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Author Topic:   In-line Fuses for Individual Electronic Devices
alfred posted 09-01-2008 01:40 AM ET (US)   Profile for alfred   Send Email to alfred  
I am in the process of hooking up a new GPS and Sounder, and they come with in-line fuses. The power tap-off point on my new boat is a distribution panel with fuses for each terminal. Do I still keep the in-line fuses or bypass them?
glen e posted 09-01-2008 08:11 AM ET (US)     Profile for glen e  Send Email to glen e     
Dump the in-line fuses; they are a major cause of problems. GARMIN in-line fuses are some of the worst.
jimh posted 09-01-2008 10:13 PM ET (US)     Profile for jimh  Send Email to jimh     
I'd keep the in-line fuses, as they will provide better protection for the device than the distribution panel fuses.

The in-line fuse protects the individual device and is chosen with a rating to match the device. The fuse at the power distribution panel protects the branch circuit and is usually chosen to have a rating in proportion to the wire size used in the branch circuit. If there is only one device on each branch circuit, then the fuses become redundant, and you could eliminate the in-line fuse.

The quality of in-line fuse holders probably varies, but I don't recall ever having a problem with one. Some are rather flimsy.

glen e posted 09-01-2008 10:42 PM ET (US)     Profile for glen e  Send Email to glen e     
totally rediculous jim - a fuse block is all you need if properly connected...and do some searching around with some professional installers of garmin products - the first thing they do is dump the inline fuses or replace them if no fuse blosk is being used...
alfred posted 09-02-2008 07:00 AM ET (US)     Profile for alfred  Send Email to alfred     
I soldered up the respective looms to use both fuses and it looks like it was the correct thing to do as I could not find the correct fuse sizes in the local automotive shop. So at the fuse block, I am using the next size up for the respective components and have the inline fuse at the correct size. There seems to be a wider amp range available in the tube fuses then the spade fuses, but I have not looked in the boat shops yet.

If I find the right size fuses for the block and have enough time, I will redo the looms.

It's all coming together, will post pics soon.

swist posted 09-02-2008 08:52 AM ET (US)     Profile for swist  Send Email to swist     
If you have an alternative to inline fuses, I would definitely go with them. Inline fuse holders are mechnically a bad design for a high-stress vibration-laden environment. Kinda like a weight at the end of a string will fly all over the place under vibration. The most common ones are also not air/vapor tight which can lead to corrosion of the metal connectors.

And if you fasten them down with tie-wraps or cable clambs you usually accomplish two things - adding more spaghetti to the rat's nest, and/or making it difficult to change the fuse, which inline fuseholders were designed to avoid in the first place!

jimh posted 09-02-2008 02:20 PM ET (US)     Profile for jimh  Send Email to jimh     
After you cut out the in-line fuse, what do you have? A splice. You can say a lot of the same things about a splice as you can about an in-line fuse in terms of its mechanical and electrical properties. They're both discontinuities in the circuit, electrically and mechanically.

I wonder how GARMIN was able to establish the huge market share it has in Marine and Aviation electronics if their hardware is so crappy that "professional installers" immediately have to replace it in order to make it work. It sounds a bit far fetched.

glen e posted 09-02-2008 03:48 PM ET (US)     Profile for glen e  Send Email to glen e     
you are amamzing...never wrong huh?

there is no splice - cut the fuse off and hook the wire to a fuse block..and yes garmin knew their fuses were crap as the new 4000/5000 units have a new waterproof ATC type blade fuse , not the crappy black tube ones they used for years that corrode like hell...all of them should be cut off and one continuous wire attaching to the fuse block..there is no use having two fuses in a line...

call sean at Electronics Unlimited in ft lauderdale if you think this is "far-fecthed"... also ask b_arrington, duct tape and sea swirler at "the other site" what they think...

jimh posted 09-02-2008 06:12 PM ET (US)     Profile for jimh  Send Email to jimh     
Glen--Your theory of installation is predicated on all the power cords supplied with marine electronics being long enough to reach the power distribution panel after you have cut off the in-line fuse. Most of the in-line fuses I see are installed near the device, not at the far end of the power cord. What do you do if the remnant power cord is not long enough to reach the power distribution panel?

A further problem occurs after you cut off the in-line fuse and the power leads are not equal in length. Usually the in-line fuse is in the positive lead, so if you cut it out, you will have excess wire in the negative lead. I suppose you could wrap this excess wire into a loop, or you could cut and splice the negative lead. Now you have two splices in the OEM power cable. Or you have a little coil of extra wire.

Another problem is the unknown skill and technique which will be brought to bear on making the splices. There is no certainty that the home-brew splice will have greater reliability than the OEM fuse holder. This is required if removal of the in-line fuse is going to yield higher reliabilty.

On a small boat the power distribution panel (particularly if it is the OEM panel from a boat made 20 years ago) may only have a few circuits, and it is entirely possible that there may be more electronic devices to be powered than there are fused circuits.

If you have a power distribution panel with plenty of circuits, and you want to use only one device per circuit, then (repeating myself) you can eliminate the in-line fuse. However, if you are going to be consistent with this technique, you better get a power distribution panel with a lot of circuits. Boats tend to acquire electrical loads with time. I keep adding devices to my small boat, and, yes, I have to use in-line fuses because I haven't enough individual circuits in my 1990 power distribution panel.

glen e posted 09-02-2008 09:47 PM ET (US)     Profile for glen e  Send Email to glen e     
These fuse blocks are all of 50 bucks and do the job very well - when I am rewiring a boat, it's the first thing I install and replace them every 5 years. If the fuse holder is closer the unit, I would splice the wire with a solder and heatshrink connection. And yes that connction is far more secure than a fuse holder with two seperate ends, a spring and a fuse that is not sealed - all which will no, a jeatshrinked "splice" is not the same...

jimh posted 09-02-2008 10:06 PM ET (US)     Profile for jimh  Send Email to jimh     
Glen--I completely agree: If you have a new power distribution panel and there are many extra circuits, and if the power cord will be long enough after you cut out the fuse, and if you are going to use one device per circuit, then go ahead, cut off the in-line fuse.

Somehow I have avoided a complete re-wiring of my boat's electrical distribution. I think it is because

--Boston Whaler did a decent job with the original installation
--the previous owner did not make a mess of things
--the current owner (me) has not added too many new devices

But I have several in-line fuses, and they're not a source of problems. On the other hand, I do not have any older GARMIN devices. But apparently the originator of this discussions doesn't either.

Bella con23 posted 09-02-2008 11:18 PM ET (US)     Profile for Bella con23  Send Email to Bella con23     
One should note that these units are very unforgiving with respect to proper value fuse protection. Remember the fuse in the fuse block protecting the electronic device needs to match what was in the factory supplied in-line fuse holder.

If you have a 1 amp fuse in the fuse holder and the device in-line fuse holder contained a 1/4 amp fuse, that would be 400 percent over recomended value. A common mistake.

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