Shore Power 101

[solanderi]

I have always used a 50 amp power cable w/ no problems on my 1985 45C but a significantly less expensive slip has come available that only has a single 30 amp line. There is a waiting list for the double 30 amp slips as well as the 50 amp slips. Can I use the 30 amp line ? Any help is greatly appreciated,

Greg

 

[MikeP]

30A sounds low for a 45 ft boat but it totally depends on how you use power. If you didn't mind juggling a/c and the stove, and/or not using all the a/c units at the same time, for example, it might work fine.

I'd suggest you check the various loads drawn by the heavy use items - should be able to do that with the amp meter on the boat's elec panel - and determine the total of the items you MUST have on at the same time. If it will fit in 30A worth of power than it would be workable.

 

[Boatsb]

I have a 41C and the 30 amps will keep the AC running but not much more. We have a 50A split to to 30's so we have one for the AC and one for the rest of the boat. If it is 30/100 I think it will be too small. If it is for some reason 220V and the boat can handle that then it should work.

 

[Pascal]

30 amp should just run two ACs and the battery charger... not much more so it depends on what you need. if you just keep the boat there and never stay aboard you should be fine.

I wonder what kind of adapter you'll need though. typically, i think the Y used to connect 220/50 to two 30amps outlets have circuitry to only activate it when both legs are on, dont' they? so if you connect just one, will you get power thru?

you'll need a straight thru adapter to power just one leg, i wonder how you select which hot of the 220/50 gets the power though

 

[Mike36c]

I'm assuming your 50a power is 220v, do you have equipment onboard that runs on 220? If so you're SOL with the 30a because it's 110v only (one leg).

 

[REBrueckner]

All good advice above; you'll never be able to run all your air conditioning and electric cooking simultaneously...

 

[Nonchalant1]

You can probably hook it up but you'll have to manage power use very carefully to not blow the 30A breaker at the dock all the time.

Your boat probably has the typical Hatteras 220V and 110V inputs. If yours is like mine, you'll have two separate 110V 50A inputs as well as the one 50A 220V input. You can split the one 30A 110V dock power supply and put it into the 2 separate 110V inputs. That requires the right connectors, like 50A to 30A pigtails if you have 50A 110V inputs. That will get power to everything on your boat except the dryer and stove, BUT BE CAREFUL NOT TO EXCEED THE TOTAL 30A DOCK POWER WHEN YOU TURN ON THINGS IN THE BOAT. I ran my 53MY that way a couple times in strange small marinas in Canada. I could only run one big AC plus the charger and the TV and lights.

Then you have try turning on only one thing at a time and watch the power being used via your ammeters in your control panel. Since your battery charger can come on at any time, check it's full charge power draw first. If that takes 10 amps, for instance, then you can only use 20 amps of power for other items to leave room for when the charger comes on at full charge. Of course, when you're at the boat at the dock, you could temporarily turn off the charger so you could use that power load elsewhere, and then turn it back on when you leave and won't be using the extra power.

Doug Shuman

 

[solanderi]

Thanks to all for the tips. My rig has a single shore power connector labled 220/50a and another single labled 120/30a. From looking at the battery charger it looks like it draws 10 amps. Does that sound low? I have to resaerch the fridge/freezer (any guesses) as well as the crusair that serves the salon. Maybe I will switch over to 30 amp here at my dock and see how everything runs from there.

The tip about watching the amp meter on the panel while I turn devices on sounds like a scene out of the movie Apollo 13, ha ha. You better believe I will be doing it. Thanks again,

Greg

 

[garyd]

Ten amps for the battery charger sounds high. If you mean ten amps into the chargeer via 120 volts. That would be 1200 watts divided by 12 volts gives 100 amps if there were no loses into the batteries. Usually the battery charge can out put up to 40 amps but that is really unusual unless the battery is low for some reason and you are using a lot of 12volt DC stuff. I have a small charles that can charge both batteries it usually runs between 0-5amps. It handles both if the inverter is off line.

garyd

 

[REBrueckner]

Is anything you wish to power 220v instead of 120 volt? Stove??

ten amps is not outlandish for a 120 volt charger...it's a maximum figure...usually they will only draw a few amps if batteries are charged...

trying 30 amps at your current location is positively the way to go...good idea!!!! ... rather than us guessing how you use your equipment from a remote location....

the fridge freezer could vary widely, try about 7 amps running at 120 volts, maybe 15 amps for one air conditioner at 16,000 BTU size...electric cook top burners are 1500 watts each, about 13 amps, unless it's 220 volts to begin....... but if you use a lower setting that limits current/power...

A fridge or freezer, being motor powered, will briefly draw higher currents at start and could be a limiting factor if total steady current draw gets close to 30 amps.

If you have a single 16,000 BTU Air Conditioner, an EER of 9 or 10 might be in the ball park suggesting 1600w or 1778 watts, maybe 13 to 15 amps.....so if you run ONE air conditioner, that uses about 1/2 your capacity and you have a good shot at limiting overall consumption to 30 amps total...

 

[Brian Degulis]

50A @240V gives you 12KW without any losses 30A @ 120 gives you 3.6KW So about a third of the power you have now. If you have a transformer you can still run 240V loads off the 120V supply but it doesn't change the watts available.

Brian

 

[Pete]

Brian has your situation well defined. If your 120v/30 amp shore power inlet is factory installed, you have a transformer that will give the correct voltage for everything in the boat. I would add one more item to check. If the only power available at the slip is 120v/30amp, chances are the installation has some age on it and was done when boats had much less power needs. Talk to some owners in adjacent slips with the same power service and ask about voltage drop when lots of owners are on their boats (hot or cold weekends). You do not want a hookup that drop the voltage significantly due to load (small wires). If they report voltages below 110 volts at times, you will not be doing your equipment any favor hooked to this service.

Pete

 

[Boss Lady]

Single phase power.

120/30a is supplied using one power leg and nuetral.
240/50a is supplied using two power legs and nuetral which are out of phase with each other.

If you use your splitter 240/50a to give you two 120/30a connectors you can connect them to a single leg of the 120/30a shore power. This will give you 120 volt service on the two 120 volt service branches of your boat supply panel and will supply 120 to all your 120 volt equipment, but it will not supply 240 to run your 240 equipment like the oven or a dryer, since they will only see 120 volts. The other issue is amperage and voltage drop as have been mentioned earlier. Depending upon the how the actual shore power wiring is wired and power loads generated by other boats and the power you need may cause voltage drops and constant breaker faults. But you may be able to manage your boat's loads well enough to not trip your individual shore power 30 amp breaker.

If the 120/30a shore power is wired so that they have two separate 30a power recepticles on separate legs in the same power pedestal, then you will have the 240 volts and sufficient amperage to run your 240 volt appliances. This is common in a lot of marinas, they just don't have 240/50 amp connectors in the power pedestal. Some times every other pedestal is on a different 120 leg, so you can get the 240 volts by connecting to two nearby pedestals.

Older marinas or smaller marinas were designed before boats demanded so much power and unless they have been upgraded will have problems with either having 50 amp connections or sufficient amperage supply to keep voltage drop to a minimum when fully loaded. Voltage drop is not good for your equipment.

If you long term dock at a marina that has power problems, you can install a buck boost transformer that will provide you with stable voltage if your boat does not have this feature. I would talk to other boat owners at your intended marina before moving there and ask them about power supply problems to make sure that you can over come them if the marina is not going to improve the situation. Also ask them about zinc errosion problems or electrolysis errosion problems, this can be caused by marina wiring or by other boats. This happens in new marinas as well, because each boat becomes part of the circuit. One boat mis-wired can cause everyone in the marina problems.

I would also talk to the marina and have them show you that the wiring is adequate for your boat. I am sure that most will have no problem discussing this with you, but the perspective will be different than the actual boat owners.