Progress in Paradise...

Progress in Paradise...  We actually had some progress today, on wiring up my new air compressor.  I ran most of the 240 volt circuit today, about 60' of the total of 85' that I have to run it.  I did the hard parts today, through two walls and into the main circuit breaker panel.  All that's left is the final 25' across a wall, and terminating in a junction box.  Should be a piece of cake to get that done tomorrow.  Then all I have left (for the air compressor) is a short run of 120 volt line for the air dryer that's built into the compressor.

The 240 volt line I was running today is comprised of three 8 gauge copper wires, colored red, black, and green.  I'm running them inside a 1/2" PVC conduit, so in cross-section it looks something like the diagram at right (the scale is approximately correct).  As you can see from the diagram, the three wires fit inside the conduit with plenty of room to spare – and yet, running those wires through the conduit proved to be quite a challenge!

Why would this be challenging?  Well, imagine moving that red wire over to the other side of the green wire.  At one point in that process, all three wires would have to fit side-by-side inside the conduit – and the conduit just isn't big enough for that to happen.  In practice what this meant is that I had to “comb out” the three wires and tape around them every foot or so, to make sure they stayed in the same orientation.  Otherwise I could never have gotten them through the conduit!  Also, I had to do this one piece of conduit at a time, so that at most I had just a single bend to navigate.  This made the process quite tedious.  Of course, if I had been bright enough to buy 3/4" conduit...

These heavy wires are needed only because the start-up current for the air compressor is unusually high.  Under full load that motor (5HP) will draw about 21 amps – but during startup, according to the documentation, it will spike as high as 35 amps.  Yikes!  So I have to have a 40 amp breaker, and that means 8 gauge wire is the smallest safe size.  That's a whole lot of copper when you're talking about an 85' run, which is what I have...