Question: Recently I had an insurance survey done on my boat. The surveyor noted that the shore power electrical outlets were improperly installed and are therefore a shock hazard risk. My insurance company now wants proof that I’ve had this error corrected before they will give me liability insurance.
The outlets are factory original. When I asked the surveyor to elaborate, he said they are upside down from what the NFPA in the National Electrical Code requires. They look like the outlet shown in Fig 1 (below left).
What’s the story here? I’m really confused. The outlets on my boat look to be installed just the way they are in my house.
Answer: Great question! This one has been debated among electrical technicians for some time.
First the facts…. The NFPA (National Fire Prevention Association), which develops the National Electric Code referenced in the US and Canada, is silent on this matter. So, your surveyor is fundamentally wrong on that count.
What’s interesting is that my extensive travels over the last ten or fifteen years have taught me that outlet installation is based more on regional preference than regulation. Here in Rhode Island, electricians seem to favor the installation shown in Fig. 2. I personally favor the installation on your boat (and in fact recommend that in my book, The Power Boater’s Guide to Electricity 2nd Edition).
Let me explain why. The round terminal shown in both diagrams is known as the “grounding terminal.” This is the terminal that will save your life in the event of a short circuit. The two flat blade type slots on the outlet are for the hot and neutral conductors, so both carry lethal power at 120 volts.
In a situation where the plug may be hanging part way out of the receptacle, which is actually a pretty common thing, the figure 2 installation will expose two “live” conductors to any metallic object dropped across the plug. That would cause a very dangerous short circuit that might not actually trip a circuit breaker. So all a toddler would have to do is touch the metal object bridging the hot and neutral terminals (or bridge the two terminals with inquisitive tiny fingers) and she will get ZAPPED!
With the ground lug in the up position, anything that bridges two terminals will be connecting either the hot or neutral to earth ground, which will trip the circuit breaker for sure. In my view this is a much safer way to go.
Alternatively, the photo in Fig. 3 shows another on board installation that offers the same advantage as the ground up approach. If a plug is partly pulled out, any connection from the top will be between earth ground and either the hot or neutral conductors. A breaker will trip.