Check your Fuse and Buss Bar Connections

[IslandHopper]

After a run on the boat last week, we were running the inverter while docked, doing our routine cleanup and running the AC and various other loads totaling around 180 amps. While I was flushing the drains and scuppers with the hatches open and I started to smell the familiar scent of burning wire, looking over at the port side hatch I saw a wiff of smoke. In a panic we shut everything down with fire extinguishers ready and I started feeling wires and visually tracking down where the smoke came from, which was the Inverter Fuse Block that had melted

After some troubleshooting, I determined that the 350A ANL Fuse for the Inverter was installed incorrectly, with the stainless washer in between the fuse and the buss. I won’t get into the technical details (unless someone wants), but in this configuration the stainless washer adds resistance, which is heat, which can lead to a fire.

Upon further investigation, I noticed that the Main Fuse and connections to the Main Buss also had similar incorrect installations.

I’d just like to suggest to everyone – next time you are on your boat (no matter what make or model), have a quick look at the fuse connections and all buss connections. If there is a washer in between the cable connector and buss – fix it or take it to a dealer that will install it correctly. Look up the manufacturers’ model for the fuse and buss blocks and ensure they are installed and torqued to proper specifications.

Our boat is a 2025 R27 LE with a 640A Lithium House battery bank. The Blue Sea Systems ANL fuse block has a Maximum torque spec of 107 in Lbs. The BEP Main buss Recommended torque is 190 in lbs (15.9 FtLbs). Please verify your specific models with manufactures specifications.

 

[Maggie Anne]

I was surprised a bit but on doing a bit of research google tells me
Yes, stainless steel washers can add significant and problematic resistance to an electrical circuit. They possess only about 8% the electrical conductivity of copper. In high-current applications, this high resistance generates dangerous heat, potentially causing blown fuses, melted fuse holders, or fires

 

[CapBonnieB]

Thank you for letting everyone know. This is a very important warning and the assessment is spot on.

 

[qirmdr]

After a run on the boat last week, we were running the inverter while docked, doing our routine cleanup and running the AC and various other loads totaling around 180 amps. While I was flushing the drains and scuppers with the hatches open and I started to smell the familiar scent of burning wire, looking over at the port side hatch I saw a wiff of smoke. In a panic we shut everything down with fire extinguishers ready and I started feeling wires and visually tracking down where the smoke came from, which was the Inverter Fuse Block that had melted
View attachment 27712
After some troubleshooting, I determined that the 350A ANL Fuse for the Inverter was installed incorrectly, with the stainless washer in between the fuse and the buss. I won’t get into the technical details (unless someone wants), but in this configuration the stainless washer adds resistance, which is heat, which can lead to a fire.
View attachment 27713
Upon further investigation, I noticed that the Main Fuse and connections to the Main Buss also had similar incorrect installations.
View attachment 27715

I’d just like to suggest to everyone – next time you are on your boat (no matter what make or model), have a quick look at the fuse connections and all buss connections. If there is a washer in between the cable connector and buss – fix it or take it to a dealer that will install it correctly. Look up the manufacturers’ model for the fuse and buss blocks and ensure they are installed and torqued to proper specifications.

Our boat is a 2025 R27 LE with a 640A Lithium House battery bank. The Blue Sea Systems ANL fuse block has a Maximum torque spec of 107 in Lbs. The BEP Main buss Recommended torque is 190 in lbs (15.9 FtLbs). Please verify your specific models with manufactures specifications.

Just to confirm what I am assuming as I didn't see it specifically stated in your post. The stainless washer should be between the bolt and the fuse?

 

[CapBonnieB]

chromiumJust to confirm what I am assuming as I didn't see it specifically stated in your post. The stainless washer should be between the bolt and the fuse?

Yes. Stainless steel is not as good as a conductor due (in part) to the same oxide (Nickel and chromium oxide)that helps prevent corrosion. As the washer heats up more oxide is generated and this exasperates the problem causing more heat. Put the fuse directly into contact with the conductor bar and the washer under the nut.