Air compressor, need your advice.

Any questions about tools or supplies. Post your compressor/gun questions here.



No Turning Back
Posts: 633
Joined: Mon Feb 23, 2004 9:10 pm
Location: Denver
PostPosted: Thu Jul 08, 2004 1:37 am
Cool. I've just seen lots of bad stuff. The house I bought a couple of years ago was about 1 step from being condemmed for the wiring. The owner was kind of a jerk and I'm sure I could have gotten him in a lot of trouble but I wanted the place. I spent a couple of hours after work every day for about 2 months rewiring big parts of it. I found things like the ground run on RED wire.



Settled In
Posts: 45
Joined: Thu Apr 15, 2004 6:30 pm
Location: Decatur, IL
PostPosted: Thu Jul 08, 2004 2:24 am
I understand. This was my first time working w/ 240, but not w/ electricity. I am the kind of person that will make sure that the positive and the neutral are in the right spot just because they belong there. I have had people tell me "oh, that doesnt matter" and it may work either way but I like to have stuff done right. Like I said, I borrowed the book and researched how it was supposed to be wired even though I was just moving it from one side of the wall to the other and could just put them where they were on the plug before and been just fine.

Ben



Non-Lurker
Posts: 1
Joined: Thu Jul 08, 2004 7:37 am
PostPosted: Thu Jul 08, 2004 9:04 am
I have the 60 gal Campbell hausfell I purchased from harbor freight 3 or 4 years ago and its still going strong. It does all you ask of it and more. The cfm pump rating isn't really a accurate measure. I use harbor freight HVLP Gun and set it at 10PSI at gun. You can paint for days with it. I also sand blast and the C/H compressor works like a champ. Word to the wise you will need a 240 outlet or 220 like you have for your electric clothes dryer. If you don’t have one you will need to install one, along with a separate 30 amp breaker. I did it myself the cost for materials was around 200 bucks. Had to run the electrical all the way over the house through the attic 140 feet of wire, because breaker box is on opposite side of house. Also installed :D weather proof conduit. Was my first electrical house wire job and I didn’t die but I did do a lot of reading. Just FYI bro. My compressor is rated 7 max hp same setup and I got it at harbor for 288 bucks out the door. Showed them a similar one at sears for 299$ and they beat the price. This was 4 years ago. but might check into it if your looking to save some money. You will also have to set the compressor on a deadened base anchored to the floor. I used pieces of 2 x 4 under the legs anchored with 3inch hammer driven anchoring bolts. The machine is very top heavy . A filter system will also need to be installed in the line to remove moisture. Make sure the filter is above the height of the compressor to get full use of moisture condensation removal. Hope this helps you and doesn’t scare you . Any ?s just message me.
UzZi
PostPosted: Thu Jul 08, 2004 9:42 am
Actually, you only need a 20 amp breaker for the (7hp peak) compressors. They draw 15amps.



No Turning Back
Posts: 633
Joined: Mon Feb 23, 2004 9:10 pm
Location: Denver
PostPosted: Thu Jul 08, 2004 8:58 pm
Similar units from different companies may have different requirements. Look at the nameplate on the one you are about to buy to see what is really required.

For 7HP (peak), 120 volts, 15 amps, here's the math:

120volts x 15 amps = 1800 watts (approx)
1800 watts / 746 watt/hp = 2.41 HP normal run
If that is 240 volts, then 4.8 HP

For the one shown above,

240 volts x 17.5 amps / 746 w/hp = 5.6 HP

Using the same formulas, a commercial 7.5 HP uses 22.3 amps at 240 volts.

See how advertisers distort the ratings? You really need to pay close attention to all the specifications when you buy or compare compressors.

By the way, 20 amp circuit would not meet electrical code for a compressor that runs at 15 amps. It might run most of the time but it would be really iffy when it starts.
PostPosted: Fri Jul 09, 2004 9:55 am
In Cobb county, GA 25% above the load is code.



No Turning Back
Posts: 633
Joined: Mon Feb 23, 2004 9:10 pm
Location: Denver
PostPosted: Fri Jul 09, 2004 8:54 pm
In the National Electrical Code, motor loads which have a high starting inrush current are figured differently than normal inductive loads. 15 amps of lights on a 20 amp circuit is fine. A motor that runs at 15 amps and may have a locked rotor current of 60 is not. A lot of localities adopt changes to the code but almost no one ever sees fit to change those kind of tables. If they do, they always make them more conservative - i.e., heavier circuits required.
A lot of things will work, sometimes even pretty well, and not meet the Code requirements. If I error, I go heavier just for less voltave drop. Low voltage is a motor killer.
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