Shore Power

Sumner · Nov 15, 2009

CaptTripps said:
OK...I have been searching thru the archives and am giving up and going to show my complete ignorance to you fine people. I wish to put shore power on our Mac25. Have one new 12 v marine battery and a mess of wires behind the fuse box. The PO has a new SS, weather proof shore power male plug-in installed in the port cockpit seat but it is not hooked up to anything. Is there some sort of converter device that I need to hook up to the plug? All I have found is info on converters/inverters. I'm just wanting to run a 30A line fromthe shore to run a few 12V lights, radio etc. while at the dock. Can anyone point me toward an archive site that has already answered this querry?

As I said, I didn't really want to add a new topic but I wasn't even sure what to look for in a search...please be patient.>><Tripps

I have a regular extension cord run from under the sink where one battery is back under the seat and rear berth and then into the Lazarette (this is a 26S) and out the vent ...............

................in the outboard well. So just the male plug is there (bottom right arrow). At home I plug an extension cord in at that point, but you could do that in a slip if power was available.

Under the sink I have a power strip plugged into the extension cord. I have two $6.00 Harbor Freight trickle chargers plugged into the power strip and one goes to each battery. If you didn't want to be plugged into shore power all the time just use a bigger battery charger on the battery, otherwise I doubt you would run the battery down while on the boat with those needs you mentioned and the trickle charger will charge the battery back up while you are gone.

You don't need 30 amps to do what you want to do.

c ya,

Sum

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walt · Nov 15, 2009

Not a response to the original post.. however important.

I want to tell about a thread on the main forum about a month ago which is important from a safety aspect.

At a marina, some kid was swimming near boats and got electrocuted and drowned. What they think happened was that a power boat was hooked up to shore power and on the boat, the AC line was close to the boat 12 volt DC wire. There was a load on the AC wire which made it hot enough to melt the insulation but not trip the marina fuse. The hot AC wire ended up in contact with the boat 12 volt DC wire which in turn basically made the boat DC ground hot. The motor was connected to DC ground so was also made hot and was in the water and this is what caused the electrocution.

If the marina outlet had GFCI, the instant the hot wire connected to the 12 volt wire, there would have been ground current though the outboard into the water and the GFCI marina outlet would have tripped. In this case, the marina must not have had GFCI and in general, you don’t know how many marinas have GFCI outlets.

It’s not a bad idea to put a GFCI outlet in the boat AC install but it is still important to keep the AC wire and the DC separated before the GFCI protection device (typically a special AC outlet). I.e., the GFCI will only protect stuff “downstream” and not before the GFCI device.

Sumner, I’m not sure what the wires are going through the vent but if it’s a combination of AC and DC wires, it’s probably not a good idea. You probably use yours like I do – mostly on the hard so it’s not an issue but I wanted to tell this story for someone who is wiring for AC use in a marina. Even with a trailer sailor, if you have the outboard alternator hooked up, it will be connected to the boat DC ground and could create the same situation as in this very sad story so we should be careful.

beamreach · Nov 15, 2009

See page 11 on this site. I made a response there to a question about installing shorepower. Seems like you've got the exspensive items out of the way. GFI outlets definitely need to be installed on your boat and use tin coated marine grade wiring in the proper gauge and proper lengths. It's all in my post. Good luck and most of all BE SAFE! I've got pictures of my wiring in my album acessible through my profile.

Paul Brinkley · Nov 15, 2009

Capt Tripps, I think there is more to it than you think, if I understand what you asked.
The Mac25 has a fuse panel with four fuses and switches for lights etc. This is 12-volt stuff and should be connected to your battery.

There is also a four breaker panel marked AC next to it. My wife thought it meant "Air Conditioning" but of course it doesn't. The PO put in the real nice SS 30A plug in the boat but that's it. Do I just run 12V wiring from the plug to the fuse panel? Of course I will need to buy a shore line cable to run to the boat. This is ALTERNATING CURRENT and is 120-volt stuff and must be kept separate from your 12-volt DC circuits. Connect your 120 volt AC breakers to your 30-amp plug with the proper size 120-volt wiring. Install 120-volt GFCI AC outlets where you want to plug in your battery charger and any other 120-volt AC equipment. Connect those outlets to the breakers with the correct size 120-volt wiring.

The system: a 120-volt cord connects the marina service to your plug which supplies 120-volt AC power to your circuit breakers which supply the same to your 120-volt GFCI outlets. Your battery charger is plugged into a 120-volt GFCI outlet and charges your battery, which provides 12-volt DC power to your 12-volt fuse and switch panel for your lights and radio.

If you are not used to working with 12-volt DC and 120-volt AC wiring, please get help from someone who is. An error here can have serious consequences. I'm sure you can find someone locally who can help. Best wishes, -Paul

Sumner · Nov 15, 2009

walt said:
..........................Sumner, I’m not sure what the wires are going through the vent but if it’s a combination of AC and DC wires, it’s probably not a good idea. You probably use yours like I do – mostly on the hard so it’s not an issue but I wanted to tell this story for someone who is wiring for AC use in a marina. Even with a trailer sailor, if you have the outboard alternator hooked up, it will be connected to the boat DC ground and could create the same situation as in this very sad story so we should be careful.

One of the wires is DC from the solar panel and another is DC from the generator and the third is a 110/120 extension cord. I don't see where any of them are interconnected since the 110 goes to a trickle charge and it is attached to the battery. I would think the negative side of the trickle charger that goes to the battery would have to be isolated from the 110 side of the trickle charger. Is that not right?

Also I'm never hooked up to AC on the water and at home "every" circuit in my house and shop is on a GFCI circuit except for the 220. I'm a firm believer in GFCI circuits and have one in an outlet box that has a cord to it so that if I'm anywhere where I'm not sure if the power I'm using is GFCI protected I plug the box into power and then plug whatever I'm using into the box.

I did misread tripps post though and didn't see that there were existing AC circuits on the boat, so my reply wasn't worth much:cry:.

c ya,

Sum

walt · Nov 15, 2009

In the boat involved in the electrocution, the AC and DC wires were also not initially connected. Likely the AC wire was underated for the application and got hot because of a big load (like air conditioning or maybe running two space heaters or??). The AC and DC wires were very near each other and the heat of the AC wire melted the insulation and then the AC hot wire was imposed on the DC. Even if this boat had GFCI protection, if the place were the wires fused is before the GFCI outlet, the GFCI wont do anything. GFCI only protects things plugged in AFTER the GFCI circuit.

In your case, chances of a problem are very small.. but it is exactly the sort of sitution which could cause this sort of problem. If your AC extention cord was underated (looks like its OK) and got very hot and melted the insulation for example from running an air conditioner or two space heaters, the AC hot wire could connect to either the solar or generator wires effectively imposing 110 VAC on your boat DC ground. If your outboard is connected to the boat ground for either electric start or an alternator, your outboard would be at 110VAC potential and if its in the water, dangerous for someone near it also in the water.

I really dont think you have much risk at all.. a series of unlikely events had to come together for the referenced accident.

Dont really mean to use your picture as an example but I just wanted to point out that running AC and DC wires close together like that especially before GFCI protection is generally not a good idea. Im not sure there are standards on this sort of thing but making sure AC and DC runs are seperated before GFCI should be one of the standards.

FYI, I do use a space heater during the winter and at 1500 watts, the extention cord can get a bit warm..I really should get one rated for higher current.

Edit - also seeing that your home outlets are all GFCI, you would be protected. Similar to a marina which has GFCI outlets. If the marina outlet would have been GFCI, as soon as the outboard got charged, some of hot AC current would have flown to ground through the water and created the imbalance in hot and nuetral lines which trips the GFCI. The marina outlet would have tripped removing AC to the boat and the accident would never have occured.

caguy · Nov 16, 2009

I have a shore power plug mounted in the cockpit close to the side so I can reach it while it is on the trailer. I use it primarily in mast-up storage to charge between sails. I hooked up a surge protector using the chord from that to wire directly to the inside of the plug. From there I plug in my trickle charger that is connected directly to the battery. The surge protector gives me 3 more additional AC outlets for charging my cell phone, computer and tools when working on the boat. The surge protector is fused with a pretty light breaker. I seldom use it at the guest docks and I have always assumed that the plugs at the docks are GFI protected. I have never looked at them closely. Can I use a GFI plug adapter for this purpose?

walt · Nov 16, 2009

Yes.. and a overall good solution.

Interesting about GFCI at marina's. You always hear about some marina's which seem to cause more electrolysis problems than others. From what I understand, this is generally caused by boats not being wired correctly on the AC side so that the electrical ground is at a different potential than the actual water ground. But at a marina with GFCI, it to some extent forces you to wire the AC correctly on the boat or the fuse keeps blowing. Of course, there are two ways to fix the problem - correct it on the boat or disable the dock side GFCI..