Dock Power Conundrum

[Fixin to]

I’m actively searching for a new boat now that my creek has been dredged, and I need advice on the 120 V service to my dock for this future 35 to 40’ cruising boat.

Currently the dock has two 20 or 30 amp cables for powered davits for an earlier boat. Our Mainship 390 took one 120 V, 30 amp cable for power at a marina which handled all dock-side needs. The last boat that we looked at had two 30 amp dock cables but a single could be plugged in depending on which systems were wanted.

Is there a typical amperage requirement for a cruising boat in the 35-40’ range? I’d sure like to avoid trenching 150’ for a new conduit. The davit motors would never be in use at the same time as boat shore power. If I only got 30 amps, I can’t envision needing more power than needed to keep the batteries charged.

I am in Virginia and the winterized boat would only need a lightbulb or two to keep temps above freezing. I know diddly about ‘lectricity.

 

[O C Diver]

Probably your number one power consumer at the dock would be air conditioning. Depending on the boat, you could have 2 or 3 of them. While you could live without the air conditioning, why would you not want to be able to use all the features of your boat when doing repairs, cleaning, or maybe the guest accommodations.

IMO, sooner or later you're going to want more power at the boat. Run service for a 50 amp 220 volt outlet. If I were doing it, I'd have that plus a single 30 amp 120 volt and a 15 amp 120 volt duplex outlet. Basically a sub panel with appropriate breakers and outlets.

Ted

 

[Bacchus]

If your current dock is 2 - 20A circuits that's not much. If 2 - 30A that a lot better.
If you decide to install more I'd go with 50A 240V and not look back. I doubt you will ever wish you had less power available.

 

[Comodave]

We have a 41’ that has 2 30 amp inlets. Our dock has 50 amp 240 volt service to it, however I only need 2 30 amp outlets so that is what I wired to power the boat. But I could add a 50 amp outlet if I need one. We may be looking for a larger boat so having the ability to have a 50 amp outlet is nice. So if you are going to rerun power then I would go with 50 amp service.

 

[rgano]

Currently the dock has two 20 or 30 amp cables for powered davits for an earlier boat. Our Mainship 390 took one 120 V, 30 amp cable for power at a marina which handled all dock-side needs. The last boat that we looked at had two 30 amp dock cables but a single could be plugged in depending on which systems were wanted.

Do you have a breaker(s) in the house or at a separate panel for the pier? How many amps is that breaker(s)?

If your "two 20 or 30 amp cables" are individually breakered, what are those capacities?

Off the top of my head, it seems that to service a twin 30-Amp 120V cable boat all you need to do is place 30-Amp plugs on the ends of those cables you have and use the 20-Amp cable on the side with the least demand.

 

[wkearney99]

This is your dock. If you get the electric wrong and someone gets injured/killed, it'll be your money/assets/insurance on the line defending the lawsuit(s). You don't want to have anything misconfigured and have it kill someone.

I know diddly about ‘lectricity.

Then you should absolutely HIRE A LICENSED ELECTRICIAN. And if there are local electrical permitting processes, FOLLOW THEM. The fees for it will seem like chump change if anything goes wrong.

 

[Comodave]

This is your dock. If you get the electric wrong and someone gets injured/killed, it'll be your money/assets/insurance on the line defending the lawsuit(s). You don't want to have anything misconfigured and have it kill someone.



Then you should absolutely HIRE A LICENSED ELECTRICIAN. And if there are local electrical permitting processes, FOLLOW THEM. The fees for it will seem like chump change if anything goes wrong.

+1.

 

[stubones99]

The reason for having "two 30 amp circuits" is when they are combined. Each 120v circuit , and combined, they make a 240v circuit. Running anything at 240vac means the cable size can be less for the same amp draw. Trenching the yard is the least of your worries, and if that's an issue, there is always underground boring which goes underground but has no trench. They simply drill a horizontal hole in the ground, hook a conduit to the other end and pull it back through the same hole. A bit more expensive, but probably not a big deal when sod, driveways, sidewalks, and other issues are involved.

 

[O C Diver]

I had 100 amp 220 volt service run from my house to the garage and 2 passes under the driveway for a lawn sprinkler system. The directional boring including the conduit pipe was $600 (their minimum). I'll never dig another trench for electrical service again.

Ted

 

[Comodave]

Last winter they bored down the street for a half mile to replace the main service lines. We had some damage to our yard but mostly due to the location of the transformer on our property line.

 

[Fixin to]

Thanks for the comments. I absolutely will use a qualified electrician. I’m trying to determine if the power at the dock can be configured to what I will need for the boat or if I need to start from scratch. I trenched it 12 years ago and I’m still vibrating from the experience.

 

[Swfla]

If you're happy with the marina's 30 amps for your Mainship's basic needs, you'll be fine with a 40' boat too. No air conditioning, hot water, microwave to be used. Refrigerator, fan, battery charger, lights will be fine. As pointed out, the circuit breaker for the current wiring will tell you the max draw. Even at 20 amps, you'll be fine. Why spend a bunch of money to upgrade wiring that you don't need. You can always do it later if the need arises.Have fun boat hunting!

 

[O C Diver]

Thanks for the comments. I absolutely will use a qualified electrician. I’m trying to determine if the power at the dock can be configured to what I will need for the boat or if I need to start from scratch. I trenched it 12 years ago and I’m still vibrating from the experience.

What size conduit did you put in the ground last time. Or did you just use direct burial cable? If conduit, check the pipe size as you might be able to remove the old wire and pull new in. I believe my 100 amp service was 2" pipe.

Ted

 

[FF]

The 50/240 setup should NEVER need an upgrade.

While the setup is being installed put an electric meter in the setup.

www.hialeahmeter.com

Rebuilt they are inexpensive , and may be useful later.

 

[Ski in NC]

I run my 38' on a single 30A/120V feed. Can run both AC's, water heater and all the little loads just fine. Any bigger a boat and I would like to have 50A/240.

When boat is not in use, I leave AC's and other big loads off. Just charger and dehumidifier.

See what boat you end up with and upgrade if needed. If it takes more power than you have, you can always run some stuff til you upgrade power.

 

[Chrisjs]

The discussion has focused on power requirements for running AC. My question is whether that is really the need? If the boat is parked on the OP's dock at the end of his yard, why would he need to run AC, except possibly in a low power dehumidification mode? I am assuming he does not live on the boat.

 

[wkearney99]

The discussion has focused on power requirements for running AC. My question is whether that is really the need? If the boat is parked on the OP's dock at the end of his yard, why would he need to run AC, except possibly in a low power dehumidification mode? I am assuming he does not live on the boat.

It isn't uncommon for folks to use their boat at the dock as a cottage. Thus running AC to cool the inside wouldn't be unusual. Everyone's style of using their boat is different.

 

[rgano]

When I bought this place in 1999, I ran 220 to the pier where it is divided to accommodate two 30-Amp cords. It also provided lighting down there. At the time I had a trawler there plus two slips for guests. We have entertained a number of guests over the years, many of them loopers as well as my brother's trawler a couple of times a year, and I let them plug in to the two 30-Amp sockets letting my boat go without any power (or just an extension cord) for the duration of their stay. Had I needed the boat for overflow sleeping, we could have gone there leaving the house to non-boater sleeping, and we would not have had to run the genny for air conditioning because we had all the shore power we needed. I also installed a 15-Amp socket to accommodate an extension cord should I have wanted to run the dehumidifier or other appliance while disconnected from the 30-Amps. Now that the trawler is gone, that 220 powers the 20,000 pound capacity boat lift the Frolic rests in, and I use one 30-Amp cable to run its small dehumidifier and battery charger in summer and those plus various heating appliances in winter. So as you can see it just made sense to fully power our mini marina.