Using one phase, of the supply, and and the "ground" to form a circuit

Hello,

Is it safe to just use "one" phase of the supply and connect it to a load and directly to the "ground" to
form the ckt/loop??

pls refer to the attachment.

Thanks in advance,
Newbie here
 

Attachments

Besoeker

Senior Member
Location
UK
Just a passing observation from the ignorant Brit.......
I have noticed that there is a tenancy to equate neutral with ground.
I know that they are not the same. As I said, just an observation...........
 

fmtjfw

Senior Member
Single-wire high-voltage distribution in Canadian "out-back" uses the ground (as in dirt) as the return path for the HV primary of the distribution transformers.
 

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
Safety is always a relative term.

My understanding is that there were wartime (WWII) system where power was distributed using a _single_ 'hot' conductor with the conduit as the 'return' wire. These _worked_ but if the conduit system were to be damaged then the conduit itself would become energized! As long as the conduit was intact, IMHO it was a distant cousin to 'safe'.

For wiring certain large appliances, it used to be permitted to install systems where the neutral was used as the 'equipment ground' for the frame of the appliance. Existing installations for ovens and clothes dryers may still used the shared neutral and ground.

Neutral and ground are usually combined in the service drop supplying a home.

In general, you want to have two separate conductors at approximately 0V relative to earth: your 'grounded' conductor which is supposed to carry current, and your 'equipment grounding and bonding conductor' which is for connecting all metal that _isn't_ supposed to carry current, to guarantee that this metal remains at 0V.

The problem with sharing 'grounded circuit conductor' and 'grounding or bonding conductor' is that if the ground opens you will now energize all of the metal connected to the grounding or bonding conductor.

-Jon
 

jaylectricity

Senior Member
Location
Massachusetts
What are those instances that can be considered "it is safe"? Will it make it safe if you'll cover everything with non-conductive materials
If the ground is an insulated conductor and it was connected to the neutral bar in a main panel and nothing else. Which in effect makes it the neutral. But like I said...pedantry.
 

Jraef

Moderator
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
Hello,

Is it safe to just use "one" phase of the supply and connect it to a load and directly to the "ground" to
form the ckt/loop??

pls refer to the attachment.

Thanks in advance,
Newbie here
Theoretically the same as "Neutral" in a grounded neutral system? Yes.

"Safe"? Define what that means. In the NEC world, the REASON why you are not permitted to use the Electrical Grounding Conductor AS the "neutral", even though they are theoretically at the same potential, is because it is in fact NOT considered to be "safe", and the NEC is all about safety. So is it "safe" as defined here? No.

"Legal", definitely NO! Because... IT IS NOT CONSIDERED SAFE!

Done all the time by DIYers and hacks? Yes, unfortunately. In fact that's one way to tell when something has been wired by a DIYer or a hack.

Done sometimes by power utilities, referred to as a "SWER" (Single Wire Earth Return) system ? Yes, but remember, utilities are NOT required to follow the NEC, they have their own rules, and maintain their own equipment. So the safety risks involved involved in a SWER system are born by THEM, not us.
 

mivey

Senior Member
Hello,

Is it safe to just use "one" phase of the supply and connect it to a load and directly to the "ground" to
form the ckt/loop??

pls refer to the attachment.

Thanks in advance,
Newbie here
No. Not safe. The ground is bonded to other metal stuff throughout the load site. The neutral is isolated from all that metal stuff (no neutral-ground bonds beyond the main disconnect).

By using the ground to carry load current, you have parallel current paths through metal stuff and can have load current running through structures, equipment, and other metal stuff at the site.

Don't do it.
 

Carultch

Senior Member
Location
Massachusetts
Hello,

Is it safe to just use "one" phase of the supply and connect it to a load and directly to the "ground" to
form the ckt/loop??

pls refer to the attachment.

Thanks in advance,
Newbie here

No, it is not safe.

There is a difference between neutral and ground. Neutral has the same voltage as ground, however neutral is intended to carry current under ordinary circumstances, and ground is not.

Neutral is ultimately bonded to ground, but this is only permitted to occur at exclusively one point on a service. Usually at the main service disconnect.


Neutral carries return current of ordinary operation.
Ground only carries fault current, in the undesired event that a live wire faults to a metal structure. Ground is bonded to all metal that doesn't intentionally carry current, in order to provide a return path and clear the protection device (eg breaker).
 

Jraef

Moderator
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
Without getting down to the conductor identification rules in 200.7 and 250.119 what code rule really says we can't do that?
Huh, you know what? You may have identified another of my internal "myths". It was my gut reaction, but when I think about it, why is that different from what the circuit would look like on a corner grounded delta 3 phase system feeding a single phase load? You are right in that identification would be crucial, but not illegal to do it? I'm now questioning my long held belief that you can't use the ground connection as a current carrying conductor. It was the way I was taught as an apprentice doing residential work, but when I got into industrial work, I guess I never made the leap of logic to recognize the inconsistency.
 

GoldDigger

Moderator
Staff member
Huh, you know what? You may have identified another of my internal "myths". It was my gut reaction, but when I think about it, why is that different from what the circuit would look like on a corner grounded delta 3 phase system feeding a single phase load? You are right in that identification would be crucial, but not illegal to do it? I'm now questioning my long held belief that you can't use the ground connection as a current carrying conductor. It was the way I was taught as an apprentice doing residential work, but when I got into industrial work, I guess I never made the leap of logic to recognize the inconsistency.
With a corner grounded three phase delta, the NEC still requires both a grounded conductor (carrying normal current) and an EGC (at ground potential, but carrying only fault current.)
The only place that I recall that is in current NEC is the old work exemption for a dryer connection that uses the same wire as neutral and EGC. But that wire has to go directly to the service panel. And not allowed in new construction.

PS: "Let's just connect it to the shell of the equipment and assume that there is a good ground somewhere? "
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Huh, you know what? You may have identified another of my internal "myths". It was my gut reaction, but when I think about it, why is that different from what the circuit would look like on a corner grounded delta 3 phase system feeding a single phase load? You are right in that identification would be crucial, but not illegal to do it? I'm now questioning my long held belief that you can't use the ground connection as a current carrying conductor. It was the way I was taught as an apprentice doing residential work, but when I got into industrial work, I guess I never made the leap of logic to recognize the inconsistency.
I know we shouldn't be able to do it, I just don't know of code section that actually says you can't use an EGC as grounded conductor.
 

mivey

Senior Member
I know we shouldn't be able to do it, I just don't know of code section that actually says you can't use an EGC as grounded conductor.
How about sections dealing with:
color requirement of neutral
insulation requirement of neutral
required grounding conductor would be missing
load current not allowed on grounding system
objectionable current
 

just the cowboy

Inactive, Email Never Verified
Location
newburgh,ny
Didn't they do that on ships

Didn't they do that on ships

If I remember right that was how they wired it on ships, when we had someone from the navy do control work they would say " thats how we did on the ship" The coil from the starter or light would go right to ground. Not sure if it still that way.
Your car also works that way common ground.
 
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