Getting things arranged in my new (new for me) shop. It has 3 phase power,
therefore the questions.

1) Do I simply run 3 wires to the machines (lathe, mill, grinder & surface
grinder) and let the conduit be the ground, or do I need a seperate ground
wire. The existing building has a few 3ph outlets (in conduit), but no
ground wires.

2) My machines will be out in the middle of the floor. Do I simply dangle a
conduit from the roof framing (15 ft. above), or, do I install a post upon
which the conduit will come down? Do I do this once for each machine?
Somebody must have a clever solution to this situation. I don't want to cut
up my slab and install wires below.

Thanks for any and all answers.

Ivan, amateur relocated to Oregon.

"Ivan Vegvary" wrote in message
news
Getting things arranged in my new (new for me) shop. It has 3 phase
power,
therefore the questions.

1) Do I simply run 3 wires to the machines (lathe, mill, grinder & surface
grinder) and let the conduit be the ground, or do I need a seperate ground
wire. The existing building has a few 3ph outlets (in conduit), but no
ground wires.

Using the rigid conduit (either EMT or the threaded style) as ground does
meets code. Code says this is discretionary - run a separate ground wire
inside the conduit if the location puts the conduit at risk from corrosion
or mechanical damage, or if you feel like it.

If part of the conduit is "flex" there are restrictions on the length and
the current rating for its use as the grounding conductor. The flex
connectors aren't as secure as EMT so it's a good idea to either not use
them at all or to run the separate ground wire.

2) My machines will be out in the middle of the floor. Do I simply dangle
a
conduit from the roof framing (15 ft. above), or, do I install a post upon
which the conduit will come down? Do I do this once for each machine?
Somebody must have a clever solution to this situation. I don't want to
cut
up my slab and install wires below.

The conduit needs to be fully supported. You'd need a post to drop it all
the way down from 15'. The more common thing is to install cord drops.
Install a box at the ceiling with a 4 conductor SO cord attached at the top
via a cord strain relief, with a L15 twistlock female cord connector at the
loose end.

If you make the cords long, they can run horizontal some and then drop down
wherever.

Using the plug and receptacle means you don't need a separate disconnect
switch.

Bob

Ivan
Two electrical questions, please

1) Run a ground wire at least equal to the phase wires. But at least #6 Bare
copper. Conduit does not cut it for ground unless you have some electrical
specifications for the conduit and the connectors. Which I have never seen or
heard of.

A plus for this will be a ground rod at the machine location drivern through a
hole drilled in the floor.

2) Run it all in conduit if possible or the code requires it. I don't think
the code allows for a 15 foot cord hanging down. Also a conduit has to be
supported evry so often. Not sure of the code for this. And above some HP
rating a safety switch is required for each machine. A 3 pole safety switch.
Securely mounted somewhere within sight of the machine when it is turned off
for whatever. Also if there is any use of 110 volts at the machine you will
need a neutral wire. And a plus for this would be to simply run the neutral to
each machine and provide for an outlef for lighting etc.

Additionally. If the machines are in a cluster it is possible to make just one
conduit run to the cluster.

If you do run conduit make it a size or two bigger to allow for growth or
change.

Hope this helps
Bob AZ

Ivan Vegvary wrote:

2) My machines will be out in the middle of the floor. Do I simply dangle a
conduit from the roof framing (15 ft. above), or, do I install a post upon
which the conduit will come down? Do I do this once for each machine?
Somebody must have a clever solution to this situation. I don't want to cut
up my slab and install wires below.

I have seen shops which run power to machines right across the floor, and
they use sheet metal double-sided "ramps" over the conduit so no one trips.
Personally, I'd just run boxes on the walls and run SO cable across the floor
in nice neat straight runs. If you have to run machinery over the cabling
then place a long 2x4 next to the cable.

Grant

On Sun, 28 Dec 2003 04:31:31 GMT, "Ivan Vegvary" wrote:
Getting things arranged in my new (new for me) shop. It has 3 phase power,
therefore the questions.

1) Do I simply run 3 wires to the machines (lathe, mill, grinder & surface
grinder) and let the conduit be the ground, or do I need a seperate ground
wire. The existing building has a few 3ph outlets (in conduit), but no
ground wires.

That's permissible, but I always like to run a separate grounding wire.
That's insurance in case something happens to the conduit, ie a joint
comes undone or becomes high resistance, so that it is no longer a
good continuous metallic circuit.

2) My machines will be out in the middle of the floor. Do I simply dangle a
conduit from the roof framing (15 ft. above), or, do I install a post upon
which the conduit will come down? Do I do this once for each machine?
Somebody must have a clever solution to this situation. I don't want to cut
up my slab and install wires below.

You want to support and protect the conduit, so a post would be best.
But you can use heavy wall rigid conduit. In effect that *becomes* the
post.

Gary

"Ivan Vegvary" wrote in message
news
Getting things arranged in my new (new for me) shop. It has 3 phase
power,
therefore the questions.

1) Do I simply run 3 wires to the machines (lathe, mill, grinder & surface
grinder) and let the conduit be the ground, or do I need a seperate ground
wire. The existing building has a few 3ph outlets (in conduit), but no
ground wires.

2) My machines will be out in the middle of the floor. Do I simply dangle
a
conduit from the roof framing (15 ft. above), or, do I install a post upon
which the conduit will come down? Do I do this once for each machine?
Somebody must have a clever solution to this situation. I don't want to
cut
up my slab and install wires below.

Thanks for any and all answers.

Ivan, amateur relocated to Oregon.



Ivan,

If you like you could run a dedicated ground conductor alongside or inside
the existing conduit--bare or insulated copper should be fine..........It
then becomes your ground path--at this juncture, the conduit is simply
grounded, where this is a requirement in the case of metallic conduit
anyways.

As to the fifteen foot ceiling drop, not sure it would be to code, but if a
plug were installed in the ceiling it would technically be a disconnect at
that point. This places the machinery into the "portable "
classification........

Personally, I would avoid running power cables across the shop floor.

The current trend is to avoid multiple ground paths.......a "star" grounding
system is preferred, whereas all grounds lead to a central point--that being
the service entrance grounding stake, via the entrance panel grounding
bussbar.

As such, I would recommend against pounding additional ground stakes in the
system other than perhaps those that will be connected only to the service
panel ground buss, and only in the event the existing stake is found to be
insuffecient.

I have taken the liberty of crossposting this thread to the alt.machines.cnc
newsgroup, as we have others there, including a resident electricial
contractor there who might well be able to answer any further questions you
might have.

( Pinging Grampaw Lucas...........)

Cheers,

--

SVL

On Sun, 28 Dec 2003 01:01:56 -0800, "\"PrecisionMachinisT\"" wrote:
If you like you could run a dedicated ground conductor alongside or inside
the existing conduit--bare or insulated copper should be fine..........It
then becomes your ground path--at this juncture, the conduit is simply
grounded, where this is a requirement in the case of metallic conduit
anyways.

Always a good plan.

As to the fifteen foot ceiling drop, not sure it would be to code, but if a
plug were installed in the ceiling it would technically be a disconnect at
that point. This places the machinery into the "portable "
classification........

Wouldn't be Code. The disconnect has to be in sight and *in reach* of
the operator. Unless you're very tall, or have extremely long arms, mounting
the disconnect 15 feet in the air wouldn't comply with the requirements.

The current trend is to avoid multiple ground paths.......a "star" grounding
system is preferred, whereas all grounds lead to a central point--that being
the service entrance grounding stake, via the entrance panel grounding
bussbar.

Yes. Star connection avoids ground loop problems, which can generate
EMI problems.

Gary

"Gary Coffman" wrote in message
...

As to the fifteen foot ceiling drop, not sure it would be to code, but if
a
plug were installed in the ceiling it would technically be a disconnect
at
that point. This places the machinery into the "portable "
classification........

Wouldn't be Code. The disconnect has to be in sight and *in reach* of
the operator. Unless you're very tall, or have extremely long arms,
mounting
the disconnect 15 feet in the air wouldn't comply with the requirements.


Perhaps a drop at ~ seven feet would do the trick then................

--

SVL

From the ceiling come down to the machine with a piece of 4 conductor cable
sized for the machine (10 gauge for 30 amp, 8 for 60 amp) put a recpticale
on the end and come out of the machine with a 2 or 3 foot cable with a plug.
You didn't say what size machines they where (Power wise not physical size)
""PrecisionMachinisT"" wrote in message
...

"Ivan Vegvary" wrote in message
news
Getting things arranged in my new (new for me) shop. It has 3 phase
power,
therefore the questions.

1) Do I simply run 3 wires to the machines (lathe, mill, grinder &
surface
grinder) and let the conduit be the ground, or do I need a seperate
ground
wire. The existing building has a few 3ph outlets (in conduit), but no
ground wires.

2) My machines will be out in the middle of the floor. Do I simply
dangle
a
conduit from the roof framing (15 ft. above), or, do I install a post
upon
which the conduit will come down? Do I do this once for each machine?
Somebody must have a clever solution to this situation. I don't want to
cut
up my slab and install wires below.

Thanks for any and all answers.

Ivan, amateur relocated to Oregon.



Ivan,

If you like you could run a dedicated ground conductor alongside or inside
the existing conduit--bare or insulated copper should be fine..........It
then becomes your ground path--at this juncture, the conduit is simply
grounded, where this is a requirement in the case of metallic conduit
anyways.

As to the fifteen foot ceiling drop, not sure it would be to code, but if
a
plug were installed in the ceiling it would technically be a disconnect at
that point. This places the machinery into the "portable "
classification........

Personally, I would avoid running power cables across the shop floor.

The current trend is to avoid multiple ground paths.......a "star"
grounding
system is preferred, whereas all grounds lead to a central point--that
being
the service entrance grounding stake, via the entrance panel grounding
bussbar.

As such, I would recommend against pounding additional ground stakes in
the
system other than perhaps those that will be connected only to the service
panel ground buss, and only in the event the existing stake is found to be
insuffecient.

I have taken the liberty of crossposting this thread to the
alt.machines.cnc
newsgroup, as we have others there, including a resident electricial
contractor there who might well be able to answer any further questions
you
might have.

( Pinging Grampaw Lucas...........)

Cheers,

--

SVL

Should have been more clear, the cable coming down from the ceiling is "SO"
type rubber covered cable
"MushHead" wrote in message
v.net...
From the ceiling come down to the machine with a piece of 4 conductor
cable
sized for the machine (10 gauge for 30 amp, 8 for 60 amp) put a recpticale
on the end and come out of the machine with a 2 or 3 foot cable with a
plug.
You didn't say what size machines they where (Power wise not physical
size)
""PrecisionMachinisT"" wrote in message
...

"Ivan Vegvary" wrote in message
news
Getting things arranged in my new (new for me) shop. It has 3 phase
power,
therefore the questions.

1) Do I simply run 3 wires to the machines (lathe, mill, grinder &
surface
grinder) and let the conduit be the ground, or do I need a seperate
ground
wire. The existing building has a few 3ph outlets (in conduit), but
no
ground wires.

2) My machines will be out in the middle of the floor. Do I simply
dangle
a
conduit from the roof framing (15 ft. above), or, do I install a post
upon
which the conduit will come down? Do I do this once for each machine?
Somebody must have a clever solution to this situation. I don't want
to
cut
up my slab and install wires below.

Thanks for any and all answers.

Ivan, amateur relocated to Oregon.



Ivan,

If you like you could run a dedicated ground conductor alongside or
inside
the existing conduit--bare or insulated copper should be
fine..........It
then becomes your ground path--at this juncture, the conduit is simply
grounded, where this is a requirement in the case of metallic conduit
anyways.

As to the fifteen foot ceiling drop, not sure it would be to code, but
if
a
plug were installed in the ceiling it would technically be a disconnect
at
that point. This places the machinery into the "portable "
classification........

Personally, I would avoid running power cables across the shop floor.

The current trend is to avoid multiple ground paths.......a "star"
grounding
system is preferred, whereas all grounds lead to a central point--that
being
the service entrance grounding stake, via the entrance panel grounding
bussbar.

As such, I would recommend against pounding additional ground stakes in
the
system other than perhaps those that will be connected only to the
service
panel ground buss, and only in the event the existing stake is found to
be
insuffecient.

I have taken the liberty of crossposting this thread to the
alt.machines.cnc
newsgroup, as we have others there, including a resident electricial
contractor there who might well be able to answer any further questions
you
might have.

( Pinging Grampaw Lucas...........)

Cheers,

--

SVL

Gary Coffman wrote in
:

On Sun, 28 Dec 2003 01:01:56 -0800, "\"PrecisionMachinisT\""
wrote:
If you like you could run a dedicated ground conductor alongside or
inside the existing conduit--bare or insulated copper should be
fine..........It then becomes your ground path--at this juncture, the
conduit is simply grounded, where this is a requirement in the case of
metallic conduit anyways.

Always a good plan.

As to the fifteen foot ceiling drop, not sure it would be to code, but
if a plug were installed in the ceiling it would technically be a
disconnect at that point. This places the machinery into the "portable
" classification........

Wouldn't be Code. The disconnect has to be in sight and *in reach* of
the operator. Unless you're very tall, or have extremely long arms,
mounting the disconnect 15 feet in the air wouldn't comply with the
requirements.

IIRC, I believe the code says the disconnect must be within 6ft of the
appliance/equipment and mounted 4 to 6 ft in elevation from the floor.




--
Anthony

You can't 'idiot proof' anything....every time you try, they just make
better idiots.

Remove sp to reply via email

"Gary Coffman" wrote in message
...
On Sun, 28 Dec 2003 01:01:56 -0800, "\"PrecisionMachinisT\""
wrote:
If you like you could run a dedicated ground conductor alongside or
inside
the existing conduit--bare or insulated copper should be fine..........It
then becomes your ground path--at this juncture, the conduit is simply
grounded, where this is a requirement in the case of metallic conduit
anyways.

Always a good plan.

As to the fifteen foot ceiling drop, not sure it would be to code, but if
a
plug were installed in the ceiling it would technically be a disconnect
at
that point. This places the machinery into the "portable "
classification........

Wouldn't be Code. The disconnect has to be in sight and *in reach* of
the operator. Unless you're very tall, or have extremely long arms,
mounting
the disconnect 15 feet in the air wouldn't comply with the requirements.

The current trend is to avoid multiple ground paths.......a "star"
grounding
system is preferred, whereas all grounds lead to a central point--that
being
the service entrance grounding stake, via the entrance panel grounding
bussbar.

Yes. Star connection avoids ground loop problems, which can generate
EMI problems.

Gary

Two different issues here. SAFETY grounding (what the NEC code requires) is
all about ground loops, lots and lots of ground loops, the more the merrier.
For safety purposes you want to make a ground connection every chance you
get. So that ground wire in the pipe is going to be connected at both ends
and possibly at several different places. The reasons for all these
interconnections is simple. When a big motor running on 3 phase 240 0r 480
volt power suddenly shorts to ground some really interesting **** happens.
Look at the circuit breaker feeding that motor. Notice it has an
Interrupting Current rating of somewhere between 10,000 and 100,000 AMPS!
That's the amount of current that can pass through the breaker in short
circuit, and the breaker can open it up without being destroyed by the arc.
Those big numbers are NOT speculative, they are easily calculated and
demonstrated. You don't want to be near the results during a real
demonstration! So what happens to all those amps trying to get back to the
source of the power? They flow EVERYWHERE in your grounding system. If it
was done right and there are no loose connections, high resistance paths
etc, then all that happens is that a fuse blows or a breaker trips. Unless
of course the electrical engineer that designed your CNC picked up a couple
of different grounds inside the machine while looking for the mythical
'clean ground' If you're feeling real lucky maybe you just gouge a part.
If it really ain't your day you may lose your CNC in cloud of smoke.

Now inside you CNC is a whole different matter. The ground is used as a
zero reference for 24 vdc, 12vdc, 5 vdc, 3.3 vdc etc. For current to flow
though you need a complete circuit, a circle or loop. No current can flow,
at any voltage, without a complete circuit. By connecting every thing in
the CNC, including the external safety ground, to just one ground point (it
LOOKS like a star radiating outwards) you ensure that no current can flow
from the safety ground THROUGH your CNC. What causes all the problems is
all the help we get from the various manufacturers of the parts used to
build a machine. Some provide 'convenient' ground points on devices, that
just happen to connect to various ground wires in cables and on circuit
boards, through different paths. If you go connecting all these without
actually checking how they are wired you will inadvertently get ground
loops. The ground loops allow current to flow from various sources, say
from the enormous surge of that motor which shorted to ground, and then bad
things happen. Sometimes people drive ground rods in hopes of getting the
mythical 'clean ground'. Sometimes it seems to work, because providing a
new path changes the current flowing in other paths. Usually though the
relief is temporary. Something big shorts to ground elsewhere in the plant
and thousands of amps of current go looking for a new path home. That's
when your local part changer earns his big bucks.

Now if we could just get the damn electronics engineers to understand the
above we could stop fighting this bull****.

Gary H. Lucas

"MushHead" wrote in message
v.net...
From the ceiling come down to the machine with a piece of 4 conductor
cable
sized for the machine (10 gauge for 30 amp, 8 for 60 amp) put a recpticale
on the end and come out of the machine with a 2 or 3 foot cable with a
plug.
You didn't say what size machines they where (Power wise not physical
size)
""PrecisionMachinisT"" wrote in message
...


SO is rated differently than romex. With 4 current carrying conductors, 10
Ga is
good for 20 amps, 8 Ga. is good for 28 amps and 6 ga is good for 36 amps.
Table 400.5


Nate


---

Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.544 / Virus Database: 338 - Release Date: 11/25/03

On Sun, 28 Dec 2003 04:31:31 GMT, "Ivan Vegvary"
wrote:

Getting things arranged in my new (new for me) shop. It has 3 phase power,
therefore the questions.

1) Do I simply run 3 wires to the machines (lathe, mill, grinder & surface
grinder) and let the conduit be the ground, or do I need a seperate ground
wire. The existing building has a few 3ph outlets (in conduit), but no
ground wires.

That used to meet the rules, but all new work should have a ground
wire run inside with the rest of the conductors, and you should
retrofit everything old that you work on as a safety matter. One
loose conduit fitting anywhere in the run (and it happens a lot) and
all your equipment isn't grounded anymore. On heavier circuits you
can use a reduced size ground, like #8 hots with a #10 ground, as long
as the ground wire gauge is heavy enough to pop the breaker on a short
circuit without damage.

If you have 240V 3-phase Open Delta "High Leg" power (two lines are
120V to ground but one line is 208V to ground) make sure to code the
High Leg with Orange wire and tapes, and be very careful not to hook
it to the control circuits of the equipment. Or to 120V loads, where
the "Magic Smoke" will escape from any device plugged in...

And if the machine takes 120V from one of those legs to ground for
the work lights or control circuits, you need to run a white neutral
wire in the conduit, too. It used to be legal to put parasitic loads
like that on the safety ground wire, but no more.

2) My machines will be out in the middle of the floor. Do I simply dangle a
conduit from the roof framing (15 ft. above), or, do I install a post upon
which the conduit will come down? Do I do this once for each machine?
Somebody must have a clever solution to this situation. I don't want to cut
up my slab and install wires below.

You can drop it from the ceiling, but you should have a vertical 2x4
there for support of the conduit - and that will also give you a place
to mount the safety switch & receptacle. You always need a way to
lock-out a piece of gear while you're working on it, and a fused
safety switch mounted within easy reach of the machine operator is the
safest way for hard-wired tools.

You could use cord drops from the ceiling, but you need to hang them
from strain relief cord grips, the wire basket "chinese handcuff"
style, or they'll pull out of the fittings from their own weight. If
you use a cord cap as the disconnect & lockout device, you'll need to
buy or build the little locking metal plug boxes that physically
enclose the machine's plug to prevent the cord being plugged in.

For the final word on how it needs to be done, call up your local
Building Inspection authority (city, county, state depending on where
you are) and have a "Hypothetical" discussion with them about how it
should be done in their area to satisfy the codes "if you were going
to do it." (Wink, nod...) They may let it slide without an inspection
(and the necessary plans, permits & fees) but you still want to do the
work right.

Don't poo-pooh locking stuff out - ALWAYS as a bare minimum at least
tag (paper note "Leave Circuit 3 Off! Working on lathe.") and tape
the breaker to the OFF position as a clue for the uninitiated. If you
have children (or employees), they sell lock adapters for most modern
breaker panels that clamp the breaker handle in the OFF position.

The first time someone turns the power back on could be deadly -
somebody pops another circuit, doesn't call you, and just goes to the
main panel and starts cycling all the breakers back on. While you're
out in the shop and have your arms inside the machine up to your
elbows...

Or worse, you forget that you weren't done with the repairs and you
turn the breaker back on & blow it up yourself...

-- Bruce --