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Old 15-07-2013, 17:25   #31
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Re: Fuse didn't Blow! Nearly a Fire!!

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Originally Posted by Teknav View Post
Hiya Brown! I really don't know what to say! So, if you want to add more toys to the circuit, you just connect them to the battery bank and add fuses to them without any load calculations and schematics modification?

Mauritz
Not sure how you got that out of my statement.

I was explaining the amusement another poster found in the idea of being provided with schematics of the boat and following them with faith that they are correct, an amusement I have to admit I share!
If it's as bad as I see on large, newer boats I don't expect better on small old boats where many people have been doing things to the various systems on the boat, with widely varying levels of enthusiasm and budgets.
I suggest instead that you trace the circuit itself to determine what is connected and why, then do your own calculations to figure out the appropriate parts required.
If someone handed me a paper and said here's what the wiring in the boat is doing, I can't simply point to that as an excuse if the boat burns down later so better to make sure it is safe myself.

Perhaps you simply have more faith in the builders than I do?
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Old 15-07-2013, 17:27   #32
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Re: Fuse didn't Blow! Nearly a Fire!!

That I have seen many times POOR connection,the contact area in the fuse holder is not a large enough area and it becomes resistance=heat
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Old 15-07-2013, 17:33   #33
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Re: Fuse didn't Blow! Nearly a Fire!!

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Originally Posted by Cheechako View Post
Yeah, that was my haha. In smaller boats, probably the best diagram that the boat ever had was the most basic system... maybe three to 6 fuses and the starter circuit. Add years to that and well........... I've never had a schem included in a mono or a cat to 47 feet. These boats were only a few years old... but if they existed... they were long gone.
Of course as mentioned by TekNav... one has to be aware of the total loads you might be putting on one circuit. But then the real world is that all those loads are never on at the same time anyway... so I guess we all compromise sometimes..
My Gemini manual had a few pages. It was nice of them to give the color codes to the in-mast wiring. The rest of it was basically red and black.

Glad you were there as the sniffer Mark.
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Old 15-07-2013, 17:38   #34
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Re: Fuse didn't Blow! Nearly a Fire!!

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Originally Posted by Teknav View Post
Is this fuse of same current rating as drawn in the boat's schematics? I'd start, by looking at the schematics. A dab of silicone grease on terminals, will retard corrosion. Take care!

Mauritz
This made me laugh too........

Mauritz, spent much time working on boats
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Old 15-07-2013, 17:57   #35
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Re: Fuse didn't Blow! Nearly a Fire!!

I'm not sure just because there is smoke there is fire. If you use Ancor wire as an example, it does not support flames. It smokes, melts and only burns if you apply flame but it does go out when flame is removed. Lots of these plastic gadgets will burn if you hold a torch to them but otherwise they just smoke and melt. That said, some plastic takes right off. To bad you can buy stuff for your boat that burns like crazy. Perhaps we need goverment regs., or not.
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Old 15-07-2013, 19:15   #36
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Re: Fuse didn't Blow! Nearly a Fire!!

wow...tens of thousands of boats out there probably have similar fuse holders wired directly to the batts for bilge pumps...in fact many have even cheaper fuse holders I suspect and not too many have had a similar occurrence...

Not sayin' there isn't a better way...but I'm not sure a world wide panic needs to be started over this burnt fuse holder or some other similar ones.
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Old 15-07-2013, 20:13   #37
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Re: Fuse didn't Blow! Nearly a Fire!!

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wow...tens of thousands of boats out there probably have similar fuse holders wired directly to the batts for bilge pumps...in fact many have even cheaper fuse holders I suspect and not too many have had a similar occurrence...

Not sayin' there isn't a better way...but I'm not sure a world wide panic needs to be started over this burnt fuse holder or some other similar ones.
Most bilge pumps are fused at 5A or so... a bit smaller than 20 A. A fuseholder that's OK at 5A isn't necessarily suitable for 20A.

The point? Don't use an under-sized holder with a high-current fuse in a high-current circuit.
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Old 16-07-2013, 00:15   #38
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Re: Fuse didn't Blow! Nearly a Fire!!

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If I understand you correctly, Mark, that fuse was connected directly to the house batteries.

That's a no-no. Only three types of fuses have high enough AIC ratings to connect directly to the house bank: ANLs, MRBFs, and Class-T. For this application, I'd use either an ANL or a MRBF type.

Your post is an excellent illustration of why the ABYC has specified Circuit Protection Devices (fuses or breakers) with at least a 5,000 amp interrupt capacity for connecting directly to a big battery bank. Devices with less than this rating can possibly fail in the closed (shorted) position which can easily cause a fire.

In your specific case, and assuming no huge transient currents (like lightning or power surges), my bet would be surface corrosion had built up on the blades of the fuse, causing significant resistance and heating.

And, yes, that can cause heat, melting, and a fire with far less than 20A current.

Bill

the smallest ANL and MRBF is 30amps. so how do you wire a battery monitor to a house bank? they require 2a fuses and require direct connection to the battery for voltage accuracy...

same with small battery chargers. the 10-20a guests etc come with the fuses on the wire already.

90% of the boats out there have fuses connected to the battery.

I have never seen a problem.

most fuse holders come with 16awg wire and are rated at 15 amps. the bigger ones are 12 or 10awg and rated for 30.

are you telling me that for a battery monitor, you put a 30a mrbf on the battery, and then connect a 2a inline fuse onto the mrbf? and somehow that 30a mrbf is going to save the 16awg wire before the 2a inline does?.....

I would love to see a 2a glass fuse weld itself shut. there is barely enough metal in there to make it across in the first place.
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Old 16-07-2013, 00:49   #39
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Re: Fuse didn't Blow! Nearly a Fire!!

Me, I used a Blue Seas Circuit Breaker rated at 30A between the controller and the battery. With 240 watts of solar I figured max of 20 Amps. Used the expensive heavy wire from Whitworths.

Sometimes I find the controller blank and the circuit breaker tripped. Don't know why, never worried about it before today. Just flipped it down to reset.

As already noted the wire and the fuse holder looked a bit flimsy. There are a few transients out there that could blow any fuse. Best to check everything's up to having a bit of a load.
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Old 16-07-2013, 01:54   #40
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Re: Fuse didn't Blow! Nearly a Fire!!

I dont see how a 30A fuse at the battery bank would have prevented MarkJ's particular case of fuse melting. I mean, it melted because of rust increasing the resistance in the spade connection? 5A would be enough to light it up and not enough to trip the main battery fuse. If the current did go over 5A, surely the fuse part of that melted assembly would have blown anyway. Not saying not have a main fuse at the battery, just saying this problem could still occur with one.

It looks to me the only guard against this, is regular inspection of all the fuse holders looking for rust. Just having every circuit correctly fused is not enough.

Or do I have all this wrong?
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Old 16-07-2013, 04:41   #41
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Re: Fuse didn't Blow! Nearly a Fire!!

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Originally Posted by smac999 View Post
the smallest ANL and MRBF is 30amps. so how do you wire a battery monitor to a house bank? they require 2a fuses and require direct connection to the battery for voltage accuracy...

same with small battery chargers. the 10-20a guests etc come with the fuses on the wire already.

90% of the boats out there have fuses connected to the battery.

I have never seen a problem.

most fuse holders come with 16awg wire and are rated at 15 amps. the bigger ones are 12 or 10awg and rated for 30.

are you telling me that for a battery monitor, you put a 30a mrbf on the battery, and then connect a 2a inline fuse onto the mrbf? and somehow that 30a mrbf is going to save the 16awg wire before the 2a inline does?.....

I would love to see a 2a glass fuse weld itself shut. there is barely enough metal in there to make it across in the first place.
I tend to agree...while sometimes there are cases where wires and fuse holders that get hot and smolder...or just get hot and finally weaken to the point where the wire just separates...rarely to they turn into infernos.

Most of the time it's hard to start a fire from just heat alone.

Again...not saying to cut corners or not wire/fuse size correctly or do poor crimps/ends...just that using a 0-20 amp fuse holder and wiring directly to the battery for bilge pumps and alarms is so common it's hard to imagine wasting the time, energy and money to worry about "some better way".
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Old 16-07-2013, 06:16   #42
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Re: Fuse didn't Blow! Nearly a Fire!!

A dab of grease in the fuse holder would have helped dissipate the heat and stop corrosion.All of my electrical connections that can not be made waterproof are filled with grease,preferably electrical grease or what ever have
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Old 16-07-2013, 07:06   #43
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Re: Fuse didn't Blow! Nearly a Fire!!

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Originally Posted by noelex 77 View Post
The fuse holder must have had a fair bit of resistance, probably for some time.

On the bright side, having now removed the defective connection, you should be getting a few more AHrs
OP says with a new fuse and holder he gets 1.5 amps more from his panels.
18 watts?
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Old 16-07-2013, 11:30   #44
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Re: Fuse didn't Blow! Nearly a Fire!!

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Originally Posted by scoobert View Post
firstly if you are pushing 14amps any distance that wire is woefully inadequate.
looks like 14G wire. you need 8G minimum. and if the run is very long your looking for 4G wire. all the wire needs to be the same size also. going from thick, to thin, to thick makes a light bulb :P if you get my point.
and where is your charge controller? its should go from the panel to your charge controller, not your batteries.......
AWG 14 wire is good to 20A in a raceway/cable installation (not more than 3 conductors) for most types of commonly used insulation, although in the US, code stipulates that AWG 14 over current devices shall not exceed 15A. AWG 12 would get you to a 20A breaker.
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Old 16-07-2013, 11:37   #45
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Re: Fuse didn't Blow! Nearly a Fire!!

The US code your quoting is for higher voltage.
No way should you have 14 awg on a 20 amp 12 volt dc circuit.
Amps and Wire Gauge - 12V Circuit
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