Installing shore power and wiring

[Cheechako]

Originally Posted by 2xcrash

Thanks. Thought it would be a no,no in the harbor. But after noticing a few other boats on the dock doing the same thing this is what i'll do.

Thanks everyone for the advice and I'll do it the right way after I get all the other bugs worked out first. Got thru hulls and engine to work on first. Safety, comfort, and then back out in the water!!!

Not saying you shouldn't install a decent setup, but it doesn't need to be complicated on a boat like that.

[mitiempo]

Originally Posted by Bor the Wolf

But please read the fine print in the advertisement or manual. Galvanic isolation in my mind means electrons have *no* path whatsoever to shore.

I am at the end of a jetty and the power line runs a several hundred yards from the actual ground point. I have measured voltages on the ground wire that far exceed the threshold of a diode bridge. Specially when there is a lot of static in the air. Does the seller of the diode bridge pay for a new propeller if his device fails? I guess not. I'd rather stick to my waterproof, mil-spec transformer and have no worries.

By the way, Isolation Transformers are used on building sites and other hazardous places. That means you don't have to get them from your local Sailing Jeweler. I got a real bargain at a military surplus store. The only thing is, they come in Navy grey only and are designed to survive WW3.

While an isolation transformer is the ideal AC shore power solution the op probably doesn't want to spend the thousand plus for a 40 to 50 lb marine rated isolation transformer. It is a Catalina 27!

Galvanic isolators work well for most of us.

[Dave Lochner]

Originally Posted by Lake-Effect

backing up a bit - I asked my question about galvanic isolators in response to bor's assertion that they don't work period... which is something i hadn't heard before. Can anyone shed more light on this? Is it a widespread problem?

Because of the way AC wiring is done on shore, if a boat is connected to shore power it is connected to every other boat on the circuit through the ground wire. In properly bonded systems the AC ground wire is also connected to the bonding system, such all the underwater metals are connected this keeps their electrical potential at the same level and helps to reduce galvanic corrosion of the various metals.

When the metals in different boats are connected via the AC ground wire, you essentially build a battery that produces around 1.2 volts DC, the electrons love it, the metals not so much. A galvanic isolator blocks DC current from flowing, but not AC current. This breaks the "battery" and one avenue for galvanic corrosion is eliminated. GIs work.

Of course if you just disconnect the ground wire in the AC system then you wold have the same effect of breaking the battery and reducing the galvanic corrosion, but at the cost of not having your AC system grounded. That's dangerous.

As noted earlier the best way to isolate the AC system is with an isolation transformer. This provides a physical break between the three legs of AC shore power (Hot, Neutral, ground) with the three legs of the boat's AC system. The downside is that these systems are expensive, bulky, and heavy. On a larger boat, they are desirable; on a steel boat they are desirable, but on a smaller fiberglass boat, not so much because of the space and weight considerations.

The big safety issue with GI's is whether they fail in a safe mode or not. Fail Safe GIs are more expensive and safer. As was noted earlier, if the diodes in a GI fail (and they can if too much current passes through them) they will not protect against galvanic corrosion (important, but not life threatening) and they may or not provide protection in the case of an AC fault to ground.

A Fail Safe GI will maintain a connection with the AC ground if the diodes should fail. With the less expensive GIs if the diodes fail the AC ground connection is broken and there is no grounding protection on the AC circuit. This is potentially life threatening.

The issue is knowing if the GI has failed. Testing a GI is not all that difficult, there are directions available online and some manufacturers provide the instructions with the GI. All you need is a decent digital volt-ohm meter that can be had for ~$50. Make the test part of your spring ritual.

[mitiempo]

Originally Posted by Dave Lochner

Of course if you just disconnect the ground wire in the AC system then you wold have the same effect of breaking the battery and reducing the galvanic corrosion, but at the cost of not having your AC system grounded. That's dangerous.

Assuming the shore ground is non-existent.

Major companies like Promariner only offer fail safe isolators now.

Excellent post.

[GordMay]

Regarding “Monitered” vs “Fail-Safe” Galvanic Isolators:

➥ http://www.deimarine.com/media/wysiw..._Liability.pdf

➥ http://www.qualitymarineservices.net...2010-25-06.pdf

[liveaboard60]

Very good thread (and thanks to GordMay and to Lake-Effect for the links to the excellent Article and documentation)..


I have a Hunter 26.5 on which a 30 amp shore power receptacle, breaker (not sure of the breaker rating at this point - still a fairly new to me boat), and 2 or 3 GFI 110vAC 15 amp outlets have been by some owner since it left the factory in 1985..
Being I was not the one who did the installation, I just don't trust it was done correctly (I haven't checked if household wiring, outlets was used, etc.).. But I am most curious about the galvanic isolator..


The kit of which questions about raised the thread boast the kit comes with a Galvanic Isolator.. I have read threads a good one which meets ABYC code is around $1000 or more so I wonder the usefulness of one with the mentioned kit, and even more important if my boat has even a "cheapo" one..


I will be on my boat this weekend, and will have do some more digging..
So thanks again for an excellent thread.. flk k

[mitiempo]

A Promariner Failsafe galvanic isolator is about $400 Cdn, so about $300 US.

It you have a double main breaker (probably 30 amps) that is good. You should also have a breaker for each individual circuit. The GFI outlets (which you should have) are not protection for the circuit. A breaker is required for each circuit - typically 15 amps.

[spraygun]

Some help

Sent from my SAMSUNG-SM-G870A using Cruisers Sailing Forum mobile app

[jeepbluetj]

I completely rewired my Catalina 30 after years of previous owners' fancy electrical work.

I used a paneltronics panel for the AC:



Around $100. The three circuits are port, starboard, and fridge. I've got a couple outlets each port and starboard.

I moved the AC out of the main panel, and right on the bulkhead (port side) behind the galley. AC inlet is on port outside coaming.

I see no reason for more than a few breakers for a 27 foot boat. Everything is gonna be plugged in anyway. (not hardwired)

[liveaboard60]

Originally Posted by jeepbluetj

I completely rewired my Catalina 30 after years of previous owners' fancy electrical work.

<snip>

Nice looking panel at around 100 bucks a fair deal..

Is the main breaker a double pole breaker??

flk k

[liveaboard60]

Originally Posted by spraygun

Some help

<snip>

Hey spraygun, if you could only buy one of the three books you spotlighted (I have only so much space), which would you choose?? Thanks in advance..

flk k

[spraygun]

Probably either of the two on the left. The truth is all three books offer a little something different. So you can just kind of use your best judgement. I bought all three from EBAY. They were not that expensive.The two on the left came from a college library.Whoda thunk it.

Sent from my SAMSUNG-SM-G870A using Cruisers Sailing Forum mobile app

[mitiempo]

The book on the left by Charlie Wing is the best for someone with little knowledge, but get the latest edition. Up to date and easy to understand.

https://www.amazon.com/Boatowners-Il...s=charlie+wing

[liveaboard60]

<LOL> Thanks spraygun.. It not the financial cost which concerns me most (though obviously it is important), it is the cost of space.. I am having to make lots of really tough decisions over what goes and what stays in moving from a 1700 sqft home to somewhere around 35 to 45 feet..


As far as little knowledge, I am an expert when it comes to residential wiring, however this boating thing where AC and DC systems have to co-exists, plus toss in the need for Galvanic Isolation, and there is lots to learn..

Thanks all for this and the other thread to which I have seen some very good info and links.. I need to go sailing.. flk k

[Golden Echo]

Here are some things to consider when wireing AC in a boat.

1. Safety First
I know this is common sense but you'd be surprised.
2. Plan your system out specifically for your boat. Make wiring diagrams and when you think you've got it perfect, sit on it for about a week and then come back to it. You'll be surprised the extra stuff you will think of.
3. Shop around
You'll be shocked at the difference in prices between retailers. Some suggested places:
Tinned Marine Wire. This is mail order from a place in Pa. The prices are good and the service is super.Inverter Service Center:
This place is mail order, they have decent prices and are located in KY I think. You can get panels, switches, GFI outlets.
Also there is Defender Marine good prices on most things.
4. If a Job is Worth Doing, It's Worth Overdoing
All the wire in my boat (The main runs) is 10 AWG. It's harder to work with but I absolutely never worry about overtaxing my circuits. If I have to plug in a 1500 watt heater I know the wire can handle it.
5. Split your circuits
For the appliances you describe you shouldn't need more than 30 amps. Split the boat into zones. Port side is one circuit, Starboard another. This way you can have a AC unit running and still use your coffee maker. Place GFCI outlets in the beginning of each circuit, this way they will protect all of the outlets in the circuit.
6. Monitoring Your Power is Important.
I know they are expensive but it's really nice to know how many amps your pulling at any time. The meter I have on my boat monitors: Amps, Watts, Hrtz and voltage. Also make sure the panel you buy has a reverse polarity indicator.
7. Tools are Everything
Get yourself a good Rachet crimper. Don't mess with the squeeze type. If you make good crimps you won't have to worry about resistance causing a fire. Also coat the wire where it gets crimped with dielectric grease. I reworded my boat in 2008 and even the crimps in the cockpit lockers still look like new.
Make sure the wire you use is tinned, I can't stress this enough. Also don't use solid core or house wire it can't stand up to the vibration.
8. Neatness counts
Make sure you label everything. You just can't remember all of that stuff. Make your runs in conduit; corugated bilge hose works great.

One last thing, and I know I'm going to get fried for this one; buy yourself a Smart Plug outlet and shore power cord. The safety features and ease of use are worth the money. This is a power cord you can hook up to your boat in the dark, with your eyes closed.


I probably missed a lot but those are the basics.


Good luck,


RB