A/C Breaker Panel

BonesD said:

So, the electrician came today.
I showed him what had happened and told him the circumstances. Turns out no one device had issue. Looks like just a bad connection that got worse with load. It’s a 30 amp service and the main double gang 30 amp breaker doesn’t trip with more than 30 + amps. Also doesn’t trip the dockside 30 amp breaker. The heater is hooked up directly to the main breaker so does not have its own breaker.
I will be replacing the 40 + year old panel with new and and adding an extra breaker or two. I will have to watch my usage.
Did you ever watch Green Acres where all the electrical had numbers and a complicated system that had to be followed so not to burn up the farm generator?

Lived to tell about it so that is a good thing.

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Sounds like a good plan. You can always use more breakers for expansion.

Xsbank said:

30 amp supply, tv, lights and then a heater? What else was on?

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All the interior lights are LED so I can run to heaters and then nothing more.

BonesD said:

The heater is hooked up directly to the main breaker so does not have its own breaker...

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Oooooh that's a no no!

Good for you to make it right now.

Ah, yes, the verdigris. Cutting back the wire to find good wire may prove unsuccessful. Likely there is insufficient slack with which to work and the entire run will need to be replaced. Here is an experience I had this summer while at anchor.

It was hot and we wanted to turn on the AC for awhile. The breaker to my 7.7kw generator popped. I thought maybe I had overloaded the system so I reset it. It popped again. I went to the breaker box, a separate Square D affair, and it was HOT to the touch. I also have a 12.5kw generator so I started that one up. When I got back home I started exploring. Opening up the box on the generator I found the two supply wires from the brushes on the generator head where they were connected to the one lead to the breaker box had corroded badly, so bad that the insulation fell away when touched and individual wire strands had broken inside. That situation was obviously the cause of the heat and it was dumb luck that a fire did not occur. Anyway, I thought, simple, just cut the wire back to good, butt splice new wire, and reconnect. Nope! Those two brush wires were corroded way back. They were hopeless. I need to replace the brushes which will have new wires attached, a winter-time project. I still have the other generator on-line so no big deal in this case.

So, it it were I, I would, as others have suggested, be replacing a LOT of wire. It's like replacing wheel bearings on a pickup truck. When one side fails, the other is not far behind.

oscar said:

The verdigris is the smoking gun.... (pun intended). You need to remove stuff until you get to fresh shiny copper, and replace with fresh shiny tinned of the appropriate gauge. You may be replacing a lot.

And since you are going to spend a lot of quality time messing with this you may consider re-doing it all with 21st century stuff. It'll feel good when you're done. Except in your wallet, but hey.... it's a boat.

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oscar said:

The verdigris is the smoking gun.... (pun intended). You need to remove stuff until you get to fresh shiny copper, and replace with fresh shiny tinned of the appropriate gauge. You may be replacing a lot.

And since you are going to spend a lot of quality time messing with this you may consider re-doing it all with 21st century stuff. It'll feel good when you're done. Except in your wallet, but hey.... it's a boat.

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My bet is, that verdigris occurred after the wire overheated some time ago, exposing the conductor, which means this isn't a new phenomenon. It's rare for it to occur under intact insulation. When a wire heats up like this, it makes the copper especially prone to corrosion from atmospheric moisture alone.

Regardless, this system needs to be inspected carefully. This could be the result of a poor crimp terminal, a loose screw connection or undersized wire/over sized over current protection. When I check, I can often get a half a turn or more on many high current terminal screws, that alone could cause this.

If you don't already have smoke detectors aboard, you should, and you should have one behind all electrical panels. More on those here https://stevedmarineconsulting.com/wp-content/uploads/2018/06/Smoke-Detectors-gearhead-may-2018.pdf

Olebird said:

And the take away is - breakers will not protect you from over heating corroded high resistance connections. In older boats - an IR scan of wiring from time to time is not a bad idea. A very good Fluke or FLIR IR scanner can be rented by the day and could save your bacon. Was more than likely the cause of the Scottsboro Marina fire.




https://jmtest.com/c/rental/rent-electrical-test-equipment/thermal-imaging-camera-rental/

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A Harbor Freight laser temp gun would have indicated trouble....but only if you know what it NORMALLY runs.

Spot check some things and get an idea of where they ought to be temp wise. Stuffing Box, muffler, Electrical Panel. Note it somewhere....heck note it right where you test it on a piece of tape until you know what normal looks like.

This was likely an arc fault.

State Farm is piloting an arc fault monitoring program using "TING" for homes. I have one on my house which is 70 years old. It "listens" for the sound of an arc fault and notifies you immediately.

I bet this same tech would transfer to the boats.https://www.tingfire.com/about/electrical-fire-problem/

I like to check the screws to see if they are tight in the summer as they will be warmer and looser that in cold weather.

Guys this is simply a loose connection that had current flowing through it.

Pretty standard failure mode BTW.

Replace the components that burned up, check the rest of the connections for tightness and go about your happy life.

BTW a standard breaker will not detect this and operate. A GFCI will not detect this and operate.

This is the kind of thing that Arc Fault breakers were designed to detect and protect against.

Steve DAntonio said:

My bet is, that verdigris occurred after the wire overheated some time ago, exposing the conductor, which means this isn't a new phenomenon. It's rare for it to occur under intact insulation.

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Color aside, I have stripped back wires as much as 5-6" and found oxidation.....

If you replace the panel, suggest you consider making up the connections on a backplane vs direct to the breakers. I can't find a picture of my main panel, but here's a Pic of the backplane. Having a custom panel made was about $1000 more expensive than a Blue Sea semi-custom configuration, but so worth it in my opinion if only for the backplane.

oscar said:

Color aside, I have stripped back wires as much as 5-6" and found oxidation.....

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The conductor is green under intact insulation? Without exposure to air/atmospheric moisture that's just not possible. Now, if the wire was submerged, that's different.

Steve DAntonio said:

The conductor is green under intact insulation? Without exposure to air/atmospheric moisture that's just not possible. Now, if the wire was submerged, that's different.

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Steve D. - The picture attached is of the hot wire connection that I found in my generator connection box when I discovered the breaker hot to the touch after having popped. The two wires on the left are the two hot wires from the brushes. The wire on the right is the hot wire to the breaker. What you see is after I removed the vinyl tape from the bundled three wires. It is not clear from the pictures but there was corrosion in both wires from the generator brushes. There was a lot of tape around the connection. The exposed wire you see was after I removed the tape and the insulation crumbled away. So, I am not understanding how that corrosion got there with no (apparent) exposure to air and certainly no exposure to water. I guess somehow there was a path to air exposure.

Now isn't that a frightening method of making that connection? You can see that a number of strands are broken. They were quite brittle no doubt from heat generated from resistance in the circuit. I had hoped to cut back the brush wires to find good wire to make make a butt connection and then rewire everything to a bus bar but the wires were brittle at least another six inches where it disappeared into the genset head. I now have to replace the brushes. Anyway, I thought I would share this picture with you.

That is a well supported connection, not...

catalinajack said:

Steve D. - The picture attached is of the hot wire connection that I found in my generator connection box when I discovered the breaker hot to the touch after having popped. The two wires on the left are the two hot wires from the brushes. The wire on the right is the hot wire to the breaker. What you see is after I removed the vinyl tape from the bundled three wires. It is not clear from the pictures but there was corrosion in both wires from the generator brushes. There was a lot of tape around the connection. The exposed wire you see was after I removed the tape and the insulation crumbled away. So, I am not understanding how that corrosion got there with no (apparent) exposure to air and certainly no exposure to water. I guess somehow there was a path to air exposure.

Now isn't that a frightening method of making that connection? You can see that a number of strands are broken. They were quite brittle no doubt from heat generated from resistance in the circuit. I had hoped to cut back the brush wires to find good wire to make make a butt connection and then rewire everything to a bus bar but the wires were brittle at least another six inches where it disappeared into the genset head. I now have to replace the brushes. Anyway, I thought I would share this picture with you.

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Electrical tape over a conductor is far different than proper, molded insulation, which is essentially air-tight.

I assume this has been worked in previously, if it was taped rather than insulated?

Steve D. - The original connection had all three three leads fastened thru that ring terminal and all three on the same plane. My plan was to extend the two generator brush leads - the two on the left - to a bus bar including the generator feed line. The lead to the right is the hot wire back to the panel through a Square D circuit breaker. That breaker box was the one too hot to touch. Anyway, the three leads were all well-wrapped with tape into a single bundle including the ring terminal with the short bolt. I removed the tape, with difficulty. The exposed wire you see is the result of the insulation having just crumbled away in my hand probably due to excessive heat. If you look closely you can see a crack in the insulation where the insulation ends.

This is not how I would have made that connection but, intuitively, I do not understand why this method failed, why these wires became cooked. My guess is that the Square D circuit breaker failed in some way and that created too much resistance in the circuit. Steve, if you had felt how hot that box was you would understand why I consider myself lucky that a catastrophic fire did not occur.

I am not even certain that a circuit breaker in the feed to the breaker panel is required given that there is main breaker in the panel that takes the generator feed, especially since the other generator we have on board - still working - is not wired through an independent breaker, at least as far as I can see.

As for the corrosion, it's a mystery to me how it could have occurred given how well-wrapped that three-wire bundle was.

Steve DAntonio said:

Electrical tape over a conductor is far different than proper, molded insulation, which is essentially air-tight.

I assume this has been worked in previously, if it was taped rather than insulated?

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The failure (overheated wire insulation) in #42 was probably caused by the lack of a proper spring washer in the stack of terminal ends.

In use the ends will get warmer and cooler as the loads change. This heating and cooling changes the thickness of the wire stack , eventually the stack will loosen and overheat .

A copper star washer will help keep the stack of terminals tight to each other ,a great rain day project to clean the terminal ends and stick in a star washer, as a box of 100 is inexpensive .

FF said:

The failure (overheated wire insulation) in #42 was probably caused by the lack of a proper spring washer in the stack of terminal ends.

In use the ends will get warmer and cooler as the loads change. This heating and cooling changes the thickness of the wire stack , eventually the stack will loosen and overheat .

A copper star washer will help keep the stack of terminals tight to each other ,a great rain day project to clean the terminal ends and stick in a star washer, as a box of 100 is inexpensive .

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FF, I didn't know that. But, in this case, the connection was rock-solid tight or so it seemed when I took it apart. I am still at a loss. In any case, when I replace the brushes, the new wires will go to a bus bar. There is plenty of room in the covered connections box on the generator to mount a bus bar.