300 Amp Optifuse keeps tripping

[aaronorange]

My 300 amp optifuse keeps tripping when I try to run the Truma AC. It’s pulling around 800-1100 w when the a/c compressor runs. The fuse randomly but often trips. This is the replacement fuse/breaker from Oliver. They sent me a new fuse right after we bought it for the same issue. I was at Oliver last fall getting the Truma a/c installed and asked them about the constant Error 20 code but they had no idea. So this year I’m not getting the error code just the 300 amp Optifuse keeps tripping. And it is very hot when I reach down to reset. Tripped again today (5/21). Everything looks good and tight. 

Edited May 22 by aaronorange

[Geronimo John]

This is serious.  Recommend an immediate call to Jason and Team!

GJ

[John Dorrer]

52 minutes ago, aaronorange said:

My 300 amp optifuse keeps tripping when I try to run the Truma AC. It’s pulling around 800-1100 w when the a/c compressor runs. The fuse randomly but often trips. This is the replacement fuse/breaker from Oliver. I was at Oliver last fall getting the Truma a/c installed and asked them about the constant Error 20 code but they had no idea. So this year I’m not getting the error code just the 300 amp Optifuse keeps tripping. And it is very hot when I reach down to reset. I have been having lots of issues when inverting and error 20 when plugged into 30 amp. Any ideas? 

I experienced this last fall. Jason E. checked out at the Texas Rally and it was diagnosed as a bad inverter breaker. Cables got hot. Oliver switched to a fuse in the 2024 or 2025 models and didn't have any more Zoro breakers.  I bought 2 and will be replacing it this week.  I think you have the same as our 2022 and it is a breaker, not fuse.

Edited May 21 by John Dorrer
Updated Comment

[aaronorange]

Thanks, what exactly did you get as a replacement? I will order a couple. Thanks again 

[John Dorrer]

I went to run the AC off the inverter to bring the lithium batteries down to 50%. Then I plugged in and the 20 error code came on. Xantrex got that resolved. When I touched the cables they were hot 

 

On our trip we went to fix oatmeal in the microwave. We were at 13.7, and battery SOC was 100%.  Set the microwave for 2:15 minutes, and at 30 seconds down to 12.1 and it shut off. 5 minutes later it was  back to 13.7.

 

Hoping the new one will cure the problem. The new trailers use a super fuse that is more reliable than the breaker.

[rich.dev]

1 hour ago, John Dorrer said:

I bought 2 and will be replacing it this week.

John, do you have a link or part# for the new fuse that you bought? 

[jd1923]

1 hour ago, John Dorrer said:

We were at 13.7, and battery SOC was 100%.  Set the microwave for 2:15 minutes, and at 30 seconds down to 12.1 and it shut off. 5 minutes later it was  back to 13.7.

I cannot see that a breaker would cause this voltage drop, in fact how is such a voltage drop possible in 30 seconds unless there is something defective with the source (battery) or the load (microwave).

Actually, since the batteries bounced back to good voltage, I suspect the microwave. The fuse should blow since the voltage drop means an extreme current draw, enough amps to blow the breaker and heat the wires in the interim.

But if the same thing happens when running A/C and Microwave, I would suspect the inverter. A breaker could not cause the voltage drop unless it had a dead short to ground and it would look burned. Strange!

Did OTT talk of cause? Probably not.

Definitely run the same test with the new fuse installed, while observing amp draw on your app.

Time for another bowl of oatmeal! (but be careful)

Edited May 21 by jd1923

[John Dorrer]

1 hour ago, jd1923 said:

I cannot see that a breaker would cause this voltage drop, in fact how is such a voltage drop possible in 30 seconds unless there is something defective with the source (battery) or the load (microwave).

Actually, since the batteries bounced back to good voltage, I suspect the microwave. The fuse should blow since the voltage drop means an extreme current draw, enough amps to blow the breaker and heat the wires in the interim.

But if the same thing happens when running A/C and Microwave, I would suspect the inverter. A breaker could not cause the voltage drop unless it had a dead short to ground and it would look burned. Strange!

Did OTT talk of cause? Probably not.

Definitely run the same test with the new fuse installed, while observing amp draw on your app.

Time for another bowl of oatmeal! (but be careful)

Oliver tested everything and said the breaker is bad. It went bad on 2nd day of ownership. Reset it and all was good and it happened again. Oliver sent a replacement. I went 2-1/2 years and it failed again. I will know on Friday, when I replace it. I will post up after I test it.

[John Dorrer]

2 hours ago, rich.dev said:

John, do you have a link or part# for the new fuse that you bought? 

Yep. I will get it posted up 

[John Dorrer]

2 hours ago, rich.dev said:

John, do you have a link or part# for the new fuse that you bought? 

[Rolind]

I can’t speak to the breaker tripping, but we had a repeated issue with error 20 that was resolved with firmware updates for the xantrex. I seem to remember there were three updates, one for the inverter, one for the remote and one for communications.  There are kind of a pain with multiple steps and very specific folder names but otherwise easy.  Good luck. We have no had any breaker tripping issues. 

[aaronorange]

That’s the same Optifuse breaker Oliver sent after I first reported the problem. Could I possibly have gotten 2 bad breakers?  Back to the drawing board…

[jd1923]

1 hour ago, aaronorange said:

That’s the same Optifuse breaker Oliver sent after I first reported the problem. Could I possibly have gotten 2 bad breakers?  Back to the drawing board…

Time for anybody needing to replace the main breaker, get a fuse and fuse holder instead. Fuses protect bidirectionally, meaning they will protect the power source (battery) and the load, inverter and/or other loads.

Breakers are OK for like a 40A or 60A DC branch, but not on the 4/0 cables between battery and inverter. A fuse will protect a ground fault at the batteries or at the inverter and a breaker will only protect one side, depending on which direction it is wired.

In our older hull, OTT had wired a 250A ANL fuse and holder between the batteries and our original 2KW inverter (check inverter manufacture's spec for correct fuse amps). When I upgraded our inverter I only needed to get an ANL for higher amperage.

You can even better protection with Class-T fuses ($$$) but ANL will perform much better than the breaker shown above and certainly is good enough. 

I would suggest these. The Blue Seas holder is rated to 750A. They have a smaller 300A holder for less money, but this one is nice, with two pairs of mounts which allows you to change the fuse without loosening the battery cables. The second link assumes you need a 300A fuse. Enjoy! 😂

https://www.amazon.com/Blue-Sea-Systems-Block-Insulating/dp/B001VIVWAW/

https://www.amazon.com/Blue-Sea-Systems-5133-300a/dp/B07D1VJ7BM/

[CRM]

5 hours ago, jd1923 said:

Time for anybody needing to replace the main breaker, get a fuse and fuse holder instead. Fuses protect bidirectionally, meaning they will protect the power source (battery) and the load, inverter and/or other loads.

Breakers are OK for like a 40A or 60A DC branch, but not on the 4/0 cables between battery and inverter. A fuse will protect a ground fault at the batteries or at the inverter and a breaker will only protect one side, depending on which direction it is wired.

 

I would like to learn more about this "bidirectional" protection. I realize fuses and breakers operate differently, have different reaction times, have their own strengths and weaknesses, etc.. but I've never heard anyone talk about their directionality in a DC circuit where the flow is only in one direction. Both respond to the amount of current flowing through them and I'm just having a hard time wrapping my head around this one. 

[CRM]

17 hours ago, aaronorange said:

My 300 amp optifuse keeps tripping when I try to run the Truma AC. It’s pulling around 800-1100 w when the a/c compressor runs. The fuse randomly but often trips. This is the replacement fuse/breaker from Oliver. They sent me a new fuse right after we bought it for the same issue. I was at Oliver last fall getting the Truma a/c installed and asked them about the constant Error 20 code but they had no idea. So this year I’m not getting the error code just the 300 amp Optifuse keeps tripping. And it is very hot when I reach down to reset. Tripped again today (5/21). Everything looks good and tight. 

Do you have a digital volt/ohm meter? If so, you can do a voltage drop test of your cables and connections while under load to determine what is causing the excessive draw to trip your breaker. If only the breaker is getting warm I would test across both terminals of it first. With a 1000 watt load and using the millivolts scale on your meter you should read less than 15mV. Much more over that and the breaker is bad. 

[jd1923]

4 hours ago, CRM said:

I've never heard anyone talk about their directionality in a DC circuit where the flow is only in one direction.

Flow in a DC circuit is in two directions which you can see when you observe the battery or inverter apps. If it is showing -A then current is flowing from the battery (source) to the load that is using the current (inverter or any DC device, lights, etc.). When the app is show +A a connected charger is supplying current back to the batteries.

The breakers used for RV and marine use are directional, meaning they will only "break" when there is a ground fault on one side. They are generally wired so that if the B+ is grounded somewhere in line past the breaker it will break to protect the batteries. In this configuration, if the 4/0 cable was to be grounded before the breaker, like say someone wrenched the positive cable to remove it from the battery post and they accidently hit the negative with the wrench, or the B+ and B- cables touch in any way, the breaker would not break and the battery would quickly overheat and fry if the connection was allowed to persist. Likelihood of this is relatively low, so hence the use of breakers is common. BTW when removing battery cables always remove the negative first and when installing always connect the positive first so that you do not create this situation.

There may be another rare case, though I'm not certain this case is true, where somehow a shore power connected charger pushed way to many amps to the batteries. Highly unlikely, but the fuse would protect in this case and the breaker would not (the breaker only looking for ground fault, not excessive current in the opposite direction). Confusing stuff, right?

Breakers are generally less dependable in their design as noted in the experience of many of you in this post and others. And the options available today with rare exceptions are cheaply made in China. They are convenient for those that do not want to replace a fuse and great for household use where to ground the wrong side you would have to have the power panel open. When a fuse blows there is definite reason. Have an extra on hand, but do not install the extra until you determine the cause of the blown fuse, as the fuse is not blowing itself like the defective breaker.

Edited May 22 by jd1923

[CRM]

1 hour ago, jd1923 said:

Flow in a DC circuit is in two directions which you can see when you observe the battery or inverter apps. If it is showing -A then current is flowing from the battery (source) to the load that is using the current (inverter or any DC device, lights, etc.). When the app is show +A a connected charger is supplying current back to the batteries.

The breakers used for RV and marine use are directional, meaning they will only "break" when there is a ground fault on one side. They are generally wired so that if the B+ is grounded somewhere in line past the breaker it will break to protect the batteries. In this configuration, if the 4/0 cable was to be grounded before the breaker, like say someone wrenched the positive cable to remove it from the battery post and they accidently hit the negative with the wrench, or the B+ and B- cables touch in any way, the breaker would not break and the battery would quickly overheat and fry if the connection was allowed to persist. Likelihood of this is relatively low, so hence the use of breakers is common. BTW when removing battery cables always remove the negative first and when installing always connect the positive first so that you do not create this situation.

There may be another rare case, though I'm not certain this case is true, where somehow a shore power connected charger pushed way to many amps to the batteries. Highly unlikely, but the fuse would protect in this case and the breaker would not (the breaker only looking for ground fault, not excessive current in the opposite direction). Confusing stuff, right?

Breakers are generally less dependable in their design as noted in the experience of many of you in this post and others. And the options available today with rare exceptions are cheaply made in China. They are convenient for those that do not want to replace a fuse and great for household use where to ground the wrong side you would have to have the power panel open. When a fuse blows there is definite reason. Have an extra on hand, but do not install the extra until you determine the cause of the blown fuse, as the fuse is not blowing itself like the defective breaker.

Ok, now I think I understand what you're talking about. I was breaking it down into a simple DC circuit in my brain and not thinking about the charging aspect (like i should have) which is where your scenario of taking the B+ off the battery and shorting it makes sense. That said, I still the Optifuse breaker  shown above would trip in this scenario since they react to current flowing through them and break thermally. The breaker in my Ollie doesn't even have B+ and load terminals on it which is what I would expect if it were directional. I did see where there are directional breakers available but they all seem to work magnetically instead. I do agree with you that fuses are the way to go, though, and will definitely be using them when I finally get around to installing solar.

[John Dorrer]

On 5/22/2025 at 1:54 AM, jd1923 said:

Time for anybody needing to replace the main breaker, get a fuse and fuse holder instead. Fuses protect bidirectionally, meaning they will protect the power source (battery) and the load, inverter and/or other loads.

Breakers are OK for like a 40A or 60A DC branch, but not on the 4/0 cables between battery and inverter. A fuse will protect a ground fault at the batteries or at the inverter and a breaker will only protect one side, depending on which direction it is wired.

In our older hull, OTT had wired a 250A ANL fuse and holder between the batteries and our original 2KW inverter (check inverter manufacture's spec for correct fuse amps). When I upgraded our inverter I only needed to get an ANL for higher amperage.

You can even better protection with Class-T fuses ($$$) but ANL will perform much better than the breaker shown above and certainly is good enough. 

I would suggest these. The Blue Seas holder is rated to 750A. They have a smaller 300A holder for less money, but this one is nice, with two pairs of mounts which allows you to change the fuse without loosening the battery cables. The second link assumes you need a 300A fuse. Enjoy! 😂

https://www.amazon.com/Blue-Sea-Systems-Block-Insulating/dp/B001VIVWAW/

https://www.amazon.com/Blue-Sea-Systems-5133-300a/dp/B07D1VJ7BM/

Oliver went to the Large Fuse starting with the 2024 or 2025 trailers. I asked Jason what the cost was with this new system. Maybe $1,200+/-. He suggest I stick with the breaker. Tomorrow I will contort my body to replace the breaker.

Edited May 23 by John Dorrer
Updated Comment

[John Dorrer]

Changed out the inverter breaker.  Turned batteries on, then inverter breaker, and finally solar.  Waited a few minutes and turned on the inverter at the remote.  Everything fired up.  I then placed a cup of water in the microwave for 2:15 minutes and it worked as it should have.

 

After speaking to Jason E. at the Mothership in February, Oliver is no longer installing the breaker system.  They are installing a more robust fuse. 

 

JD, I agree with you on the use of a fuse vs. breaker.  I asked Jason what the cost to switch out and it was, I believer over4 $1,000.  Jason suggested I stick with the breaker.

 

Hopefully this will last for awhile.  I bought 2 breakers, so I have one in the closet.

[jd1923]

2 hours ago, John Dorrer said:

JD, I agree with you on the use of a fuse vs. breaker.  I asked Jason what the cost to switch out and it was, I believer over4 $1,000.  Jason suggested I stick with the breaker.

John, if you like and when you make it out to Arizona, buy the parts I listed above (just $100 with tax and including a backup fuse) and in an hour, we'll make the change.

Service costs for custom work (most auto/RV service) is crazy these days! I could not afford our Oliver and tow vehicle, let alone the many other vehicles on our property if I had to pay for service. It's a labor of love! Hull #113 made it to the Mothership for service twice prior to our ownership, but not likely again. It's too far (that cost alone is infeasible for us), too much in service costs and it's well beyond warranty!

I have a service policy here. When one vehicle breaks down, I park it until I have time to make the repair. In the meantime, I switch insurance to another that is ready to go! We also have cars for fair-weather driving and AWD trucks for winter. My insurance agent loves me! 🤣