Proper Gauge Wire For Accessories

[Uncle Phil]

Looking at wiring my new ST1100 and the various stuff I add.
Heated gear - full kit - about 20 amps
Hi/Low Fiamm Blaster - about 20 amps
Heated Grips - about 5 amps
Figure the fuseblock will be in the tailpiece, the 'plugs' will be at the front of the bike.
What gauge, given the length, would you suggest for the 20 amps and the 5 amp uses?

 

[ST Gui]

16ga should be sufficient for 5A and 14ga for 20A. I'd probably just use 14ga minimum for both assuming it wasn't cost prohibitive. Buy one size/roll and be done. I'd even be tempted to just to 12ga for full kit heated gear if the insulation isn't too thick but it might be overkill even for 20A.

 

[Coop]

Would this help?

12 Volt Wiring: Wire Gauge to Amps – Offroaders.com provides information and entertainment to 4×4 enthusiasts worldwide

www.offroaders.com

 

[Uncle Phil]

Would this help?

12 Volt Wiring: Wire Gauge to Amps – Offroaders.com provides information and entertainment to 4×4 enthusiasts worldwide

www.offroaders.com

That's where the confusion starts - different online sources (and I've looked at a lot of them) vary from 14-16 gauge for 20 amps to this one that says 10-12 gauge if you run 10-12 feet (if I'm reading it correctly) - which can be pretty easy depending on how you route the wire.
I'm usually in the 14g for the 20 amps and 16g for less than that and have never had a 'melt down' on any of the three bikes.
But I was curious as to what others do and the idea of all 14 gauge is not a bad one.
I also like the 'six pack' set of wire.
Since I use a lot of relays I am also looking at a 'relay holder' box that also has places for fuse holders.
It would be easy to run a switched hot, a always hot, and a ground into the box and just bolt connections to the proper incoming wire.
That way everything would be in tailpiece and easy to access if there is an issue.

 

[st11ray]

Easternbeaver uses 12ga for horns and fuse box to battery. Everything else is pretty much 14ga.

 

[Larry Fine]

I'm a Master Electrician and licensed contractor. The biggest danger of using a too-small conductor is insulation damage, which in turn causes short circuits and, in extreme cases, electrical fires. Proper fusing is a must!

The next effect is reduced performance due to voltage drop, which is of much more concern in 12-volt systems than in 120-volt systems. Voltage drop is dependent on only two factors: current and circuit resistance.

Time of use is also a consideration. A horn is used for one or two seconds, while heated clothing and handlebars are considered continuous loads, even though they cycle on and off to maintain a set temperature.

'The code limits #14 wire to 15a, #12 wire to 20a, and #10 wire to 30a. Of course, that's in building wiring, but it's a great guide-line. Also, a circuit should not be run at its capacity on a continuous time basis.

While our circuit lengths are much shorter, a given voltage drop has ten times the effect at 12v as it does at 120v. For a continuous 20a load, I would use #10 wire till the last connection to the accessory wiring.

A single large conductor to a convenient splitting point, like a terminal or fuse block, allows several loads to share the capacity, as long as it's large enough for all simultaneously-used accessories. Load diversification.

 

[Coop]

I just used14 gauge for everything. What confuses me is the tiny wire used in the PIAA loom.

 

[SMSW]

I just used14 gauge for everything. What confuses me is the tiny wire used in the PIAA loom.

If you look at the ST's wiring harness there is very little #10 wire or even #12. The manufacturers are planning that NOTHING else will be added to their circuit, they might be using higher temp insulation (tho I doubt it is very much higher than (some) primary wire which is rated a little higher than 100deg C), and they are very cost conscious. They are also designing their wiring w/ a very low safety factor - look at all the problems we report with terminations. I cannot remember ever seeing a problem with a car's wiring. Sure moisture has a role to play, and yes, I am ignoring corrosion caused by road salt, but mc' seem to have more electrical gremlins.

That said, I'm a retired electrician, etc. like Larry, and I echo everything he said. Since I don't load my circuits up very much at all, and tend to run few items per circuit, I use fuses closer to the actual load (load +20%, then the closest fuse to this), and run almost exclusively #14 wire - mostly because I don't want to stock multiple colors in several different sizes. When I was working and running my own company, things were different - and I stocked a variety of sized wire (stranded only) in several colors.

Uncle Phil, I'd suggest you use the chart. And check the full load of your heated gear, add 20% of that (using watts, if you wish) divide by 12 and that will give you the current flow. Then pick your wire size. I don't know about you, but I find I very rarely run my Warm n Safe above half way, so there will be extra room above the actual
load. Rules of thumb are fine, but when you can, run the calculations to make sure. We are talking simple math here.

 

[heffly]

Differences in load carrying capacities of wire can be due to strand rate, insulation type, ambient exposure. Higher strand rates carry loads better, temp range of insulation and how much cooling the wire receives.
In addition resistive loads are much more stable than inductive loads. So current carrying capacity can be different for same size wire.

 

[Larry Fine]

ANY heat produced by electrical wiring is waste energy that is not being consumed by a load to produce a desired result. It's better to not create heat than to have to dissipate it. Connections usually suffer worse than the middle of a length of wire.

 

[mello dude]

Since I use a lot of relays I am also looking at a 'relay holder' box that also has places for fuse holders.

@UnclePhil.... I'm interested in what "relay holder" box you are looking at. I hadnt heard of such a thing...

btw - wiring is cheap, I always overbuild what I'm working on. Then I never have to be concerned about it.

 

[ST Gui]

Since I use a lot of relays I am also looking at a 'relay holder' box that also has places for fuse holders.

jheath (IIRC) showed one in an old post that I thought was very tidy. I looked around here and couldn't find a similar style. Maybe somebody knows of one other than the typical Blue Sea and others.

A single large conductor to a convenient splitting point, like a terminal or fuse block, allows several loads to share the capacity, as long as it's large enough for all simultaneously-used accessories.

I thought about doing that very thing – making a B+ buss from the battery to front and back. Not only diversify the load but making connections easier and more convenient.

 

[Trapperdog]

That's where the confusion starts - different online sources (and I've looked at a lot of them) vary from 14-16 gauge for 20 amps to this one that says 10-12 gauge if you run 10-12 feet (if I'm reading it correctly) - which can be pretty easy depending on how you route the wire.
I'm usually in the 14g for the 20 amps and 16g for less than that and have never had a 'melt down' on any of the three bikes.
But I was curious as to what others do and the idea of all 14 gauge is not a bad one.
I also like the 'six pack' set of wire.
Since I use a lot of relays I am also looking at a 'relay holder' box that also has places for fuse holders.
It would be easy to run a switched hot, a always hot, and a ground into the box and just bolt connections to the proper incoming wire.
That way everything would be in tailpiece and easy to access if there is an issue.

Keep in mind that online charts are generally referencing either a 15% or 3% Voltage drop for spacific gauge and run distances. This usually explains the different gauge requirements. Some critical components will not tolerate a %15 drop necessitating a heavier gauge wire to bring the loss to %3. Remember wire length is calculated for the round trip. Lighter gauge tinned wire can also be used as its loss over distance is much less than non tinned.

 

[Larry Fine]

I thought about doing that very thing – making a B+ buss from the battery to front and back. Not only diversify the load but making connections easier and more convenient.

On my '96 Nighthawk 750, I ran a pair of #10 wires from the battery terminals to the headlight shell, the positive protected by a fusible link. Each wire lands in an encapsulated bar made for aluminum house wire repairs. Three screw terminals with an anti-oxidant already in them and self-insulating. Pic:

I used this new feed to supply unswitched direct power and direct ground to the headlight with a twin-relay mod, a relay-modded Wolo Badboy air horn, the Alpine amplifier behind the stereo (when the Vetter Rooster was on it; it now has a Vetter Windjammer 5 on it) and a cigarette-lighter socket. Pic:



The fairing and the K&G Engineering saddlebags/trunk/backrest assembly are from the early 1980s. I got everything, including the mounting bracketry for $50 (yes, $50) from a guy rebuilding a 1982 CB750 into a cafe racer or something like that. I had to drive about 2.5 hours each way, but still a bargain.

I call it a CB750ST; you can see why. Not in the pics, but I have a pair of lowers for the fairing. Pic of an example:

 

[Uncle Phil]

Well, I've also found out that a lot of wire maybe a certain 'gauge' (Chinese made) but not AWG (American Wire Gauge) which seems to be a little 'heavier'.

@UnclePhil.... I'm interested in what "relay holder" box you are looking at. I hadnt heard of such a thing...

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I don't mine 'overbuilding' and usually do, but I've not used 10 gauge on any accessories (included horns and heated gear) and have not had any troubles at all on three bikes in 300,000 miles. So I'm even more confused between 'theory' and 'practice'! Now I'll have to check what I used on my other bikes and what lengths I will actually be running. It seems length has a lot to do with what gauge you use. I'm always amazed at how small a gauge Honda uses in their harnesses in most places.

 

[CYYJ]

I've used two different auxiliary distribution busses for my ST motorcycles - in 2001, I used a Blue Sea fuseblock on my ST 1100, and in 2015, I used a FZ-1 Fuse block (a newer version of the same idea) on my ST 1300.

I think that the most important consideration when installing an auxiliary electrical bus on our motos to power various add-ons and farkles is to have a single (large) fuse supplying power to the auxiliary bus. This enables the user to completely disconnect all power from the aux bus and effectively "restore the bike to stock electrical wiring" by pulling a single fuse when troubleshooting is needed.

I don't want to be stuck by the side of some rural road in the middle of the night trying to figure out what farkle I added is giving me electrical problems. By keeping all the farkles and add-ons on a separate bus, and feeding that bus with one fused wire, I isolate all the add-ons.

I power the auxiliary bus directly from the positive battery terminal, first through a fuse located very close to the battery, then through a relay that is triggered by the "accessory" fuse that Honda provides as stock on both models of ST. The FZ-1 fuseblock has this relay built-in, for the ST 1100, I added a simple automotive relay.

Below are pictures of the original Blue Sea fuseblock on the ST 1100 (vintage 2001), and the more modern FZ-1 fuseblock (from 2015) on the ST 1300. There is a good write-up here in the forum about the FZ-1 fuseblock, that is what I used as guidance when I did my install.

Michael

Blue Sea Fuseblock - ST 1100




FZ-1 Fuseblock

 

[SMSW]

Differences in load carrying capacities of wire can be due to strand rate, insulation type, ambient exposure. Higher strand rates carry loads better, temp range of insulation and how much cooling the wire receives.
In addition resistive loads are much more stable than inductive loads. So current carrying capacity can be different for same size wire.

Strand rates in the range of wire that we are talking about are pretty standard. You are not going to find much difference in strand rates. If you go to welding cable, colored, higher temp insulation (similar to THHN or Primary wire SXL) is not available, but the stranding is very very fine to reduce resistance and heat for large loads. I'm also not sure if it is made in small wire gauges.

 

[RaYzerman]

Read a bunch a while back about 12V applications... insulation ratings are key, but as has been said, why create heat in the first place. From experience, you need a 12ga. wire for a Stebel horn. Piaa's are very low draw. I question all your heated gear (for 1 person) is 20A.... more like 10? I use 16 ga. for that, and that is what most heated gear folks supply you with. Using a lot of big gauge wire can get bulky in a hurry..... you just have to plan it out. Fuzeblock main feed is a 12 gauge wire.... shoulda been 10 ga IMHO. I wouldn't run a horn through it (why?).

 

[ST Gui]

I don't mine 'overbuilding'

That 18-way box takes overbuilding to a level I hadn't (and wouldn't) consider! The box I saw had one relay and may 6 fuses and was much smaller. 2-3 of those would be fine or a Fewer-way marine box.

but I've not used 10 gauge on any accessories (included horns and heated gear) and have not had any troubles at all on three bikes in 300,000 miles.

If I used 10ga it would only be for a front to back buss.

Blue Sea Fuseblock - ST 1100

That installation is a thing of beauty! Is the FZ-1 mounted behind that bracket or is it cloaked?

Each wire lands in an encapsulated bar made for aluminum house wire repairs.

That's a slick little unit. Does it have some kind of anchoring or is that where you get creative?

I question all your heated gear (for 1 person) is 20A.... more like 10?

20A might be a little high for one person. But 10A seems too light if there's cold weather. Not CA cold but actual cold. That could mean a jacket liner gloves pants and possibly socks. Maybe not 20A but over 10 if we're planning for worst case scenario.

I picked up a nice six-pack of 14G wire from Amazon, in six colors, red/black plus four more.

Are there any contraindications for copper clad aluminum wire? I'm sure we don't need 100% oxygen free digital ready pure copper but I'm curious. The specs for that six-pack say it's not AGW American Wire Gauge. How close is it? I'm guessing it's closer to 16 that 12?

 

[CYYJ]

That installation [Blue Sea fuseblock] is a thing of beauty! Is the FZ-1 mounted behind that bracket or is it cloaked?

It was originally mounted aft of the silver bracket, which is why it is not visible. When I later installed a MC Cruise cruise control, the computer for the cruise control had to go in the tail of the ST 1300, so I removed the bracket and embedded the FZ-1 in foam blocks to hold it.

The picture below shows the present configuration.

Michael

FZ-1 Fuseblock (aft of cruise control)