Serious Electrical Short - Why didn't the circuit breaker trip?

[Jimmer]

On May 6, 2022, I'm towing my 2021 Reflection 2021 Travel Trailer from my house to Great Meadows Campground in Shenandoah National Park. After about 1 hour and 15 minutes of driving, I pull over to the side of the road to make sure my batteries are not getting run down by run my absorption Norcold 1210 fridge running in AC mode off of the inverter. Batteries are near 95% but I turn the fridge off of AC as I have a mountain to climb and don't want any extra load from the alternator. When I was outside of the camper, I smelled something electrical burning, and I looked around, but didn't notice anything. The inverter was working fine, RV batteries are charged, things seem like they're OK, no smell of burning noticable in the RV at the control panel.

45 minutes later, we pull into the campground, and the Victron Multiplus II 2X120 is no longer inverting. On the Victron touch panel, there's an inverter overload fault. This inverter can put out a constant 2400 Watts. At 120 volts, that's 20 amps. At this time, the fridge was not on AC power, so there was effectively no load on the inverter, yet it shut down due to an overload. I turned the inverter back on and there was an immediate overload of the inverter. I turned off the main 50 amp circuit breaker of the RV power panel and again turned on the inverter: no overload. I turned off all individual 120 volt circuit breakers and turn on the main 50 amp breaker, no problems. I turn on the breakers one by one, and as soon as I turned on the electric fireplace circuit breaker, the inverter goes into an overload. As long as I kept the fireplace circuit breaker off, everything worked perfectly so it was a good weekend. (Note that when I was traveling, the fireplace was turned off.)

Today, I investigate, and the connection where the solid romex 120 volt wire transitions to the flexible 120 volt for the slide/fireplace wiring looks suspicious. There had to be short inside of this connection assembly.

(1) why did it take 14 months of use for this short to happen?
(2) why did the inverter which can put out a constant 20 amps turn off (and thankfully save a fire from happening) instead of the 15 amp breaker for the fireplace trip?

Here are the pics:

[Cate&Rob]

Grand Design uses Molex connectors (like in your pictures) to connect the solid copper house wire to stranded flexible wire for the transition to a moveable slide. These connectors are not watertight and must be kept in a dry location. There have been problems in the past (resulting in a recall) with these connectors lying in water in the underbelly, corroding and shorting similar to your pictures. To create this much heat must have been a high resistance short, drawing less than the 15A which would have opened the 15A breaker. Why the inverter was able to sense this, but the breaker did not, is an interesting question.

Rob

[howson]

Jimmer
First--super glad it wasn't any worse than what is shown in your pictures. As Cate&Rob has mentioned, there was a recall for this exact condition. See https://gdrvowners.com/forum/operati...number-20v-362

Regarding your circuit breaker vs inverter question, according to a Victron Webinar (snip below) in a Max Power (output voltage less then normal) condition (I interpret this could be as severe as a short) the inverter will stay powered for 30 cycles. Since our inverters operate at 60Hz, that means the inverter reacts to the overload within 1/2 second. I suspect that's faster than the circuit breaker can heat up and open.



Howard

P.S. Victron Webinar is here: https://www.youtube.com/watch?v=4SXtGIx0x5w

[Jkwilson]

Not a short. Things would have been damaged much more severely or the breaker would have tripped with a short. Likely you had a loose connection that may have arced some and definitely got hot. No extra current, so the breaker didn’t trip.

[Jimmer]

Thank you all for the quick replies. Based on what people wrote, I believe water got into the connection:

(1) It was raining pretty hard on the drive when this happened
(2) the foam sealant around the hole where the 3 AC lines exit through the side of the frame was not completely sealed at the top. The top Molex connector is the one that fried.

I'm going to rig up a test outlet directly to the circuit breaker that was used for the fireplace, and see if how much current it takes to trip the breaker.

Jkwilson , The fireplace was turned off when this happened, and that AC line is dedicated to just the fireplace. A loose connection would not generate heat if there was no current running through wire since the fireplace was off. Water inside the connection causing the short makes the most sense, especially as there was a recall for because when water gets into the connection, this type of heat can be generated.

Lesson to all: Make sure the hole where the AC wires pass through your frame to the slides is properly sealed and water cannot follow the wires through the frame into the Molex connectors. In the picture below, the round wires are the ones for AC. Be sure those wires are completely sealed up where they pass through the frame.

[Jlawles2]

It is possible that the connector issue was drawing less than 15 amps and the combined usage of all things on the inverter exceeded the wattage. What other items are running on the inverter? Were any of them active at the time?

[ncitro]

Jimmer i never really loved those connectors. I only have a couple in mine (only one living room slide) but I replaced them with a couple of these I had laying around from another project. I definitely did not pay this price, either they've gone way up or it's one of those things cheaper in stores.

Woodhead 15W33 Watertite Wet Location Straight Blade Connector, Yellow - Heavy-Duty Industrial Plug with Strain Relief Cord Seal, 2 Pole/ 3 Wire, 20 A 125V Rating https://www.amazon.com/dp/B0025Q4J2M...ing=UTF8&psc=1

[howson]

Jimmer

Since sorting out the electrical wires under my 315 (part of the "soft hose project") I've learned quite a bit about Molex connectors. Next time the coroplast comes down for whatever reason I'm going to add Molex's weathertight boots. One of the variant's spec sheet is attached, too, downloaded from here: https://www.mouser.com/ProductDetail...252B0Xlw%3D%3D

[howson]

Jimmer -- was the gap in the coroplast a result of the work done on your 315RLTS by Lippert (leveler gear) or MORryde (IS and brake install) or was this an original OEM factory install issue?

[Scott'n'Wendy]

Why it didn't trip? A standard Breaker takes a sustained high current demand. An arc is very transient. There are arc breakers that will trip in that situation, but they are not installed in RV's.

[Jimmer]

Jimmer -- was the gap in the coroplast a result of the work done on your 315RLTS by Lippert (leveler gear) or MORryde (IS and brake install) or was this an original OEM factory install issue?

Howard, based on timing, I was looking to blame Lippert or MORryde. However, the coroplast was in place. If you look at my picture form post 5 of this thread, you can see the connectors/wiring for the back/driver's side leveler. There wasn't much of a gap were that wire went between the frame and the coroplast, but I really wasn't paying too much attention to that when I took down the coroplast. I did notice that the spray-in foam insulation sealing up the wiring at the frame had a bit of a gap in it where the three 120 volt lines exit through the frame. I believe that the water came in because the spray in foam came out of place due to age.

Why it didn't trip? A standard Breaker takes a sustained high current demand. An arc is very transient. There are arc breakers that will trip in that situation, but they are not installed in RV's.

Scott, yes I looked up how a standard breaker works, and it does take a sustained over current. One web site I just found says that the breaker can still be in spec and not trip at 1.4X the rated current (21 amps), and at 30 amps, the breaker will not trip for at least 100 seconds. So, I'm really lucky that this happened when I was running off of the inverter and not shore power, because the inverter shut down first!! (Note, there was nothing running off of the inverter at the time. The output of the inverter according to my Victron touch screen when nothing is running is 24 watts (draw from the microwave display, clothes washer display, etc.).

[Jimmer]

Jimmer

Since sorting out the electrical wires under my 315 (part of the "soft hose project") I've learned quite a bit about Molex connectors. Next time the coroplast comes down for whatever reason I'm going to add Molex's weathertight boots. One of the variant's spec sheet is attached, too, downloaded from here: https://www.mouser.com/ProductDetail...252B0Xlw%3D%3D

Howard, thanks for this information. I think I'll be replacing the original connectors now with watertite connectors. Note that you don't have to take down the coroplast to do this job. There are merely two philips head screws holding the wire-passthrough section to the frame. Simply take out those two screws and the original non-water-tight Molex connectors can come right out through the hole in the frame. See picture 5 of this post to get an idea of what I mean.

[Scott'n'Wendy]

Scott, yes I looked up how a standard breaker works, and it does take a sustained over current. One web site I just found says that the breaker can still be in spec and not trip at 1.4X the rated current (21 amps), and at 30 amps, the breaker will not trip for at least 100 seconds. So, I'm really lucky that this happened when I was running off of the inverter and not shore power, because the inverter shut down first!! (Note, there was nothing running off of the inverter at the time. The output of the inverter according to my Victron touch screen when nothing is running is 24 watts (draw from the microwave display, clothes washer display, etc.).

Breakers are handy, but fuses protect you better.

[Cate&Rob]

I ran into similar corrosion problems with corrosion of those Molex connectors on my much earlier build Reflection. At that time, the wires came out though a similar hole in the frame rail, but there was no closeout plate. The Molex connectors require at special crimping tool and the connection to the wires is by knife slots which I don't think is a good idea for connection points that are going to bounce during travel. The recall fix for this situation is for a dealer to secure undamaged Molex connectors to something higher up to keep them dry and to replace any suspect connectors. Since I was looking for a fix well before the recall. I used standard extension cord replacement ends, one side for the solid copper house wire and the other side for the stranded flexible wire. This allowed me to use the screw terminals inside these connectors which can be secured with hand tools and are (in my opinion) better in a moving environment. I secured these (three white connectors in the upper left of the 3rd picture) as high as possible under the main floor where they have remained dry and secure for several years. Inside the coroplast is a yet another "rat's nest" of wiring (2nd picture). Something else to tidy up if you drop the coroplast to get these connections to a dry location.

Rob

[Jimmer]

There are non-water resistant connectors of 120 volt lines being used in an area subject to moisture. The "fix" which suspended the molex connectors off of the coroplast keeps them in the air and attached the frame. However, this is still an area that is somewhat wet. Here are pictures of the wires passing through the frame for the dinette/recliner slide. The foam on this side has fallen off, and you can see a small part of the molex connector. I think I'm going to order the water resistant connectors of Howards post to prevent this from happening again.