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

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

Reply
 
Thread Tools Search this Thread Display Modes
Old 09-03-2007, 01:34 PM   #16
UAW SKILLED TRADES
 
Stubbie's Avatar
 
Join Date: Jan 2007
Location: Kansas
Posts: 5,015
Rewards Points: 8
Share |
Default

feed back voltage when using double breaker


Mike for what it is worth do a search on phantom voltage. It is a very common occurrence to register these feedback and feed thru voltages using a high impedance digital meter. Some of the reason for this is that many digitals do not put a load on the circuit being tested. You will get the same phenomena when testing the neutral to ground at a receptacle if the neutral is open in the circuit. You can also get 120 volts on the neutral on the load side of a light bulb if the neutral is opened and the switch in the on position.

Here are a couple explanations:

http://en.wikipedia.org/wiki/Phantom_voltage
www.nema.org/prod/wire/build/upload/Bulletin%2088%202003.doc



Stubbie


Last edited by Stubbie; 09-03-2007 at 01:40 PM.
Stubbie is offline   Reply With Quote
Old 09-04-2007, 04:30 AM   #17
Member
 
Join Date: Sep 2007
Posts: 106
Rewards Points: 0
Default

feed back voltage when using double breaker


Thank you Stubbie for the links. I now understand what is going on and what "phantom" voltage is.
sluggermike is offline   Reply With Quote
Old 09-08-2007, 03:05 AM   #18
Member
 
Join Date: Sep 2007
Posts: 106
Rewards Points: 0
Default

feed back voltage when using double breaker


I hate to beat this subject to death, but when using 12/3 romex should the red wire be on one leg of the panel and the black wire be on the other leg, or can you attach the red and black wires to a double thin wafer breaker that has two individual breakers on the same leg of the panel? It doesn't seem to me that it would make any difference. I've already tried it thinking that I would get rid of the false reading that was on the circuit that was turned off, but it didn't make any difference. I now understand the phantom voltage thanks to you'll. I'm now curious about the above stated question. Thanks again.
sluggermike is offline   Reply With Quote
Old 09-08-2007, 07:50 AM   #19
Electrical Contractor
 
jbfan's Avatar
 
Join Date: Jun 2004
Location: Newnan GA
Posts: 5,793
Rewards Points: 18
Default

feed back voltage when using double breaker


"I hate to beat this subject to death, but when using 12/3 romex should the red wire be on one leg of the panel and the black wire be on the other leg "


Yes. This is the cirrect way to do this.


"Can you attach the red and black wires to a double thin wafer breaker that has two individual breakers on the same leg of the panel?

NO. All the current from both circuits would be returning on the netural, and if both circuits are closed to max, the the netural would be undersized for the current
__________________
Yes I am a Pirate, 200 years too late. "Jimmy Buffett"
jbfan is offline   Reply With Quote
Old 09-08-2007, 01:11 PM   #20
Member
 
Join Date: Sep 2007
Posts: 106
Rewards Points: 0
Default

feed back voltage when using double breaker


I will put the hot wires on two different legs of the panel as you suggested. It seems to me that you still have the same amount of current returning to the box on the neutral since it is being used by both circuits when using 12/3?
sluggermike is offline   Reply With Quote
Old 09-08-2007, 07:16 PM   #21
Licensed Pro
 
Join Date: Mar 2007
Location: SC
Posts: 1,541
Rewards Points: 0
Default

feed back voltage when using double breaker


Quote:
Originally Posted by sluggermike View Post
I will put the hot wires on two different legs of the panel as you suggested. It seems to me that you still have the same amount of current returning to the box on the neutral since it is being used by both circuits when using 12/3?
You need to remember Mike, that the neutral carries the difference in current between the two hot legs. That means when the two hots are each carrying the same current, the current on the neutral is zero.
HouseHelper is offline   Reply With Quote
Old 09-09-2007, 02:13 AM   #22
Member
 
Join Date: Sep 2007
Posts: 106
Rewards Points: 0
Default

feed back voltage when using double breaker


Unfortunately for me, I don't know much about electrical theory. Is it good, or is it bad that when both hots are drawing the same current that the neutral current is zero, and why? Thanks
sluggermike is offline   Reply With Quote
Old 09-09-2007, 03:29 AM   #23
Newbie
 
Join Date: Sep 2007
Posts: 1
Rewards Points: 0
Default

feed back voltage when using double breaker


The transformer on your pole out front puts out 220v on it's two legs. The neutral goes to the transformer to the middle of the secondary winding. When you test between a hot leg and neutral you are measuring half the transformers output. Two 110v loads using both legs with a shared neutral sorta end up wired in series. When the loads use differing amounts of power, i.e. 10 amps on one leg, 12 on the other, the surplus 2 amps has to get back to the transformer some how. That's what the neutral is for.
silas99 is offline   Reply With Quote
Old 09-14-2007, 11:32 AM   #24
Member
 
Join Date: Sep 2007
Posts: 50
Rewards Points: 0
Default

feed back voltage when using double breaker


the 50 volts is not a phantom voltage, you are creating a series-parallel circuit when you use the common neutral. you are reading the voltage that is passing through the appliance that is energized. The 50 volts represents the balance of the voltage drop accross that appliance

As somebody else mentioned, the NEC DOES require in all residential buildings that multiwire circuits must be connected with a two or three pole interrupting device so configured that all handles open and close simutaneously.

The full load current of the energized appliance passes through that circuit when only one pole is opened, and presents a lethal danger to home owners who are not qualified to do their own work.
buffalonymann is offline   Reply With Quote
Old 09-14-2007, 11:49 AM   #25
Once fried, twice shy.
 
elkangorito's Avatar
 
Join Date: Sep 2007
Location: Thailand
Posts: 251
Rewards Points: 0
Default

feed back voltage when using double breaker


Quote:
Originally Posted by buffalonymann View Post
the 50 volts is not a phantom voltage, you are creating a series-parallel circuit when you use the common neutral. you are reading the voltage that is passing through the appliance that is energized. The 50 volts represents the balance of the voltage drop accross that appliance

As somebody else mentioned, the NEC DOES require in all residential buildings that multiwire circuits must be connected with a two or three pole interrupting device so configured that all handles open and close simutaneously.

The full load current of the energized appliance passes through that circuit when only one pole is opened, and presents a lethal danger to home owners who are not qualified to do their own work.
I have no idea in what country this situation exists but my question is simple:

Is the neutral permitted to be earthed at the Main Distribution Board (breaker box)?

Australia uses the TT system to distribute its' power. This system allows the use of the MEN system (Multiple Earthed Neutral), which in turn greatly improves the safety of the supply for users. Some people argue that broken neutrals cause a problem in this system but this is not so.

So, are neutrals allowed to be earthed in other countries (i.e. US) & if so, how?


BTW, earthing the neutral gets rid of all the 'phantom' voltages that you speak of. There are very few people in Australia who have this problem because of the MEN system. The only ones who have this problem are 'outback' users who use an SWER (single wire earth return) system.
__________________
Switchboard design engineer & Licensed Electrician (Australia).

Last edited by elkangorito; 09-14-2007 at 11:52 AM.
elkangorito is offline   Reply With Quote
Old 09-14-2007, 11:57 AM   #26
Member
 
Join Date: Sep 2007
Posts: 50
Rewards Points: 0
Default

feed back voltage when using double breaker


Quote:
Originally Posted by elkangorito View Post
I have no idea in what country this situation exists but my question is simple:

Is the neutral permitted to be earthed at the Main Distribution Board (breaker box)?

Australia uses the TT system to distribute its' power. This system allows the use of the MEN system (Multiple Earthed Neutral), which in turn greatly improves the safety of the supply for users. Some people argue that broken neutrals cause a problem in this system but this is not so.

So, are neutrals allowed to be earthed in other countries (i.e. US) & if so, how?


BTW, earthing the neutral gets rid of all the 'phantom' voltages that you speak of. There are very few people in Australia who have this problem because of the MEN system. The only ones who have this problem are 'outback' users who use an SWER (single wire earth return) system.


My first thought with multiple earthed neutrals is the creation of varying voltages accross the grounding conductor, which should not have any voltage on it.

We utilize three basic conductors in our systems. (1) The ungrounded conductor(s), (2) the grounded conductor, (3) the grounding conductor

Our grounding conductor is derived by insulating it from the grounded conductor at the first distribution panel from the xfmr
buffalonymann is offline   Reply With Quote
Old 09-14-2007, 12:08 PM   #27
Once fried, twice shy.
 
elkangorito's Avatar
 
Join Date: Sep 2007
Location: Thailand
Posts: 251
Rewards Points: 0
Default

feed back voltage when using double breaker


Quote:
Originally Posted by buffalonymann View Post
My first thought with multiple earthed neutrals is the creation of varying voltages accross the grounding conductor, which should not have any voltage on it.

We utilize three basic conductors in our systems. (1) The ungrounded conductor(s), (2) the grounded conductor, (3) the grounding conductor

Our grounding conductor is derived by insulating it from the grounded conductor at the first distribution panel from the xfmr
I'm interested in (2) of your answer, the grounded conductor. Exactly what is this & how is this achieved?

The MEN system is achieved by grounding the neutral at the distribution board & by having only one (1) earth stake. As expected, an Earth Fault Loop Impedance check is required before energisation. Also, each supply transformer is delta/star (star secondary) & so the neutral at each transformer is earthed . Also, the neutral is earthed every third power pole (or so). This sysetm provides a dual path (very low impedance) back to the transformer & therefore allows the circuit protection to work effectively & quickly.
__________________
Switchboard design engineer & Licensed Electrician (Australia).
elkangorito is offline   Reply With Quote
Old 09-14-2007, 12:16 PM   #28
Member
 
Join Date: Sep 2007
Posts: 50
Rewards Points: 0
Default

feed back voltage when using double breaker


Quote:
Originally Posted by elkangorito View Post
I'm interested in (2) of your answer, the grounded conductor. Exactly what is this & how is this achieved?

The MEN system is achieved by grounding the neutral at the distribution board & by having only one (1) earth stake. As expected, an Earth Fault Loop Impedance check is required before energisation. Also, each supply transformer is delta/star (star secondary) & so the neutral at each transformer is earthed . Also, the neutral is earthed every third power pole (or so). This sysetm provides a dual path (very low impedance) back to the transformer & therefore allows the circuit protection to work effectively & quickly.
It appears that you are referring to outside distribution, i was referring to inside distribution.

I am certified on inside work, but I believe our outside distribution is configured similarly as yours. I'm quite sure the Utility 'earths' the neutral or "grounded conductor" This is why it is called the grounded conductor. Our Utilities provide both star and delta primaries
buffalonymann is offline   Reply With Quote
Old 09-14-2007, 12:18 PM   #29
Member
 
Join Date: Sep 2007
Posts: 106
Rewards Points: 0
Default

feed back voltage when using double breaker


Say, Speedy Petey and Stubbie what do you think about the recent posts by buffalonymann and elkangorito? Are they talking about wiring 120 volts in the US, or are they talking about wiring outside of the US where they use 240 volts? I thought I had the phantom voltage figured out until now.
sluggermike is offline   Reply With Quote
Old 09-14-2007, 12:21 PM   #30
Member
 
Join Date: Sep 2007
Posts: 50
Rewards Points: 0
Default

feed back voltage when using double breaker


I'm a Master Electrician in New York State. Its not a phamtom voltage, the 50 volts is the balance of the voltage drop across the engerized appliance

buffalonymann is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
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
Circuit breaker panel - Advice needed justtired Electrical 15 12-13-2007 05:55 AM
Outdoor breaker panel questions lhoney2 Electrical 12 07-19-2007 05:44 PM
Breaker Buzz SkipI Electrical 2 07-13-2007 07:48 PM
Holy smoking commander breaker drogosandybanks Electrical 13 01-10-2007 02:34 PM
single vs. double breaker Neil_K Electrical 3 11-14-2004 11:02 PM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.