Jess wrote:

On Mon, 12 Sep 2005 15:51:38 -0500, Jess
wrote:

Hi all,

I would like some help / advice in outfitting my shop.

My question is, which voltage should I specify - and why?

Update:

Thanks for all the help so far.
OK, the 440v is out. Any future 400+v requirements will be avoided or
met with my own transformer and new top notch gear downstream.

Delta vs Wye?, 208 vs 240 ?
It seems like there are some definite compromises there.
In particular - whether or not you have 110v single and 240v single
available, and whether you have three well balanced legs? (if I
understand correctly).

Any other additions to the delta / wye 208 /240 debate would be
greatly appreciated.

Thanks again for all the help.
Jess

Here's my opinion, for what it's worth, applied to a non-commercial shop
in the U.S. The problem with 480V is not so much a safety issue (and
the real danger is the available fault current more than the voltage) as
one of economics. 480 volt wiring methods are the same as with lower
voltages, but the power panels and breakers tend to be more costly and
you'll need to provide for 120/240 single phase loads with a separate
panel and transformer on a branch circuit. Unless you have several
motors in the greater than 10 to 15 hp range rule 480V services out from
the start.

120/208 wye service is not really appropriate for a shop either, this
service is good for lighting but not so good for motor loads, save it
for the next strip mall or office building you build. It's 208 because
that's what your stuck with when you set out to get 120 volts phase to
neutral in a wye connection.

For a hobby or small commercial shop go with a 240v center tapped delta
service. You get 240 three phase and 240/120 single phase all out of
one panel. Yes, you'll end up with a few unused slots in the panel due
to the 'high leg', but who cares. If it's a mystery as to which phases
supply which voltages to neutral don't even take the panel cover screws
out and leave it to someone who knows, but it's really no big deal. The
power company, at least around here, prefers this service as it
generally has a lower installed cost, they can get by with just two
transformers and wire it open delta. To you, the end user, it generally
won't matter. You'll have extra work to due for single voltage 480V
motors, but most machine tool motors are of the dual voltage variety
anyway. I'm hard pressed for a valid reason to even consider another
service for a small shop.

Regards
Paul
--
-----------------------------------------
It's a Linux world....well, it oughta be.
-----------------------------------------