New to me boat, Need help with shore power wiring

[cvcsmkr]

Just purchased an express catamaran. It has (2) a/c units, 10k & 16k.

Id like to run the 10k a/c & receptacles off a 3k inverter. I'll add the easy start to keep starting amps to minimum.

Boat currently has a 9kw diesel generator, so plenty of power there.

Im trying to figure out how to setup the shore power/ac panel connections. We'll be over 30 amps between the 2 a/c's, electric cooktop, etc.

Should i use a 50a/240v and just use one of the legs?

I need something that is going to be common for shore power connections for south florida & the bahams.

Thanks in advance.

[smac999]

I would forget trying to run the A/C off the inverter.

what is the current shore power? if it came with 2 a/c units I would imaige the boat would already be wired to run them. unless they only every ran on the gen.

to get equal power from shore as then gen you'd need a full 240v 50a panel with both legs.

another less power option is dual 30a plugs.

[cvcsmkr]

Originally Posted by smac999

I would forget trying to run the A/C off the inverter.

what is the current shore power? if it came with 2 a/c units I would imaige the boat would already be wired to run them. unless they only every ran on the gen.

to get equal power from shore as then gen you'd need a full 240v 50a panel with both legs.

another less power option is dual 30a plugs.

Why should I forget the a/c on inverter?

If I do twin 30’s, my concern is if the 30’s are on different legs.

[CharlieJ]

We'll be over 30 amps between the 2 a/c's, electric cooktop, etc.

To develop 30AAC will require a bit more than 300ADC from the battery bank. A very difficult demand even on a LFP battery bank.

[smac999]

Originally Posted by cvcsmkr

Why should I forget the a/c on inverter?

If I do twin 30’s, my concern is if the 30’s are on different legs.

with dual 30's you'd have 2 main breakers and 2 panels. they would never cross or join. half the boat on one and half on the other. legs wouldn't matter.

put the 2 ac units on one and everything else on the other.

it's just an option that is out that. depends what your marina slip has.

dual 30's or 50a 240 would be the most common. 50a 120v is not common.

[GordMay]

Greetings and welcome aboard the CF, cvcsmkr.

[cvcsmkr]

Originally Posted by CharlieJ

To develop 30AAC will require a bit more than 300ADC from the battery bank. A very difficult demand even on a LFP battery bank.

I was planning on a 900ah lithium bank.

If my math is right, we can run 12 amps for 8 hrs. 10a for a/c and 2a for circulating pump.

What am I overlooking?

[S/V Illusion]

Originally Posted by cvcsmkr

I was planning on a 900ah lithium bank.

If my math is right, we can run 12 amps for 8 hrs. 10a for a/c and 2a for circulating pump.

What am I overlooking?

I think you confused the amp hr draw. It may be 12 amp hrs at 120 v but the draw off 12 v batteries is 120 amp hrs. Plus inverter inefficiency making it closer to 150 amp hr. From a 900 ah bank, that results in 50% depletion in 3 hours.

[Bowdrie]

CharlieJ is correct, trying to run AC units from batteries is a losing proposition.
Time to fire-up the generator.

[cvcsmkr]

Originally Posted by Bowdrie

CharlieJ is correct, trying to run AC units from batteries is a losing proposition.
Time to fire-up the generator.

Im not a light sleeper, the generator is very loud & vibrates entire boat, I dont see anyway I could sleep on the boat with it running.

[Bowdrie]

Originally Posted by cvcsmkr

the generator is very loud & vibrates entire boat, I dont see anyway I could sleep on the boat with it running.

That situation describes the vast majority of small boats, no matter the size/type of batteries.
With the load(s) you envision, you're behind the curve from the first time you flip the switch.

[Gudgeon]

I have Air Con on the boat, 16, 10 and 10 BTU units. They are on a 50 amp breaker with each unit having a breaker at 30 amp. When operating all three units I have tripped the 50 amp breaker if two units start up at the same time even with the soft start installed. I have two 120 Volt ac circuits on the boat one has the air con units and pump the other has all of the other loads. Our genset is quite enough to run the air con. We have not had to operate the aircon with the genset but a few times in a wind less anchorage. You will find that you need the air con more in a marina than in an anchorage. As most say it is a loosing battle trying to operate air con off an inverter.

[Sailshabby]

Originally Posted by cvcsmkr

Im not a light sleeper, the generator is very loud & vibrates entire boat, I dont see anyway I could sleep on the boat with it running.

Get a small Honda type generator.

[Redline452]

Originally Posted by S/V Illusion

I think you confused the amp hr draw. It may be 12 amp hrs at 120 v but the draw off 12 v batteries is 120 amp hrs. Plus inverter inefficiency making it closer to 150 amp hr. From a 900 ah bank, that results in 50% depletion in 3 hours.

Almost right except for the use of "hrs" where it doesn't belong. The OPs error was comparing aircon current consumption at 120VAC with inverter current consumption at 12VDC.



I think you confused the amp draw. It may be 12 amps at 120 v but the draw off 12 v batteries is 120 amps. Plus inverter inefficiency making it closer to 150 amps. From a 900 ah bank, that results in 50% depletion in 3 hours.


Same conclusion: not practical. And the "3K inverter", presuming that's kilowatts, isn't up to the task of running the aircon.

[Wallaby]

A/C is great when tied to the dock. When tied to the anchor, there is usually enough breeze through the hatches. Forget ports--they are next to useless since the wind comes over the bow. In windless conditions, I make do with Caframo fans, two per cabin, multiple speeds, built in timer, low power draw, and very quiet.



As for running the A/C at anchor? Never done it, and likely never will. I have a 7KW generator, however, it is only used for battery charging, making water, heating water, and refrigeration.



Regarding 'power wiring', dual 30amp circuits allow me to use most marinas without problems. With one A/C (16K BTU) and the watermaker on one circuit, I can usually get away with only one power cord.