# Bonding screw main panel/ grounded neutral



## js5518 (Dec 4, 2018)

Hi, thanks for any help! I just realized that there wasn't a bond screw in my main panel. I know it is supposed to be installed only in the 1st/ main panel. What could happen if it isn't in? Second question maybe more complicated? Subpanel with three wires hot/hot/ neutral no bond screw but accidently connected neutral to ground and powered on. Two smoke alarms popped and I turned breaker off. I fixed the neutral wire and tried again and the two alarms that popped then smoked while watching them. Cut power and removed the alarms that popped and smoked. What happened electrically? I know I was stupid but want to understand what happened. All other breakers and neutral now connected in that box without any problems. Just alarm breaker is off. I guess it powered the neutral somehow and blew them? Be nice please


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## nealtw (Dec 5, 2018)

I will leave the bonding issue for those that know for sure.

Okay we know the mistake you made, what were you actually doing when you did it. Are the detectors interconnected? When you pulled them, did you un wire them or just pull the little plugs out?


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## afjes_2016 (Dec 5, 2018)

It would help if you posted pictures of both the panels so we can see what you have. Also you state the first main panel does not have a bonding screw. How many wires are going into that panel. Are you sure you do not have a disconnect prior to that panel.

Also, what do you mean by you _fixed the neutral_. What was wrong with the neutral?

Yes, the sub panel needed 4 wires going to it not 3. Hot, hot, neutral and ground.


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## js5518 (Dec 5, 2018)

Yes the detectors were interconnected. I unplugged each one to quiet. The subpanel is connected with conduit so maybe that's why there isn't a separate 4th wire for ground. There is a disconnect at the meter socket 100 ft from house. Could it be bonded there? Not sure? What did the power up with the neutral actually do? Fixed neutral, was accidently connecting to ground and then returning it to neutral. That is what I don't really understand? Thanks


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## WyrTwister (Dec 5, 2018)

nealtw said:


> I will leave the bonding issue for those that know for sure.
> 
> Okay we know the mistake you made, what were you actually doing when you did it. Are the detectors interconnected? When you pulled them, did you un wire them or just pull the little plugs out?



     By Code , the first panel or disconnect must have the neutral & earth ground bonded together .  If you have an outside main , that is it .

     All other panels do not have the neutral and ground bar bonded .  And must be feed with the neutral , hots & an earth ground .

Wyr
God bless


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## nealtw (Dec 5, 2018)

js5518 said:


> Yes the detectors were interconnected. I unplugged each one to quiet. The subpanel is connected with conduit so maybe that's why there isn't a separate 4th wire for ground. There is a disconnect at the meter socket 100 ft from house. Could it be bonded there? Not sure? What did the power up with the neutral actually do? Fixed neutral, was accidently connecting to ground and then returning it to neutral. That is what I don't really understand? Thanks


Sounds like you wired the detectors with a dead short. Hooking neutral to ground is wrong but it would not have caused your problem.


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## js5518 (Dec 5, 2018)

Thanks. Yes, it was wrong. To be clear, it was the feed neutral and not the detector neutral.  That is fixed. If the subpanel was energized with hot/hot and no neutral would that then be 240 to connected breakers? Something definitely popped and smoked the detectors?  It is all back the way it was now. I think it is correct but still want to understand what caused it, short, 240 or what? WyrTwister I have a meter socket outside 100 ft from house with a 200 amp breaker and would it be bonded in there and then not bonded at the house circuit panel? Is that what you were saying?


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## nealtw (Dec 5, 2018)

js5518 said:


> Thanks. Yes, it was wrong. To be clear, it was the feed neutral and not the detector neutral.  That is fixed. If the subpanel was energized with hot/hot and no neutral would that then be 240 to connected breakers? Something definitely popped and smoked the detectors?  It is all back the way it was now. I think it is correct but still want to understand what caused it, short, 240 or what? WyrTwister I have a meter socket outside 100 ft from house with a 200 amp breaker and would it be bonded in there and then not bonded at the house circuit panel? Is that what you were saying?


So you had it hooked to ground and then discovered the mistake and moved the neutral with out turning off the main?


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## js5518 (Dec 5, 2018)

No, the main and breaker feeding the subpanel was off.  The neutral was in the subpanel. Then yes it was fixed. The only question now is what actually happened and not what is right or wrong.  The exception being that bonding screw in the house main panel which is # 1 in the house but after the outside meter with 200 breaker 100 ft away.


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## hornetd (Dec 5, 2018)

Without the pictures someone already asked for we can only guess but here's mine.  With the panel energized without the neutral connected to the main bonding jumper at the outside disconnect; no matter where the break in the neutral occurred; the voltage across the individual branch circuit would depend on which of the energized conductors had the most load connected to it.  The voltage of the more heavily loaded energized conductor will be lower than the voltage of the less heavily loaded energized conductor.  The greater the disparity in the loading the greater the voltage difference will be.  Keeping in mind what I said about this being a guess; or in other words pure speculation on my part; what may have happened is that the smoke detector circuit may have been subjected to a voltage which was markedly higher than the smoke detectors could withstand.  Unlike the 600 volts which the entire wiring plant can be expected to be insulated to, individual devices such as smoke detectors, GFCI receptacles, built in timer switches, appliance controls... may fail at a much lower voltage to ground.  It is entirely possible that an imbalanced load and no neutral connection was the cause butt that does not mean that it was the cause!  The only way we may be able to give you a much more reliable answer is if you provide a picture which clearly shows the connection which was previously open.  So if you want to actually know the cause of your problem then take the picture and post it.  If my purely speculative guess is good enough then good luck to you and the Boston Red Sox because you'll both need it!  

-- 
Tom Horne


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## hornetd (Dec 5, 2018)

js5518 said:


> No, the main and breaker feeding the subpanel was off.  The neutral was in the subpanel. Then yes it was fixed. The only question now is what actually happened and not what is right or wrong.  The exception being that bonding screw in the house main panel which is # 1 in the house but after the outside meter with 200 breaker 100 ft away.


A huge issue, which is not yet clear to me; is whether the Feeder from the outdoor Service Disconnecting Means has a separate Equipment Grounding Conductor (EGC) run with the Grounded Current Carrying Conductor (Neutral) and the energized conductors.  I believe that you said that the Main Bonding Jumper; in the form of a machine screw that connects the neutral buss to the panel cabinet; was not installed in the house panel when you first energized that panel.  If that is true then even if there is an EGC run with the feeder from the outdoor disconnect the bonding screw would be unlikely to prevent the damage.  Whether the Feeder to the house was required to have an EGC run with it when it was installed would depend on which addition of the electrical code was in effect when the permit for that work was issued.  Providing that the work was finished in the time allowed by the permit, the permits issue date carves the code which was in effect at that time into stone in regards that installation. 

--
Tom Horne


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## hornetd (Dec 5, 2018)

js5518 said:


> *Some original text deleted so as to limit my reply to one question.*  The exception being that bonding screw in the house main panel which is # 1 in the house but after the outside meter with 200 breaker 100 ft away.


  The answer to this question is; If an Equipment Grounding Conductor (EGC) was run with the other feeder conductors supplying the house the installation of a bonding jumper between the neutral buss and the House panel's cabinet is not merely not required but it is actually prohibited.  What is required, regardless of whether or not an EGC was run with the feeder,  is the installation, at the house, of a Grounding Electrode System which includes all of the electrodes named in the article 250 which are present.  In the absence of one of the named electrodes that is not an underground metal water pipe an additional electrode is required consisting of a minimum of two driven rods at least eight foot long and six feet apart. 

--
Tom Horne


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## js5518 (Dec 5, 2018)

Tom. Thanks! This set up has been operating for about 18 years. I did not actually do this neutral myself but have been trying to help. Don't know about the EGC being run with the feeders? I do know there is at least 1 rod near the house. I was asked what happened and was not able to explain it. Yes, I know that it would only be bonded at the first location and didn't really think about it being outside at the meter disconnect. No water pipe to connect with here, well water. The bonding screw is definitely not in the main panel inside the house. Not in the sub. Your answer about the smoke detector circuit is probably the answer I was trying to understand. The connection was fixed and don't what I would take picture of now? I will open the outside meter box tomorrow and see if there is 3 wires and ground. I think there is a rod at meter and at the house and just the 3 wire feed. Don't really know the code from 18 years ago. If safety would be better with another rod at either location it would be simple enough! The subpanel is located 2 ft away from the house main and connected with conduit with no separate ground but three wires, hot/hot and neutral which was the incorrectly attached wire to ground bar of sub which attached to the neutral in the house main panel. The sub panel is not bonded. The subpanel is now connected correctly minus the possible bare ground to main panel ground bar. The whole house is conduit pipe which was code.


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## hornetd (Dec 5, 2018)

Is the water pipe to the pit adapter metal?  Is the well casing metal?  If the well has a metal casing it makes a very effective grounding electrode.  If the water pipe to the pit adapter is plastic, as many are, then the challenge will be to run a Grounding Electrode Conductor (GEC) to the well casing if it is metal. 

If there is no Equipment Grounding Conductor run with the Feeder from the outdoor Service Disconnecting Means (SDM) then the house panels cabinet should be bonded to the feeder neutral just as it would be if that panel were the location of the SDM.  Each building that is supplied by a Service which is located outside that building has to have a Building Disconnecting Means that meets all of the requirements for an SDM.  That includes the requirement that the building be disconnected with six throws of the hand.  In other words not more than six Switches, Fused Pull Outs, or Circuit Breakers can be needed to completely disconnect the building.  Does the house panel have a main breaker?  This all makes it fairly important that you find out whether or not an EGC was run with the Feeder Conductors which supply the house.

As I already wrote a Grounding Electrode System that meets all the requirements for a Service must be installed at each separate structure which is supplied from the outdoor SDM enclosure.  Although the code required Grounding Electrode System can be a minimum of two driven rods which are eight feet long or longer and are driven at least six feet apart that is not a very effective electrode system in most soil types.  If you can you will want to install a Ground Ring.  That is a number two American Wire Gauge copper conductor which circles the entire house at a minimum depth of 30 inches.  If it would be less wire to reach the well, and the well has a metal well casing, than that makes a very good Grounding Electrode.  That conductor would need to be buried at two feet below the finished grade so there is no reason not to bury it as deeply as is practical.  If you use a machine to do the trenching then the maximum practical depth for that machine should be used.  The deeper a bare GEC or Ground Ring conductor is buried the more effective a part of the Grounding Electrode System it will be until you are down to the permanent moisture level.  Once you get to a foot under the permanent moisture level there is no point of going any deeper if the other requirements for depth of bury have been met.   If you cannot install a Ground Ring and attaching the Grounding Electrode Conductor to a metal well casing is impractical then you will need to drop back to rearranging the two driven rods to be more effective.  To do that you drive the second rod at least twice the length of the longest rod away from the first rod in a trench that is at least 30 inches deep.  The two rods are driven through the bottom of the trench, which puts the entire rod 30 inches underground, and the Grounding Electrode Conductor is laid in the bottom of the trench.  You also use the number two copper which would be required for a Ground Ring rather than the much smaller number six AWG which the code allows for the GEC to a Driven Electrode.  Testing done by the National Institute of Standards and Technology (NIST) show that this in the minimum practical Grounding Electrode System which will be effective in providing an adequate ground for a home. 

Do let us know what you find at the Service Disconnecting Means.  A picture of that assembly would be really helpful. 

--
Tom Horne


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## js5518 (Dec 6, 2018)

I will look tomm. Well is not metal. For sure when house was built 1 rod was required, pretty sure? Ring not possible. Adding another rod is possible assuming this is now required or better safety?  Detached garage is shut off completely from house main and garage has main breaker for shutting off circuits while in garage. Subpanel is shut off with breaker in main. House has main shut off and then everything is shut off from meter breaker at meter. All this stuff was inspected and approved????????????????I do see things done wrong, based on what I am learning here!


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## WyrTwister (Dec 6, 2018)

js5518 said:


> Thanks. Yes, it was wrong. To be clear, it was the feed neutral and not the detector neutral.  That is fixed. If the subpanel was energized with hot/hot and no neutral would that then be 240 to connected breakers? Something definitely popped and smoked the detectors?  It is all back the way it was now. I think it is correct but still want to understand what caused it, short, 240 or what? WyrTwister I have a meter socket outside 100 ft from house with a 200 amp breaker and would it be bonded in there and then not bonded at the house circuit panel? Is that what you were saying?



     That is how I interpret code and what I would do .  However there is a distinct possibility the installer may not have run the earth ground for that 100 foot ( just 2 hots and the neutral ) .

     That 200 amp breaker is THE MAIN .  All other panels must , by code , have neutrals and grounds separated .  

     By design , neutral is a current carrying conductor .  By design , the earth ground kind of " stabilizes " the neutral .  But the only time it carries a true current is when one of the hots shorts out to earth ground .  To facilitate tripping / blowing the over current device .

     The neutral is there for function .  The earth ground is there for safety .

     If you hook up the hots to a panel ( with some / all the CB's ( circuit breakers on ) , the 120 VAC circuics will experience any where from 0 - 240 VAC .  Depending on what is actually turned on .

Wyr
God bless


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## js5518 (Dec 6, 2018)

So, you would consider the outside 200 amp breaker as the main? This is where it should be bonded and everything after is separated ? Then each other box would require it's own means of ground to earth? They are but I think only 1 rod per box. I figured that the smoke alarm components couldn't handle whatever was put through  them. The wires supplying them seem fine it was just the alarm itself.  I know for sure the detached garage ground from rod goes to the neutral bar with other neutral connections. Will change that by adding bar in the box for ground wire. Been that way for 18 years!  Thanks


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## WyrTwister (Dec 6, 2018)

The 200 amp CB is the main .  That is where the neutral should be bonded to earth ground and where the ground rod ( or other grounding electrodes ) should be terminated .  From there downstream , they are essentially feeder grounds or equipment grounding conductors .

     In practice , at the house , other grounding electrodes may or may not be terminated at the ground ( not neutral ) bar .  Not sure about the best interpenetration of code on that , but if it is , not at any sub panel .  As far as I know , in our area , metal conduit is still considered a legal ground .  But we always run a ground conductor .

     We do a few residential service calls , but have not done new houses for ages . 

     I agree , the wire to the smoke detectors would not normally be damaged in such a case , even though the smoke detector is toast .

     In the case of a detached garage , I would have to look that up .

Wyr
God bless


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## js5518 (Dec 6, 2018)

Outside.


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## js5518 (Dec 6, 2018)

main inside


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## js5518 (Dec 6, 2018)

sub inside next to main attached with conduit


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## js5518 (Dec 6, 2018)

detached garage


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## hornetd (Dec 6, 2018)

js5518 said:


> sub inside next to main attached with conduitView attachment 21354


The Grounded Current Carrying Conductor (Neutral) is not marked as required by the National Electric Code (NEC).  It is not clear to me if the termination point on the buss bar that was used for the Neutral is actually large enough for that size of conductor.  I notice that the larger add on lug which is specifically provided to terminate the Neutral is not used so I cannot help but wonder why.  I cannot tell if the conduit nipple which was used to route the feeder conductors to the Feeder Supplied Panel is bonded to the Cabinet at each end.  That may not be technically required by the NEC but it is certainly good practice.  Best practice would have been a seperate Equipment Grounding Conductor (EGC) connected to the GEC buss bar in the second panel and to the Neutral buss bar in the house's Building Disconnecting Means enclosure cabinet.  Bonding the Feeder nipple with Bonding Bushings would not only assure the electrical continuity of the nipple but also guard against any future corrosion of the contact between the Nipple and the two panel enclosure cabinets. 







-- 
Tom Horne


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## hornetd (Dec 6, 2018)

js5518 said:


> detached garageView attachment 21355








The thing that jumps out at me is that two terminals on the neutral buss were used to terminate a single stranded conductor.  That is never a permitted practice under the National Electric Code because the terminals are not being used in compliance with their listing and labeling.  There are add on lugs which are listed to be attached to the buss bar for terminating these larger conductors. 

I'm also wondering were that bare stranded conductor comes from.  Is it in the feeder from the house?  I think that is were you said the Garage Feeder originates.  Is there another conductor that serves as the Grounding Electrode Conductor (GEC) or is the split bare stranded conductor the GEC?  A picture of the entire panel would be helpful. 

--
Tom Horne


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## hornetd (Dec 6, 2018)

js5518 said:


> Outside. View attachment 21352








There are a couple of possibilities here which may be useful now or in the future. 

This may seem an off the wall question but were is the water pressure tank located, that is supplied from the well, and were is the breaker located which supplies power to the well pump and it's controls?  I ask this because best practice with water pumps which may be used to supply water for first aid firefighting is to supply the pump with power from a source which is not located in any of the buildings which may need first aid firefighting effort.  That is one of the reasons that separate well houses are often built to protect well heads and pressure tanks.  If an additional disconnect were to be installed at the Service Disconnecting Means (SDM) location to power the water pump it is allowed to tap off it's supply from ahead of the 200 Ampere main breaker which is serving as the SDM.  That still leaves you with only two breakers to shut off the service but it is worth knowing that the National Electrical Code specifically allows the disconnecting means for such a water pump to be excluded from the maximum of six switches, fused pull outs, or circuit breakers that can be used as the Service Disconnecting Means. 

The second thing that occurs to me is that since you have another breaker space in the meter mains enclosure you could install an additional breaker to supply the detached garage.  That would accomplish at least two things.  The first would be to make more power available for the house as the Garage's load would not be going through the existing 200 ampere circuit breaker.  The second would be to free up two breaker spaces in the panel which includes the Building Disconnecting Means for the house.  

-- 
Tom Horne


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## hornetd (Dec 6, 2018)

js5518 said:


> main insideView attachment 21353








I do not see a bonding screw installed in this panel as a Main Bonding Jumper.  I also do not see an Equipment Grounding Conductor (EGC) from the Feeder that goes back to the Service Disconnecting Means.  That is because I am *assuming* that the bare copper conductor that terminates right beside the Feeder's Neutral Conductor is a Grounding Electrode Conductor (GEC).  [Which may mean that "***/U/Me" is in play here.  That means "To make an *** out of you and me."]  Have I got it right or is that bare copper conductor the EGC from the supply Feeder? If there is no EGC run with the feeder from the Service Disconnecting Means (SDM) then there is no fault clearing pathway from the EMT which serves as the EGC for each of the circuits supplied by either panel in the house.  One of the two fault clearing pathways must always be present!  Either the Building Disconnecting Means enclosure cabinet is bonded to the neutral of a three wire Feeder OR the cabinet is connected to an EGC that is run with the feeder conductors all the way back to were the SDM's Main Bonding Jumper connects that EGC to the Neutral conductor of the Utility's Service Drop or Lateral.  There has to be a way for ground fault current to get back to the secondary winding of the utility's transformer so that sufficient current will flow to quickly open the breaker of the circuit which has a ground fault.  In the absence of that fault current path exposed conductive parts of the entire house electric system will become energized at or near 120 volts relative to any grounded conductive surfaces in the house.  That means that several deadly traps could exist between those two kinds of surfaces all over the house just waiting for someone to touch one of each at the same time.  

--
Tom Horne


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## js5518 (Dec 6, 2018)

hornetd said:


> There are a couple of possibilities here which may be useful now or in the future.
> 
> This may seem an off the wall question but were is the water pressure tank located, that is supplied from the well, and were is the breaker located which supplies power to the well pump and it's controls?  I ask this because best practice with water pumps which may be used to supply water for first aid firefighting is to supply the pump with power from a source which is not located in any of the buildings which may need first aid firefighting effort.  That is one of the reasons that separate well houses are often built to protect well heads and pressure tanks.  If an additional disconnect were to be installed at the Service Disconnecting Means (SDM) location to power the water pump it is allowed to tap off it's supply from ahead of the 200 Ampere main breaker which is serving as the SDM.  That still leaves you with only two breakers to shut off the service but it is worth knowing that the National Electrical Code specifically allows the disconnecting means for such a water pump to be excluded from the maximum of six switches, fused pull outs, or circuit breakers that can be used as the Service Disconnecting Means.
> 
> ...


Tank is in the same room as the house main panel. The breaker is in this panel. The detached garage is not even close to that meter and not really any practical way to change. Not sure I follow on the Building disconnect? The house is disconnected with the 200 amp breaker in the house main? So this meter location is not bonded and would require the bonding screw in the house main panel?


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## js5518 (Dec 6, 2018)

hornetd said:


> I do not see a bonding screw installed in this panel as a Main Bonding Jumper.  I also do not see an Equipment Grounding Conductor (EGC) from the Feeder that goes back to the Service Disconnecting Means.  That is because I am *assuming* that the bare copper conductor that terminates right beside the Feeder's Neutral Conductor is a Grounding Electrode Conductor (GEC).  [Which may mean that "***/U/Me" is in play here.  That means "To make an *** out of you and me."]  Have I got it right or is that bare copper conductor the EGC from the supply Feeder? If there is no EGC run with the feeder from the Service Disconnecting Means (SDM) then there is no fault clearing pathway from the EMT which serves as the EGC for each of the circuits supplied by either panel in the house.  One of the two fault clearing pathways must always be present!  Either the Building Disconnecting Means enclosure cabinet is bonded to the neutral of a three wire Feeder OR the cabinet is connected to an EGC that is run with the feeder conductors all the way back to were the SDM's Main Bonding Jumper connects that EGC to the Neutral conductor of the Utility's Service Drop or Lateral.  There has to be a way for ground fault current to get back to the secondary winding of the utility's transformer so that sufficient current will flow to quickly open the breaker of the circuit which has a ground fault.  In the absence of that fault current path exposed conductive parts of the entire house electric system will become energized at or near 120 volts relative to any grounded conductive surfaces in the house.  That means that several deadly traps could exist between those two kinds of surfaces all over the house just waiting for someone to touch one of each at the same time.
> 
> --
> Tom Horne


Yes, that bare wire is the grounding rod for supply. Need to use bonding screw for that panel?


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## js5518 (Dec 6, 2018)

hornetd said:


> The thing that jumps out at me is that two terminals on the neutral buss were used to terminate a single stranded conductor.  That is never a permitted practice under the National Electric Code because the terminals are not being used in compliance with their listing and labeling.  There are add on lugs which are listed to be attached to the buss bar for terminating these larger conductors.
> 
> I'm also wondering were that bare stranded conductor comes from.  Is it in the feeder from the house?  I think that is were you said the Garage Feeder originates.  Is there another conductor that serves as the Grounding Electrode Conductor (GEC) or is the split bare stranded conductor the GEC?  A picture of the entire panel would be helpful.
> 
> ...


Yes, that wire needs to be moved to ground bar instead of the neutral bar. That goes to a ground rod, not from house. Does that neutral look bonded? Do I need to remove that center screw?


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## js5518 (Dec 6, 2018)

hornetd said:


> The Grounded Current Carrying Conductor (Neutral) is not marked as required by the National Electric Code (NEC).  It is not clear to me if the termination point on the buss bar that was used for the Neutral is actually large enough for that size of conductor.  I notice that the larger add on lug which is specifically provided to terminate the Neutral is not used so I cannot help but wonder why.  I cannot tell if the conduit nipple which was used to route the feeder conductors to the Feeder Supplied Panel is bonded to the Cabinet at each end.  That may not be technically required by the NEC but it is certainly good practice.  Best practice would have been a seperate Equipment Grounding Conductor (EGC) connected to the GEC buss bar in the second panel and to the Neutral buss bar in the house's Building Disconnecting Means enclosure cabinet.  Bonding the Feeder nipple with Bonding Bushings would not only assure the electrical continuity of the nipple but also guard against any future corrosion of the contact between the Nipple and the two panel enclosure cabinets.
> 
> 
> 
> ...





js5518 said:


> detached garageView attachment 21355





hornetd said:


> The Grounded Current Carrying Conductor (Neutral) is not marked as required by the National Electric Code (NEC).  It is not clear to me if the termination point on the buss bar that was used for the Neutral is actually large enough for that size of conductor.  I notice that the larger add on lug which is specifically provided to terminate the Neutral is not used so I cannot help but wonder why.  I cannot tell if the conduit nipple which was used to route the feeder conductors to the Feeder Supplied Panel is bonded to the Cabinet at each end.  That may not be technically required by the NEC but it is certainly good practice.  Best practice would have been a seperate Equipment Grounding Conductor (EGC) connected to the GEC buss bar in the second panel and to the Neutral buss bar in the house's Building Disconnecting Means enclosure cabinet.  Bonding the Feeder nipple with Bonding Bushings would not only assure the electrical continuity of the nipple but also guard against any future corrosion of the contact between the Nipple and the two panel enclosure cabinets.
> 
> 
> 
> ...





hornetd said:


> The Grounded Current Carrying Conductor (Neutral) is not marked as required by the National Electric Code (NEC).  It is not clear to me if the termination point on the buss bar that was used for the Neutral is actually large enough for that size of conductor.  I notice that the larger add on lug which is specifically provided to terminate the Neutral is not used so I cannot help but wonder why.  I cannot tell if the conduit nipple which was used to route the feeder conductors to the Feeder Supplied Panel is bonded to the Cabinet at each end.  That may not be technically required by the NEC but it is certainly good practice.  Best practice would have been a seperate Equipment Grounding Conductor (EGC) connected to the GEC buss bar in the second panel and to the Neutral buss bar in the house's Building Disconnecting Means enclosure cabinet.  Bonding the Feeder nipple with Bonding Bushings would not only assure the electrical continuity of the nipple but also guard against any future corrosion of the contact between the Nipple and the two panel enclosure cabinets.
> 
> 
> 
> ...


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## js5518 (Dec 6, 2018)

I definitely appreciate the help! Honestly my head is hurting...……………..Thanks


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## hornetd (Dec 7, 2018)

To Mark the Neutral conductor you can paint it white or grey where it is accessible.  There is a product called "Liquid Electrical Tape"  which is available in white, green, and red.  I have found it easy to use for marking conductors and since it is made to insulate wires and is UL listed I can be reasonably sure that it will not harm the insulation.  There are also paint markers with latex paint in them in quite a few colors.  Latex paint is also safe to use on wire insulation.  Alternatively you can simply apply a single wrap of white or gray electrical tape over the visible portion of the neutral conductor in each panel.  That is really awkward to do once the wire is in place and energized.  In this case you could simply open the breaker that protects the Feeder conductors from the panel cabinet which holds the Building Disconnecting Means to the adjacent Feeder supplied panel.  You could then take the Neutral out of it's terminal lug to make taping it a lot easier.

I'm still waiting for you to tell us whether there is or is not an Equipment Grounding Conductor run with the other conductors of the Feeder from the meter mains Service Disconnecting Means to the house or from the house to the detached garage.  I'm guessing that the feeder to the house was built before the National Electric Code required an EGC with feeders which supply separate buildings but I would like to have that confirmed.  If the Feeder from the house to the garage was installed later it may have a EGC run with it even if the Feeder to the house does not.  

So the question is Do four wires enter the house panel as the feeder from the meter mains assembly or only three.  The same question again for the Feeder to the garage.  How many wires are run.  Is it three or four.  

-- 
Tom Horne


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## hornetd (Dec 7, 2018)

js5518 said:


> Tank is in the same room as the house main panel. The breaker is in this panel. The detached garage is not even close to that meter and not really any practical way to change. Not sure I follow on the Building disconnect? The house is disconnected with the 200 amp breaker in the house main? So this meter location is not bonded and would require the bonding screw in the house main panel?


If there is no Equipment Grounding Conductor (EGC) run with the other Feeder conductors then you have to set up the Building Disconnecting Means exactly like a Service Disconnecting Means and install a main bonding Jumper in the Building Disconnecting Means cabinet to connect the Neutral Buss to the enclosure and thus connect any raceways which are connected to that enclosure to the Neutral.  In the absence of an EGC run with the Feeder the Feeder Neutral must do both jobs of carrying the normal load current and carrying any fault current back to the Neutral of the utility's Service Supply Conductors and thence back to the secondary winding of the utility's transformer.  

When there is an EGC run with the Feeder conductors then it provides the pathway for any current flowing from a fault to the non current carrying metal parts of the system back to the secondary of the utility's transformer.  One of the reasons for using a separate EGC to carry fault current is that it eliminates the possibility of voltage drop or a high resistance connection in the neutral conductor raising the voltage of exposed non current carrying metal parts of the electrical system to a higher touch potential than is safe for the building occupants.  

-- 
Tom Horne


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## js5518 (Dec 7, 2018)

hornetd said:


> To Mark the Neutral conductor you can paint it white or grey where it is accessible.  There is a product called "Liquid Electrical Tape"  which is available in white, green, and red.  I have found it easy to use for marking conductors and since it is made to insulate wires and is UL listed I can be reasonably sure that it will not harm the insulation.  There are also paint markers with latex paint in them in quite a few colors.  Latex paint is also safe to use on wire insulation.  Alternatively you can simply apply a single wrap of white or gray electrical tape over the visible portion of the neutral conductor in each panel.  That is really awkward to do once the wire is in place and energized.  In this case you could simply open the breaker that protects the Feeder conductors from the panel cabinet which holds the Building Disconnecting Means to the adjacent Feeder supplied panel.  You could then take the Neutral out of it's terminal lug to make taping it a lot easier.
> 
> I'm still waiting for you to tell us whether there is or is not an Equipment Grounding Conductor run with the other conductors of the Feeder from the meter mains Service Disconnecting Means to the house or from the house to the detached garage.  I'm guessing that the feeder to the house was built before the National Electric Code required an EGC with feeders which supply separate buildings but I would like to have that confirmed.  If the Feeder from the house to the garage was installed later it may have a EGC run with it even if the Feeder to the house does not.
> 
> ...


There are only 3 wires for both buildings. There is a rod at meter, house and garage. Sorry, thought I indirectly answered that.


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## hornetd (Dec 7, 2018)

js5518 said:


> There are only 3 wires for both buildings. There is a rod at meter, house and garage. Sorry, thought I indirectly answered that.


I thought that was what you were implying but I needed to be sure.  As I said earlier the code is carved in stone for that installation as the version in effect at the time the permit was issued.  No one can require you to go back and change it now. 

Bringing the Grounding Electrode System up to present code at each of those locations will not actually accomplish anything effective in improving the Grounding Electrode System's performance over what it is now.  So don't bother putting in a second rod unless you are going to do the work to make the system more effective. 

If you actually want to improve the Grounding Electrode System's performance then dig a trench that is 20 feet long between the existing rod and the new one.  If the building has a basement or a deep foundation which extends more than four feet underground then you will also want to keep the second rod at least it's own length away from the underground structure.  If the structure is too close to the property line to do that then get it as far away from the underground structure as possible.  The trench should be at least 30 inches deep and deeper is better.  So if you rent a mini backhoe and it's effective reach is four feet then you dig the trench four feet deep.  Once the trench is dug then you drive the second rod through the bottom of the trench leaving just enough showing to connect the Grounding Electrode Conductor to.  Install a Grounding Electrode Conductor of #2 AWG or larger bare copper in the bottom of the trench and use it in place of the code minimum #6 AWG.  Use heavier style of acorn clamp to connect the #2 AWG to each of the ground rods.  Replace the existing Grounding Electrode Conductor from the Service Enclosure or the Building Disconnecting Means enclosure to the first rod with #4 AWG.  Back fill the trench and your done. 

To get an idea of what you are building read the description of a Ground Ring in the National Electric Code (NEC). 

_"250.52 Grounding Electrodes.
(A) Electrodes Permitted for Grounding.
(4) Ground Ring. A ground ring encircling the building or structure, in direct contact with the earth, consisting of at least 6.0 m (20 ft) of bare copper conductor not smaller than 2 AWG."_  Copyright National Fire Protection Association (NFPA).  Quoted under the fair use exception.

As you can see the installation which I am suggesting is the equivalent of a minimum length Ground Ring.  Since it includes two driven rods that are more than six feet apart it also meets the NEC requirements for

_"(5) Rod and Pipe Electrodes. Rod and pipe electrodes shall not be less than 2.44 m (8 ft) in length and shall consist of the following materials.  
(a) Grounding electrodes of pipe or conduit shall not be smaller than metric designator 21 (trade size 3⁄4) and, where of steel, shall have the outer surface galvanized or otherwise metal-coated for corrosion protection.  
(b) Rod-type grounding electrodes of stainless steel and copper or zinc coated steel shall be at least 15.87 mm (5⁄8 in.) in diameter, unless listed.  

250.53 Grounding Electrode System Installation.
(A) Rod, Pipe, and Plate Electrodes. Rod, pipe, and plate electrodes shall meet the requirements of 250.53(A)(1) through (A)(3).  
(1) Below Permanent Moisture Level. If practicable, rod, pipe, and plate electrodes shall be embedded below permanent moisture level. Rod, pipe, and plate electrodes shall be free from nonconductive coatings such as paint or enamel.
(2) Supplemental Electrode Required. A single rod, pipe, or plate electrode shall be supplemented by an additional electrode of a type specified in 250.52(A)(2) through (A)(8). The supplemental electrode shall be permitted to be bonded to one of the following:
(1) Rod, pipe, or plate electrode
(2) Grounding electrode conductor
(3) Grounded service-entrance conductor
(4) Nonflexible grounded service raceway
(5) Any grounded service enclosure
Exception: If a single rod, pipe, or plate grounding electrode has a resistance to earth of 25 ohms or less, the supplemental electrode shall not be required.  
(3) Supplemental Electrode. If multiple rod, pipe, or plate electrodes are installed to meet the requirements of this section, they shall not be less than 1.8 m (6 ft) apart.  
Informational Note: The paralleling efficiency of rods is increased by spacing them twice the length of the longest rod."  _
Copyright National Fire Protection Association (NFPA).  Quoted under the fair use exception.

The combination of a Ground Ring which lacks only the encirclement of the entire building and the two driven rod electrodes at least six feet apart gives you a minimally complaint Grounding Electrode System under the NEC which is also a more effective system than most homes that do not have Underground Metal Water Piping have. 

Tests done by the National Institute of Standards and Technology (NIST) show that the system I am suggesting is far more effective than the minimum required by the NEC [<25 Ohms or two driven rods] and sufficient to serve the protective grounding needs of most homes. 

--
Tom Horne


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## hornetd (Dec 7, 2018)

js5518 said:


> There are only 3 wires for both buildings. There is a rod at meter, house and garage. Sorry, thought I indirectly answered that.


You definitely need to install the green screw in the First panel at the house.  That screw is the Main Bonding Jumper for that building.  That is the panel that has the building's main breaker; which the National Electric Code (NEC) calls the Building Disconnecting Means.  Without that screw installed there is no Effective Fault Current Path.  

-- 
Tom Horne


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## hornetd (Dec 7, 2018)

js5518 said:


> Yes, that bare wire is the grounding rod for supply. Need to use bonding screw for that panel?







Yes you need to use the bonding screw.  Without it you will have no "Effective Fault Current Pathway."


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## hornetd (Dec 7, 2018)

js5518 said:


> Yes, that wire needs to be moved to ground bar instead of the neutral bar. That goes to a ground rod, not from house. Does that neutral look bonded? Do I need to remove that center screw?







Do not remove the center screw!  It connects the Building Disconnecting Means enclosure to the Grounded Current Carrying Conductor (Neutral).  It is part of the 'Effective Fault Current Path" from any "Ground Fault" that occurs in the garage.  Without that screw any fault which occurs in the garage will raise the touch potential of all conductive surfaces in the garage to the system voltage of 125 volts to ground.  Since the concrete floor of a garage is usually conductive the absence of that Bonding Screw would set up a deadly trap for anyone who touched the metal face plate of a switch. 

The Neutral is bonded because the Neutral Buss is bonded to the enclosure by that Green Screw.  

In a building supplied by a Feeder that does not include an Equipment Grounding Conductor the Neutral buss and the Equipment Grounding buss are one and the same.  That is why the Neutral Buss must be bonded to the enclosure so that any raceways or metallic cables which are connected to the panel's cabinet will also be connected to the neutral to provide an effective fault current path.  

--
Tom Horne


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## hornetd (Dec 7, 2018)

js5518 said:


> Yes, that wire needs to be moved to ground bar instead of the neutral bar. That goes to a ground rod, not from house. Does that neutral look bonded? Do I need to remove that center screw?


No the Grounding Electrode Conductor does not need to be moved to the Equipment Grounding Buss.  It just needs to be terminated to the Neutral buss in the correct size lug.  

-- 
Tom Horne


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## js5518 (Dec 7, 2018)

hornetd said:


> Do not remove the center screw!  It connects the Building Disconnecting Means enclosure to the Grounded Current Carrying Conductor (Neutral).  It is part of the 'Effective Fault Current Path" from any "Ground Fault" that occurs in the garage.  Without that screw any fault which occurs in the garage will raise the touch potential of all conductive surfaces in the garage to the system voltage of 125 volts to ground.  Since the concrete floor of a garage is usually conductive the absence of that Bonding Screw would set up a deadly trap for anyone who touched the metal face plate of a switch.
> 
> The Neutral is bonded because the Neutral Buss is bonded to the enclosure by that Green Screw.
> 
> ...


So, the only thing that needs to be done in this box is use large lug for the bare stranded wire, but leave on neutral buss bar?


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## js5518 (Dec 7, 2018)

js5518 said:


> So, the only thing that needs to be done in this box is use large lug for the bare stranded wire, but leave on neutral buss bar?


Sorry just saw your reply.


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## js5518 (Dec 7, 2018)

I will also make those changes in the subpanel connected to the main. Mark neutral, use large lug. Anything else? When we are done with this I will throw something else at you. Ha ha


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## hornetd (Dec 8, 2018)

js5518 said:


> So, the only thing that needs to be done in this box is use large lug for the bare stranded wire, but leave on neutral buss bar?


Yes that is correct.  

-- 
Tom Horne


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## js5518 (Dec 9, 2018)

hornetd said:


> Yes that is correct.
> 
> --
> Tom Horne


Tom, just want to be clear here. There is a meter with 200 amp breaker and ground rod. Then there are 3 wires to house with square d 200 amp breaker with it's own ground rod connected to neutral bar. So, this inside 1st panel is apparently not bonded but should? If the bond screw on that panel is top right on neutral bar it isn't there. I tried a ground screw from smaller box and it appears to be short. It would go in the smaller box but don't think in the 200 amp box. It is, I believe S series Square D QO box? Thanks


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## hornetd (Dec 9, 2018)

Yes that first panel in the house needs to be bonded so that the enclosing cabinet and all of the metallic raceways, such as EMT tubing, connected to it will be connected to the Grounded Current Carrying Conductor (Neutral).  Since there is no Equipment Grounding Conductor in the Feeder which supplies that panel from the combined meter and Service Equipment the Neutral has to do two jobs.  It's first job is to carry the difference of the current that is flowing on the two energized conductors back to the source of that current at the transformer's secondary winding.  It's second job is to carry any current which is flowing from a ground fault back to that secondary winding so that the fault will not raise the touch potential of the normally de-energized conductive portions of the electrical system to an unsafe level for human safety while also allowing the current to cause the circuit breaker to open and thus clear the fault.  There is no other way for fault current to return to it's source in the transformer secondary than threw that screw.  

Use a non conductive flashlight to look into each of the holes in the top horizontal portion of the Neutral Buss bar.  The one which has a threaded hole in the back wall of the enclosing cabinet right behind the hole is were the green painted screw will  be installed.  If memory serves that hole is usually square in SquareD panel assemblies but keep in mind that I have been inactive for a long time.

That screw, which will serve as the Building Bonding Jumper, should be tightened until it's head is in hard contact with the Neutral buss bar.  DO NOT ATTEMPT TO USE ANY OTHER SCREW!  The bus bar is aluminum and would be constantly at war with any ferrous metal; which is any metal that is made from Iron Ore without the addition of significant amounts of other metals so as to change it's properties.  Any steel screw which has not been rendered Stainless by the addition of other substances will corrode if placed in close contact with Aluminum.  The resultant Aluminum Oxide is not a good conductor and will serve as a highly resistive point in the fault current pathway.  

That is why the Bonding Screw is coated with a conductive green coating to prevent direct contact between the mild steel thread in the back wall of the enclosure cabinet and the threads of the screw until the connection is made up tight.  That coating subsides away; is squeezed out by the pressure of the tightened connection; from some of the contact area enough to allow direct contact while at the same time making the contact area air tight.  By excluding air containing oxygen from the contact area corrosion is prevented and the connection will remain fully conductive for the life or the installation.  

You may need to go to an electrical supply house to obtain the properly sized bonding screw.  Write down the entire model number of the panel and take a clear and readable picture of the label with a smart phone or a digital camera so that the supply house counter staff can look up the correct screw for that panel.  Save yourself some time and call ahead.  If they have any trouble identifying your panel send them the picture of the label.  

-- 
Tom Horne


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