Re: Question about AC power distribution in CNC controller box

Nowhere did I say I intended to tie the 2 power inputs together... I
don't understand why this became the understanding.

My intent is to supply the controller board and 2 low power AC
devices (switched with solid state relays) with one 120v 10A power
entry module and then power the 120V transformers (motor power
supply) and the spindle with a completely seperate 120v 15A power
entry module. Line and Neutral will NEVER get near each other...

The question is how to ground the two 120V seperate power inputs. Do
I put 2 ground posts or 1? I fail to see the difference between
having 2 boxes, each with their own ground posts but the chassis
bolted together vs. 1 box with two ground posts to the chassis.

I think the safest option is to have a box within a box for space
saving purposes, while still keeping some physical isolation between
the two AC inputs, but electrically, this should be the same as 2
ground posts in one box. Right?

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Don Rogers <Don@C...> wrote:
> At 01:41 AM 7/16/03 +0000, you wrote:
> >Are you saying that code requires design to 220V?
> >
> >If I build the other box, is it an issue if the cases are bolted
> >together?
>
> Look, running two 120V lines into a box that will create 240V is
not a good
> thing to do. Likewise, running 240V into a box and spiting it to
120V is
> not a good thing to do. Don's rule (mine, and never mind the
national
> electrical code after I almost fried my self) is that only one
supply
> circuit breaker (house, shop, etc) can supply a power cord, and
only on
> power cord to a box.
>
> If you are running 120V transformers, etc, use a single 120V
supply. If
> you need to run 240V, use transformers, components, etc that are
240V rated
> and wired.
>
> The National Electrical Code requires a floating neutral beyond the
entry
> point of a building. Ground and neutral can only be common at the
entry
> point. Any sub panels, or distribution points must isolate neutral
and
> ground. Running two 120V lines into a controller box and tieing
neutral
> and ground together will violate the code. Floating them in the
same box
> can create a safety hazard.
>
> If your components are 240v/120V rated, by all means run 240 to
them as it
> will be less expensive to run as you are using a balanced current
draw on
> the main line, and the meter will spin slower. But don't run two
120V
> lines to get the 240V.
>
> Sorry for the rant, but after dam near getting electrocuted because
the
> jerk who wired my previous house ran two circuits into a light
switch box,
> and on both sides of neutral. I killed the one side, and started
working
> on a outside light, thinking I had killed the box. After a very
loud pop,
> and the neighbor kids calling out, "Hey Mr Rogers, are you OK?". I
> formatted my rule stated above. One circuit into a box. Period.
>
> Don