Compressor Wiring

[fishEH]

I bought a Puma 12V compressor to supply air to my ARB locker and for filling up tires.
Its mounted in the cargo area of my '98 Discovery.
What gauge wire should I use to draw power from the battery? Do I need to run a negative from the battery too, or can I just ground it to the frame near the compressor?

 

[HillbillyfromAL]

Your ground depends on how well your tucks battery is grounded to the chassis. If its good you won't have any problems. As far as ga I used 8 for my ARB compressor max draw was around 30amps I believe.

 

[HillbillyfromAL]

Your ground depends on how well your tucks battery is grounded to the chassis. If its good you won't have any problems. As far as ga I used 8 for my ARB compressor max draw was around 30amps I believe. Just go off the max amps and length of wire. It never hurts to go up one size either. Also use high quality cable the fine strand stuff is better than the coarse.

 

[fishEH]

Klahanie, how do you like the Puma? I've only used mine once to test it out, and that was off a deep cycle battery in my garage. I was impressed how quickly it filled my 265/75/16.
Looks like I need to source some 6-8ga wire.

 

[Antichrist]

For a 15' run (allowing for routing bends) #10 will have a volt drop of .5v, #8 will have a volt drop of .32v, #6 will have a drop of .18v. So #10 would be ok and there's no need to go larger than #8.
As long as your battery to chassis and body grounds are good you can ground it to either the body or chassis.

 

[fishEH]

Electrical isn't my specialty so I appreciate all the help. Does the ground, whether to frame or battery, need to be the same size as the power lead?
I have a bunch of copper stranded 8ga wire, but its the coarser household stuff. Would that be sufficient?

 

[LandCruiserPhil]

Starting amperage of a PUMA is 30A and will ramp up to 50A prior to shutting off. I would run #6 to the compressor. If you are using the frame as a ground make sure you have an equal size wire from the battery neg, to the frame. Most of the time the large neg. from the battery goes to the engine block not the frame.
I also find a throttle lock speeds up the airing up process.

 

[LandCruiserPhil]

A little data on the durability of the PUMA
Purchased in early 2005
Over 100 hours of use to date
Longest cycle 4 1/2 hours continues without shutting off
Will remove a 6 lug tire torqued at 105lbs with an IR 3/8 tuned gun without waiting.

 

[YukonRob]

/slight hijak
Is it possible to (easily) divorce the tank from the compressor, but still use both as components in a system?

 

[fishEH]

A little data on the durability of the PUMA
Purchased in early 2005
Over 100 hours of use to date
Longest cycle 4 1/2 hours continues without shutting off
Will remove a 6 lug tire torqued at 105lbs with an IR 3/8 tuned gun without waiting.

Great to hear. I was holding out for an ARB compressor but this came up at $150 shipped so i jumped on it.

 

[Antichrist]

Ok, I was taking Puma at their word and figuring 30amp. If it really draws 50 then yeah, you want #6 for that distance.
Disco's have a battery to body ground of the right size, starting in '96 or '97, but I've seen them removed, so make sure it's there.
Use automotive wire, it's not as prone to vibration fatigue.

And, I surmise, lowers the current draw. That's why I figure the 30A fuse blew during a period of battery voltage only, without alternator output.

No, it doesn't lower the current draw. If you were running it with the engine off it wouldn't be supplied with as much voltage so you'd get a higher volt drop, the wire (and fuse) would get hotter and the fuse would blow.
When I'm calculating volt drop I always use the 12v figure to allow for worst case scenario.

 

[Sheep Shagger]

If I ever get a ammeter, I'll test it, to see if the current reading is the same with a supplied voltage of ~12v and ~14v.

You and Antichrist are both saying the same thing, just using different terms.


Power is what the electric motor takes, power being Watts. Ignoring start up and shut down pulses of the motor, let's say is needs 100watts to run. Volts * Amps = Watts

100w / 12v = 8A (12v = good battery / car not running)
100w / 10v = 10A (10v = Bad battery / car not running)
100w / 14v = 7A (14v = good battery / car running)

So, the amps over the cable will change depending on the battery & alternator state. So on a sub-par cable, it will get hotter and overheat with the lower voltage scenario as Amps are the limiting factor in a cable.

 

[fishEH]

/slight hijak
Is it possible to (easily) divorce the tank from the compressor, but still use both as components in a system?

Yes absolutely. You need a few plumbing fittings from any local hardware store. I seriously considered(and wanted) to do this. The main reason I didn't is because I still wanted easy access to the tank to drain the air/vapor from it on a regular basis. This meant not putting it under my cargo shelf. I also dind't want to mess with running the lines to my locker and for tire fill to another location.

 

[YukonRob]

Thanks for the info!

 

[fishEH]

Another question, this time regarding the switch.
I want to leave the switch at the compressor ON and turn it on/off via a switch on the dash. I could use recommendations on how to do this. I'm assuming I should use a relay. Do I need a special relay for amperage this high? What about wiring the switch to close ground? I've heard this may be safer but have never done it.
Thoughts?