Adding 50a service to existing 30a boat

[wgerstmyer]

Sorry for the naïveté here.
We want to upgrade to a smart plug shore power cable. I know we need a new addition inlet on board to receive the smart connection, but Instead of just replacing the 30a cable, I’m wondering why the cable and inlet couldn’t be 50a and tied into our existing 30a panel without major work: while the initial line in would have to be upgraded to a thicker wire, aren’t there fuses and breakers on all existing circuits to prevent too much amperage from flowing into each circuit? And open up the potential for more circuits on the panel?
If there are shore pedestals that don’t really provide the listed 30a from shore, wouldn’t this be more likely to provide at least the 30a, and allow the addition of more outlets or ability to draw more current?
In addition, I was thinking of occasionally still using the 30a cable with our pigtail (30a-to-15a) to run one more appliance separately or even creating another inlet connected to a new 30a panel to supply a few outlets just off it.
All observations welcome.

[Sailmonkey]

You’ll also need to replace the cable between the shore inlet and the panel.....unless you’ve got a 30 amp breaker directly behind the shore inlet on the boat.

Otherwise, no real problem other than the huge cable.

[billknny]

Have you price a 50AMP cable yet? That might be all it take to change your mind....

[wrwakefield]

Wgerstmyer,

Assuming your boat is currently wired for N American 115V AC, you will more than tripple your available AC wattage by rewiring for 50A 115/230V AC. [The 50A service provides you with two 115V AC hot legs to distribute instead of the one you now have with your 30A panel.]

That is how our boat is wired. [With two Smart Plug 50Amp inlets for convenience, not simultaneous use... they have a lock-out selector breakers so only one at a time can be hot...]

As we travel in summer, I still typically use the 30A shorepower cord [since it is much easier to handle] and we are only using it for water heater and battery charger... Our 10 AWG 3 conductor 30A cord has a 50A Smart Plug fitted to it to eliminate troublesome adapters...

In winter [think electric heat] and other times as needed, we use the 6 AWG, 4 conductor 50A cord. It is a beast to handle and stow. [Not an issue if you don't move around a lot...]

This can all be accomplished, but you will be doing quite a bit of rewiring on the infeed and distribution side of things if you wish to tripple your available wattage; and you will be optimized only for N American shorepower... [Which may not be an issue...?]

As Bill K mentioned, sit down when you start researching the costs of this upgrade.

Best wishes with your project.

Cheers! Bill

[ranger58sb]

Originally Posted by billknny

Have you price a 50AMP cable yet? That might be all it take to change your mind....

50A cable is really heavy, too.

-Chris

[Bill O]

Instead of a 50A service, could possibly go w/2-30A inlets. The separate 30A cords are easier to handle. Depending on how your boat is set up electrically you may not always need the full 50A service (30A may do).

What equipment do you have or are planning to add to the boat to run off shore power? In our last boat, the big shore power users were the water heater, A/C unit and battery charger. Only when we wanted to run all of them at once did we need the 2-30A, otherwise a single 30A service would do 90% of the time.


Bill O.

[Lancerbye]

I have both 50/125 and 30/125 . The 30 is just wired parallel to the 50 with 10 ga. , but the 50 is wired to the 50 amp panel breaker with 6 ga. I haven't used the 50 amp cord in 10 years.

[TrentePieds]

wgerstmyer:

You haven't said what sort of boat you have. It is a BIG boat that requires 50A. A shoreside 2-bedroom apartment in Vancouver gets by handsomely on 100A and that includes electric baseboard heating in the winter.

Are you coming at this "problem" from the "wrong end", maybe? As others have also pointed out, it is not necessarily the case that "bigger is better", Have you done a power budget so you know what your boat REQUIRES?

Remember that what goes through the "umbilical" is what the boat "sucks up" when all your wizard devices are working at the same time. It is not what get's "pushed" from the shore end. There is rarely, if ever, a need for all your juice consumers to be working at the same time. In fact you have to work at it to make them do that, so it's unlikely that you'd ever need to suck more than 30A through the umbilical.

So my recommendation is to do a power budget. It's quite simple really, and if it is new to you, we'll be glad to help you.

Cheers

TrentePieds

[stormalong]

Originally Posted by wgerstmyer

Sorry for the naïveté here.
If there are shore pedestals that don’t really provide the listed 30a from shore, wouldn’t this be more likely to provide at least the 30a, and allow the addition of more outlets or ability to draw more current?

All observations welcome.

What TrentePieds said is right. You are looking at this backwards. A fifty amp cordset can carry 50 amps safely. If the shore power source cannot supply 30 amps going to a fifty amp cordset will not provide additional current.

And Bill O also has a good point - the cost of two 30's is far less than a single 50 and they are much easier to handle.

You need to asses your power demands. I have lived aboard a 44 foot boat in the winter with reverse cycle A/C for heat with two 30 amp cords - one being dedicated to the reverse cycle A/C. But I have also lived aboard on a single 30 amp source using space heaters, again in winter - a little more challenging but doable.

Tell us more about your power needs.

[ramblinrod]

Originally Posted by wgerstmyer

Sorry for the naïveté here.
We want to upgrade to a smart plug shore power cable. I know we need a new addition inlet on board to receive the smart connection, but Instead of just replacing the 30a cable, I’m wondering why the cable and inlet couldn’t be 50a and tied into our existing 30a panel without major work: while the initial line in would have to be upgraded to a thicker wire, aren’t there fuses and breakers on all existing circuits to prevent too much amperage from flowing into each circuit? And open up the potential for more circuits on the panel?
If there are shore pedestals that don’t really provide the listed 30a from shore, wouldn’t this be more likely to provide at least the 30a, and allow the addition of more outlets or ability to draw more current?
In addition, I was thinking of occasionally still using the 30a cable with our pigtail (30a-to-15a) to run one more appliance separately or even creating another inlet connected to a new 30a panel to supply a few outlets just off it.
All observations welcome.

If your goal is a belt and suspended solution (move up to a 50 A cordset, so that it is more robust and more capable, of safely carrying 30A than a 30A cord set, then go for it.

Your idea of using two cord sets is more complicated. To pass survey, two shore power inlets cannot be connected to the same AC circuits. (There must be an “exclusive or” switch or they must be connected to separate, isolated circuits.)

To add breakers is also more complicated. You have to ensure the connected loads due not exceed the panel and feeder cable ratings.

If you are not well versed in marine electrical standards and highly skilled in marine electrical wiring, for the latter two scenarios I recommend hiring a “certified” and “insured” (insist on seeing both certs with your own eyes) marine electrical tech.