Power draw on a liveaboard boat

dodgydingo · #1 (**permalink**) 07-07-2008

I am considering buying a boat and live aboard her.. I have a question about power consumption. How much power is there available to use if I know that my Marina will supply 30amps.

I am unclear how much that can actually run. I am a web designer so I was hopeing to use my main 24" Dell LCD as not only computer monitor but my TV as well. I will have a laptop driving that, lights at night... fans for circulating the air.. and then in the winter there will be electric heaters going, bubblers to keep the ice from forming around the boat...

Can I expect with 30amps to be blowing the fuse often with the usage I am imagining.. is it expected to be juggling power sockets the entire time?
I just don't know what to expect...

The Marina said they provide 50amps as well.. but this boat I am considering is a Hunter 33 Cherubini... I don't think it can accomodate more than 30amps.. or am I wrong? If not, how much of an ordeal/cost is it to upgrade it to 50amps?

I have sooo many questions.. but still determined to join the liveaboard lifestyle.

sailingdog · #2 (**permalink**) 07-08-2008

30 amps is about 3000 watts. If you figure out what the wattage of the different devices you're going to need to use aboard the boat, and that includes the refrigerator, battery charger, lights, computer, etc... you'll have an idea if you're going to need more electrical power or not. A high-powered laptop nowadays is only about 85 Watts...at least that's what my MacBook Pro 2.5 GHz system requires. I doubt a 24" LCD panel is much more than that... The biggest use of electricity aboard a liveaboard boat is the heaters in the winter-time. An electric heater can draw 1000-1500 watts.

Chances are pretty unlikely that the Hunter 33 was equipped for more than 30 Amps of shore power. Most sailboats are relatively low power usage over all, since they're dependent on their battery banks when at anchor, and getting used to a huge electrical need at the dock means you'll run into problems when at anchor. A lot of power boats I know of have two 30 Amp or even two 50 amp shore power circuits.

There are a lot of ways you can cut your power usage. LED-based lighting goes a long way to reducing your electrical loads. The bubblers will generally not be plugged into the shore power stanchion box that your boat is connected to, nor to the outlets in your boat...so they're not really an issue IMHO.

Upgrading to a 50 amp shore-power system is a PITA, and will generally cause you more problems than it is worth IMHO. Most marinas, if you take the boat cruising, do not have 50 Amp shore power feeds for boats the size of yours.

If you figure the laptop and panel are 200 watts together, and you use another 1000 watts for the heater in the winter time, you've got about 1800 watts to play around with. A good 40-amp three-stage battery charger would be 500-600 watts, but means that you can power your lighting and such off the DC side of the boat and limit much of your additional 120 VAC needs.

dodgydingo · #3 (**permalink**) 07-08-2008

Wow thank you so much for that reply. I feel a lot better about it now. I happen to also have a Macbook Pro so its good to know how much it draws. I just realized I could plug my UPS into my laptop and get some power draw readings from it and get my LCD usage.

The heating sounds like it will work out fine. The boat also has a propane heater as well which would be a nice complement to the electric heating I would imagine so I will be just fine.

Thanks again, that info is worth gold.

poopdeckpappy · #4 (**permalink**) 07-08-2008

Quote:

Originally Posted by dodgydingo

Can I expect with 30amps to be blowing the fuse often with the usage I am imagining.. is it expected to be juggling power sockets the entire time?

I just don't know what to expect...

.

Right now I'm sitting here on a Dell E1705, watching Hannity & Colmes on a 26" flat screen TV with the coffeemaker brewing a fresh pot in the galley with a AC salon light on, my wife is up forward with a fan running listening to a book on her Ipod home with a light on while brushing the dog, the refer and HW heater have both cycle though and just a few minutes ago I nuked a rice bowl for 90 seconds..............

We have 30amp SP with 25 amp breakers on the AC side of the dist. pnl, have yet to trip the breaker.

camaraderie · #5 (**permalink**) 07-08-2008

30amps should be fine. The bubblers are generally powered separately from the boat..but a 1hp model will generally draw around 8-10 amps which in combination with a heater and other stuff might trip your breaker. You may need a second dock plug (even a 15amp would work) for the bubbler(s)

TOMINDC2 · #6 (**permalink**) 07-08-2008

You also should read up on how batteries work. It is not normally wise to draw down the batteries below 50% capacity without hastening the death of the cells and lowering recharge capacity (more expensive batteries are sometimes more forgiving). On a small monohull, 30Amps of shore power is all you can handle without redoing, at significant cost, the boat's electical system -- totally not worth it. Unless you have air conditioning and a plasma TV, you are unlikely to overwhelm your electical shorepower system.

You can increase at sea/anchor capacity by installing more and/or bigger batteries, slap on a solar panel or two for battery top-off, and treat yourself to a good quality inverter to manage AC and DC power automatically. The downside is that this all adds weight. My 2 AGMs are so heavy that they will only leave the boat when replacement is required. I keep them charged with a big solar panel 365. You may also be able to charge your bank faster with a higher capacity engine alternator.

It is best to hire a marine electrician to advise you on any significant system upgrades. Electrical is not something your should cheap out on, because if you get it wrong, the cost to set things straight can really snowball.

turfguy · #7 (**permalink**) 07-09-2008

This brings up a question on Air Conditioning? Does anyone know what a 16000 btu AC unit on a boat draws? I know when I had the Motorhome the AC would set off the 30 amp breakers in campgrounds. Everything else always was ok.
Thanks
turf

sailingdog · #8 (**permalink**) 07-09-2008

Most boats, especially ones under 30' LOA, aren't going to require a 16000 BTU AC unit.

turfguy · #9 (**permalink**) 07-09-2008

Quote:

Originally Posted by sailingdog

Most boats, especially ones under 30' LOA, aren't going to require a 16000 BTU AC unit.

The boat I am looking at is a 36' Hunter and it does have a 16000 btu AC unit. I think that is the standard unit that comes from factory.
turf

sailingdog · #10 (**permalink**) 07-09-2008

Quote:

Originally Posted by turfguy

The boat I am looking at is a 36' Hunter and it does have a 16000 btu AC unit. I think that is the standard unit that comes from factory.
turf

in that case, you should probably start your own thread on that, istead of highjacking this one. It would help if you said what AC system the boat has installed.