Smart Plug

[BradC]

A year ago I swapped out my shore power cord for the SmartPlug after the cord and plug from the previous owner had a melt down. I wanted to be extra safe.

A year later, the Smart Plug just did what they say it's not supposed to do. Tripped the breaker thankfully and no fire. Damage is limited to the Smart plug. The rear wiring on the boat side is unscathed. The shore power cord beyond the SmartPlug is also fine. Damage limited to the SmartPlug connection itself.

Boat is in a covered slip and cord is not exposed to any tension. Not sure what caused the short and subsequent burnup. i reached out the company and they have yet to respond so I thought I'd post it here as a potential warning to those who may feel they are safe from such things when using this plug.
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[Xsbank]

How many watts were you drawing?

I think this makes my point on the other plug thread.

 

[rslifkin]

Being that the breaker tripped, something caused an overcurrent. The plug took some damage, but for the most part, the breaker did its job as seen by the lack of wire damage. This wasn't the typical high resistance plug failure, as those often happen below breaker trip load.

 

[tiltrider1]

Two melt downs in one year. You have an issue. You need to find out the cause. It’s not the shore power cord. Next time the whole boat could go up in flames.

 

[twistedtree]

My first guess looking at the plug would be that it has been repeatedly plugged in under load. Is that possible? I don't think any plug will stand up to that.

 

[SteveK]

There is a wire between the smart plug and the boat main breaker. Is that undersized? Also it looks a 30 amp plug, is the main breaker 30 amp. Is there a power take off before the main breaker.

My shore cord is #8 and when I went to install the smart plug I found my cable from old plug size at #10 going to the breaker, which I changed immediately as to me that is a weak link in the line.

 

[Comodave]

10 gauge wire is rated for 30 amps A/C so it should be fine. Nothing wrong with using #8 but not necessary.

 

[SteveK]

10 gauge wire is rated for 30 amps A/C so it should be fine. Nothing wrong with using #8 but not necessary.

Dave I prefer continuity of size, and since old plug was scorched it still makes sense to have same gauge wire to the main breakers. Why is the 30 amp cable #8?

Edit I am reminded that a continuous load should be no more than 80% of rating, so #10 is good for 24 amp, and #8 is good for 32 amp.

 

[Comodave]

But the L5-30 should not be run at more than 70 to 80% of the 30 amps so it doesn’t really matter that you have larger wiring. Continuity of wiring size is an ok reason though.

 

[rslifkin]

Most 30 amp shore cords I've seen are 10ga, not 8ga. 50 amp is typically 6ga, although depending on the grade of wire, 8 is sometimes acceptable.

 

[BradC]

10 ga wire to the breaker. 30 amp service. Never disconnected under load. Only thing running is the marine ac/heat drawing just over 8 amps and the refrigerator @ 2. PowerShare system through the inverter for battery charging that reduces charging when AC amp demand increases. Can’t find any evidence of temp increase in any wire at the electrical panel or the panel itself using a laser thermometer. I check the temp of the shore power cord by touch ever single time I come aboard the boat. Never more than slightly warm on occasion. Previous meltdown was a faulty connection in the rear of the shore cord from what appeared to be a cut and rewired cord not noted until after the incident and breaker didn’t trip.

 

[SteveK]

Most 30 amp shore cords I've seen are 10ga, not 8ga. 50 amp is typically 6ga, although depending on the grade of wire, 8 is sometimes acceptable.

My old 50 foot factory cable dock end is for 30 amp. I would not have known the wire size was #8 until cutting off the boat end to replace with smart plug.
Now, on searches I see that the available30 amp shore cables state #10 as standard.

makes me wonder if over the years with usual cutbacks of quality the old ways were changed to go with the minimum #10 needed size. I have two other factory made cables over 20 years old I may cut off an end just to see.

But, the unused old line feed wire is still there to be checked, maybe it is actually a #12 and shore cable is a #10 like you are saying. I will need remediation school if I misjudged the sizes.

 

[CharlieJ]

Full disclosure: I have been a SmartPlug dealer since they were introduced and I have installed about 50 of them over the years.

I know for a fact that a properly installed 30A SmartPlug will pass well in excess of 30A indefinitely with a minimum temperature rise.

Based on the photos my assessment is that there was a high resistance at the boat side wire/plug connection that caused the heat that melted the area around the line lerminal.

I have seen the following issues with DIY installations:
1. Insufficient insulation removed and the clamping screw contacts the conductor partially on the insulation and partially on the copper.
2. Insufficient torque on the screws. Spec is 14-20 inch pounds for the inlet or the plug.
3. Cord seal not properly seated allowing water intrusion.
4. Improper installation of the cord strain relief.

I recommend that the OP contact SmartPlug by email or phone.

 

[tiltrider1]

Full disclosure: I have been a SmartPlug dealer since they were introduced and I have installed about 50 of them over the years.

I know for a fact that a properly installed 30A SmartPlug will pass well in excess of 30A indefinitely with a minimum temperature rise.

Based on the photos my assessment is that there was a high resistance at the boat side wire/plug connection that caused the heat that melted the area around the line lerminal.

I have seen the following issues with DIY installations:
1. Insufficient insulation removed and the clamping screw contacts the conductor partially on the insulation and partially on the copper.
2. Insufficient torque on the screws. Spec is 14-20 inch pounds for the inlet or the plug.
3. Cord seal not properly seated allowing water intrusion.
4. Improper installation of the cord strain relief.

I recommend that the OP contact SmartPlug by email or phone.

Don't forget to mention that people routinely drop their cord ends in the water but then promptly forget that they did it because it continues to work fine until it burns up 6 months later due to corrosion resistance that they can no longer identify because the end is now burned up.