my inner peace
They use the same front side panel in several applications but this is the one you're looking for. part 3130 and you may have to change a branch breaker or 2 for your system

Screenshot_20221206-145907.png
 
Last edited:

longy

Overlord of Anarchy
6,986
1,282
San Diego
Glad to see you're considering adding safety. ABYC wants to see ANY (AC or DC) circuit protected AT IT"S SOURCE regardless of amps carried.
Call blueseas directly, I've had good service from them while ordering their custom panels. I expect they do have a part to do what you want. If you are going to have a sub panel after this input breaker then one 30 amp breaker fed off of main breaker would suffice. If you plan to feed HVAC units directly from this box (ABYC wants this box within 10' of input socket) then maybe a 25 a and a 10 amp sub breaker would suit. But this depends if you can mount this box in an easy access location
 




Top