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-   -   30a 240v air compressor circuit (http://www.diychatroom.com/f18/30a-240v-air-compressor-circuit-4015/)

crecore 09-21-2006 07:31 PM

30a 240v air compressor circuit
 
Wiring for future compressor at link below:

http://www.portercable.com/index.asp?e=547&p=4703

Before I insulate I want the circuit run to the compressors future home. I dont see much data there regarding the loads but it says 30a 240v. I know I need 10 ga cu but...

From my minimal experience... All dryers require 4 wires. Some welders require 4 wires (most do not). Ive never seen a 240 compressor require 4 wires. agree?

So do I run 10-2 and plan to use black hot, white hot and bare ground?

or do I run 10-3 and then if I only need 3 wires cap the whites and use red hot, black hot, bare ground?

The reason I ask is one for cost, but also for safety and code. I know on a 120v circuit it is illegal to ever use a white as hot at a receptacle or appliance (light). You can in a switch box or junction box and mark with tape. So in the case of 10-2 one of the whites would be hot. Is the code different for 240v because it sure seems that Ive seen this before.

thanks!

mdshunk 09-21-2006 07:37 PM

You only run the 3-wire stuff to your dryer because it is not straight 240. It's 240/120. Your compressor is straight 240, 30 amp, just like a water heater. Just run 10-2 to the compressor diconnect location, and remark the white conductor with black tape at each end. Code compliant and quite normal.

crecore 09-21-2006 07:52 PM

Quote:

Originally Posted by mdshunk (Post 18813)
You only run the 3-wire stuff to your dryer because it is not straight 240. It's 240/120. Your compressor is straight 240, 30 amp, just like a water heater. Just run 10-2 to the compressor diconnect location, and remark the white conductor with black tape at each end. Code compliant and quite normal.

Makes sense. Many welders are also 120/240 and have a 4 prong plug so thats why they would need 3 wire+ground. I new it was "normal" enough that I had seen it... but that doesnt always mean it's according to NEC. I wish my Dad taught me more of this stuff. I picked up enough to get myself in trouble. Luckily I'm smart enough to know what I don't "know completely" and I respect electricity! Some people on this board are going to get themselves in trouble! yikes. thanks!


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