ANL Fuse/holder getting real hot

[hellosailor]

rom-
Little things like fuses are easily counterfeited or mismarked. And ANL fuses from "audio" brands won't perform the same way as marine or good commercial brands, so it might be worthwhile replacing the fuse with one of those pesky expensive brand names. (Worst case, you'll have a spare.)

When you say you want a breaker that trips before the fuse does, also be aware that both fuses and breakers "trip" after ## minutes of ## load. So you may find a 300-amp nominal fuse trips after 60 seconds of that load--where a breaker (and there are different types of breakers, magnetic versus thermal) might trip after 15 seconds. Or vice versa.

That's usually published in the manufacturer's specs for the device, you'd want to check that if the values are even vaguely close but you want to make sure which one trips first.

[mitiempo]

Originally Posted by hellosailor

rom-
Little things like fuses are easily counterfeited or mismarked. And ANL fuses from "audio" brands won't perform the same way as marine or good commercial brands, so it might be worthwhile replacing the fuse with one of those pesky expensive brand names. (Worst case, you'll have a spare.)

When you say you want a breaker that trips before the fuse does, also be aware that both fuses and breakers "trip" after ## minutes of ## load. So you may find a 300-amp nominal fuse trips after 60 seconds of that load--where a breaker (and there are different types of breakers, magnetic versus thermal) might trip after 15 seconds. Or vice versa.

That's usually published in the manufacturer's specs for the device, you'd want to check that if the values are even vaguely close but you want to make sure which one trips first.

Good points above. Blue Seas states that their ANL fuse will handle up to 600% of their rating for a bit over half a second and almost 150% of their rating for 500 seconds - over 8 minutes.

Graph from Blue Seas shown below for their 400 amp ANL fuse.

[mitiempo]

Missed the graph. Should show now.

[evm1024]

Use an IR heat gun to find the temp of the cables, lugs, in and out of the fuse and such.

I has something like this where it appeared that the type T fuse was getting very hot. In fact I thought that the heat of the fuse was conducting over to the lug.

But it turned out to be a bad crimp on the lug. The lug was hotter than the fuse.

I swapped the suspect cable end to end and the heat followed the lug.

Just a thought....

[RaymondR]

A few years ago on another boat I had two incidents of over heating connections on two high ampage circuits both caused by the same thing.

The first was a new cranking battery which would not crank. It came with two washers on each post which I installed either side of the cable termination. The new battery would not crank the engine and whilst looking for a warm connection, which usually indicates a bad connection, I found both positive and negative connections were hot. On removing the washers and scratching them I found they were all stainless steel. If you look at the metalurgy og 316 stainless it's not far from nicrome resistance wire. Replaced the washers with brass ones and no further problems.

This incident prompted me to revisit an anchor winch motor I had been having trouble with.

The anchor winch motor has three terminals which access two sets of field coils. One terminal is common and the other two are one each for up and down on the winch. It's designed this way so that a H bridge is not required to reverse the motor. The soldered connection on the up terminal had un-soldered itself a number of times requiring me to remove and strip down the motor to re-solder it. When I checked I found that rather than have what I thought were chrome plated brass washers the troublesome terminal had SS washers. Replaced them with brass washers and never had another problem and the winch ran about twice as fast when loaded.

If your fuse has SS washers rather than chrome plated brass or if the terminal post bolts are SS it may be the cause of the problem.

[smac999]

Originally Posted by rom

Yes Mike and I think that is for a 105°C rated cable. GordMay is also right if he is talking about 60°C or maybe 70°C cables.

Anyway, the problem is the ANL fuse and/or fuse holder. The shunt on the negative side remains rather cold in that 400A test of mine. Of course washers are on the good side and both the fuse and the holder are like new and clean.

As for the question about conversion to 230VAC. I now have 2 victron multiplus 3000 in parallel that are capable of killing my batteries or worse set the DC cables on fire.
First I need a proper DC fuse, at this stage it seems 350A seems to be the max because of that ANL problem.
Second, 230VAC output of the multis go into a 30mA breaker currently rated 40A. That is way too much, as it is the DC fuse that will trip should I use the electric oven, coffe machine, and water heater at the same time...
So what I want is a 230VAC breaker to be as high as possible, yet it should trip before the DC fuse. If I am limiting 230VAC with a 16A breaker, the system may then use up to 340A from the batteries. 16A x 230V = 3680 / 0.9 (efficiency) = 4088 A / 12V = 340 A. But I don't think that formula is correct, that was my question.

neither fuse / breaker should be blowing. the inverter should go into an over current fault electronically and just shut off. if you are blowing stuff. they are too small and blowing before the inverter maxes out.

each victron 3000 should have it's own 400a fuse, battery swtich, and own cable run to battery bank. probably in 4/0 or double 2/0. whatever that is in mm. that is 800a feeding your inverters. that should never blow. how big is your battery bank? hopefully well over 1000ah. are both fuses getting hot? or are you trying to run both inverters through a single fuse?

the 40a output breaker is actully on the small side for max output. because of the boost function. if you have a 16a shore power cord. the inverter can actully put out 16a + 6000w = 42a.

I wouldn't make that smaller. but make sure the AC wire from inverters to AC panel can handle that.

if you can't figure out which part is getting hot, I would swap out the fuse holder, fuse, and cable lugs one at a time and see what is causing it. it should not be getting hot. while you're at it, buy Class T fuses instead. they are better for inverters.

[Zil]

If there are washers on a terminal they must be in the position that NO current will pass through the washer. Not any kind of metal.

[FlyingScot]

Originally Posted by kmacdonald

It's normal for fuses to get hot at amperages close to their rating. They melt open at their rated amperage and their temp increases in proportion to current.

Exactly my thoughts. You don't run fuses at or near their max. Fuses are for wire protection. Continuous load should be under 80% IMO.

What does ABYC say?

[RaymondR]

Originally Posted by Zil

If there are washers on a terminal they must be in the position that NO current will pass through the washer. Not any kind of metal.

Sorry mate, I don't think there is any kind way to state it, but this is a ridiculous statement.

[evm1024]

Originally Posted by RaymondR

Sorry mate, I don't think there is any kind way to state it, but this is a ridiculous statement.

Sorry to say that he is more correct than not.

Nigel Calder's Boatowner's Mechanical and Electrical Manual 3rd edition page 186 "Conductivity of Metals and Bolted Connections" has a full description of the problem.

The stacking order of a bolted connection is quite important.

Simply stated you want the tabs of the fuse to be in direct contact with the bus bar that it is bolted to. If you put a washer on the stud first then the fuse you have introduced the resistance of the washer into the major path of the current as well as an additional contact.

If the washer is made of silver, copper (high conductivity) you will see minimal resistance.

Brass conducts at a rate that is 26% that of copper, bronze has even less conductivity and stainless steel conducts only 3% that of copper.

If you put a stainless washer under the fuse (between the fuse tab and the buss) they you have introduced a significant resistance and at high currents it will get hot. Perhaps hot enough to start a fire.

This is what he was saying.

Regards.

[rom]

Originally Posted by mitiempo

Good points above. Blue Seas states that their ANL fuse will handle up to 600% of their rating for a bit over half a second and almost 150% of their rating for 500 seconds - over 8 minutes.

Graph from Blue Seas shown below for their 400 amp ANL fuse.

Yes good points from you two, buying fuse & holder from bluesea was what I had in mind. I would have like to get some feedback from CF users if any. The tips of my ANL fuses are so thin I can hardly believe they can handle their rating for a long time. But looking at the pictures at bluesea it seems the higher amp fuses are thicker, so maybe the solution is there.

Thank you for showing that graph from bluesea. I forgot about it, now it is disturbing. So it seems a ANL fuse from bluesea will handle 150% of its rating forever ?! A 300A fuse is actually a 450A ? That would be dangerous don't you think ?

[rom]

Originally Posted by smac999

the 40a output breaker is actully on the small side for max output. because of the boost function. if you have a 16a shore power cord. the inverter can actully put out 16a + 6000w = 42a.

This is off topic, I should not have mixed those 2 problems in the same thread. This is way more complex than a hot ANL fuse and requires a lots of explanation. Quickly, the main reason why I installed a second multi (in parallel) is to have redundancy as I am depending more & more on 230VAC. I also needed a little bit more power for the electrical oven. The problem is that the cabling has now become undersized (95mm2), and so is the battery at 1000Ah, for a load that can easily reach 500A. But it's not a real problem as I never intended to use that much power, 350A from time to time and for a short period is pretty fine.
You understand how those inverters work, that's good. Basically I think I have two choices. Install a 16A breaker at the ouput of the inverters (could be 18A if it exist, 20A would be too much) in order to maintain the 12VDC bellow ~340A at battery output. Being limited to that 16A full time is no big deal as I don't have a genset and I do not plug in marinas. The other option would be to software limit each multi to 8 or 9A output. Easy but I am not sure I want to rely on a software option for such a critical matter. A third option would be to carry a lot of spare ANL fuses, well ...

[witzgall]

I don't think you can software limit the output of a multi, only the AC input.

Chris

[mitiempo]

Originally Posted by rom

Yes good points from you two, buying fuse & holder from bluesea was what I had in mind. I would have like to get some feedback from CF users if any. The tips of my ANL fuses are so thin I can hardly believe they can handle their rating for a long time. But looking at the pictures at bluesea it seems the higher amp fuses are thicker, so maybe the solution is there.

Thank you for showing that graph from bluesea. I forgot about it, now it is disturbing. So it seems a ANL fuse from bluesea will handle 150% of its rating forever ?! A 300A fuse is actually a 450A ? That would be dangerous don't you think ?

No it is not dangerous. In any proper installation the wiring is sized for the max load plus a margin beyond that. The fuse is not there for anything but a short circuit. If a fuse blows under load then it is the incorrect fuse.

[Zil]

DC. Use the proper sized wire for least voltage drop. Use a fuse sized to the capacity of the wire. That is the only correct choice. AC. Use breaker for the output required. 15amp, 20amp, 30amp. Use the correct outlet sized to the output. Don't burn to the water line.