10 Deadly Conditions

[GordMay]

From Blue Sea Systems http://www.bluesea.com

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Ten Deadly Conditions to Check for in Your Boat's Electrical System ~ Part 1

Blue Sea Systems’ engineering department has identified 10 conditions that, when present in your boat’s electrical system, can cause serious problems. Five of these conditions are presented here. The second five will be presented in the October newsletter.

1. Incorrectly sized wire

There are several problems that occur when sizing wire for a boat’s electrical system using the ABYC 105̊C tables:
• Using wire with less than 105̊C insulation.
• Bundling wires together or burying them in thermal insulation.

However, usually wire size isn't a problem because:
• Most DC large loads are short term.
• Most DC wire is chosen for voltage drop and is therefore larger than the minimum recommendations from the ABYC tables.

More: http://www.bluesea.com/Article_detai..._ID=292&id=376

2. Running fuses continuously at full ratings

When matching circuit protection to the wire it protects, two facts contribute to the complexity of this task:
• The amperage at which fuses actually blow, and circuit breakers actually trip, is considerably higher than their nominal ratings, the rating usually marked on the unit.
• Wire and circuit protection devices heat up dramatically when they carry 100% of their rated value for several minutes or more.

More: http://www.bluesea.com/Article_detai..._ID=292&id=377


3. Not using the shore power cord locking ring

The shore power cord locking ring maintains a solid connection between the power cord plug and hull receptacle. When this connection isn’t secure, motion can cause the plug to wiggle back and forth in the receptacle, compromise the electrical connection, and result in dangerous heating.

More: http://www.bluesea.com/Article_detai..._ID=292&id=378


4. No “Green Wire” or poor-quality connection between DC negative and AC safety ground

Without a good connection between DC negative and AC safety ground, stray AC current may enter the DC ground system. When this happens, AC current may enter the water around a boat and injure or kill swimmers near the boat.

The green wire can be tested and indicate continuity but be unable to safely carry enough current to trip a circuit breaker during a fault. There are ways to check the quality of the connection.

More: http://www.bluesea.com/Article_detai..._ID=292&id=379
and: http://www.bluesea.com/Article_detai..._ID=292&id=380

5. Using ordinary plug-in AC receptacle testers to check ground integrity

Ordinary plug-in AC receptacle testers are so sensitive that they will indicate a good ground even if the only connection is through a prop shaft or thru-hull fitting to water. A better way to test for ground integrity is to connect the shore cord to the boat and bring the shore plug back to a position near the electrical panel. With all on-board AC sources turned off, use an Ohm meter to check that the ground prong is solidly connected to the boat’s safety ground system. Check to the “U” ground at each receptacle by dragging around the shore cord end and meter to test at each receptacle.

Summary

Avoiding these deadly conditions will make your boating experience far more safe and pleasurable. Take time to check your boat’s electrical system and look for these conditions. Contact your local ABYC electrician.

[Alan Wheeler]

Gord, this would be an excellent paper for our new topic heading we are discussing.

[GordMay]

Ten Deadly Conditions to Check for in Your Boat's Electrical System - Part 2
http://www.bluesea.com/Article_detai..._ID=292&id=387

In the September newsletter, 1 through 5 of the ten deadly conditions were presented at: http://www.bluesea.com/Article_detai..._ID=292&id=383

Deadly conditions 6 through 10 are presented below

6. Using non-ignition protected devices in explosive areas, or, making areas explosive with dinghy fuel and barbecue bottles

It is dangerous to store dinghy fuel or portable barbecue bottles on board boats that are not designed for ignition protection. This includes diesel propulsion fuel or gasoline-fueled systems for externally mounted outboard motors. Bringing alternative fuels on board, even in small quantities, can lead to explosive situations.


7. Hot/Neutral reversal on AC connectors at the dock or onboard

If a shore cord is incorrectly wired so that the hot and neutral wires are reversed, there is inadequate AC circuit protection. Your boat should have a two pole main breaker if wired for 120V. It should also have a reverse polarity indicator or warning device.

8. Undersized or absent inverter and charger DC grounding

Inverters and battery chargers are bridges between a boat's AC and DC power systems. The high voltage of the AC system presents a shock hazard and can be lethal if it exists on an ungrounded case. The DC system is not normally a shock hazard but can provide a lot of current, and so is potentially a source of fire. A suitable ground must be installed between the AC and DC system.

9. Missing or faulty GFCI

According to the ABYC Standards, when an AC receptacle is installed in a head, galley, machinery space, or on a weather deck, it shall be protected by a Type A Ground Fault Circuit Interrupter (GFCI). These GFCI's protect receptacles and therefore the appliances that are plugged into them. It is possible to use the output of one GFCI receptacle to feed other receptacles and permanently-wired devices thereby protecting these downstream receptacles and devices.

10. Operating power tools in potentially explosive atmospheres

Portable power tools operated by batteries or by AC have brush-type universal or DC motors. The spinning commutator generates sparks and the space is usually well ventilated and even has a fan forcing outside air through the space. Electric drills, routers and saws are bad. Shop vacuums are worse. They are designed to collect air and dirt through the hose and bring it inside. The air passes through a filter and then some of it through the motor. More than one explosion has taken place when a wet/dry vacuum was used to vacuum up a fuel spill in the bilge. A shop vacuum is a wonderful way to pick up water spills, but it also excellent at mixing and igniting explosive gas. Nobody thinks about getting killed by a vacuum cleaner but it can take out the operator, the boat and possibly the neighbors!

Blue Sea Systems, Inc. Copyrighted 2006.

[Boracay]

So how do I go working on a boat with double insulated power tools?
There is no practical connection to earth, even though my power has a safety switch.

[delmarrey]

Double insulation is fine to keep one from being electrocuted but they still spark.

Flammable gases can explode with the proper amount of oxygen/gas mixture. Fortunately, most people are saved by that improper mix. Either too much vapor or not enough oxygen and visa versa.

The best tools to use if in question about the atmosphere are air driven tools. But then again one should be worried about their lungs.

Professionals use a Multi-Gas Monitor before operating tools in a confined space (bilges) especially if there is the odor of flammables.

Mass ventilation is the key.........................._/)