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Basic Electricity - Page 12 - Practical

Basic electricity for boat builders, boat repairers and owners. What you need to know about the electrical systems on your boat. Working on AC Circuits, safety, good practices. Videos, Basic wiring techniques.

Learn to speak electricity!

 Electrical Terminology: Glossary Of Electrical Terms

Practical Wiring Installation Techniques:

The first, most important thing when installing electrical systems is Safety!

Never work on a live circuit except to take voltage and current measurements. The correct way to do this is:

1. Shut the power off. 
2. Connect the meter or instrument.
3. Turn the power on. Read the values.
4. Turn it off.
5. Disconnect the instruments.

See 5 Reasons to Never Work  On A Live Circuit

Wear Rubber Sole Shoes: Insulate yourself from the ground.

Never work with wet hands or while standing on a wet surface.

Do not use power tools that have frayed, cracked or melted cords. Use good quality industrial grade cords of at least 20 amp rating. Do not use household (two wire) extension cords. They do not have a third green grounding wire so you are not protected from shock if you accidentally contact a live circuit.

Buy good quality tools. Why pay more?  Quality tools are almost always guaranteed by the manufacturer.  They perform better, last longer, and rarely break, and some will be replaced free if they do break.   Cheap tools will break and can injure you when they do. Again, it's all about safety.  This is just as true of electrical tools as it is of wrenches, hand tools and power tools.

If possible, buy hand tools that have insulated handles. For instance, adjustable wrenches, screwdrivers and pliers.  They should be insulated so you do not accidentally contact a live circuit and ground at the same time causing a short and a shower of sparks.

Electrical tools, such as drills and soldering guns should be double insulated. This prevents you from being shorted to ground and getting a nasty shock.  If possible use cordless, battery operated tools.  They are safer than AC powered tools around the water.

Use Eye Protection:  A good set of safety goggles is essential.  Always wear eye protection when working with lead acid batteries or other caustic liquids such as gasoline.  Also wear gloves.  Acid leaves nasty burns.  Most DIYers don't have an eyewash station so make sure you have lots of water available.  If you do get acid in your eye, have enough water handy that you can flush out your eyes for at least fifteen minutes. This can happen!  It has happened to me.  See a doctor immediately after flushing out your eyes. 


Chapter 1: Electricity Basics - The Properties of Electricity and Key Terms

Chapter 2: Important Facts About Electricity.

D. M. Fischer on Marine HVDC Grounding from Bill Southworth on Vimeo.

The Kevin Ritz Story on Electro Shock Drowning


Boat Electrical

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Wiring and connectors:

1. Always select good quality materials. Wire, connectors, terminals, bus bars and panels should all be good quality marine equipment. This is no place to scrimp or try to save a few pennies. Remember, the most common fires on boats are electrical fires. Most are due to bad high resistance connections. Do it right!

2. Have a plan. Know what you are going to do before you start installing things. See Electrical Planning

3. Use good quality tools.  A cheap crimping tool will give you a bad crimp that will loosen and allow moisture into your connections. This will cause corrosion and high resistance connections.  Buy a good ratcheting type crimper.  This will give you good crimps that don't come loose.

4. If you decide to solder, use good quality solder and soldering tools. Learn how to solder so you don't get cold solders.  A bad solder is going to cause a bad connection. Do not use solder alone. If you crimp and solder, crimp first, solder second.

5. Seal electrical connections with a good quality sealant such as dielectric grease and a heat shrink wrap to keep moisture out.  If possible buy connectors with heat shrink insulation pre-installed.

6. Use the correct size connector for the wire and use the correct size crimp on the crimping tool for the connector.  This is very important.  Otherwise you will get a loose crimp and the wire will eventually work free or break.

Battery Terminal Connectors:  

Use good quality terminals that do not use wing nuts to connect the wire to your battery.  33 CFR 183.420(g): Each battery terminal must not depend on spring tension for its mechanical connection to the terminal.   ABYC E-10.8.3, Storage Batteries:  says that wing nuts are not to be used to connect any terminals to batteries for wire larger than six (6) gage.  Since most battery cables are four (4) gage or larger, then wing nuts should not be used at all. The concern is that they will loosen from shock and vibration. 

Do not use connectors that rely on spring tension. Connectors need to be tightened with a bolt.  See the illustrations on Page 36 of  for the correct type of battery terminal connectors.

Heat Shrink Tubing And Connectors, AAA protection, How to install and repair.

When your boat is on the hard (ashore) and you are using power tools, do not power them from the boat (inverter, generator etc.). You no longer have a green grounding wire connection to ground on board.  Power them from a good quality extension cord from a power source at the marina or place where you are working, or use cordless power tools. Tell the marina staff what you are doing.  They can keep an eye on you in case there is an accident.

Do not run extension cords onto your boat when it is sitting in the water. Would you plug in a power tool and then stand in a bathtub full of water?  That is what you are doing!  Use cordless power tools or power them from the on-board shore power to maintain the shore ground connection. 

To connect two wires together or to connect a wire to a buss bar or electrical equipment, terminals must be used. ABYC E-11.15.3.   Bare wire to stud connections with the wire wrapped around the connector are not allowed. Good terminal connectors are required. The part of the terminal that surrounds the wire should be insulated and sealed against moisture.  Buy connectors with heat shrink insulation if possible.  

Terminals should be ring or captive spade. Captive Spade terminals have tangs on them that prevent them from being pulled off, and ring terminals have to be lifted off.    ABYC has standards (ABYC E-11) for terminals that say they must not be able to be pulled off the connection under a specific pound pull.  The amount depends on the wire size. A sixteen gauge wire must not pull off under a ten pound pull.  A 4 gauge wire must resist a 70 pound pull.  So use the correct wire terminals.

Test Equipment

Learn to use a Digital VOM.  A Volt-Ohm-Amp Meter (also called a multi-meter) is essential for anyone doing electrical work.  You do not need to spend a lot of money on this. You can pick up a good digital VOM at any home improvement or hardware store, or a Wal-Mart, or any store that sells tools.  They vary in price from $12.00 USD and up to several hundred.  But all you really need is something to measure voltage, amperage, resistance, and continuity.  Any multi-meter will do this.  I have an inexpensive one by Cen-Tech that I can carry in my coat pocket that does the job just fine. It cost about $13.00 USD new. I bought it used for $5.00.  I realize this sounds counter to what I said about buying good quality tools.  But you can get a good quality VOM for not a lot of money. You don't need a professional grade VOM, which can cost anywhere from hundreds to thousands of dollars. 

Get a Receptacle Tester. 
receptacle testerFor testing AC circuits a receptacle tester is a very good tool to have.  You simply plug it in and the lights tell you if the circuit is good, whether there is a ground fault or reverse polarity, or if the circuit is dead.  The last is vitally important if you are working on the circuit.  I have seen these for as little as $8.00 USD.  A great item to have for testing AC circuits on a boat! I picked up one free as a giveaway at a boat show. 

Links to Offsite References:
Wiring Your Boat

© 2007 All rights reserved. revised 04/27/2021


Basic Electricity
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