Converter fuses blown, twice in 2 years, problem?

[WineStream]

I'm not electrical guy so I've never paid much attention to the two 30A fuses on the back side of my IOTA DLS-45 converter. I know they are there, but not exactly what/how they protect. Almost 2 years ago, I had an electrical "loss" to 12V while camped at a campground. I had not "just hooked up"...I had been hooked up there for over a day. Nevertheless, I troubleshot to the converter and found both 30A blade fuses blown. I replaced them and went on with life. Now, almost 2 years later, I return home from a problem-free camping trip this last weekend and proceed to hookup the trailer in the front year as we unpack and clean. All was well until this afternoon when I went out there and noticed the fantastic fans operating very slow (this was the only load still on the 12V system). I did the usual checks and eventually was led to the converter and found, again, both 30A fuses blown. I replaced them and as of now, all is still well.

I checked on IOTA's website and the fuses are labelled as reverse polarity fuses. So why the heck have they blown twice now when connected to a steady, known-good source? To me, a fuse is something that blows when there's a problem. It really isn't something that should happen during "steady-state" unless something changes. Can fuses get "old"? This doesn't seem likely as there's a number of them in my 2000 Ford that have never blown. Any other ideas from the electrical guys out there why my "reverse polarity" fuses might be blowing about every 2 years on my converter? As much as it's not often, it also sucks to have to replace them.

[HowieE]

I have to ask how you know you were connected to a "Good Source". If the polarity at the campground was reversed most 120 volt items would work and you would not notice anything. However it would blow the fuses and you would be running on the batteries all weekend as far as the 12 volts system was concerned. The fact that you mention the fan was running slow indicates the batteries were almost dead. Was the frig still running when you got home? It would stop at about 9 volts.

Replace the fuses and carries a receptacle tester, a few bucks at the Big Box Store, for the future.

[jm2]

Originally Posted by WineStream

I checked on IOTA's website and the fuses are labelled as reverse polarity fuses. So why the heck have they blown twice now when connected to a steady, known-good source? To me, a fuse is something that blows when there's a problem.

Any other ideas from the electrical guys out there why my "reverse polarity" fuses might be blowing about every 2 years on my converter? As much as it's not often, it also sucks to have to replace them.

Jason,

essentially the same story as yours with our Iota unit one year ago, when the unit was two years old.... ask for your RMA now - the 3rd time the fuses blew, the unit output became 0 volts....

and yes, the fuses are a pita to release and replace!

best,

[TG Twinkie]

The fuses are on the load side (12v DC) they are there to protect the converter if the battery or solar panel is connected wrong. They don't have anything to do with the 120 volt AC.
There is no such thing as "reverse polarity" in an AC circuit. Thus the name alternating current. AC reverses polarity 60 times per second. ie 60 cycle or 60 hertz.
I would suspect something like a surge or short circuit. Perhaps when plugging or unplugging the UCord from the TV. It may be possible to blow these fuse if the AC power source connections are reversed and the neutral side if the AC wiring is connected to the chassis. The neutral side of the AC power wiring in the trailer should not be connected to the chassis in any way. It is called a "floating neutral" and even if the AC power is connected wrong would not make the chassis hot. If the chassis becomes hot because the neutral and hot leg on the AC side are reversed. Then somewhere in the trailer there is a neutral either wired to or shorted to the chassis. This situation is a safety hazard and should be resolved without delay.
The converter I have uses the new automotive spade type fuses and are readily accessible.

[WineStream]

Hmm...I guess there's a few possibilities. None of which I can rule out without a lot of time / tear-down and none which I can definitively say, "that's it!" I'll answer some questions that have been posed and see if that narrows things down a bit.

I cannot be 100% confident as there are always false-positive checks, but I assume my known-good sources to be that way because one is a campground that I stay at annually, it's well kept, I say at the same site every year, and have stayed there using both of my Airtstreams. Only had an issue the one time. The other known-good source is my house. I've used it for years to plug in to. It's a relatively new house (<10 years old) and the wiring was done by a professional contractor (not me! :-)). My little plug-in tester tells me they are good, too. So, for those reasons, I have deemed the supply in both conditions to be known-good.

All things were working fine when we got home from the trip, although the battery could have been at full charge and it took 24+ hours of sitting in the front yard for the fans to run it down and I would not have noticed that it wasn't charging. It had no issues with charging during our 3 night campground stay this past weekend. One of the first tasks when arriving home is to clear out the fridge and turn it off, so no indicator there.

Thanks for the input, Joe. I hope this is not the case with mine. The IOTA was in my trailer when I bought it, so I really don't know how old it is. There likely won't be an RMA for it, just a charge on my credit card for a new one when the day comes!

Thanks for the U-cord idea. I suppose I could get the truck near the trailer and plug in / unplug a few times to test it. That was indeed an event that happened once we got home. Although, I hope that I don't have to go into the trailer and check the fuses each time I unplug from the truck. My IOTA has the spade / blade fuses as well so once laying eyes on them, they are easy to change. Problem is that the IOTA fuses are on the opposite end from the 12V fuse panel and the whole rack is mounted where the original Univolt went, which in my layout is tucked underneath the shelf in the shower / bathtub area. If I make the 12V fuse panel readily accessible, then the IOTA fuses are buried and vice-versa. I have thought of mounting the rack under the mid-bed rather than its original location but regardless, I would still have to move the bed, remove cushions and contort myself or otherwise use a flexible mirror in order to check fuses. I didn't think the IOTA fuses would be the most often thing blowing, so I chose to favor easy access to the 12V fuse panel and keep the converter out of the way.

I think my path at this point is to discuss the issue with the folks at IOTA and to buy a couple packs of 30A fuses to put in the travel tool bag. I guess replacing every 2 years isn't toooo bad?!?

[WineStream]

I never got a chance to call IOTA today...hopefully tomorrow.

But, at least when I got home tonight, the fans were still running full-speed and the battery was at full charge. The trailer is unplugged and back in the barn now so not much more troubleshooting. I will post when I talk with IOTA if there's interesting info to share.

[garry]

The fuse is only protecting from reverse polarity on the battery side if you did not mess with the batteries the only thing I can think of is if the fans had a faulty switch and you reversed the fan direction or you plugged something into the inside 12VDC outlet that caused the problem.

I admit the above is a stretch but something caused the fuses to blow.

[WineStream]

That's a good point...

I switch the direction of the rear fan often and usually while it's running. It's my understanding, though, that this is an OK operation on a fantastic fan. If this was the root cause, I would expect that each time I reverse the fan that it should blow the fuses?

[richinny]

since you now have extra fuses and experience, i nominate you to do research :-)

i wait until it comes to a slow spin as i believe this puts a very high demand on the fan motor and wiring.

[HowieE]

Originally Posted by WineStream

That's a good point...

I switch the direction of the rear fan often and usually while it's running. It's my understanding, though, that this is an OK operation on a fantastic fan. If this was the root cause, I would expect that each time I reverse the fan that it should blow the fuses?

Switching the direction of a DC motor has no effect on anything. One of the differences between AC and DC current is that.

[WineStream]

I called IOTA today and got connected with a very knowledgeable and helpful guy named Joe. I explained the situation leading up to fuses blowing 2 years ago as well as 2 days ago. A very quick response came from Joe that the amperage control in the converter is bad. He said there's 2 ways to blow those fuses. One is to connect the battery backward. Since I have not disconnected the battery recently, he said that was obviously not the cause. The other cause would be for more than 60A to pass outward from the converter. I mentioned the scenario of pulling the umbilical or reversing the fans. Joe's response was very matter-of-fact: the only way to blow the fuses is a backward battery connection or by the converter making too much amperage. He re-iterated that the amperage controller was faulty. He elaborated that one can even take the + and - output wires and touch them together and it will not blow the fuses. I inquired as to repair and he was very honest and said that it's cheaper just to buy a new one.

I am happy to have such a definitive response. For now, I am going to live with the fuse replacement. If it gets more frequent or the converter stops working altogether, then I'll shell out the $ for a new one. Until then, it's been shown twice now that the fuses do their job quite well so I don't feel in danger of fire or damage to the trailer.