Re: Question about AC power distribution in CNC controller box

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