Air compressor help

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kolelt

New member
Got a free air compressor with a tank. It came of a tow truck. It's actually a beast little compressor. So I took it of the tank, and modified it a little to accept a regular hose. And my plan is to extend the wires, add a inline fuse or breaker , a ON/off switch and alligator clips so i can hook it up to battery. I'm good at doing electrical but not good at trying to determine what size of switch, and fuse I need. The compressor has 10awg wire.

This is the pressure switch that it was hooked up to.



This is the tank


How I got it. The compressor looks bigger then a viair but not crazy big. It actually is pretty silent. Looks strong made in Taiwan. Plus it was FREE!! I could in future hook up the tank under the truck.


Anyway, there are no other info on the compressor it self. I'm sorry for posting this in 3rd gen area.
 
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kolelt said:
Got a free air compressor with a tank. It came of a tow truck. It's actually a beast little compressor. So I took it of the tank, and modified it a little to accept a regular hose. And my plan is to extend the wires, add a inline fuse or breaker , a ON/off switch and alligator clips so i can hook it up to battery. I'm good at doing electrical but not good at trying to determine what size of switch, and fuse I need. The compressor has 10 awg wire.
Click to expand...

so yeah under the cap there is says 20 amps if you get everything that will handle the 20 amp rating you will be fine.

charts like this are nice to look at.
Wire Gauge Amps Ratings for 12 volt Automotive Systems

If you have any more questions let me know, just get things for 20 amps or more, but remember a fuse is good so that if the system does pull more current, the fuse burns up instead of your wire harness
 
OK, first of all, you can't run the power through a switch, way too much amperage for just a switch, you need to power it through a relay, preferably a continuous duty solenoid. That motor is way too big for a switch.

Now, using the data on the pressure switch, which is probably meaningless but all you have. We can apply Ohm's law.

20A at 125V

125/20 = 6.25 Ohms

Reversing that for 12 Volts

6.25 x12V = 75 Amps

That's some mean draw there dude, like 6 gauge wire for 2 feet!

But maybe the motor is smaller than it looks. ??

:couch2:
 
IBallEngineer said:
OK, first of all, you can't run the power through a switch, way too much amperage for just a switch, you need to power it through a relay, preferably a continuous duty solenoid. That motor is way too big for a switch.

Now, using the data on the pressure switch, which is probably meaningless but all you have. We can apply Ohm's law.

20A at 125V

125/20 = 6.25 Ohms

Reversing that for 12 Volts

6.25 x12V = 75 Amps

That's some mean draw there dude, like 6 gauge wire for 2 feet!

But maybe the motor is smaller than it looks. ??

:couch2:
Click to expand...

It is not that big as it looks. Probably bigger then viair. The original wires that are attached to the compressor are 10gauge. So seems 10g is plenty. But damn if your math is correct then that is big.
[MENTION=14772]shootmymime[/MENTION] that's what I though. But I didn't know if I can go of the pressure switch. I was thinking wiring in a inline fuse @25amp and a switch rates for 30amps ?

Anyone else ?
 
yeah super mean current draw estimate.

My question to the OP is how was it hooked up on the tow truck? Didn't it have a switch and fuse? Why not bring that stuff over to your truck? :cowboy:
 
kolelt said:
It is not that big as it looks. Probably bigger then viair. The original wires that are attached to the compressor are 10gauge. So seems 10g is plenty. But damn if your math is correct then that is big.


[MENTION=14772]shootmymime[/MENTION] that's what I though. But I didn't know if I can go of the pressure switch. I was thinking wiring in a inline fuse @25amp and a switch rates for 30amps ?



Anyone else ?
Click to expand...



You don't need a switch, That's what your pressure switch is on the tank. You just need some wires and hook up a fuse.


Sent from my iPhone using Tapatalk
 
shootmymime said:
You don't need a switch, That's what your pressure switch is on the tank. You just need some wires and hook up a fuse.


Sent from my iPhone using Tapatalk
Click to expand...

The pressure switch is dead. Doesn't work. My friend works for a shop that also does towing. So that's how he got it.

Judging by the wires on the compressor. There's 2 wires. Red hot and black ground the red has a connector on it. Looks like to attach it to the battery. It's about 2 feet long.

You guys say it's a lot of juice. Then. Why does the pressure switch say 25amps ?

again it has 10gauge wire to it ? Let me take more photos
 


Pressure switch 10gauge wires




So I don't know if should go of IBallEngineer or the pressure switch ratings ? 25amps ? Really is a beast compressor I don't wanna buy a viair. Trying to save money.
 
kolelt said:
The pressure switch is dead. Doesn't work. My friend works for a shop that also does towing. So that's how he got it.

Judging by the wires on the compressor. There's 2 wires. Red hot and black ground the red has a connector on it. Looks like to attach it to the battery. It's about 2 feet long.

You guys say it's a lot of juice. Then. Why does the pressure switch say 25amps ?

again it has 10gauge wire to it ? Let me take more photos
Click to expand...

It says 25A because that's what the switch contacts are rated for not what the pump amp draw is. You need the switch to act as a starter for the pump. If left to say an on/off switch you could run too high a pressure which would run the pump out of it's rated operational range and cause problems.

Edit: Also you'll need about a 50A breaker for protection. You wont draw that but for you application, that will provide adequate protection. Also, that little arm is like an on/off switch as it opens the pressure switch contacts.
Furthermore,your clamp idea probably wont work either assuming your talking about jumper cable type clamps.
 
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JRZEE2000TR4LTD said:
It says 25A because that's what the switch contacts are rated for not what the pump amp draw is. You need the switch to act as a starter for the pump. If left to say an on/off switch you could run too high a pressure which would run the pump out of it's rated operational range and cause problems.

Edit: Also you'll need about a 50A breaker for protection. You want draw that but for you application, that will provide adequate protection. Also, that little arm is like an on/off switch as it opens the pressure switch contacts.
Click to expand...

But don't the switch contacts have to able to hold the proper amps

Gotcha ya. So you think a 12v 50a circuit breaker would be adequate? I'm not running the tank. So the compressor isn't going to need a shut off valve. My use is to hook it p to battery with alligator clips. And hit a switch and air up.

I like the idea of breaker. As it works as a switch to.
 
JRZEE2000TR4LTD said:
It says 25A because that's what the switch contacts are rated for not what the pump amp draw is. You need the switch to act as a starter for the pump. If left to say an on/off switch you could run too high a pressure which would run the pump out of it's rated operational range and cause problems.

Edit: Also you'll need about a 50A breaker for protection. You want draw that but for you application, that will provide adequate protection. Also, that little arm is like an on/off switch as it opens the pressure switch contacts.
Click to expand...

The pressure switch is rated for 125V AC which is totally different anyway, I was just giving an example, based on that. Seeing the pump and motor in context it probably isn't going to draw 75 amps. But I can't see running the power through a switch, a 40A bosch relay maybe. And at least a 40A fuse. 2 feet of 10G will handle that, but if it were me I'd go a little bigger. Heck I run 8g to my amp, and it's only 200W!
 
JRZEE2000TR4LTD said:
It says 25A because that's what the switch contacts are rated for not what the pump amp draw is. You need the switch to act as a starter for the pump. If left to say an on/off switch you could run too high a pressure which would run the pump out of it's rated operational range and cause problems.

Edit: Also you'll need about a 50A breaker for protection. You want draw that but for you application, that will provide adequate protection. Also, that little arm is like an on/off switch as it opens the pressure switch contacts.
Click to expand...

Correct. The switch rating is typical for a 125/250V system with a much bigger compressor. Still, a 3/4hp 12V motor looks to draw about 58 amps just looking at a few other motors. So a 10ga. wire is good to 100A at up to 10'. So you could probably go 12' or 13' with 58A draw allowing for starting load. But you would want more than a 50A fuse. A relay like this should work:

https://www.amazon.com/uxcell-28VDC-Power-Relay-JQX-62F/dp/B008BXEW3O
 
TheDurk said:
Correct. The switch rating is typical for a 125/250V system with a much bigger compressor. Still, a 3/4hp 12V motor looks to draw about 58 amps just looking at a few other motors. So a 10ga. wire is good to 100A at up to 10'. So you could probably go 12' or 13' with 58A draw allowing for starting load. But you would want more than a 50A fuse. A relay like this should work:

https://www.amazon.com/uxcell-28VDC-Power-Relay-JQX-62F/dp/B008BXEW3O
Click to expand...

Whoa there Ol' Rusty!! Where did you get those numbers? 100A through 10G for 10'? OMG that'd by hot melted goo in no time!

http://assets.bluesea.com/files/resources/newsletter/images/DC_wire_selection_chartlg.jpg

http://www.gridgit.com/postpic/2010/01/wire-gauge-amp-chart_466330.jpg

http://i358.photobucket.com/albums/oo26/milosusa/Z1%20to%201000/h12cblchrt-o_large_zpsa8611f02.jpeg
 
 
Hard to find any specs on 12V motors bigger than your thumb. But Northern Tool sells a 3/4 HP 12V DC motor that draws....wait for it....58Amps. Haha!

OK, so at this point, through that pile in the trash and buy a viair(sp)or something else. Their 400C is rated at 28A max draw.

Or scrounge some old jumper cables and make it work!
 
Ohms Law

IBallEngineer said:
OK, first of all, you can't run the power through a switch, way too much amperage for just a switch, you need to power it through a relay, preferably a continuous duty solenoid. That motor is way too big for a switch.

Now, using the data on the pressure switch, which is probably meaningless but all you have. We can apply Ohm's law.

20A at 125V

125/20 = 6.25 Ohms

Reversing that for 12 Volts

6.25 x12V = 75 Amps

That's some mean draw there dude, like 6 gauge wire for 2 feet!

But maybe the motor is smaller than it looks. ??

:couch2:
Click to expand...

IBall: would you show me where in Ohms Law that you multiply ohms x volts and end up with Amps???:wow2: Using Ohms Law (EIR)with your information of 6.25 ohms, 12v you come up with 1.92 amps....using (PIE) with 12v you come up with 240 WATTS!!!....In an A/C system the 6.25 is impedance, not Ohms. You can't mix A/C values with D/C values in the same formula. :shrug:
 


Yes or no?

Not throwing this bad boy out. This blows viair out of the park. Viair biggest portable compressor is 40A. What is a 10 or 20 extra amp gonna do ? ( pump your tires faster !!!)

But seriously not throwing it out because it's free. I just have to make it work. Anything below what you guys say.... anything below 50amp breaker it will trip ! Right ? So you recommend 50amp or 60?
 
The wire that is on the compressor now is 10g and says 600W on it.



Had my friend put a flair end on it. Made it so it accepts the standard fittings.

On the compressor it shows you can use nail gun lol.
 
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