Fuse Block Wiring

[Francis]

After studying some of the very helpful posts on this Board concerning fuse block installations I think I am ready to attempt mine. I have several questions however and would appreciate the experience of others.

 

1. Most diagrams show an in-line fuse between the battery and the relay that powers the fuse block. Some diagrams show this fuse as 15 amps. What ratings could or should this fuse have?

2. I will run an autocom Pro7 system. What fuse size should I use in the fuse block for this gear?

3. I will run PIAA 1100X auxialiary lights with relays. What size fuse should I use in the fuse block here?

4. I will probably run another set of light as well. Probably the Hella ff50 or the Hella FF100's(if they are legal on a motorcycle). What size fuse should I run in the fuse block for this installation?

 

At present I am not planning to run a GPS or radar detector.

 

The fuse block I have purchased is the Centech AP1 which has 5 fuses running 8 "hot side" outputs. I plan to mount it under the left side removable plastic panel as shown in plans by RickP and others on this site.

 

Any help, suggestions, and hard earned "tips" would be appreciated.

 

Francis

[JonathanE]

Francis,

 

I'll give you my $0.02. Answers are regarding the question numbers referenced.

 

1) I haven't personally used a fuse, but that's because I've kept my fuse block close enough, and the wiring well enough protected, that I didn't see the electrical engineering need for a fuse in this applcation.

 

If your fuse block is far away or your wiring experience not so deep, the fuse rating should match the current rating of the wire you use.

 

2) An amp will do, but fuses are supposed to be based on the rating of the wire you are protecting. Remember, fuse are fire protection devices, sized to reduce the risk of fire if the wire is shorted to ground.

 

3) Two PIAA 1100 bulbs draw 22 or more amps. Install a 30 amp fuse and #10 wire.

 

4) It all depends on what they draw. You should always over-build any electrical circuit because the difference in cost is negligible and the hassle of a bike burned to the ground is huge. I overdo most everything by 50 to 100 percent.

 

LIke I said, just my $0.02. I'm not even a licensed EE.

[Nevets]

What Jonathan says!

[Global_Rider]

What fuse size should I use in the fuse block for this gear?

 

I would use wiring for future expansion. As you've stated, you'll be installing a second set of lights, but even if you don't...

 

What can that fuse block handle? Usually they'll have a per cricuit limitation and an overall limitation.

 

I'd use 10 gauge multi-stranded wire with a 50 amp fuse. If your fuse block is right next to the battery, I wouldn't even bother with an inline fuse. I didn't. BMW doesn't.

 

Wire Gauge & Current Limits

[Global_Rider]

If your fuse block is far away or your wiring experience not so deep, the fuse rating should match the current rating of the wire you use.

 

The distance between the battery and the fuse block will determine what wire size to use for a certain current draw, so that the voltage drop is negligible.

 

See the link in my previous post. It does that calculation for you. The voltage drop at maximum current draw should be no more than 0.5 volts in a 12V system. Using 10 AWG copper with a 50A current draw in a 12V system, I'm dropping only 0.1V.

[ShovelStrokeEd]

Francis,

I have not yet read the other posts on this subject but some guidelines might be in order.

 

You size the main fuse to protect the wiring between the fuse block and the battery.

 

You size the secondary fuses to protect the wiring between the fuse block and the component you are connecting to that fuse.

 

None, repeat, none of the components you mentioned are really protected by the fuses. The Autocom draws so little current as to be negligable. A 2 amp fuse would be fine as would 18 gauge wire.

 

The remaining stuff, depending on bulb size will draw more current and the wiring should be sized accordingly.

 

I would suggest 10 gauge wire from the battery to the main fuse and from their to the relay. 30 Amp capacity for the relay and a 25 amp fuse on the line.

 

Assuming (always a bad thing) that the lights carry 55w bulbs you will have 110 watts of power required for the lights. That is roughly 8 amps at the typical voltage regulator output of 13.8 volts. Assuming a wire size of at least 16 gauge, a 10 amp fuse would be appropriate their. Got to 14 gauge wire and you can use a 15 amp fuse.

 

Notice I mentioned wire size in conjunction with fuse amperage, not components. The why is fuses protect wires, not components. If you follow the guidlines I have given, you will have a trouble free installation and need not worry about the heating of wires or shorted components taking out your wiring harness.

 

Also, for the high current carrying wires, I would recommend you use solder connectors or solder the crimp connectors after crimping and then protect with heat shrink tubing. Beware also the low dollar components you find at auto parts stores. They often don't come with good connections and more fires and melted harnesses have been caused by poor crimp connections than any amount of shorted components.

[JonathanE]

Assuming (always a bad thing) that the lights carry 55w bulbs you will have 110 watts of power required for the lights. That is roughly 8 amps at the typical voltage regulator output of 13.8 volts. Assuming a wire size of at least 16 gauge, a 10 amp fuse would be appropriate their. Got to 14 gauge wire and you can use a 15 amp fuse.

Oops, my bad. I doubled up on the PIAA current. I did measure the current load on my PIAAs, a few years ago, and each "pair" of PIAAs drew 11 amps. In my opinion, use 12 gauge wire minimum, preferrable 10, and fuse it at 15 or 20 amps.

 

 

I'd use 10 gauge multi-stranded wire with a 50 amp fuse.

It may be overkill, but I don't fuse circuits higher than the NEC tables for conductors in raceways, since they are rarely in "free air". That is why I choose to protect number 10 wire with a 30 amp fuse. If I want more current, then I use more copper. It may be a tad excessive, but it has been stated before that:

 

"Multhaup's First Law of Engineering is:

Anything worth doing, is worth overdoing."

[Global_Rider]

It may be overkill, but I don't fuse circuits higher than the NEC tables for conductors in raceways, since they are rarely in "free air". That is why I choose to protect number 10 wire with a 30 amp fuse.

 

But my power feeds are in Free Air. And with the size and length of wire (12") I am using, each length only has to dissipate 5 watts (if that) at 50 amps.

 

In my case, I'm not even concerned about which fuse as I chose not to use one.

 

Those current ratings are for a continuous draw, so a 50 amp fuse would be more than being conservative.

[steve.foote]

Those current ratings are for a continuous draw, so a 50 amp fuse would be more than being conservative.

 

Let's see, 50 amps x 14 volts = 700 watts. What do you plan on hooking up? Toaster oven? Refridgerator? Air conditioner?

[Jim VonBaden]

Those current ratings are for a continuous draw, so a 50 amp fuse would be more than being conservative.

 

Let's see, 50 amps x 14 volts = 700 watts. What do you plan on hooking up? Toaster oven? Refridgerator? Air conditioner?

 

 

Jim

[Global_Rider]

Let's see, 50 amps x 14 volts = 700 watts. What do you plan on hooking up? Toaster oven? Refridgerator? Air conditioner?

 

Yeah, yeah, wise ass! I happened to have some nice 10 AWG multi-stranded copper wire and the wire fit nicely into the terminals I had, so it soldered nicely. At least I'll never have hot junctions. And like I stated, I didn't use a fuse. I don't need one.

 

Besides, the R1150 GS Adventure ain't no toy. It has a real alternator on it not like them other models.

[RickP]

Francis, Thanks for the plug, but remember I stole my basic setup from Rightspin.

 

I used a 30AMP mini-fuse between battery and the "power-up" relay. I have used a 15A on the PIAA's for a year without problem. Moto-lights probably only need a 10A. The Gerbing harnesses come with 15A from the factory and I think I running a 7.5A (socks and jacket liner).

 

Remember, when the fuses are easily accessible (not hidden under the tank, under the tupperware) you can experiment and run the minimum necessary. The dealer originally installed my lights with a 25A under the tank, because who wants to have to troubleshoot that in a motel 6 parking lot.

 

Improve the breed, take pictures. -RickP.

[Francis]

Thanks everybody for your input. You all have been very helpful and have steered me in the right direction. Glad we could also get the physics and math about volts, amps, wattage, and power-wire size out in the open. The question I have now is what size wire should be run for the switching side of the relays? Is this a 16 guage application or is this also a larger sized wire application?

 

Francis

[ShovelStrokeEd]

Switching size wire. Assuming we are talking about the coil of the relay you could even run 22 gauge wire for that. The coil only draws a few milliamps.

[Francis]

In looking at the left side mounting location of my fuse block under the removable black plastic cover as per the posting from RightSpin I got to thinking that summer rain could be a problem here.

 

Question: can I mount the fuse block in a "project box" (either metal or plastic) with a lid on it without running into a problem with fuse block heat or electrical issues?

[Ken H.]

Question: can I mount the fuse block in a "project box" (either metal or plastic) with a lid on it without running into a problem with fuse block heat or electrical issues?

Yes. If something is heating there, something is wrong. There should be no heat generated at all.