Inline fuses and Fuse Block?

[olmpilot]

I'm in the process of rewiring the accessories and lights on my 18.6' seaswirl. I'm installing a ST Blade fuse block under the helm to help centralize all the wiring and minimize trouble finding faults. My question is "Do I still need inline fuses for things such as fish/depth finder, 12v recepticle, radio, vhf, etc. If I wire them into the fuse block?" If not, do I simply splice out the current inline fuses and reconnect the wires without them? PS, I have a few questions but will post them as separate posts to keep them organized and on-topic. Hope that is okay. <br /><br />Thanks!

 

[18rabbit]

Re: Inline fuses and Fuse Block?

Everything gets fused (or put on a circuit breaker). You should not be using ATO (blade) fuses on a boat. They have an aluminum conductor inside and aluminum conductors are an absolute no-no on a boat. That said, ATO fuses are about as convenient as fusing gets…color coded, easy to pull/replace, and less surface area to expose to corrosion. I get a headache from just trying to read the fuse rating stamped on the tiny metal barrel of a bus fuse…and bus fuses are preferred…tho there seems no end to the ATO fuses used on boats…and as mentioned, for very good reason. The issue with aluminum conductors is not present with ATO fuses but the ABYC has not exempted them from their "no aluminum conductors" standards.<br /><br />No, you do not need to double fuse your electronics. When engaged in rewiring, consider your electrical goodies in one of two categories, conductors (wires, anything that carries current) and appliances (VHF, 12v receptacle, ff, margarita blender, etc). Both conductors and appliances need to be protected form over-current. This is done with either fuses or breakers, or both. If you are fusing to protect the conductor, your fuse size is rate there with the wire rating and the fuse should be physically placed near the power source. If you are fusing to protect an appliance, the fuse rating may exceed the appliance’s current rating to allow for ‘start up’ without popping a cork. These fuses are place near the appliance, at the opposite end of the conductor, furthest from the power source.<br /><br />Since your wire capacity will inevitably exceed the current demands of the appliance, you can fuse near the power source to protect the conductor with an undersized fuse…or appropriately size for the appliance. If your wiring will handle 10-amps, the VHF is rated for 5-amps, so you follow the VHF’s manf suggestion and put the VHF’s fuse (7.5 amp) near the power source, thus protecting both the wiring and the appliance. This only works when you have one appliance per conductor. If you get into branch circuits you need to protect the conductor independently from each appliance.

 

[18rabbit]

Re: Inline fuses and Fuse Block?

Ok, some things you did and/or didn’t want to know (but only because I am waiting for the other half to get ready to go to marina…).<br /><br />Note on aluminum conductors: They were used for wiring in older houses until someone figured out constant current through aluminum created more heat at the connection than with any other conductor. UL did extensive testing of this, using various aluminum conductors supplying current to light bulbs that were left on for years in the lab...5+ years, and then evaluating the integrity of the aluminum. Big problems at the connections. Some aluminum conductors did not make it, some were excessively hot to the point of melting things, etc. Tin coated aluminum conductors did better than all-aluminum conductors. Bottom line: aluminum conductors may be safe at their connections, but also may not.<br /><br />If aluminum conductors were really that dangerous, I would expect a lot more older homes to spontaneously burst into flames. If it weren’t that big a deal, there would be a specification for its use (aluminum is cheaper than copper)...there isn’t a spec...except to say “do not use”. The blades on an ATO fuse are tin coated aluminum. They are an aluminum conductor...specifically, an aluminum conductor that makes a connection, well...a pair of connections, hence their exclusion from use in the ABYC (and other) standards... “thou shalt not use any aluminum conductors on thy mini-ark.” But then you see ATO fuse blocks offered by reputable marine electric manufacturers, such as Blue Sea Systems. Hummm!?!?!? Fwiw, I have never seen an electrical problem with the use of ATO type fusing on a boat. Also, they are nowhere to be found on either of my boats.<br /><br />The “ST” (screw terminal) is a given, but has nothing to do with the actual fuse. Be sure you properly crimp an appropriately sized ring connector to the end of your conductors. Do not loop the stranded wire around the screw and tighten it. Do not use the fuse block’s screw terminal to secure your wiring. Securely anchor/clamp your wire right at the fuse block, leaving only enough wire to allow you to make that screw terminal connection. There should be no stress on, or flexing in the wire between this anchor point and the fuse block’s screw terminal<br /><br />Other consideration: All conductors must be routed as high as possible/practical and anchored/clamped (secured against excessive flexing) at a minimum of every 18-inches. Use as many anchors as needed to prevent as much flexing as possible. You can bundle the wires together but do NOT bundle any twisted pair! Avoid bundling any AC and DC circuitry together. If the wires are routed through an area that is exposed to water (bilge or deck area) the conductors must be enclosed in an appropriate non-metallic conduit. All conduits have a rating as to the size & number of conductors that you can safely route thru it. When you are routing your wires, try to keep them as far as possible away from the compass…ideally a minimum of 1-meter away in all directions.<br /><br />Lastly, you do not have to, but I strongly encourage you to label ALL of your wiring at both ends of every conductor. If you bundle wires together, label the bundle as well. Also label your fuse block indicating what the fuse is for and the appropriate replacement fuse size. And following the marine electrical wiring color-code is fun and will look very pretty when you are done.

 

[bossee]

Re: Inline fuses and Fuse Block?

Hi,<br />I use Blue Sea systems<br />ST* Blade Fuse Block With Cover - 12 Circuit with Negative Bus<br />PN: 5026<br />*Screw Terminal<br /><br /><br /> http://www.bluesea.com/product.asp?Product_Id=30990&d_Id=7463&l1=7463&l2= <br /><br />It use blade fuses.<br /> http://www.bluesea.com/product.asp?Product_Id=24026&d_Id=7223&l1=6609&l2=7223 <br /><br />I have no problem (so far) with this setup in my boat.<br /><br />Is this really bad to use in a boat?<br /><br />/Bo

 

[18rabbit]

Re: Inline fuses and Fuse Block?

BO - I 'pasted' a fraction of second before you (0.00000000139th of a second difference, as per an Olympic Games stop-watch). See the post just above yours.

 

[bossee]

Re: Inline fuses and Fuse Block?

OK 18Rabbit seems to give a good answer. I will continue to use my Blue Sea systems ST Blade Fuse Block with ATO blade fuses. All cars I have owned use these ATO blade fuses and they have never caused any problem for me. <br />And as a side note I can tell You the environment here in Sweden in winter is relly bad environment for all electrical in a car (cold, moisture, salt on roads etc). My boat does not come close this bad enviroment, and my boat is only in water for 3-4 months every year in freshwater (not saltwater) usually May/June-Sept. Rest of the time it is inside a warm garage.<br /><br />/Bo

 

[olmpilot]

Re: Inline fuses and Fuse Block?

After reading the great information here, I think I will take my chances with the "aluminum" fuses. However, I have one other question: If I fuse for my "appliances" at or near the helm with the fuse block, would it be a wise idea to fuse for the "conductor" inline at or near the battery on the line that powers the fuse block? Realizing that I will know if that fuse blows because "everything" will lose power at once. Excepting that I'm only powering accessories through the fuse block. I'm going to leave the gauges/ignition, engine as originally wired.

 

[18rabbit]

Re: Inline fuses and Fuse Block?

If I am understanding you correctly, you have a single (+) and a single (-) from the battery to the distribution area (your fuse block & ground distribution). This would be the situation involving branch circuits that I described above. Each ‘branch’ conductor off the fuse block needs protection. Additionally, the main (+) and (-) from the battery to the distribution point needs its own protection. Fuse (or breaker) within a foot of the battery for the capacity of the main power lines. Then fuse at the distribution as per the appliance manufacture’s recommendation for the appliance. This will also protect the branch circuit’s conductor because inevitably these wires can handle more current than the appliance requires.

 

[olmpilot]

Re: Inline fuses and Fuse Block?

Yes, I have a single (+) and (-) running from the battery to the same blue sea fuse box with negative ground that Bo mentioned above. I have fused the (+) 12g wire at the battery with a 30 amp fuse and run about 14 feet to the fuse block. Then I have my other accessories connected directly to the fuse block with 16 g wire and ring connectors and heat shrink insulation. So, are you saying that each accessory that comes off the fuse block (i.e. vhf, lowrance, 12v recepticle, lights, etc.) need to also be fused between the fuse block and the accessory because they are "branch circuits"? Each device is connected to it's own terminal (12 terminal block). I thought that the fuse in the block was there to protect the accessory?It' is only about 18" from the fuse block to all the accessories, because I mounted it under the helm.<br /><br />Are there any devices that MUST be run straight to the battery and not routed through the fuse box?<br /><br />Thanks!

 

[18rabbit]

Re: Inline fuses and Fuse Block?

The fuse in your fuse block should be sized per the appliance mfg’s recommendation for that specific appliance. Whatever that fuse rating is it should be less current than what AWG 12 wire can carry so you are protecting both the appliance AND that 18-inches of branch circuit wire. You do not need any add’l fusing. You did good. <br /><br />There is nothing that MUST be connected straight to the battery. In smaller vessels it doesn’t always make sense to run the battery power to heavy-duty distribution blocks and back to the engine’s starter. Sensitive electronics (like VHF) wants clean power and a battery provides clean power. On smaller vessels it is sometimes easier to filter the power into the VHF if there is a problem. Bilge pumps are sometime wired directly to the battery so they are not on the batteries on/off switch…they always have power available should it be needed while a boat is sitting in its slip.<br /><br />On my boat the battery EVERYTHING is on the other side of a battery switch, no exception.

 

[olmpilot]

Re: Inline fuses and Fuse Block?

The reason that I did all this was to avoid what happened last weekend, when somewhere, there was a short when I installed my anchor light (maybe in the 4 splices that I removed between it and the switch?!?!?!). But when I got the short, since they were all daisy chained, it killed the bilge, nav lights, horn and wiper. So, I wanted to make sure it was all independent and so that "I know" where all the splices fuses and runs go. I'm sure it's overkill for a 18.6 foot boat, but I prefer the secuirty of knowing right where to look for a problem, and won't get stuck in a downpour taking on about 1" of water an hour and having to trace down and cut bilge wires to get the water out.<br /><br />I tested everything last night and it all worked wonderfully - Even the Nav lights which never worked before (again because of the 2 splices and seriously strained connections!!). Now I just need to get that battery switch installed and all will be done. Thanks for the information and help 18Rabbit! <br /><br />Rick

 

[18rabbit]

Re: Inline fuses and Fuse Block?

Rick – it’s NOT overkill! You did it right and for the right reasons. Any boat that has more than a couple appliances should have a fuse or breaker box.