In my main shop I have 3 power "busses": one each at 117VAC, 220VAC, 220VAC3ph.
The 220VAC (single phase) is run with a 30 amp breaker and 10 gauge copper
stranded wire. The wire physically runs from the breaker to a box just the other
side of a stud from the panel box, maybe 16", then it splits. One run goes along
the west wall of my shop, and the other run goes up and over the ceiling and
then down and along the east wall of my shop. On the east side is connected my
5hp air compressor (this is a very real Leeson 5hp motor, this isn't Sears
ratings here). On the other side is my welder outlet. I'm basically a one-man
shop, so I don't exceed any ratings by running multiple machines simultaneously.
This works very well on my 3-phase bus, but it fails on the 220 bus because the
air compressor runs when it wants to. If it comes on when I'm welding, the 30A
breaker pops. So I've learned to shut off the compressor when I'm welding, no
big deal.
I've lived like this for several years. However, I recently got a 60A plasma
cutter. This machine needs shop air, lots of it, so I can't shut off the
compressor while I'm cutting. And the breaker pops if I don't stop cutting
immediately when the compressor kicks on. So I clearly have to install a larger
breaker. I'm probably going to replace the 30A breaker with a 50A breaker. The
question is, do I have to pull new wires? It would be possible, the wiring is
all in surface 3/4" EMT conduit. I'm thinking however, that maybe I can get away
with just making the one piece of wiring that goes from the breaker to the J-box
where it splits, and keep the 10 gauge runs along the wall, since only half of
the current will flow down each wall.
I know what the electrical inspector would say. This shop is never going to get
inspected, and if it did, it would instantly fail as would any other shop with a
non-UL-approved shopbuilt 3 phase converter wired in. The question is what do I
really have to do here.
Thanks!
GWE
- posted
15 years ago