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Question about Disconnecting Means between Main Service and a Subpanel?

Question about Disconnecting Means between Main Service and a Subpanel?

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  #1  
Old 05-18-15, 12:24 AM
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Question Question about Disconnecting Means between Main Service and a Subpanel?

Greetings to all,


NOTE: An Image is attached. And please read carefully as my next specific concern and question may not be as easy to explain for me in English.


From a 100Amp Main Service Panel that have the Neutral and Ground properly bonded together as a Main Service, I will use a 60Amp Double Pole Breaker to feed a Subpanel in a detached building. I will use Two #4 Wires for the Ungrounded Conductors and Two #6 Wires, One for the Neutral Grounded Conductor and One for the Ground Grounding Conductor. The Neutral and Grounding Conductors will NOT be bonded in the Subpanel as required by code. I will also use a Grounding Electrode consisting of a 8feet Cooper Rod at the detached building using #6 Wire from the Rod to the Grounding Bus Bar at the Subpanel. Everything is perfect to this point... However, because the Subpanel will have a few circuits I want to also use a dedicated Disconnect Means in the detached building in order to be able to turn off the entire electricity to the Subpanel at any given moment, WITHOUT needing to go inside the Main Building to do so. For that, I have decided to use a 60Amp Main Lug Small Panel that will have another 60Amp Double Pole Breaker, and from there continue to the Subpanel that will have Direct Feeding as a Subpanel without a Main Breaker. So far all that is also perfect... except that the Main Lug Small Panel that I want to use and all of those kind available ONLY have 3 Wire Lugs NOT 4 Wire Lugs like the Subpanel.

So my concern is: I want to install a 60Amp Main Lug Small Panel before the Subpanel at a corner of an exterior wall of the detached building in order to function as a Disconnecting Means... but problem is the 60 or 70 Amp Main Lug Small Panels ONLY comes with 3 Wire Lugs NOT 4 Wire Lugs; therefore, I can connect the 2 HOT Wires and the Neutral Wire coming from the 60Amp Breaker at the Main Panel, BUT I CAN'T connect the Grounding Conductor that comes from the Main Service to feed the Subpanel...

So, question is: Can I maintain the continuity of the GROUNDING CONDUCTOR just using a Full Length Grounding Wire all the way to the Subpanel without connecting it to the IN BETWEEN Disconnecting Means, just connecting the Two HOT and 1 Neutral, as long as I still connect the Grounding Conductor at its Grounding Lug in the Subpanel???


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My conclusion is that I just have to connect the Two Hot Wires and the Neutral at the IN BETWEEN Disconnect Means; and just run the Grounding Conductor all the way from the Main Service Panel directly to the Subpanel Grounding Lug.

Am I right about this?


Thank you a lot.
 
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  #2  
Old 05-18-15, 12:54 AM
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Every disconnect and panel needs to be grounded. When you purchase your panels just get the optional ground bar that gets screwed to the metal enclosure through predrilled holes.

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You could also use a dual lug.... nut and bolted to the disconnect.

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  #3  
Old 05-18-15, 01:06 AM
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PJmax,

So I connect the #6 Grounding Wire that will run from the Main Service Panel to the Disconnect Means using an additional Ground Bar, and from that additional Ground Bar I continue running the Grounding Wire to the Subpanel Grounding Lug.


Excellent.


Thanks a lot.


Jos
 
  #4  
Old 05-18-15, 01:09 AM
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PJmax,


Update: I like that Dual Lug Nut option a lot more. I will better use that one to connect the #6 Grounding Wire at the Disconnect Means in this case.


Thanks for the images.


Jos
 
  #5  
Old 05-18-15, 01:55 AM
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Where is this intermediate disconnect in relation to the sub-panel? Normally the sub-panel in the outbuilding IS the disconnect for that building and using a main breaker panel is the easiest. Next easiest is a "back-fed" circuit breaker in a main lug panel with the main lugs not being used. In this latter case a circuit breaker hold down device must be used to keep the back-fed circuit breaker in place even if the panel front is removed.

Now IF you want this intermediate disconnect in a different location than the sub-panel, say on the outside of the building, then you could use a 60 ampere air conditioning disconnect (pull-out switch). There is no need to actually have a circuit overload device (fuse or circuit breaker) for this disconnect. At any rate, the double lug that PJ shows IS the easiest solution for the equipment grounding conductor. Make sure that you scratch the paint from the disconnect enclosure where the double lug is attached to ensure good contact with the enclosure.
 
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Old 05-18-15, 02:43 PM
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Thumbs up

Furd,

You are right about that the Subpanel can be converted into a Main Breaker Panel and that will serve as a Disconnect Means; however, in this particular case my Subpanel is installed on an inside wall around 12feet away from any of the exterior walls in the detached building; that's why I want to use a separated Disconnect Means that will be located at one side of the detached building on an exterior wall in the outside of the building providing faster, easier access to the Disconnect Means in an event of an emergency.

I was either considering to use an AC Disconnect. Let's see which one I choose, a 60Amp AC Disconnect or a Small Main Lug Panel depending on their availability in my nearest Lumber Yard, Hardware Store at my current location.


Thanks for your reply.

Jos
 
  #7  
Old 05-18-15, 07:30 PM
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Question An Overcurrent Protection Simple Question:

Greetings to all,

This time this will be a simple question.

If I have a 60Amp Double Pole Breaker at the Main Service Panel that will feed a 60Amp Subpanel, BUT in between the Main Service Panel I also have another 60Amp Double Pole Breaker installed in a Small Panel that will serve as a Disconnecting Means...

... in the case of An Overcurrent Event above 60Amps from the Subpanel, which 60Amp Breaker will trip first? Will trip the one at the Disconnecting Means first leaving the one at the Main Service Panel ON, or will both trip at the same time???


Thanks a lot.


Jos
 
  #8  
Old 05-18-15, 07:43 PM
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Since your new question is related to your other question I have merged your two threads.

Since it only serves as a disconnect you really only need to use an unfused disconnect. As to which breaker it is a roll of the dice. Even if all the same kind slight difference between them will cause one to trip first. Which one though can't be determined. Even outside factors could determine which. For example sun shining on a breaker box might put that breaker in a higher ambient temperature and thus make the breaker slightly warmer. The slightly warm temperature might cause it to trip sooner on a slight overload over an extended time frame. Dead short no way to know.
 
  #9  
Old 05-18-15, 07:46 PM
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Ummm.... Ray. What happened to my reply.
 
  #10  
Old 05-18-15, 08:25 PM
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Poltergeist. .
 
  #11  
Old 05-18-15, 08:39 PM
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Hi ray2047,

Since it only serves as a disconnect you really only need to use an unfused disconnect.
Correct. However, I have to confess that I am personally more inclined to use a fused disconnect or a Circuit Breaker as a Disconnecting Means because using an unfused disconnect in the event of an overcurrent it will definitely trip the 60Amp Breaker at the Main Service Panel; therefore I will have to access the main building in order to re-establish the electricity to the Subpanel in the detached building. I'm personally looking to minimize the need to enter the main building for such instance.

As to which breaker it is a roll of the dice. Even if all the same kind slight difference between them will cause one to trip first. Which one though can't be determined. Even outside factors could determine which. For example sun shining on a breaker box might put that breaker in a higher ambient temperature and thus make the breaker slightly warmer. The slightly warm temperature might cause it to trip sooner on a slight overload over an extended time frame.
A smart, clever answer, no doubt about it. I do agree with those and possibly more factors that should be taken into consideration. However, notice that the Breaker at the Disconnect Means will be the one that will be installed in the outside while the one at the Main Service Panel is in the interior of the main building, therefore if those factors will be present, they will have influence over the one at the Disconnect Means possibly tripping it first; which in this case is good for me because that is the one I wish trip before the one at the main service panel, if it ever happens.


Nevertheless, I do believe that in a ''Perfect Scenario'' where all the variables, factors, etc. remain controlled and where everything will be working perfectly (not likely to happen in reality) the 60Amp Breaker at the Disconnecting Means should trip first leaving the one at the Main Service Panel ON, AS LONG AS THE OVERCURRENT WAS ORIGINATED FROM THE SUBPANEL... HOWEVER, it is true that in Reality that could not occur, possibly because of several other variables, factors, etc. so the 60Amp Breaker at the Main Service Panel may still trip first or at the same time the Disconnecting Means trip; requiring to access the main building to re-establish the electricity to the Subpanel.


Finally, I think I have just decided to go with the Circuit Breaker at a Small Panel instead of an AC Disconnect for the Disconnecting Means, my reasons are that with the Non Fused AC Disconnect there will not be an Overcurrent Protection in between the Subpanel and the Main Service Panel but at the Main Service Panel only; and also because a Fused AC Disconnect, this one provides overcurrent protection but will require to change the fuses after an overcurrent event... while using an additional 60Amp Breaker in a Small Panel as the Disconnect Means will also provide an additional Overcurrent Protection in between the Subpanel and the Main Service; that will please me a lot more in this particular/personal project.


Soon I will upload pictures of the whole electrical project completed and explaining more details.


Thank you a lot.


Jos
 
  #12  
Old 05-18-15, 08:50 PM
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You can put a 50A breaker at the sub panel. Then it should trip before the 60A breaker.
 
  #13  
Old 05-18-15, 09:08 PM
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PJmax,

Understandable... but I want the Subpanel to strictly have a direct feed, No Main Breakers at the Subpanel (a personal choice in this case). I already complete wiring all the circuits and installed all their respectively Circuit Breakers at the Subpanel. Later I will upload images of the project.

Thanks.
 
  #14  
Old 05-18-15, 09:14 PM
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Ummm.... Ray. What happened to my reply.
- PJmax

Poltergeist.
- ray2047




Hallo ray2047,

Das war seltsam. Ich weiß nicht was erwidern PJmax spricht. In jedem fall, posten ihre erwidern erneut PJmax.


Vielen Dank.


Jos
 
  #15  
Old 05-18-15, 09:37 PM
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Aparently PJ geschrieben, als ich bewegte den Pfosten, und es wurde in den Äther verloren.
 
  #16  
Old 05-18-15, 09:45 PM
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Aparently PJ geschrieben, als ich bewegte den Pfosten, und es wurde in den Äther verloren.
Höchstwahrscheinlich. Ich dachte dass auch. Seine antworten war verloren.


Danke.


Jos.
 
  #17  
Old 05-19-15, 01:30 AM
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Use a 50 ampere circuit breaker in the intermediate (outside) panel to ensure it will trip on overload before the 60 ampere CB inside the house. There is no way to control which CB will trip first on a short circuit.

OR, if the wiring will support it, use a 60 ampere CB in the intermediate panel and a 70 ampere CB in the house.
 
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Old 05-19-15, 02:35 PM
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Hi Furd,

OR, if the wiring will support it, use a 60 ampere CB in the intermediate panel and a 70 ampere CB in the house.
That definitely sounds more convenient for me.

The Hot Wires will be #4 THHN/THWN; the Neutral (maybe I use #4), and Grounding will be #6 THHN/THWN running in proper PVC Schedule 40 Heat/Corrosion Resistant Conduit; running a maximum of 50 to 60 feet from the Main Service Panel to the Subpanel. So yes, the wires can support up to 70Amps. I have decided to go with your recommended setup then, using a 70Amp Circuit Breaker at the Main Service Panel and the Intermediate Disconnecting Means panel will use a 60Amp Circuit Breaker.


Excellent. Thanks for your advice.


Jos
 
  #19  
Old 05-20-15, 03:35 PM
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Exclamation About Grounding Wire at Intermediate Disconnecting Means???

Hi,

NOTE: This specific Post contain terms of debatable nature; some of these terms are difficult for me to explain them properly in English. I hope that still my concerns about the next issue can be understood.

Last time I agreed to attach an additional Double Lug to the Small Panel to properly install the #6 Grounding Wire that will come from the Main Service and continue to the Subpanel...

HOWEVER... I just found that some GE Small Main Lug Panels for Outdoor Applications come in PLASTIC... yeah in plastic...


Like this one: GE PowerMark Gold 125-Amp 4-Space 8-Circuit Outdoor Main Lug Circuit Breaker Panel-TPL412RP - The Home Depot


So, now I believe (possibly wrong) that using this plastic box I don't need to connect the #6 Grounding Wire from the Main Service Panel to this box, therefore I can just run three wires (2 Hot, 1 Neutral) from the Main Service to the Intermediate Disconnecting Means, and finally to the Subpanel; and just install the additional Grounding Electrode Rod to the Subpanel Grounding Bar, and that will serve as a separate Grounding for the Subpanel itself.

Am I right???


BUT I ALSO BELIEVE THAT I AM NOT RIGHT; and therefore, I will still need to run the #6 Grounding Wire from the Main Service Panel directly to the Subpanel even if I don't connect it to this PLASTIC main lug box, BUT definitely still need to directly run the Grounding Wire all the way to the Subpanel...

BUT THEN I ASK: Why Manufacturers insist to make these Main Lugs Boxes for only 3 wire lugs by default, instead of make them with 4 wire lugs? If is clearly understood that MOST applications will still need to run a fourth wire for Grounding???

I'm asking all this because my concern is that I wonder why Engineers aren't doing nothing to improve the designs of their products in order to meet most post-modern applications, without the requirement to perform additional custom changes to the metal main lug boxes???

For example, we previously agreed that in my case I can attach an additional double lug for the Grounding wire to the metal main lug box... but then I wonder if there is an application where you can actually install a metal main lug box using only 3 wire lugs without requiring to attach an additional lug or ground bar for Grounding IF AFTER ALL is required by code that all metal main lug boxes, etc. need to be Grounding??? So Probably NOT.

Finally, that's why I personally really wonder: Why Manufacturers don't make all Metal Small Main Lugs boxes with 4 Wire Lugs by DEFAULT, like most Subpanels have???


Please feel free comment, reply and debate my concerns regarding this issue.


Thanks a lot.


Jos
 

Last edited by JosiQDIY2015; 05-20-15 at 03:58 PM.
  #20  
Old 05-20-15, 11:35 PM
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So, now I believe (possibly wrong) that using this plastic box I don't need to connect the #6 Grounding Wire from the Main Service Panel to this box, therefore I can just run three wires (2 Hot, 1 Neutral) from the Main Service to the Intermediate Disconnecting Means, and finally to the Subpanel; and just install the additional Grounding Electrode Rod to the Subpanel Grounding Bar, and that will serve as a separate Grounding for the Subpanel itself.

Am I right???
Yes and no. Obviously it would do no good to "bond" the equipment grounding conductor (EGC) to the plastic enclosure so you are correct about that part. However, you still need to extend that EGC from the point of supply (the service panel) to the sub-panel and beyond to the final loads. The Grounding Electrode Conductor (GEC), that number 6 copper that runs from the equipment grounding bus in the sub-panel to the ground rod (Grounding Electrode) for a panel in a separate (detached) structure is NOT a substitute for the EGC but is for lightning protection.

So you still need four conductors from the service panel to the sub-panel. Going through the intermediate disconnect you may either run the EGC unbroken through the disconnect enclosure or you may have a splice inside the enclosure.


Now as to your other question, remember that the term "sub-panel" does not exist in the NEC. The manufacturers cannot know how their panels will eventually be connected and since money drives all things in the world they supply the absolute bare necessities in the panels and then sell accessories (like equipment grounding busses) separately.
 
  #21  
Old 05-21-15, 11:53 AM
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Hi Furd,

Obviously it would do no good to "bond" the equipment grounding conductor (EGC) to the plastic enclosure so you are correct about that part. However, you still need to extend that EGC from the point of supply (the service panel) to the sub-panel and beyond to the final loads.
Correct. If I use the Plastic Enclosure I will still extend the Grounding Wire from the Main Service to the Subpanel. The Final Loads all have Ground as I used 14/2 with bare Ground wire and 12/2 with bare Ground wire properly connected to the green screws in Outlets and Switches and to Metal Electrical Boxes for Ceiling Lights and Fans.

So you still need four conductors from the service panel to the sub-panel. Going through the intermediate disconnect you may either run the EGC unbroken through the disconnect enclosure or you may have a splice inside the enclosure.
That's the term I was trying to communicate; I will then run the Grounding Wire unbroken if I use the Plastic Enclosure. And I will not splice the Grounding wire if I use the plastic enclosure as is not needed in such case. Thanks for teaching me the proper terms.

Now as to your other question, remember that the term "sub-panel" does not exist in the NEC.
Correct. I should said why Small (in terms of less spaces for less circuits available) Lug Panels only come with 3 wire lugs while most Big Main Lug Panels (big in terms of more spaces for more circuits available) come with 4 wire lugs... However, I has been investigating an even Big Main Lugs and Main Breaker Panels seems to come with 3 wire lugs. But personally (an opinion) I prefer Main Lugs that comes already with 4 wire lugs or even 5 like the ones from General Electric PowerMark Gold that I have bought.

The manufacturers cannot know how their panels will eventually be connected and since money drives all things in the world they supply the absolute bare necessities in the panels and then sell accessories (like equipment grounding busses) separately.
Correct. I'm an aware of that; definitely selling separate accessories generate a lot of profit, while manufacturing their products to absolute bare necessities reduce manufacturer costs and help to maintain selling costs at reasonable prices. However, I am personally a fanatic of Manufacturers that believe in Post-Modern Innovation, Improvement and Higher efficiency in their Electric Products; for me, if there is a Main Lug/Breaker Panel, etc. that comes with 4 wire lugs, instead of 3 wire lugs from factory, that's the one I will always buy doesn't matter if it will cost me a little more.

This is my thinking: ''The more innovated the product is, the more I will be willing to invest more money on the product; because it satisfy me to know that Engineers at those Manufacturers are thinking towards the future.'' - JosiQDiY2015 Jos Lewis Von Sant. May 21, 2015.

Is better to have a 4 wire lugs available at every Main Lug or Breaker Panel and don't need to use one of the lugs; than need all 4 lugs and just have 3 lugs available. That's my personal way to see things with more Sense of Innovation and Efficiency.


Furd, Thanks a lot for your excellent reply; I appreciate it.


Jos
 
  #22  
Old 05-21-15, 12:29 PM
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When you use the terms "three lugs" and "four lugs" I suspect that you are referring to panels that have a single neutral bus (three lug) and two neutral buses (four lug). Two neutral buses would be more common on a larger panel and would have a neutral bus on each side of the panel. These two neutral buses will have a factory-installed bar connecting the two buses so either may be used for the neutral connections and, in the case of a service panel, the equipment grounding conductors. In some panels the connecting bar is field-removable so that one bus may be used as neutral and the other as equipment ground when the panel is used as a sub-panel.

The fact of having two buses is not indicative of any improvement over a single neutral bus. It DOES give you more connection points when used as a service panel without having to add the auxiliary equipment grounding bus. Each neutral wire must connect to a single hole/screw in the neutral bus. Most panels will allow two equipment ground wires of the same size to occupy a single hole/screw on a combined neutral/equipment ground bus or a separate equipment ground bus. Check the door label for what is allowed.
 
  #23  
Old 05-21-15, 04:17 PM
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Hi Furd,

When you use the terms "three lugs" and "four lugs" I suspect that you are referring to panels that have a single neutral bus (three lug) and two neutral buses (four lug). Two neutral buses would be more common on a larger panel and would have a neutral bus on each side of the panel.
Correct. Those are the proper terms. Now that the terms are clarified, I state that I prefer to buy Main Lugs that comes with Two Neutral Buses from factory.

These two neutral buses will have a factory-installed bar connecting the two buses
Most of them have the two neutral buses factory connected; but not all of them.

In some panels the connecting bar is field-removable so that one bus may be used as neutral and the other as equipment ground when the panel is used as a sub-panel.
Correct, The ones I have bought doesn't have the two Neutral buses connected, but you can still use included bonding screws to convert every neutral bus bar to Ground or to remove the bonding screws and therefore using both as Neutral bus bars.

The fact of having two buses is not indicative of any improvement over a single neutral bus. It DOES give you more connection points when used as a service panel without having to add the auxiliary equipment grounding bus.
I have to strongly disagree with you on that statement. I still believe that having two buses is a Clear Improvement; because if it does give you more connection points without having to add any additional equipment grounding bus then THAT'S CLEARLY A LOT OF IMPROVEMENT AND HIGHER EFFICIENCY, the improvement and Efficiency I'm looking for to invest my money on electrical products.


Thanks for your reply.


Jos
 
  #24  
Old 05-21-15, 09:51 PM
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Just curious..... are we getting close to a resolution here ?
 
  #25  
Old 05-21-15, 10:46 PM
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PJmax,

What that question means?
 
  #26  
Old 05-22-15, 09:17 AM
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(Furd) The fact of having two buses is not indicative of any improvement over a single neutral bus. It DOES give you more connection points when used as a service panel without having to add the auxiliary equipment grounding bus.
I have to strongly disagree with you on that statement. I still believe that having two buses is a Clear Improvement; because if it does give you more connection points without having to add any additional equipment grounding bus then THAT'S CLEARLY A LOT OF IMPROVEMENT AND HIGHER EFFICIENCY, the improvement and Efficiency I'm looking for to invest my money on electrical products.
You must have a different definition of efficiency than I. While it MIGHT make slightly more efficacious usage of the time spent in wiring it has zero effect upon the electrical operation of the circuit(s).

In a dual-voltage panel where all the loads utilize the higher voltage, the neutral is not even used and in that instance the second neutral bus would do nothing but increase the cost of the panel. In a panel where all the loads were at the lower voltage, the addition of a second neutral bus may be necessary to have a sufficient number of neutral connections. In a typical residential setting there is usually no need for the second neutral bus for a "service" panel and a "sub" panel is always going to need a separate, bonded equipment grounding bus. Now whether a re-connected (re-purposed) factory installed neutral bus is the perfect answer in this last example is a matter of debate. My position is that it is not the perfect answer and the additional cost of fitting a second neutral bus to ALL panels is simply not justifiable.
 
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Old 05-22-15, 01:13 PM
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Hi Furd,

Those are great arguments. Thanks for your replies, I appreciate all of them.

I have learnt a lot in the discussions of this Post.


Thanks a lot.


Jos
 
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