wiring a 10A charger and running w/ other 110V appliances

[brentthemountainguide]

So last month I happily moved aboard my 1980 Catalina 27 docked at the Great Salt Lake Marina. and life is pretty good right about now. But winter is quickly approaching and I'm hoping to completely rewire the boat to clean up the PO's wired mess and could use some advice. After reading several books and googling like crazy I still cant find the answers I'm seeking.

First off I have a new Eel 30A 125V power cord connecting shore power to a 30A stainless steel inlet on the boat. from there I was considering installing a 50A AC breaker panel and ensuring all AC wiring is rated to 50A. Seems safer or at least as safe as running 30A wiring, but am I understanding this correctly? Maybe I still need a 30A breaker to protect the power cord and inlet. Since the shore power is only 30A, I should be able to run a 10A battery charger, 13.7A draw electric heater, plus a couple 40w bulbs and laptop all off the AC circuit at the same time right? if the draw reaches 30amps the shore power simply won't supply enough juice and the battery charger will decrease output, lights dim etc. but the 50A breaker will not trip and the wiring wouldn't fry (cause a fire) since it's got much higher capacity. My concern is running a heater (or maybe 2) while away from the boat and returning to find the breaker tripped.

Second, I picked up a Guest 12 volt 10 amp battery charger (5Ax2) to keep the two house batteries topped off. To wire this I could plug in directly into the 110v outlet downstream of the AC breaker, but seems simpler to run it directly off of the AC circuit breaker. I suppose the 10A charger rarely draws the full 10 amps but when it does I think I'd get close to the 30amp limit and certainly couldnt run two electric heaters without switching off the battery charger. I was hoping for a realistic estimation of this before I draw up the wiring diagrams. Lastly, is there any reason not to run the battery charger output directly to the two batteries or is there an important reason to go through the battery switch while in the "both" position.

Any insight is appreciated! thanks!

 

[Ron20324]

Re: wiring a 10A charger and running w/ other 110V appliance

IF YOU HAVE A 50 BREAKER ON THE BOAT, THE 30 SHORE BREAKER WILL TRIP FIRST, AND YOU'LL FIND YOURSELF GOING ASHORE TO RESET IT. THERE'S NO SENSE SPENDING $$$ FOR 50-AMP WIRE AND BREAKER WHEN 30 WILL SUFFICE. YES, LARGER 50-AMP-RATED WIRE IS A SAFETY PLUS, BUT IT'S WASTED MONEY. DO IT W/ 10 GAUAGE AND 30 AMPS BREAKER ON THE BOAT. SOMEONE ELSE WILL MENTION AN INTERMEDIATE BREAKER CLOSE TO THE INLET IF YOU'RE PLANNING ON DOING THE JOB abyc CODE-WISE..

 

[JohnShannon]

Re: wiring a 10A charger and running w/ other 110V appliance

I think you have a slight confusion as to the AC draw of your 10A charger.

Your 10A charger will put 10A 14V into the battery, that is 140W figure 80% efficiency for converting the 120V AC to 14V DC and you have an AC side load of 168W for the battery charger.

So the AC side current will be about 2.5A, well it would be except for the fact that the charger likely has bad i.e 0.5 power factor.

So the AC side current of your 10A charger will be around 5A rather than the 2.5A that power analysis would lead you to believe or the 10A that it seems you expect.

So your loads are

battery charger 5A, 13.7A heater, 120W of light bulbs?? try LED's man = 1A
and a laptop 30W = 250mA

total current is about 20A no problem for 30A breaker.

 

[brentthemountainguide]

Re: wiring a 10A charger and running w/ other 110V appliance

Oh yea Duh! Thanks Ron I should have figured the dock breaker would have tripped first. makes sense to trip the boat breaker instead. I'll plan to just add the 10 gauge wiring and stick with a 30A breaker. And thanks for the calculation John. I had'nt considered the conversion of decreased amps becasue of the voltage difference. Electricity 101, right. As far as LEDs I was planning to change over all of the DC lighting to LEDs but didnt think it was as important for the AC lighting. Is it worth considering, too?

 

[Joe]

Re: wiring a 10A charger and running w/ other 110V appliance

On my C27 there is a 30 amp master at the bus.. there is another breaker between the master and the charger. The charger is wired DIRECTLY to the battery posts. Check the charger's instruction manual. I have three AC outlets on the boat's shore power system and run heaters, lights, tv, power tools, etc.

If you invest in an AC panel.. with a master and 3 breakers you can put the charger on one, the water heater on another and the outlets on the third.

 

[Stu Jackson]

As far as LEDs I was planning to change over all of the DC lighting to LEDs but didnt think it was as important for the AC lighting. Is it worth considering, too?

Just get the curly light bulbs, less AC energy than standard filament bulbs. LEDs for DC lights.

 

[onecoolair]

Re: wiring a 10A charger and running w/ other 110V appliance

Now a days....Most common is to have two 30 amp service connections. One is the A side and the other is called the B side.....A is for all house outlets,Water heater,Microwave,120 outlets,Battery Charger,etc....Then B side is reserved for air conditioning, heat, maybe water heater,etc....With a 2-30 amp double pole breakers with in a few feet inside the boat after the shore power service connections on the boat...At the dock will be a 50 amp 125/250 breaker for service at the dock is the new standard. Using a "Y" spliter adapter 125/250-50amp male with two female 30 amp connections for power two 30 amp power cords. One for A side and one for B side.
BTW....Must be sure to avoid brown outs....which will shorten the life of most electronics and air conditioning 120 volt raw water pumps..
For all my electronic equipment tv's computers I have all that stuff plugged into a UPS..surge protected back up. Just like I do at home or the office.

 

[kloudie1]

Re: wiring a 10A charger and running w/ other 110V appliance

Most of the time, the battery charger will be putting out a lot less current to charge the batteries.. so unless you try to run two heaters (water and air) and have very discharged batteries that are cool, a standard 30 ampere feed will not be an issue. But do it correctly with a panel and breakers for the AC side.

 

[Maine Sail]

As a point of reference a Xantrex TruCharge 20 battery charger draws 4 amps AC/120V, when supplying the full rated output of the charger.

 

[j_schoenfeld]

Leave the heater on while your away??

Don't let Dave catch you, it could be big trouble.......

 

[brentthemountainguide]

Re: Leave the heater on while your away??

I'm not worried about Dave (the harbor master) "catching" me as my only intention is to gather more info so I can ensure a more efficient and safer electrical system. I'm still in the research stage of this upgrade so techincal insight is welcomed.