Added: Melecio Blosser - Date: 03.05.2022 06:25 - Views: 32698 - Clicks: 7058
It only takes a minute to up. Connect and share knowledge within a single location that is structured and easy to search. Why does a power sub panel have to have separate neutral and ground bars other than code satisfaction?
Also, does the sub panel need a ground wire connected back to the main panel in the same building? If you have the neutral and ground bonded at a subpanel, then you'll get neutral return current through the ground wire back to the main panel since there are now multiple paths. Even worse, as Tester points out, if the neutral ever has a fault, everything will continue to work but you'll have all the current on the ground, which also means that you can now be electrocuted by touching the panel chassis, for example.
The ground and neutral must be bonded only at one place in the main panel to avoid this. A main breaker on a sub-panel is not necessary because this is in the same building if you are in a different building then NEC That said, having a main breaker in the sub-panel is also acceptable. For whatever reason economy of scale, I guess "main" panels are often sold cheaper. I recently purchased a small breaker panel which included a main breaker and a couple 15A breakers for almost half the price of a similarly-sized sub-panel which didn't include any breakers.
This is regardless of being in the same structure or not. As stated above current flows from the hot wire through the device and returns on the neutral wire. It is used for one thing and one thing only!!! To provide a short to trip the breaker. I asked the electrical inspector who tagged me on the first time I installed a sub panel in my home. I am not an electrician but understand the concept The inspector could not answer my question of WHY??? He said because code says you can't! After careful consideration it came to me WHY!
The further from the ground bar in the panel the more resistance in the white wire. The further you go the higher the voltage potential on the white wire gets. Ground is not covered in most cases. If you touch the white wire after the lamp you will get a jolt. When you touch the wire at the ground lug you won't.. Just OHMS law. Maybe this will help you understand why ground should not be hooked to white at any place but the ground bar in the main panel.
up to this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. Why does a subpanel need separate ground and neutral? Ask Question. Asked 6 years, 8 months ago. Active 4 years ago. Viewed k times. Does a sub panel need a main breaker if there is one at the main? Improve this question. Add a comment. Active Oldest Votes. Subpanel main breaker A main breaker on a sub-panel is not necessary because this is in the same building if you are in a different building then NEC Improve this answer.
If you have the grounding and grounded neutral bonded at the second panel, you will have current on the grounding conductor. If for any reason the grounded neutral drops out, all the current will be on the grounding conductor. If the second panel is in a seperate building, the main breaker satisfies the disconnect requirement.
Tester wouldn't a GFCI in the sub panel prevent that? The grounding and grounded conductors are bonded at the main panel. If they're also bonded at a second panel, any current on the grounded conductors of the panels branch circuits will use both the grounded and grounding conductor to return to the main panel. This is because some of the current will be returning on the grounding conductor. Machavity Tony Tony 11 1 1 bronze badge. I see what you're saying but when you apply Ohms law, it doesn't seem that ificant If you run 20 amps through it, that gives a voltage drop of around 5 volts ignoring connector resistance.
If you bonded the ground and neutral at the panel, that would cut the resistance back to the main panel in half, so there'd be around 2. Well after reading what you said again.. YES if the ground and neutral were cut I was only considering that the ground itself would be carrying a current and that current would be greater the further away from the ground lug. What you say is very valid! Thank you! Featured on Meta. Linked 1. Related 4.
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