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Old 14-01-2019, 13:36   #1
rom
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ANL Fuse/holder getting real hot

Hello everyone, I have a fuse holder that allegedly handles 750A but I can hardly reach 400A for a few minutes before it gets cray hot. Temperature increases around as well of course. 95mm2 cable on the left, copper bar to the right. Right now the fuse is a 425A, maybe not a true ANL ? Any ideas ?Click image for larger version

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Also, is there a way to tell what should be the max. 230VAC amperage (fuse) if I decide that 400A is the max 12VDC ? (let's pretend the inverters work at 90% efficiency)
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Old 14-01-2019, 13:42   #2
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Re: ANL Fuse/holder getting real hot

The amperage a fuse opens at is not a function of voltage but they are rated at a max volage.
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Old 14-01-2019, 13:55   #3
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Re: ANL Fuse/holder getting real hot

Look for a loose connection, extra washers where there shouldn't be any, bad crimps, etc. Anything causing impedance may be heating up. Take the fuse out and look for corrosion. Etc.
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Old 15-01-2019, 01:32   #4
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Re: ANL Fuse/holder getting real hot

Are your washers between connections? There was just a post on this. A bad cable crimp could also do it.

I don't understand 2nd q. The inverter manual should provide the dc and ac fusing to use and cable sizes.
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Old 15-01-2019, 03:41   #5
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Re: ANL Fuse/holder getting real hot

Quote:
Originally Posted by rom View Post
... 95mm2 cable on the left, copper bar to the right. Right now the fuse is a 425A, maybe not a true ANL ? Any ideas ...
A 95 mm2 Cu cable is only rated about 292A free air, or 250A bundled.
A 185 mm2 Cu cable is rated just over 400A
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Old 15-01-2019, 04:05   #6
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Re: ANL Fuse/holder getting real hot

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Originally Posted by GordMay View Post
A 95 mm2 Cu cable is only rated about 292A free air, or 250A bundled.
A 185 mm2 Cu cable is rated just over 400A
The BlueSeaSystems app seems to think that a 2m 95mm2 conductor terminated on a fuse should be fine handling 412a

That's all well and good but the OP is stating that it's the fuse getting how not the cable.
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Old 15-01-2019, 04:59   #7
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Re: ANL Fuse/holder getting real hot

There can be large differences between ampacity data/ratings from different sources.
Metric values are taken from ISO/FDIS 10133.
The following plot compares five standards. These curves show that AC ratings tend to be lower than DC ratings (e.g. NEC versus ABYC).
For DC applications, the JASO (Japan) and ABYC (US) ratings are similar, and the ISO (EU & Brit') ratings are about 15% lower (than ABYC).

I prefer the more conservative rating.





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Old 15-01-2019, 05:00   #8
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Re: ANL Fuse/holder getting real hot

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Originally Posted by mikedefieslife View Post
The BlueSeaSystems app seems to think that a 2m 95mm2 conductor terminated on a fuse should be fine handling 412a

That's all well and good but the OP is stating that it's the fuse getting how not the cable.
Yes Mike and I think that is for a 105C rated cable. GordMay is also right if he is talking about 60C or maybe 70C 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.
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Old 15-01-2019, 10:18   #9
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Re: ANL Fuse/holder getting real hot

power (Watts) =Voltage * Amps
Volts = Resistance * current (Amps)

As you work through your electrical calculations, try to use the correct units. It will give you more confidence in your results and will help others interpret your questions.
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Old 15-01-2019, 10:28   #10
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Re: ANL Fuse/holder getting real hot

There should be no washers between the fuse holder and cable lugs. I can see a 425A rated fuse get warm to hot when reaching 400 amps. I would try a new fuse.
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Old 15-01-2019, 10:32   #11
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Re: ANL Fuse/holder getting real hot

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.
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Old 15-01-2019, 10:43   #12
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Re: ANL Fuse/holder getting real hot

Quote:
Originally Posted by GordMay View Post
A 95 mm2 Cu cable is only rated about 292A free air, or 250A bundled.
A 185 mm2 Cu cable is rated just over 400A
Agree with GordMay as to favoring towards utilization of conservative ratings.
Same holds true for selection of ground tackle. Big is good.

The single 95 mm2 cable does appear to be very inadequate for the apparent DC current draw of 400 amps. Not sure what the temperature rating of the insulation of the cable is on this vessel. Assuming 60 C rubber, then it's DC ampacity may be only 258. A higher temperature insulation would provide for higher ampacity but the conductor will nonetheless be hot, just the rubber will not be as inclined to melt.

I2R analysis:

258 Amps X 258 Amps = 66,564 versus 400 X 400 = 160,000

Reference http://www.aeicables.co.uk/literatur...entRatings.pdf

Snipet therefrom copied and attached below.

From looking at the picture of the fuse holder the washer does appear to be on the outside [nut side] of the ANL. Washers make for great resistors so don't place them between the fuse and the holder.

Can't be certain but there appears to be some heat stress to the block of the ANL holder, OP should examine to see if it has been cooked and in need replacement.

I hate dealing with low voltage high amperage power sourcing. 12V DC being such a poor legacy, but there you go.
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Old 15-01-2019, 10:43   #13
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Re: ANL Fuse/holder getting real hot

What in the world are you doing with a five kW load at 12 volts? Have you considered upgrading to 24 volts or running a generator to supply that load rather than an inverter? What is the capacity of your battery bank?
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Old 15-01-2019, 10:53   #14
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Re: ANL Fuse/holder getting real hot

Can't see the entire system layout, but there appears to be negative cables in contact by crossing positive cables. If such contacts [e.g, crossings] of opposite polarity are on non-fuse protected circuitry, i.e., towards the DC battery source and not down circuit of the DC fuse that would be inappropriate layout of cabling and not to standard.

Only a safety issue if and when the insulation breaksdown or wears due to rubbing. I see cable ties on some of the cables which forces the cables to touch.
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Old 15-01-2019, 11:26   #15
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Re: ANL Fuse/holder getting real hot

That is a lot of amperage.

If it were me, after re-evaluating the wiring rating, connectors, etc., I would consider replacing the ANL fuse block with a more robust Class T block and fuse.

Best wishes getting ahead of that potentially dangerous sutuation.

Cheers! Bill
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