shore power thermal fuse to prevent fires

[vpbarkley]

I recently learned that ~ 10% of boat fires are attributed to AC power. In many cases the fire starts in the area around the shore power entry. In each case the breaker in the power post did not trip.

It's likely that corrosion caused increased resistance, resulting in contacts +/or conductors becoming excessively heated. The heat was sufficient to cause flammable material in close proximity to ignite.

A simple approach to arrest this problem would be a thermal fuse located at each power entry, wired to disconnect the load from the circuit. This would limit temperatures thus preventing a fire.

Self-resetting thermal switches are not permitted for safety reasons. But a thermal fuse would have to be replaced before power would be restored.

I would welcome any helpful feedback from the group.

[vpbarkley]

Here is some information about thermal fuses:

https://www.apogeeweb.net/electron/w...a-thermal-fuse

[vpbarkley]

A manual reset thermal switch is another option.

[smac999]

This is what the smart plug was. But it did not meet code becsuse it turned back on itself when cooled. So the new ones no longer shuts off. Now it’s just a better connection.

[vpbarkley]

Originally Smart Plug had a thermal cutout device. That posed a hazard as it reenergizes the circuit of its own volition.

I'm proposing a thermal fuse or a manual reset thermal switch. Neither can reenergize the circuit on its own. That's the difference.

[goboatingnow]

Originally Posted by smac999

This is what the smart plug was. But it did not meet code becsuse it turned back on itself when cooled. So the new ones no longer shuts off. Now it’s just a better connection.

Perhaps a better plug design then the stupid Marinco design might be a better approach

[rwidman]

Originally Posted by smac999

This is what the smart plug was. But it did not meet code becsuse it turned back on itself when cooled. So the new ones no longer shuts off. Now it’s just a better connection.

You have to wonder about a company that would design, manufacture and sell an electrical product that violates the National electrical Code.

[rwidman]

Originally Posted by vpbarkley

Originally Smart Plug had a thermal cutout device. That posed a hazard as it reenergizes the circuit of its own volition.

I'm proposing a thermal fuse or a manual reset thermal switch. Neither can reenergize the circuit on its own. That's the difference.

You could certainly design something like that and install it on your own boat. Bringing something like that to market and making a profit is a different story.

[rwidman]

Originally Posted by goboatingnow

Perhaps a better plug design then the stupid Marinco design might be a better approach

The problem with replacing the "stupid Marinco design" is that it is the industry standard. You could come up with a better design (Smart Plug did) but it won't fit any boats. To make it work, the inlet on the boat must be replaced. Now you have a boat that needs a special cord to connect to shore power. And you can't string two cords end to end for a longer reach because the male and female connectors are no longer compatible.

[CharlieJ]

@rwiidman #9

To make it work, the inlet on the boat must be replaced.

True. The SmartPlug inlet is a direct replacement for the Marinco/Hubbell inlets.

Now you have a boat that needs a special cord to connect to shore power.

Actually only the boat end of an existing cable has to be converted to be compatible with the SmartPlug inlet.

And you can't string two cords end to end for a longer reach because the male and female connectors are no longer compatible.

Not really. Only one shore power cable needs to be converted. The shore end remains the same and will plug into the boat end of a secondary cable that has not been converted for the SmartPlug.

[vpbarkley]

Actually the SmartPlug inlet is not a direct replacement for the Marinco/Hubbell inlets. Their marketing material says it is but it is not. The mounting hole spacing is oversized by .07". You wind up with binocular holes. Not too Smart.

[s/v michaela]

A simple way to avoid "the burn" is to grease your connection with electrical grease. It prevents the carbon build up which results in resistance and heat. As a lineman we grease all connections to prevent this from happening.

[GreenWave]

Originally Posted by vpbarkley

Actually the SmartPlug inlet is not a direct replacement for the Marinco/Hubbell inlets. Their marketing material says it is but it is not. The mounting hole spacing is oversized by .07". You wind up with binocular holes. Not too Smart.

This can be addressed in about 30 seconds with a file or dremel tool. Likely only a showstopping issue in the smallest of boats.


I just replaced two on my sailboat and the hole size/shape was one of the easier parts of the install. I will note that the temperature of the cords is much lower (by hand feel only) after switching. For less than my inusrance deductible I have replaced two inlets and bought new cords, greatly diminishing the fire hazard.