Gunner said:
Doug Miller wrote:
Rich. wrote:
a foot. With THHN, I can safely install nine #12s in one 1/2" EMT, for 4
_completely independent_ 20A circuits (4 phase conductors, 4 grounded
conductors, and one grounding conductor).
Actually, by code you can have 6 phase conductors, 3 neutrals, and use
the EMT as your ground, giving you 6 circuits instead of just 4.
I would like to know where you have 6 phase service?
He didn't say that. The context makes it very clear that by "phase conductors"
he means what the NEC refers to as "ungrounded conductors", or, in the
vernacular, "hot wires".
I won't go into the use of EMT as a ground source.
EMT is explicitly permitted by the NEC as an equipment grounding conductor.
[2008 National Electrical Code, Article 250.118(4)]
Yes, on the solid run, but not after any couplings, connectors etc..
A Greed Wire is to be inserted in the pipe to insure a real grounding
system and each box is to be connected to this ground.
You can not use EMT or the like for a grounding source directly, it
has to have a ground wire in it and the attached equipment in the
circuit also connects to this same ground.
As for the article you popped up, I think you'll find it proteins to
the use of EMT as a grounding buss point, meaning, several grounds can
come off this point using ground clamps from a single run with no
couplings how ever, a main ground source must be bonded to this pipe.
If you truly believe otherwise, then you are practicing very dangerous
habits.
Haven't you ever heard of galvanetic issues with EMT hardware?
I work in a manufactory facility where we still have a lot of older
machines using the access boxes as the ground sources for attached
equipment with no internal ground wire feed from the main buss. I can
say in the time that I have been there, we have seen several fires from
lose EMT hardware connections causing arcs because the attached
equipment was having ground issues.
With dust,oil and paint that has been apply to these machines, it
makes a nice catalysis for a fire.
Most of the time if your lucky, the lose connects will weld them
self's long enough to force the protection to initiate.
Then the various Licensed Electricians who installed machines etc over
the years at the factory I finished tearing down yesterday were all
doing it illegally. 75,000 sq ft and no grounds in any of the
boxes/runs.
California btw..Anaheim.
yeah, I bet their GFCI's really worked reliably in wet places.
I bet workers just love how they got shocks now and then from
aux equipment.
P.S.
Old mills are grand fathered in, unless, they do updates. Any
new installations are suppose to follow code. also, years ago
it was common when switching the mill over to higher voltages, they
kept on using lower voltage receptacles. There was a transition period
allowed to give plenty of time for the switch over, mean while, they
simply did things like 480 volts in a 240 volt receptacle.. AUX
equipment would use the 208/240 etc. plugs with 480 in it.
Still today, this is being done! shame! shame!
There are exceptions to the rules how ever, insurance companies
love to force these old places to update their basic electricals with
modern wiring systems, cause they know these old mills are full of code
violations.! and grounding and old clothe wire is a big one these days,
along with wire rungs not out of reach or being protected via something
like a jacket (romix) or pipe with a ground in it.
Voltages below 50, can ignore most of everything that is in there how
ever, in this state, maybe others, the state government is now
attempting to enforce (more) low voltage licenses, installers licenses
etc.. of just about anything.
Just goes to show, its all about the money..
---
You should see the screw up that had to be corrected, hacked if you ask
me. we had a long run, a service installed from one of our 2000 amp sub
panel over to a machine that has a 500 HP drive in it along with some
other goodies. 3 EMT pipes were run, one for each phase, 2 1000 MCM in
each pipe. They ran a ground wire only in one pipe. Now keep in mind,
these pipes are running in parallel from the sub panel over to the
machine. Doing thermo imaging, we found 2 pipes were getting hot when
the machine was under heavy operation for a while. That started a
investigation. Its then we found that only 1 pipe had the ground wire
pulled.
All this was done by licensed contracted electricians. We do this
when the job is to large for the in house electricians.
The problem was correctly, not the way it really should of been, but
it covered it. We placed pipe ground clamps on both sides of each emt
connector and connected with copper bar. We later found out, that ground
couplers are made for cases like that in old factories that didn't have
ground wires in. oh well. Expensive as hell, just like the large amp
fuse adapters.
