A distinction can be made between Standards and Good Practices. The Standards are the minimum guidelines provided by a recognised authority to ensure that a satisfactory level of safety and efficiency is maintained. In Canada it is Transport Canada that sets and enforces the Standards for ship construction, and a section of the Standards specifically addresses the Electrical System. The Transport Canada Standards vary depending on the size and intended use of the ship; whether the vessel is more than 20 metres would be a size distinction, or whether the vessel is a recreational vessel or a passenger vessel would be an example of type distinction. The American Boat and Yacht Council (ABYC) is a recognised authority for recreational boat construction standards and is often cited by governments and government agencies, including Transport Canada, as an acceptable standard, and ABYC in some respects goes further than TC with the scope and range of their standards for recreational vessels, but even ABYC’s standards are the minimum requirement. Good Practices maintain the Standards while going a step further to improve reliability and practicality.
In this article we will have a look at some of the Good Practices that should be considered when doing electrical work on a boat. Some of these good practices were learned the hard way over years of doing marine electrical work, mostly on recreational boats, while others were learned from exposure to other electricians while working with them and recognising the value of the extra time and effort put into their work to improve reliability and safety. Most of these good practices focus on connection work as poor connection work is a primary point of failure or inefficiency.
Common Mistake: “Butt Splice”
In-line connections are common, and one of the most common methods used for in-line connection work is a ‘butt splice.’ Butt splices, although allowed by the Standards, are poor practice and should only be used as a temporary repair when necessary. An open-ended butt connector is prone to water intrusion, and exposure to the harsh marine environment often causes the conductor to become corroded. Since that corrosion is often concealed by the butt connector’s insulator, it often goes undetected until it becomes a point of circuit failure. The reliability of a butt splice will be improved by using a heat shrink butt connector and can be further improved by using an uninsulated butt connector and a long piece of adhesive heat shrink tubing over the uninsulated connector; but a butt splice by its very nature still has shortcomings.
A butt splice, if it must be remade because it was used to connect a device, shortens the line side of the circuit when the connection is remade. Over time the conductor can become too short to be remade; we have seen this very commonly with light fixtures, and replacing the conductor on some devices, like light fixtures, can be very difficult. Furthermore, because a butt splice is insulated, the connection cannot act as a reliable circuit test point.
Solution: Disconnects
A better solution for connecting to a device in a dry area like a light fixture is to use disconnects. The disconnects on the line side can be reused on a load device if the device is changed out, and the unconnected disconnect can be used as a voltage test point for the line side of the circuit. An even better solution is to use a terminal block and ring connectors if there is adequate connection space, as the terminal block solution provides the same advantages as a test point and easy reconnection point, but also due to the stability of the connection it is very reliable, and the circuit can be tested while connected adding additional troubleshooting information. Terminal blocks should at minimum be covered, and the best solution is to have the terminal block inside of a junction box. In my work history there was a project with many electricians involved, and there was one electrician that insisted that all connection work was done inside an electrical enclosure or a waterproof junction box: not a bad philosophy.
Common Mistake: “Nut and Bolt” Connection
Another type of in-line connection that is allowed by the Standard but is not a Good Practice is a “nut and bolt” connection. While not as commonly seen, when it is encountered it is often on a high amperage cable, and because of the high amperage the issues with a nut and bolt connection can be more pronounced. Even when done right using lock washers and heat shrink as an insulating cover, this type of connection can still be problematic.
Solution: Insulated Post
A better solution, if there is need to make a cable-to-cable connection, is to use an insulated post. An insulated post forms the same type of connection with the added advantages that it can be secured to the boat and can be monitored for soundness. Again, the post must be covered (most often these high amperage posts come with a cover or insulating cable boot), and ideally the connection will be made inside of a junction box.
Common Mistake: Electrical Tape
Finally, the use of electrical tape as an insulator on connectors and lugs rarely has long lasting effectiveness. Although electrical tape is a good insulator, the adhesive will typically not keep the tape on the wire and/or cable, especially if the environment or conductor gets warm. When the tape does come off, which it eventually will, not only is the connector now missing its insulation, but the tape can end up in the bilge, potentially jamming the impellor of a bilge pump or blocking a bilge intake hose, which can be a safety hazard.
Solution: Adhesive Heat Shrink
Adhesive heat shrink is the obvious choice to apply to connectors and lugs to not only provide insulation, but also seal out moisture.
There is in fact quite a long list of examples of where the Standards do not necessarily come to the level of Best Practice, but this short article highlights a few of the more common examples and may provide a bit of guidance and exposure to good practices for safe and reliable marine electrical systems. There are many good technicians out there who have benefitted, as we have, from guidance and exposer to both good and bad wiring practices. When looking for an electrician for your next marine project find someone who cares about their work and goes beyond the minimum level of the Standards and into the realm of Good Practices.
Lyle Pahl is a Marine Electrician on Vancouver Island doing business as Alpha To Omega Marine Electrical since 2001.