I keep bringing it up because I'm failing to understand how a 3 line mains + earth ground system poses no danger to a utility guy while a 3 line + earth ground system in a detached poses a danger to a home owner. Unless I just got my 'lineman' and 'electric company guy' terminology mixed up. Is it the alternate electric paths in a household that don't exist in the grid?
3 vs 4 wires for detached structure w/grounding rods
- Thread starter ching0n
- Start date
dave*99
Well-known member
A lineman is the electric company guy that connects your house to the POCO etc.
If you wear a linemans boots, gloves, hardhat and safety glasses in your house you will be as protected as he is. Qualified electrical workers are in a different exposure class than you in your house.
They are trained, they expect everything they touch to be energized, they wear protective personal equipment (PPE).
In your house and yard you may be wet, barefoot, etc. There may be faulty appliances or wiring, unbalanced loads it goes on and on. The lineman knows all 3 of those wires coming into your house represent some level of danger. He avoids bodily contact etc.
BTW, the lineman doesn't care if you have 3 or 4 wires to your subpanel. It's on the other side of his electric meter. It's covered by a different set of rules and codes. He may not even understand the ramifications. Rest assured, when he connects those 3 wires to your house, he will be wearing his PPE.
OP seems to be thinking hypothetically about his outbuilding to house connection being similar to service to main panel connection. Seems the disconnect (pun intended) is he's only equating risks from perspective of lineman vs homeowner working on the electric under controlled circumstances whereas in actuality unforseen hazards may be present to others, children, pets etc who may just be out in the yard not thinking about protecting themselves from unforseen electrical shock hazards. IDK seems the prudent course is to run four wires with unbonded neutral as others have stated.
Correct. Also a lineman has proper training, wears PPE, is isolated in a bucket, and transformers in the grid eliminate many of the dangers a clueless happy homeowner may get tangled up in. (But he/she still has to behave!)
This turned into a though experiment. I've clarified that I won't do anything that's not code, so that means 4 lines. The main question here is that yes, while a lineman will be protected to the gills and have expertise, if a hazard which is present and he's aware of is similarly created in a 3 wire sub scenario for a home owner.
ok, the 'alternate path & no surprises' makes sense to me since there's no extra paths (ideally) for a lineman to worry about since only pros are supposed to touch the grid.
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My point was there are others potentially at risk besides the homeowner in the latter scenario who may not even be aware there are potential hazards at play so the my detached building sub connected to house main is substantially the same as house main connected to utility is not really apples to apples.
ETA the mechanical connections are similar but the hazards are different.
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dave*99
Well-known member
Before we had air bags and seat belts, you could still drive a car. Before we had 4 wire systems you could still energize a light bulb. These developments were driven by safety concerns and incidents.
Going back to Thomas Edison and DC distribution, he only needed 1 wire and the earth to power a bulb. But was it safe?
From the web:
In Edison's early direct current (DC) electricity distribution system, he initially used the Earth as the return conductor, meaning the current would flow through the ground back to the power source instead of a dedicated return wire; however, this practice caused issues like stray voltage and shocks, leading Edison to later develop a three-wire system with a dedicated neutral wire for a safer return path.
Going back to Thomas Edison and DC distribution, he only needed 1 wire and the earth to power a bulb. But was it safe?
From the web:
In Edison's early direct current (DC) electricity distribution system, he initially used the Earth as the return conductor, meaning the current would flow through the ground back to the power source instead of a dedicated return wire; however, this practice caused issues like stray voltage and shocks, leading Edison to later develop a three-wire system with a dedicated neutral wire for a safer return path.
wyliesdiesels
Well-known member
is the lineman gonna be touching the plumbing, metal appliances, etc in your house? nope.... lineman's work stops at the meter.
no there is no alternate pathways in a grid....the poco doesnt bond plumbing lines to the HV neutral up high on the pole.... c'mon man apples to oranges
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Metal-Marc
Well-known member
At this point, OP is arguing for the sake of arguing.
you keep bringing up the lineman and the house when the whole time I'm trying to draw an analogy of the lineman's upward risk to the sub's upward risk to the homeowner. As to the risk of lineman and other metal structures/lines, I'm unfamiliar w/the grid which is why I asked if there is an analogous risk.
edit: my bad for poorly communicating that thought.
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wyliesdiesels
Well-known member
sorry man i have no clue what youre not understanding or what point youre trying to make.....
I went back and re-read all posts. I think I finally "got it" in post 41 what you tried explaining in post 10. There are no current carrying 'alternate' paths for a lineman to worry about above the meter if we think of a home drop as analogous to a "detached" structure between a main and a sub thus making the comparison as you say, apples and oranges.
Chuckster in NJ
Well-known member
mike93lx
ALLIANCE MEMBER
Extra spicyNow onto the next subject: A 3 phase ungrounded delta system.
Metal-Marc
Well-known member
How does it relate to a lineman?Now onto the next subject: A 3 phase ungrounded delta system.
Snapped-off
Well-known member
Just like a submarine.Now onto the next subject: A 3 phase ungrounded delta system.
dave*99
Well-known member
Or we could do earth current in a multi-grounded neutral.
Dagny
Well-known member
Maybe this will help. Draw a picture of an old 3 wire system with several 120 volt loads and a bunch of metal tools,drill press air comp. ect. Now go to the house and remove the neutral connection. all of your metal tools will shock you.
Now do the same with a 4 wire none of your tools will shock you.
Now do the same with a 4 wire none of your tools will shock you.