Standard Outlet vs. 30 amp Shore Power

Johnb · Jun 1, 2015

1 Do you actually mean you got a standard to 30 amp adapter

2 Get a power tester (the type with 2 yellow and 1 red lights) and plug it in to the dock outlet to ensure the outlet is wired right.

3 Use a ground fault interrupter plugged in to the dock outlet at all times

4 Remember you are probably only good for 15 amps, so don't connect more than about 1500 watts worth of load at any one time

5 As a general rule, disconnect at the dock outlet before anywhere else. DO NOT just disconnect the boat and leave a powered up cord on the dock. Reverse that order when hooking up again.

Capt jgw · Jun 2, 2015

The twist lock are not waterproof, they just ensure the cord stays plugged in. You can tie a piece of light line around the cord and outlet to do the same thing.
15 amp connections on a dock are not proper, I would check your local electrical codes to see if it's even legal.

uncledom · Jun 2, 2015

Actually according to the NEC all exterior outlets must now have an in service cover. That means that the cover must be able to close and keep water from entering the outlet while the cord is plugged in. I suspect that in the future you will see the power post designs change, as they should, to make them more impervious to water at the connection.

Capt jgw · Jun 2, 2015

And most likely an adapter won't fit under the cover. A pigtail type would, but then the connection to the cord is out in the weather.

McIntoshUSA · Jun 2, 2015

Also good to know. I know someone who had his boat plug into shore power (power was off) and a tree got hit by lightning then ran down the cord and hit his boat. I always unplug my boat during storms now just to be safe even when the power is off. "of course when I remember."

Gunni · Jun 2, 2015

kvalerio said:
We are sailing our new boat home Friday to our neighborhood dock which does not provide a 30 amp shore power receptacle. The dock has several standard electrical outlets which we noticed a couple other boats were plugged into. We purchased a 30 amp to standard outlet adapter, but I would like to know the safest way to use this adapter and remain plugged in using this configuration since it would obviously not be waterproof or as secure as a 30 amp receptacle.

You simply need to comply with amp-rating for the dock receptacle supply. Most likely 15 amps. Which means whatever you power up with your shore power circuit will be limited to 15 amps, maybe 12 amps to be safe.

This really isn't a good long-term solution, a dock should have 30 amp service at minimum, wired to code by a competent electrician.

JK_Boston_Catalina310 · Jun 2, 2015

Most of these are good points.

Johnb said:
1 Do you actually mean you got a standard to 30 amp adapter

2 Get a power tester (the type with 2 yellow and 1 red lights) and plug it in to the dock outlet to ensure the outlet is wired right.

3 Use a ground fault interrupter plugged in to the dock outlet at all times

Not so quick here. You might have a GFCI outlet at the dock. You don't want to plug a GFCI pigtail into a GFCI outlet. Not necessarily a bad thing but could be over protected and you could get a couple of issues if you plug a 15-amp GFCI pigtail into a 20-amp GFCI outlet. Instead I recommend you look at the dockside outlet first and determine if it is GFCI protected. If it appears to be, get a GFCI tester and test the outlet. This tester would be instead of the one mentioned above. It does the same as that one but tests the GFCI as well.

4 Remember you are probably only good for 15 amps, so don't connect more than about 1500 watts worth of load at any one time

Maine Sail has advised numerous times to never load a circuit more than 80%. So if you have a 15 amp plug you should only pull 12 amps through it. In this setup I would probably go a little less.

I would also get a good, thick (10AWG I think is the thickest common commercial cord at a box store) outdoor electrical cord. Even then I would be cautious about leaving it on unattended. I might even consider plugging the pigtail into the outlet and then running a 30 amp shore power cord from the pigtail to the boat.

5 As a general rule, disconnect at the dock outlet before anywhere else. DO NOT just disconnect the boat and leave a powered up cord on the dock. Reverse that order when hooking up again.

The procedure I use like a religion is as follows:

Shut off 120V breakers on the boat's electric panel.
Shut off the power at the shore power pedestal.
Disconnect the boat end of the shore power cord.
Secure the cap on the end of the shore power cord (I have a SmartPlug instead of the standard shore power cord).
Coil up the shore power cord and secure it to the pedestal.

If I had this setup I would get a small solar panel to keep the batteries topped off while I am away from the boat. I would not leave the boat plugged into shore power.

Good luck and fair winds,

Jesse

Ron20324 · Jun 2, 2015

I'd say get a good exterior-rated 12-gauge (maybe 14) power cord to plug into the dock outlet. Put the adaptor on the boat end. You can limit and control the connections to weather alot better. You could put the adaptor right onto your boat's input connector, and save the 30-amp cord being exposed to the weather. It WILL get dirty just being outdoors.

At my condo-marina with both 15/20 and 30 outlets, we do not allow the 15/20's to be left with a power cord plugged in unless you are actually there. All too often (as it is right now) the GFCI on the dock goes belly up and we do not have AC until someone replaces the outlet.

IH82BL8 · Jun 2, 2015

Remember you are probably only good for 15 amps

My marina has 30 amp service at the dock but only 15 amp service on the hard. I was unable to keep my batteries charged when the boat was on land because the battery charger kept tripping the breaker. Once back in the slip it worked perfectly. Hopefully, you won't run into this.

Stu Jackson · Jun 2, 2015

Boat electrical systems

kvalerio said:
I am embarrassed at my lack of knowledge on this subject, but I am trying to learn and this seems to be a good place to do so! Thanks in advance.

Welcome to our little world here. Don't be embarrassed. None of us was born an electrician.

It's simply a matter of learning and application.

One of the first things you should do is buy a good book on boat electrical systems. Charlie Wing's book is one of the better ones, goes from A to Z without being either too basic or too "heavy." It's a great start point.

Then you need to do some detective work on your own boat to find out how it is wired so you can answer the question about battery switch positions and charging.

Much of your reading will be learning how batteries operate and how to treat them right by charging them properly.

In addition to books, you can learn a lot from this link:

Electrical Systems 101 http://c34.org/bbs/index.php/topic,5977.0.html

Good luck, happy reading and have a great season on your new boat.

JK_Boston_Catalina310 · Jun 2, 2015

kvalerio said:
Thank you all for taking time to answer my questions. Your comments have been extremely helpful.

We never used shore power with our last boat (a well loved, but VERY outdated 1974 Bayfield 23) so the whole shore power thing is new to us. The previous owner of our new Hunter 27 kept it consistently plugged in at his marina and was surprised we didn't plan to do the same at our dock. Would plugging her in once or twice a week while we are present be sufficient to keep the batteries charged rather than keeping her consistently plugged in and unattended as the former owner did? If so, how long should these charging periods last? In addition, the former owner kept his batteries set to "All" while the boat was docked and plugged in. We always turned ours off in our old boat to make sure they didn't lose their charge. If we turn the batteries off in the new Hunter, will the auto bilge pump still be functional? I am embarrassed at my lack of knowledge on this subject, but I am trying to learn and this seems to be a good place to do so! Thanks in advance.

No one can answer most of these questions for you. You need to know what your boat has for equipment (i.e. battery sizes and condition, charger, etc.) and what kind of loads you are running. You mentioned the bilge pump, those could be wired to stay on or they could be wired through the switch. You need to look at the actual wiring to tell. Do you have refrigeration you plan to keep plugged in?

First thing you should do is read the following 3 articles.

1. 1/BOTH/2/OFF Switches Thoughts & Musings

2. Battery Fuse Sizing - How?

3. What Is A "Deep Cycle" Battery?

You should also spend some time on the Catalina 34 IA tech wiki. It doesn't matter that your boat is a Hunter a lot of the information there will help you. I would start with the "101" series.

We went from a C&C24 that was basic, very minimal power, no water, no head, etc. to our Catalina 310. There was a very steep learning curve to get all of the basics for all of the systems down. Sounds like you are in for a similar experience. Just spend some time learning what you have and how to properly maintain it and you will love having a lot of these systems on the boat.

Good luck and fair winds,

Jesse

Stu Jackson · Jun 2, 2015

C34 tech wiki link

You can get to the tech wiki that Jesse mentioned from the link at the top of the page on the link I previously noted.

Jesse's blog is also a good resource.

Benny17441 · Jun 2, 2015

I did that in the past for an extended period of time with no issues. I plugged a 12 gauge wire extension cord to a pig tail adapter into the shorepower plug of the boat. For weather proofing I wrapped up the connection with plastic tape and kept it elevated from the deck by securing to one of the lifelines. It lasted for years with no issues in our Florida weather. I think that once I may have replaced the tape. You do have to realize that you only have 15A service and not overload the circuit. I used mine while docked to power the battery charger. Talk to the other boaters to see what they are doing and check on your marina policy about power cords.

Davidasailor26 · Jun 3, 2015

IH82BL8 said:
My marina has 30 amp service at the dock but only 15 amp service on the hard. I was unable to keep my batteries charged when the boat was on land because the battery charger kept tripping the breaker. Once back in the slip it worked perfectly. Hopefully, you won't run into this.

How big is your charger? 15 amps at 120 volts is equivalent to 150 amps as 12 v, so even subtracting for some efficiency losses, I wouldn't think you'd be tripping the breaker with anything less than a 100 amp charger. Are you sure someone at the marina wasn't turning off the breaker when seeing it unattended, as is the policy at some marinas?

Ron20324 · Jun 3, 2015

Charge one battery at a time for less AC draw?

IH82BL8 · Jun 4, 2015

How big is your charger? 15 amps at 120 volts is equivalent to 150 amps as 12 v, so even subtracting for some efficiency losses, I wouldn't think you'd be tripping the breaker with anything less than a 100 amp charger. Are you sure someone at the marina wasn't turning off the breaker when seeing it unattended, as is the policy at some marinas?

The owners manual says it draws 20A. It was tripping the breaker within about 1/2 second each time I turned it on.

Charge one battery at a time for less AC draw?

That's a good thought. I wish I'd thought of it at the time.

JK_Boston_Catalina310 · Jun 4, 2015

The draw and ways to reduce it entirely depends on the charger you have. And even if the manual lists something, verify the make and model of the charger. I am on my third charger on a 2001 boat. They do go, especially the cheap ones that come with the boats and the cheap ones sold at West Marine.

As far as reducing amperage, charging one battery at a time won't do it. Most chargers will put out the same amperage regardless of the number of banks. If you have a 40 amp charger and attach two banks, each bank will get 20 amps. Only attach one bank and that bank gets 40 amps. However, many of the newer chargers allow you to reduce the output. Our Xantrex Truecharge 2 40 amp charger can do from 10%-100% of the output. So in the past when I was charging the batteries off of a 2000 watt generator, I had to reduce the charger to 60% so that it didn't cause the breaker on the generator to blow.