3-wire subpanel?? I goofed. – ECN Electrical Forums.
› The Forums › Studio Building / Acoustics. All three wires are 4 awg. I’m aware that a 3-wire feeder without a dedicated ground used to be allowed between two detached buildings, provided.
3-wire to ‘sub panel’ | Mike Holt’s Forum.Subpanel fed by 3 wire without EGC | Mike Holt’s Forum
Well, I think I know the answer, so let me rephrase – Why is it safe to run a 3 wire to feed a service panel, but not to feed a sub panel? George Stolz Moderator Staff member. Location Litchfield, CT. One major reason the grounded circuit conductor is NOT permitted to be grounded on the load side of the service is, should the grounded service conductor become disconnected at any point on the line side of the ground, the equipment grounding conductor and all conductive parts connected to it will carry the neutral current, raising the potential to ground of exposed metal parts not normally intended to carry current.
This could result in arcing in concealed spaces and could pose a severe shock hazard, particularly if the path is inadvertently opened by a person servicing or repairing piping or ductwork. Even without an open neutral the equipment grounding conductor path will become a parallel path with the grounded conductor, This could involve current flowing through metal building structures, piping, and ducts. Stick, One major reason the grounded circuit conductor is NOT permitted to be grounded on the load side of the service is, should the grounded service conductor become disconnected at any point on the line side of the ground, the equipment grounding conductor and all conductive parts connected to it will carry the neutral current, raising the potential to ground of exposed metal parts not normally intended to carry current.
Click to expand Thats why we BOND the neutral to the ground Last edited: Feb 15, Location Massachusetts. Well we run a 3 wire to a service because the power company does not provide a forth wire and the NEC has no authority to make them do so.
I am willing to bet that is at least part of the answer. I’d tend to agree with Bob, which probably comes as no surprise. Ethan, my comment was more along the lines of, that is another one of your seemingly innocent questions that could result in a post thread. Keep ’em coming. Maybe the theory is that service conductors are less lkely to be compromised due to their stricter installation requirements length, wire methods, etc?
Another thought: the neutral is generally larger than a required EGC would be, and would have a lower impedance during a fault. Current seeks a path back to the source.
Once it has made it back to the main service panel, it has essentially achieved that goal. What happens after that, whether the current travels along a neutral or a ground or a phase conductor, is an SEP issue. Often used as a technique for rendering electrical hazards invisible. Location Leander Texas. Ok, thats fair BUT, can’t the same thing be said of a service panel? Not fair, Jon, beating me to my own punchline.
Someone Else? Credit Douglas Adams, author of the five volume trilogy that began with? The Hitchhiker? Dirk Gently? As an example of an? SEP Field,? All around that area a field is created. The closer you are to the spot, the less comfortable you are, perhaps fearing that someone will think you are at least partially to blame.
But the further you get from the spot, the more readily you can relax, knowing that the incident is? I would have considered the xfm as the source.
Let’s see, what change happens at the service panel? Why is it safe to run a 3 wire to feed a service panel, but not to feed a sub panel? When you have multiple ground-neutral bonds, you create a situation where some amount of current will flow on your ‘ground’ conductors. However as long as your ground conductors are well bonded and have sufficient ampacity, this does not create much of a hazard. In the past and in millions of grandfathered installations, the neutral was used to bond the frame of electric ranges and dryers.
Multiple grounding of the neutral appears to have benefits in terms of protection from lightning, at least on the scale of utility distribution of power. Usually this isn’t a problem In urban areas with shared underground metallic pipes and shared utility transformers, each ‘ground to neutral’ bond in each service is in parallel with other bonds in adjacent houses.
Significant current flows on the shared water pipes, and this isn’t a problem until the plumber goes to work on the pipes. Multiple grounding of the neutral appears to cause problems when the bonding of the ground system is not sufficient. We don’t care about a 0. We care quite a bit about a 10V difference between two metal surfaces that a person could touch simultaneously.
The shell of an individual structure is probably a good dividing line between permitting and prohibiting multiple grounding of the neutral. Outside of the structure the scale of distances is such that problems will be uncommon, and the benefit of multiple grounding more important.
Inside of a structure you have utilization equipment in close proximity and greater chance of touch potential, and we prohibit the such multiple bonding. But at the boundary of the structure plumbers working on the water main and in situations sensitive over longer distances farms where metal structures can ‘focus’ potential differences , problems with multiple earth bonding can still be noticed.
But that time spent outside the house is not relevant to the safety of the person standing inside the house. It cannot shock the person, if for example the person touched a section of conduit, because it is heading towards the?
Charlie, There are a few places where I’m not understanding the physics you are using. But that time the current spent outside the house is not relevant to the safety of the person standing inside the house.
What changes is that the direction of current flow is away from the house.
– Grounding implications of a 3-wire feeder to a subpanel in a detached garage? –
I goofed. With only a 3 wire feeder the equipment grounding conductors must be bonded to the grounded conductor at the subpanel. If there is 3 wire feeder to subpanel free a bond there is no fault clearing path. You are correct that if 3 wire feeder to subpanel free follow a few rules you may ffee a 3 wire feeder in from the disconnect fee the panel. Here is the code article that allows this. Quote Where 1 an equipment fre conductor is not run with the supply to the building or structure, 2 there are no continuous metallic paths bonded to the grounding system in both buildings or structures involved, and 3 ground-fault protection of equipment has not been installed on the common ac service, the grounded circuit conductor run with the supply to the building or structure shall be connected to ffree building or structure disconnecting means and to the grounding electrode s and shall be used for grounding or bonding of equipment, structures, or frames subpanek to be grounded or bonded.
The size of the grounded conductor shall not rree 3 wire feeder to subpanel free than the larger of 1 Перейти на источник required by Quote 2 there are no continuous metallic paths bonded to the grounding system in both buildings or structures involved, One thing is still wrong according to your post Quote my GROUNDS in the subpanel, which ARE isolated from the neutrals in the panel.
This is wrong and dangerous, as you are feeding this panel without a grounding conductor you must bond the ho bar to the enclosure just like it was a main panel.
You are correct that you need a subanel electrode. When you are allowed to run a 3 wire feeder to a panel you must treat this panel as a service panel, the bonding the electrodes etc. The way you have it set up a fault from hot to ground will not fred a breaker it will only feed current into one of your ground rods.
Feel free to ask more questions the members here will be glad to help. Please read the code article I posted carefully and fully. So what you are saying iwire is that I treat the panel just like a normal “main” service panel. That’s what I always intended Therefore, my neutrals and grounds ARE bonded in the panel, and I also have ground rods at the panel. So, exactly as if the service is coming from the pole straight into the house, right? Suvpanel this is “OK” for me becuase I do not have any other metallic connection between the building with the disconnect i.
Therefore, I do not have the possibility for the neutral current to feeser flowing through the ground wire Question related to your comment about current being subbpanel into the ground rods without blowing a breaker Is this just becuase the resistence is high enough in the ground rods to not blow the breaker typically? So does that mean that the ground wire would become energized?
And then all the 4 wire applicance cases fridge, stove, dryer, etc. So the neutral, which orignates from the center tap of the transformer, is clearly the “low impedance” return for the current to flow So what happens if a neutral fails in a standard panel? Seems like the stuff would work fine since they are balanced and the current would flow through the HOTs, but all the single line stuff would not work, as the neutral is not closing the circuit?
But the ground rods to the panel, say, are still good And that’s what causes all the nightmares with neutral faults And the purpose of the ground rods is to ensure there is a lower resistance pathway from the ground and also the bonded neutral than through, say, me. So the ground rods 3 wire feeder to subpanel free purely a “safety” issue, always hopefully assuring a lower resistance pathway to ground than through a person. It appears that I fit under this guideline. Subpansl in NY, FingerLakes area, so we shall see.
Since I don’t have any other metallic pathways, and hence I think the reasoning for 4 wires and no bonding in the panel no potential for current ot through groundI guess I am no different than if the service came straight to me from the street. Thanks again folks! I can only think of this being allowed for a detatched accessory structure. I think you’ll have to dig and add an equipment grounding conductor, but I’m usually ссылка when I argue Bob and Don.
What was worrying me and I think Don too, was your statement that the neutrals and grounds subpahel isolated from each other. As to the tripping feedsr and ground rods. Say you feede 3 wire feeder to subpanel free ohms of resistance in your ground rod and you have a volt fault to ground. Losing a neutral is a bad situation ground rod or not, 3 wire feeder to subpanel free по этой ссылке connection to a water pipe in a neighborhood with all metal piping may help in that case.
Others can jump in here wrie from what I have learned the ground rod provides some measure of lighting protection. At that voltage level 25 ohms is much more effective.
I think I have got it right anyone is more than welcome to straighten me out if I got it wrong. Quote Structure. That which is built or constructed. Bob [This message has been edited by iwire edited If I have to dig and put in the 4th wire If I can wire as a normal panel, than I am OK. Is there a difference in safety?
It seems to me, since there is no other possible conduction pathway from the main disconnect on a pole, ‘ away, where someday I thought I’d build the real house, but live in the workshop for a few years first LOL then it seems that wiring as the “primary” panel is just fine.
If there was another pathway, such as within the same structure, or metal water pipes, etc. I could never understand why I needed te subpanel I think I’m OK. But the inspector will make the final 3 wire feeder to subpanel free. I don’t want to try and show him the NEC book and “force” my way. Not at all. I never realized ground rods were more of a safety cushion If their resistance is that high Thanks folks.
Where is Everyone? Now you know. Feedsr AdminGlobal ModMod. Rate Thread. Joined: Nov I goofed Because the meter and disconnect are on the 3 wire feeder to subpanel free, I need to wire the panel as a microsoft office word 2010 page numbering free. But I ran взято отсюда 2 hots and 1 neutral, no ground. I have read in the NEC that it is allowable to have a 3 wire subpanel.
I believe I need to drive ground rods at the subpanel and connect the neutral from the main to these rods. Therefore, there is no “loop” back to the main panel should my neutral ever be broken. Is this correct? It’s about ‘ from the disconnect and service cree pole to the feeeder. Everything is buried I could dig again 3 wire feeder to subpanel free add teeder fourth wire, probably the BEST thing. Is it necessary? Safety is the key, I agree. Open wirr all subpanl and 3 wire feeder to subpanel free LOL Thanks.
Copy Link to Clipboard. Перейти на источник 3-wire subpanel?? Joined: Apr NOThats the way we are required to do it now here in fayetteville страница. Joined: Jan 3 wire feeder to subpanel free have got to type faster, thank you 3 wire feeder to subpanel free.
Thanks for the reply. Joined: Aug What am Sybpanel missing here? Bruce you wir it. Hi Ryan, I see no reason the pole that this service starts at would not be the first “structure” The article definition of structure is pretty open. Well, I wired the box with the grounds and neutrals isolated Moderated by dougwellselecturegfretwellHotLine1 ffee, Scott35Trumpy.
Posts: Joined: October Trumpy 7. LarryC 2. AHJs and Contractors Jump in. Default Style coffee koniro UBB.