Why Can't You Connect Ground/Neutral Bus Bars On A Sub - Electrical - Page 3 - DIY Chatroom Home Improvement Forum


Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Electrical

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Display Modes
Old 03-10-2011, 09:27 AM   #31
Member
 
Join Date: Nov 2007
Location: Nashua, NH, USA
Posts: 6,976
Rewards Points: 2,048
Default

Why can't you connect Ground/Neutral bus bars on a sub


Quote:
Originally Posted by 1488rob View Post
I have a question towards this.. On my mainpanel of the halfbuilt house I bought both the neutral and ground wires are wired to same buss and it passed. All breakers are on that side. when I add breakers to the left side wil I be able to wire both neutral and ground to the ground buss?, :
(correction made) Yes for ground wires, no for neutral wires.

In the main panel the "neutral" bus is (should be) connected (bonded) to the panel using a metal strip or a wire or by having a screw that digs into the back of the panel. The "ground" bus is already bonded by being rigidly fastened to a spot on the back of the panel where the paint was scraped off. (correction made here later) Then it does not make any difference whether ground wires are connected to the "neutral" bus or "ground" bus. Neutral wires must all be connected, one per hole or set screw, to the bus where the fat neutral from the service drop is attached.

Two or more ground wires may be taken off the bus, wire nutted to a pigtail of size equal to the larger(est) of them, and just the pigtail re-attached to the bus to free up holes for other wires. Two or more neutrals may not be so pigtailed although we have seen neutrals congregated on a different bus where a crossbar or fatter jumper wire, sized for the sum of the respective circuit amperages, joins the two busses.

Advertisement

__________________
Forget super sized fries. The Washington Redskins could promote healthy eating with First Lady Obama by choosing a (red skinned) turnip for a mascot.

Last edited by AllanJ; 03-11-2011 at 09:20 PM.
AllanJ is offline   Reply With Quote
Old 03-10-2011, 10:35 AM   #32
I=E/R
 
a7ecorsair's Avatar
 
Join Date: May 2010
Location: Minnesota
Posts: 2,052
Rewards Points: 1,000
Default

Why can't you connect Ground/Neutral bus bars on a sub


I think we are all in agreement that current wants to return to its source and in fact, it can't go any other place. You can connect a jumper cable from one terminal on your car battery to a grounded rod and nothing will happen. There is no complete circuit.
Residential housing power is feed to the house using a transformer. A transformer provides isolation between the primary and secondary side. I other words, the current flowing in the primary winding does not pass to the secondary winding. So, in the case of my house, I have 7200 volts on the primary side and 240 volts on the secondary side.
This transformer is connected to my house by three wires and we all know how this is done. This secondary winding is MY SOURCE. As I use electricity, current flows in a big loop around this isolated connection between the house and the transformer. Some between the two hots and some returns through the neutral. I don't need a "ground" for this to work. In fact, if I'm standing on ground and touch a hot lead I don't have a return path to my source. Or do I? Here is where the problem starts. The power company, when they installed the transformer, connected a #6 to the transformer case, which is also connected to the centertap of the secondary winding, for lightning protection. This creates a problem for the house wiring. With this ground wire connected to the transformer secondary, my source, there is now another return path to the source which has to be dealt with. Also, if lighting hits the transformer, the neutral wire will carry some - a lot - of the current to the main panel where it will find its way to earth through the grounding electrode conductor which must be landed on the neutral bar, not the ground bar.
a7ecorsair is offline   Reply With Quote
Old 03-11-2011, 05:57 PM   #33
Member
 
WaldenL's Avatar
 
Join Date: Jan 2009
Location: Nassau, Long Island, NY
Posts: 349
Rewards Points: 268
Default

Why can't you connect Ground/Neutral bus bars on a sub


Quote:
Originally Posted by a7ecorsair View Post
... find its way to earth through the grounding electrode conductor which must be landed on the neutral bar, not the ground bar.
And why is that (I mean electrically, not "because it's code")? After all, the neutral and ground bars should be bonded in the main panel. I can think of two reasons, namely, the bars _should_ be bonded, but may not be, and because the wire bonding the two may not have sufficient current carrying capability. But those are guesses. Why must it be landed on the neutral bar?
WaldenL is offline   Reply With Quote
Old 03-11-2011, 06:18 PM   #34
Master Electrician
 
Join Date: Mar 2010
Location: Indiana
Posts: 2,975
Rewards Points: 2,206
Default

Why can't you connect Ground/Neutral bus bars on a sub


Because the neutral of the service is how the fault current returns to its source which is the transformer.
brric is offline   Reply With Quote
Old 03-11-2011, 07:55 PM   #35
I=E/R
 
a7ecorsair's Avatar
 
Join Date: May 2010
Location: Minnesota
Posts: 2,052
Rewards Points: 1,000
Default

Why can't you connect Ground/Neutral bus bars on a sub


Quote:
Originally Posted by WaldenL View Post
And why is that (I mean electrically, not "because it's code")? After all, the neutral and ground bars should be bonded in the main panel. I can think of two reasons, namely, the bars _should_ be bonded, but may not be, and because the wire bonding the two may not have sufficient current carrying capability. But those are guesses. Why must it be landed on the neutral bar?
Your second guess is pretty close. It also limits the number of connections between the neutral and the GEC to two.
a7ecorsair is offline   Reply With Quote
Old 03-11-2011, 08:54 PM   #36
Master Electrician
 
Join Date: Mar 2010
Location: Indiana
Posts: 2,975
Rewards Points: 2,206
Default

Why can't you connect Ground/Neutral bus bars on a sub


Quote:
Originally Posted by a7ecorsair View Post
Your second guess is pretty close. It also limits the number of connections between the neutral and the GEC to two.
What "two" connections are you referring to?
brric is offline   Reply With Quote
Old 03-11-2011, 09:10 PM   #37
I=E/R
 
a7ecorsair's Avatar
 
Join Date: May 2010
Location: Minnesota
Posts: 2,052
Rewards Points: 1,000
Default

Why can't you connect Ground/Neutral bus bars on a sub


The neutral wire connection to the neutral bar and the GEC's connection to the neutral bar.
a7ecorsair is offline   Reply With Quote
Old 03-11-2011, 09:35 PM   #38
Master Electrician
 
Join Date: Mar 2010
Location: Indiana
Posts: 2,975
Rewards Points: 2,206
Default

Why can't you connect Ground/Neutral bus bars on a sub


I see. I didn't understand the "two" as being two conductors connected at "one" point.
brric is offline   Reply With Quote
Old 03-12-2011, 09:49 AM   #39
Member
 
Join Date: Feb 2010
Location: Oklahoma
Posts: 979
Rewards Points: 502
Default

Why can't you connect Ground/Neutral bus bars on a sub


Quote:
Originally Posted by a7ecorsair
I think we are all in agreement that current wants to return to its source and in fact, it can't go any other place. You can connect a jumper cable from one terminal on your car battery to a grounded rod and nothing will happen. There is no complete circuit.
Residential housing power is feed to the house using a transformer. A transformer provides isolation between the primary and secondary side. I other words, the current flowing in the primary winding does not pass to the secondary winding. So, in the case of my house, I have 7200 volts on the primary side and 240 volts on the secondary side.
This transformer is connected to my house by three wires and we all know how this is done. This secondary winding is MY SOURCE. As I use electricity, current flows in a big loop around this isolated connection between the house and the transformer. Some between the two hots and some returns through the neutral. I don't need a "ground" for this to work. In fact, if I'm standing on ground and touch a hot lead I don't have a return path to my source. Or do I? Here is where the problem starts. The power company, when they installed the transformer, connected a #6 to the transformer case, which is also connected to the centertap of the secondary winding, for lightning protection. This creates a problem for the house wiring. With this ground wire connected to the transformer secondary, my source, there is now another return path to the source which has to be dealt with. Also, if lighting hits the transformer, the neutral wire will carry some - a lot - of the current to the main panel where it will find its way to earth through the grounding electrode conductor which must be landed on the neutral bar, not the ground bar.
For residential power poles - It should be noted that the #6 referenced above is also connected to the earth (at the bottom of the pole). All poles have metal earth connections. THIS is why you may have a problem by touching a hot lead while standing on the ground.

If an entire electrical system were never to be grounded, then we could touch individual hot conductors while standing on the ground, without fear. But, we're grounded, so hands off.
jlmran is offline   Reply With Quote
Old 03-12-2011, 09:59 AM   #40
I=E/R
 
a7ecorsair's Avatar
 
Join Date: May 2010
Location: Minnesota
Posts: 2,052
Rewards Points: 1,000
Default

Why can't you connect Ground/Neutral bus bars on a sub


Thanks for adding the ground rod. I was typing faster than I was thinking.
a7ecorsair is offline   Reply With Quote
Old 03-12-2011, 10:53 AM   #41
Member
 
Join Date: Feb 2010
Location: Oklahoma
Posts: 979
Rewards Points: 502
Default

Why can't you connect Ground/Neutral bus bars on a sub


Actually I've never seen a rod at a pole. Usually just the wire coiled and attached at the bottom face of the pole, or a plate attached to the bottom face of the pole.
jlmran is offline   Reply With Quote
Old 11-07-2012, 02:05 PM   #42
Newbie
 
Join Date: Nov 2012
Posts: 5
Rewards Points: 10
Default

Why can't you connect Ground/Neutral bus bars on a sub


I know this is an old thread, but I thought it was important to add my answer for anyone who might come along and read it. While what you are saying is correct in theory, the whole reason why it's important for the neutral and equipment ground conductors to be isolated at the washing machine is in the case of a wiring error; e.g. say that the washing machine chassis is tied to neutral as in your example. However, what if some homeowner or helpful brother-in-law wired the outlet in reverse? Then instead of neutral going to the chassis in your example, the hot would go there instead. If a barefoot person standing in a puddle of water touched the chassis, then the circuit would be completed to ground through the person's body. It was for this reason that the 3rd ground terminal was added as a clean path to the breaker panel (where it is bonded to the neutral bar) so it could trip the breaker in the event of a short. The distinctive ground terminal greatly reduced the odds that either of the two current carrying wires would ever get accidentally tied to the chassis.

Quote:
Originally Posted by sky jumper View Post
ok so I understand if neutral and ground are connected at an outlet (or device), ground could become a return path for current. my question is so what? since neutral and ground are tied at the service panel, neutral is always at ground potential. this is AC - so it's the hot that varies +/- 170Vpk above and below ground potential, not the neutral. so what if the chassis of the washing machine is tied to neutral? you and the chassis and neutral are all at ground potential anyway, so nothing will happen. your body's resitance is many magnitudes more than a copper wire, so no current will flow through you even if it does flow through the chassis of the washing machine.

ok now assume there's a fault in the washing machine (or stove top) that shorts "hot" to chassis - it will blow the circuit breaker immediately, even if neutral is tied to hot. no danger there.

ok now assume that nuetral is somehow open circuited somewhere in the house (so the chassis is not grounded or tied back to panel neutral) AND AT THE EXACT SAME TIME there just happens to be a fault inside the device that shorts hot to chassis (you see, if either happened first the device would harmlessly stop working, so you'd know something was wrong and get it fixed) -- ok with simultaneous faults (VERY unlikely) you now you have the potential for a hot chassis. BUT why would you assume that a separate ground wire would neccesarily prevent this? I would argue that whatever disruptive action caused the neutral to open (e.g. a contractor's recip saw) would also cut the ground connection to the device (and probably the hot too) since they are all run together. for the life of me I can't imagine a scenario where only the neutral would open circuit AND at the same time a device suffers an internal short to chassis.

if anyone out there has a real world example of this I'd love to hear it.
vgb88 is offline   Reply With Quote
Old 11-07-2012, 02:33 PM   #43
Member
 
Missouri Bound's Avatar
 
Join Date: Apr 2011
Location: Almost Arkansas
Posts: 2,764
Rewards Points: 2,000
Default

Why can't you connect Ground/Neutral bus bars on a sub


Quote:
Originally Posted by junkcollector View Post
You would have parallel paths back to your main panel; your ground would be carrying some of the current that your neutral should be carrying. The ground is normally a non current carrying conductor.

Only in the case of a fault. The main panel shares grounds with neutrals.

Advertisement

__________________
Do you want it your way or the right way?
Missouri Bound is offline   Reply With Quote
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Electrical Panel Bus Bars dave_80 Electrical 22 01-21-2010 11:18 PM
Basement toilet: Watergenie - how to connect to main stack GD73 Plumbing 1 12-21-2009 11:13 AM
How to connect switch to GFCI breaker? firemanter Electrical 3 10-28-2008 08:46 PM
Repairing Futon metal bars? mikehende General DIY Discussions 9 01-24-2008 10:04 AM
Adding a phone line to an older connect point cramsmith General DIY Discussions 3 11-23-2005 12:35 PM




Top of Page | View New Posts