Extension cord splitter gets melty

[Brucey]

So was just going about the day when my Rosie and associated loads shut off.

Power goes from Rosie ac out via 6AWG to this breakout box:

https://www.amazon.com/gp/aw/d/B0CSYPY7Y7

From one of the 5-20 outlets I have one of these 20A extension strips connected:

https://www.amazon.com/gp/aw/d/B094DKJ9GT

Then from this strip I have an extension cord going down to the basement. At the end of that cord I have this three way splitter. Connected were a chest freezer, an upright freezer and another extension cord with no load.






My thought is that the upright freezer was pushed back from its regular position while some furniture was moved a couple days ago and caused the plug to be only partly inserted in the socket leading to heat and arcing and meltiness.

What does seem odd is that the 20A circuit breaker (15A?) in the southwire extension didn't trip, and neither did the no name pos in the outlet box. Rosie shutoff with Over Temp and Peak Over Current faults to stop the magic smoke. I do have the ground floating if that makes a difference, Rosie isn't connected to the grid.

 

[ricardocello]

Wow, scary. What is the total running current of the two freezers (as listed on the nameplates hopefully)?

If the plug wasn't all the way in, maybe the burn marks would look like that, but I'm not sure.
Coincidentally, I own one of those yellow-jacket 3-way splitters too.

What gauge was the extension cord from the power strip to the 3-way splitter? And how long?

I'm thinking there was significant voltage drop, which caused the current to increase, but not above the 20A needed to trip, but enough to melt things on the loose connection. Just guessing.

 

[Brucey]

Wow, scary. What is the total running current of the two freezers (as listed on the nameplate hopefully)?

If the plug wasn't all the way in, maybe the burn marks would look like that, but I'm not sure.
Coincidentally, I own one of those yellow-jacket 3-way splitters too.

What gauge was the extension cord from the power strip to the 3-way splitter?

Maybe 150W between them if that, 7 cuft chest freezer and then 21 cuft upright was the one that scorched.

12 gauge Southwire 50ft top of the line:

https://www.amazon.com/gp/aw/d/B0B9YTJSHD

 

[ricardocello]

Maybe 150W between them if that, 7 cuft chest freezer and then 21 cuft upright was the one that scorched.

12 gauge Southwire 50ft top of the line:

https://www.amazon.com/gp/aw/d/B0B9YTJSHD

Well, you didn't skimp on the extension cord.
Let's see what others think. And I'm glad you found it.

Why did the Rosie shutdown again? Does it log the overcurrent event?

 

[robbob2112]

MMMMM ... melty goodness...

It doesn't cause higher current usage when you have the plug half out, just a bad connection and heat generation - no reason to blow a breaker unless something shorts or pulls more than

Cut the end off and put a new one on... I'd probably cut back a foot on the wire... might use a 2-gang metal box with a clamp on the cord and make certain to connect the ground wire to the shell.

 

[rogerheflin]

What does seem odd is that the 20A circuit breaker (15A?) in the southwire extension didn't trip, and neither did the no name pos in the outlet box. Rosie shutoff with Over Temp and Peak Over Current faults to stop the magic smoke. I do have the ground floating if that makes a difference, Rosie isn't connected to the gr

There would have never been an over-current event. The only device that is made to prevent this sort of issue is the hated AFCI.

It only takes a few amps arcing on a loose connection to generate a lot of heat. If the units are frost free then it might have been when the defrost cycle was running, as that sustains 600w or more for 20-60 minutes or so, and runs 1 or 2x per day on most models.

 

[Brucey]

Well, you didn't skimp on the extension cord.
Let's see what others think. And I'm glad you found it.

Why did the Rosie shutdown again? Does it log the overcurrent event?

Shutdown with a code 217:



Nothing out of the ordinary load wise versus yesterday.

 

[Brucey]

There would have never been an over-current event. The only device that is made to prevent this sort of issue is the hated AFCI.

It only takes a few amps arcing on a loose connection to generate a lot of heat. If the units are frost free then it might have been when the defrost cycle was running, as that sustains 600w or more for 20-60 minutes or so, and runs 1 or 2x per day on most models.

Something caused the Rosie to shut off with an error for "peak overcurrent fault", perhaps it has some type of arc fault detection on the ac output though I've never read of such a thing?

Once I moved the extension strip from the Rosie output to the grid, the strip circuit breaker started to work (would trip off until I unplugged the farked extension cord).

 

[SparkyJJO]

What does seem odd is that the 20A circuit breaker (15A?) in the southwire extension didn't trip, and neither did the no name pos in the outlet box.

Not odd. A bad connection won't increase current draw, so the breakers won't trip. However, if it melted enough, it could have generated a partial short inside there eventually, leading to an overcurrent situation that the inverter responded to faster than the breakers would. Rosie may have killed it after 5-10 seconds of overcurrent, while the breakers would take 15-20 seconds to heat up enough to trip (as an example with numbers pulled out of thin air).

 

[Brucey]

Not odd. A bad connection won't increase current draw, so the breakers won't trip. However, if it melted enough, it could have generated a partial short inside there eventually, leading to an overcurrent situation that the inverter responded to faster than the breakers would. Rosie may have killed it after 5-10 seconds of overcurrent, while the breakers would take 15-20 seconds to heat up enough to trip (as an example with numbers pulled out of thin air).

Makes sense. Midnite specify a 60A AC breaker and can surge to 20kW, so 10kW per leg? So there must be some firmware logic there to protect against such eventualities, excessive slew rate or something. I have an mneac60 breaker ready just not wired in. Will be dispensing with the plastic breakout box and going straight to a metal 14-50 receptacle.

 

[Brucey]

MMMMM ... melty goodness...

It doesn't cause higher current usage when you have the plug half out, just a bad connection and heat generation - no reason to blow a breaker unless something shorts or pulls more than

Cut the end off and put a new one on... I'd probably cut back a foot on the wire... might use a 2-gang metal box with a clamp on the cord and make certain to connect the ground wire to the shell.

The freezer side plug was fine I just wiped down the black goop off the prongs and plugged it into fresh single extension cord, no more splitters. Going to get rid of the 7 cuft chest freezer takes a lot of room and just go with 21cuft upright.