Air horn compressor current?

[p.dath]

How much current does a "typical" automotive air horn compressor draw?

[pete376403]

The Fiamm horns on my GS1100 draw around 5 amps - enough to warrant running them via a relay rather than letting the wimpy little handlebar switch contacts carry the load. And they are f*ckin LOUD

[p.dath]

The Fiamm horns on my GS1100 draw around 5 amps - enough to warrant running them via a relay rather than letting the wimpy little handlebar switch contacts carry the load. And they are f*ckin LOUD

I have a Fiamm horn fitted to my bike (via a relay), but it has a 20A fuse in it. I was thinking this sounds a bit big, like maybe someone blew a fuse and smacked in what they had lying around.

Might try a 10A fuse (like the majority of fuses on my bike) and see how it goes.

[slofox]

The Stebel Nautilus is reputed to draw "less than 18A"...

[Taz]

All I know is when i use air horns in the falcon the lights dim a little........

[davereid]

The air-horns on my 650 draw 15 amps. Id suggest a 20 amp fuse located as close to the battery terminal as possible, and cable rated for 20 amps minimum. Hang the relay across the terminals designed to toot the original tooter, then your factory loom carries only the current needed to pull the relay in - well under 0.25 amps. Then you are tootin..

[{.bLanK}G_o_D]

Have a look at the compressor. It will (or did) have a plate, tag, sticker with all the relevant information including current draw.
If not, measure it with an ammeter.
If you compressor draws 5A, a 20A fuse is waaaaaaays too big.
But then again, motors have a surge of current on start up, my advise would be to find the model of the compressor so you can find out the manufacturers recommendations.
Or just trial an error.

[p.dath]

Have a look at the compressor. It will (or did) have a plate, tag, sticker with all the relevant information including current draw.
If not, measure it with an ammeter.
If you compressor draws 5A, a 20A fuse is waaaaaaays too big.
But then again, motors have a surge of current on start up, my advise would be to find the model of the compressor so you can find out the manufacturers recommendations.
Or just trial an error.

The plate doesn't have the current draw on it, and my multi-meter (both of them) can only measure current draws up to 10A, and I'm not keen ot fry a meter.

[davereid]

The fuse should be rated as low as possible, but its actually protecting the wiring, not the load. Run cable rated at, at least 20amps, put the fuse as close as you can to the battery and don't worry-guts about the compressors actual load. In the event of a failure the fuse will blow before the cable catches fire... thats why you use 20 amp cable. It IS best practice to use a smaller fuse if you can, but shit, sometimes you cant.

[imdying]

my multi-meter (both of them) can only measure current draws up to 10A, and I'm not keen ot fry a meter.The A line will be fused, even on a cheapy.

[p.dath]

The A line will be fused, even on a cheapy.

Funnily enough, my cheaper one has "not fused" written next to the 10A terminal.

[CookMySock]

The fuse [is] actually protecting the wiring, not the load. [..] In the event of a failure the fuse will blow before the cable catches fire...This is a fundamental aspect of wiring that many do not grasp. The fuse size is related to the wiring size, not the current draw from the load.

The fuse is solely there to prevent wiring fires. So the fuse must be a size larger than the load, and critically, the cabling must be a size larger than the fuse.

Steve

[p.dath]

This is a fundamental aspect of wiring that many do not grasp. The fuse size is related to the wiring size, not the current draw from the load.

The fuse is solely there to prevent wiring fires. So the fuse must be a size larger than the load, and critically, the cabling must be a size larger than the fuse.

Steve

I think I might look into this further. Assuming a 12VDC load at 20A (the fuse size), what should the AWG size of the wire be?

[imdying]

Google is awesome.

http://www.powerstream.com/Wire_Size.htm

[CookMySock]

Assuming a 12VDC load at 20A (the fuse size), what should the AWG size of the wire be?I dunno. :lol:

Thick enough to instantly blow the fuse in a fault condition. Buy a box of fuses and test.

Steve

[Juzz976]

Fuses are selected as Circuit Protective Devices, thus includes A: Wiring and B: Connected Load.

If your using a 20A fuse to protect 20A Cable and your connect load will catch fire at 15A continous then you havn't acheived much.
Also a fuse has a fusing factor...how much fault current required for an instant blow or how long it will take to blow in overload conditions.
A 20A fuse wont blow at 20A.

Also if your connect your fuse in parallel to the main fuse (off Battery) you can either cook your alternator, trip alt fuse or drain battery if combined load exceeds the alternator output.

If you use a fuse where its current rating is high enough and the current drawn through it on top of the total current drawn from other sub circuits you'll blow ya fuse a few mins up the road.

Also an overload or sub ciruit fault can potentially blow the main fuse if there isn't descrimination between upstream devices. Ie a down stream device of the wrong trip/fusing factor and current rating for the upstream device supplying it.

Breaking capacities/Fault ratings don't come into it as there is veryvery little prospective short circuit current available.

In summary wiring it whack may cause you some greif, either today tmrw or 6months down the track....
I'd hate to be out of town on a ride press the horn and the whole damn bike goes dead, not cool.

[{.bLanK}G_o_D]

Fuses are selected as Circuit Protective Devices, thus includes A: Wiring and B: Connected Load.

Correct.
All those who said a fuse is only there to protect the wiring, you are sew wrong. Tisk tisk :nono:
Please never touch any high voltage equipment, I have seen so much dodgy wiring in my time it's scary. I've even seen questionable to dodgy stuff done by registered electricians.

[{.bLanK}G_o_D]

I think I might look into this further. Assuming a 12VDC load at 20A (the fuse size), what should the AWG size of the wire be?

How long is a piece of string? Or wire in this case.
Resistence in a conductor increases over distance.
Possably not relevent in the case of an air hone on a bike, your cables arn't going to be that long. But anybody working with electricity should know that.

[davereid]

Fuses are selected as Circuit Protective Devices, thus includes A: Wiring and B: Connected Load..

Absolutely true.

But the man wanted a simple fix to a simple problem, and he couldn't measure the current draw. Experience suggests that the horns will draw 15-18 amps. If the cable is rated at well over 20 amps and the fuse is located close to the battery, a 20 amp fuse is ideal.

Its quite true to suggest that a fault in the load may cause a fire at loads less than 20 amps. Such is the real world. The load can be disconnected by taking a finger off a button. The rider may crash, the fuel pipe may fall off, a tree may fall on your head, the emperor (most likely) has no clothes.

I would absolutely buy your switchboard. But I'd stick cable safe for 30A and a 20A fuse on my tooter, and sleep soundly.