# circuit breakers on PV systems are a violation



## backstay (Feb 3, 2011)

Is this a question on a test? You size on the inverter because panel output changes with temp and that is an odd number. I would never run a 9600 watt system through a 60 amp panel.


----------



## Rap2 (Dec 17, 2010)

Im just saying what ever the inverter puts out added to whats coming into that breaker will exceed the rating of its bus rating which is the lug (unless the lug has its own rating)


----------



## Rap2 (Dec 17, 2010)

I did not mention a panel, but I will take it out of the equation to better illustrate my point.

Lets say you had a 60 amp stand alone breaker inside its own enclosure with lugs on line and load side, and just to take wire size out of it, lets say you used #1 THHN on either side.

The lugs on either side of that breaker which is a bus are rated to the capacity of the breaker which is 60 amps so on the load side of the breaker where the PV is connected to will fed by 2 sources the utility at 60 amps and the PV at 40 amps.

I know this is done all the time, but how is it not a violation about what the NEC says about feeding a bus or feeders at no more than 120% of capacity.


----------



## backstay (Feb 3, 2011)

Rap2 said:


> I did not mention a panel, but I will take it out of the equation to better illustrate my point.
> 
> Lets say you had a 60 amp stand alone breaker inside its own enclosure with lugs on line and load side, and just to take wire size out of it, lets say you used #1 THHN on either side.
> 
> ...


You say it's done all the time but it's not. If you had 60 amps of load on the panel and 40 from the array. You would have 20 from the utility.


----------



## Rap2 (Dec 17, 2010)

The PV is not a load, it is a power generating source at it is contributing 40 amps of power to the lugs on the load side of the breaker and the utility is contributing 60.


----------



## Bootss (Dec 30, 2011)

backstay said:


> You say it's done all the time but it's not. If you had 60 amps of load on the panel and 40 from the array. You would have 20 from the utility.


,what percentage of the time do you have to upgrade the panels on an existing system when you add solar?


----------



## Rap2 (Dec 17, 2010)

705.12(D)(2)
(2) Bus or Conductor Rating. The sum of the ampere ratings
of overcurrent devices in circuits supplying power to a
busbar or conductor shall not exceed 120 percent of the rating
of the busbar or conductor.

So if you have a 100 amp sub panel being fed by a 100 amp breaker from the utility you can not add more than a 20 amp breaker worth of PV which is about 15 amps of actual power if the breaker is sized correctly to protect the inverter.


----------



## backstay (Feb 3, 2011)

Rap2 said:


> The PV is not a load, it is a power generating source at it is contributing 40 amps of power to the lugs on the load side of the breaker and the utility is contributing 60.


Where are you finding these 60 amp rated busses? Old fuse panels. Most are 40, 70, 100, 125, 150, 200 or 225 in a 1ph type of panel. Why would you install a panel rated at 60 amps and then feed it with an 40 amp PV system.



Rap2 said:


> 705.12(D)(2)
> (2) Bus or Conductor Rating. The sum of the ampere ratings
> of overcurrent devices in circuits supplying power to a
> busbar or conductor shall not exceed 120 percent of the rating
> ...


So install a 200 amp panel and feed your 40 amp PV into that.


----------



## backstay (Feb 3, 2011)

Lep said:


> ,what percentage of the time do you have to upgrade the panels on an existing system when you add solar?


Almost never, most are fed into the meter main on the pole. They will be 200 amp usually. Some are 360 amp(400) if the system is large.


----------



## Rap2 (Dec 17, 2010)

There is no panel just a breaker, the lugs on the breaker itself are rated at 60 amps as it is the name plate rating of the breaker. Since its were the wires connect its considered a bus.


----------



## backstay (Feb 3, 2011)

Pictures help.


----------



## Rap2 (Dec 17, 2010)

Take this picture as an example, I assume PV is hooked up to the Breakers inside, what ever amperage the PV is back feeding the breaker plus the amperage of the breaker coming from the utility exceeds the the rating of the breaker.

The NEC says you can not exceed a bus bar or feeder or panel by 120% of its rated capacity.

No mater what size wire you use the lug or bus on the breaker itself where you land the wire is only rated for the breaker size, in every case the PV will over load it.


----------



## backstay (Feb 3, 2011)

Rap2 said:


> Take this picture as an example, I assume PV is hooked up to the Breakers inside, what ever amperage the PV is back feeding the breaker plus the amperage of the breaker coming from the utility exceeds the the rating of the breaker.
> 
> The NEC says you can not exceed a bus bar or feeder or panel by 120% of its rated capacity.
> 
> No mater what size wire you use the lug or bus on the breaker itself where you land the wire is only rated for the breaker size, in every case the PV will over load it.


You are wrong, there is no "amperage" coming from the utility.


----------



## Big John (May 23, 2010)

I'm having a hard time following what's being described here, but it almost sounds like you're talking about backfeed conditions being _additive _on top of consumption.

Power flow doesn't work like that. If you have a customer consuming 60A through a utility tie, and you turn on that customers solar system to "backfeed" 20A worth of current to the utility, you don't start passing 80A through the main breaker. Instead you've _reduced_ the consumed amount to 40A.

If your local solar production were to match the building consumption exactly, the amount of current flow through the utility tie would be zero.


----------



## Rap2 (Dec 17, 2010)

Big John said:


> I'm having a hard time following what's being described here, but it almost sounds like you're talking about backfeed conditions being _additive _on top of consumption.
> 
> Power flow doesn't work like that. If you have a customer consuming 60A through a utility tie, and you turn on that customers solar system to "backfeed" 20A worth of current to the utility, you don't start passing 80A through the main breaker. Instead you've _reduced_ the consumed amount to 40A.
> 
> If your local solar production were to match the building consumption exactly, the amount of current flow through the utility tie would be zero.


Thank you, I do understand that.

What I am saying is the PV in your example is pumping out 20 amps and the utility is supplying 60 amps, if at any point along that path something is rated at 60 amps it is being fed by 2 sources and the total of those 2 sources can not exceed 120% of the rating of that point. (IE the 60 amp breaker)


----------



## backstay (Feb 3, 2011)

Rap2 said:


> Thank you, I do understand that.
> 
> What I am saying is the PV in your example is pumping out 20 amps and the utility is supplying 60 amps, if at any point along that path something is rated at 60 amps it is being fed by 2 sources and the total of those 2 sources can not exceed 120% of the rating of that point. (IE the 60 amp breaker)


Why do you have an 80 amp load on a 60 amp breaker? What happens when it gets dark and your 60 amp feed has to sustain this 80 amp load? I think you have had this explained to you a couple of times. May I suggest take a class in basic electricity.


----------



## Rap2 (Dec 17, 2010)

backstay said:


> Why do you have an 80 amp load on a 60 amp breaker? What happens when it gets dark and your 60 amp feed has to sustain this 80 amp load? I think you have had this explained to you a couple of times. May I suggest take a class in basic electricity.


I have never mentioned anything about a load, but since you brought it up...

If you were to tap the point where the 20 amps of PV meets the 60 amps of power supplied by the utility and that point was rated at 60 amps you could supply that load with 80 amps of power at least while the sun is shining and according to basic electricity 20 amps is coming from one side and 60 from the other and would not really over load that portion of a bus or conductor but that portion of a bus or conductor is being fed by more power than what it is rated, if it is rated at 60 amps.


----------



## Rap2 (Dec 17, 2010)

backstay said:


> You are wrong, there is no "amperage" coming from the utility.[/quote
> 
> 
> Sorry I did not see this reply, I did not mean to imply that I thought the current was coming from the utility going anywhere while the PV was back feeding.
> ...


----------



## AK_sparky (Aug 13, 2013)

Rap2 said:


> I ment the Utility can potentially feed power to the circuit the PV is on and the PV can potentially feed power to the same circuit, if any point of that circuit is rated less than 120% than the combined total of both sources of power it is a violation of NEC 705.12


Yes, and like someone else said already, why would you feed 80A worth of load with a 60A panel?


----------



## AK_sparky (Aug 13, 2013)

Rap2, you need to draw pictures for this, 'cuz you makin' no sense!


----------



## Rap2 (Dec 17, 2010)

AK_sparky said:


> Rap2, you need to draw pictures for this, 'cuz you makin' no sense!


I cant find any exception to 705.12's 120% rule in the NEC. If you take it literally you can find a point on most PV installs that are in violation of it.

That is the conversation I was trying to start I don't know where I went wrong.


----------



## Rap2 (Dec 17, 2010)

How would you install 10 Micro inverter branch circuits on a 200 amp service if each circuit requires a 20 amp breaker?

You could land all 10 breakers in a 200 amp panel and since your back feeding something around 150 amps on the 200 amp panel. That would work electrically but it would be a clear violation of 705.12

OK so you up the panel to a 400 amp panel to solve that problem.

But now even if your panel is main lug or a 200 amp main breaker, your feeders are now in violation of 705.12 so you upgrade those to 400 amp.

So you figure out how to cram 400 amps worth of wires into the service's 200 amp breaker to solve that problem.

Well on one side of that breaker there is the utility which is not governed by the NEC but you landed your400 amps of feeders on the side that is.

So you still kinda in violation of 705.12 because of the lugs/bus on that breaker are rated 200 amps.

So on a last act of desperation you replace the sites first point of over current protection with a 400 amp breaker!!

Now you your totally compliant with NEC 705.12!!

Just give the utility a call and tell them that their 200 amp service is feeding a 400 amp breaker..... Im sure they will be thrilled.


----------



## AK_sparky (Aug 13, 2013)

I don't use the NEC, so I don't know what the code actually says. Can you paste it here?


----------



## Big John (May 23, 2010)

I assume he's talking about this section:


> *705.12 Point of Connection.
> *The output of an interconnected electric power source shall be connected as speciﬁed
> in 705.12(A), (B), (C), or (D).
> 
> ...


 But ten 20A microinverter circuits would be perfectly fine on a 200A breaker according to that.


----------



## backstay (Feb 3, 2011)

Take my panel in the picture. It has two 30 amp breakers backfeeding a ML 70 amp panel. The OCP is 30x2=60. That is less than the 70 amp rating. The source (PV) is 25 amps, 25x2x120%=62.5. None of that broke the NEC. Now you claim that the utility somehow supply's to this panel, but there is no load to it. Only back to the service. That service panel is a 200 amp with no loads. How is any of this breaking code? I also don't connect on the supply side of the service. I can not think of a reason to do this.


----------



## Rap2 (Dec 17, 2010)

backstay said:


> Take my panel in the picture. It has two 30 amp breakers backfeeding a ML 70 amp panel. The OCP is 30x2=60. That is less than the 70 amp rating. The source (PV) is 25 amps, 25x2x120%=62.5. None of that broke the NEC. Now you claim that the utility somehow supply's to this panel, but there is no load to it. Only back to the service. That service panel is a 200 amp with no loads. How is any of this breaking code? I also don't connect on the supply side of the service. I can not think of a reason to do this.


That is a violation of 705.12D2 without a doubt.

you have 60 amp of PV in a 70 amp panel and the OCP from the 200 amp service, though you didn't mention it, I assume has to be at least 60 amps.

Which means the 70 amp bus in that panel is being fed by 2 sources at 60 amps each which is 120 amps. 

Loads are not mentioned in NEC705.12D2.

It dosen't matter that you have no loads in that panel, even if you put a sign on the enclosure "PV only never hook a load to this panel" (which they used to let us do) it its still a violation.

Thanks for your reply, This is what I wanted to discuss...


----------



## Big John (May 23, 2010)

Rap2 said:


> That is a violation of 705.12D2 without a doubt.


 You keep saying this. I haven't seen anything in this thread where that appears to actually be true.

I don't do much solar, but I know _Backstay _does a ton: I don't see the code violation you claim he's created. If you're including the panel main in your calculations, that's incorrect for the reasons already explained. The utility tie breaker is not a "power production source."


----------



## Rap2 (Dec 17, 2010)

OBTW the 200 amp panel that is servicing your 70 amp panel cant accept more than 40 amps of PV.

That is also a violation.

If you are feeding the 70 amp panel with a 70 amp and not a 60 amp breaker it is even more of a violation.


----------



## backstay (Feb 3, 2011)

Rap2 said:


> That is a violation of 705.12D2 without a doubt.
> 
> you have 60 amp of PV in a 70 amp panel and the OCP from the 200 amp service, though you didn't mention it, I assume has to be at least 60 amps.
> 
> ...


No I don't have 60 amps of PV in the panel. There is 50 amps. Your first mistake. You are pulling parts of code out of context. You don't understand what you are talking about. You say the utility can supply more power than the system is rated for, but the utility can provide more power to a service on any system, PV connected or not. If they couldn't, you would experience voltage drop. And the 200 amp OCP at the service is for the service panel, there is another breaker feeding the 70 amp panel. So now you made conclusions about systems you didn't have facts about.


----------



## telsa (May 22, 2015)

backstay said:


> No I don't have 60 amps of PV in the panel. There is 50 amps. Your first mistake. You are pulling parts of code out of context. You don't understand what you are talking about. You say the utility can supply more power than the system is rated for, but the utility can provide more power to a service on any system, PV connected or not. If they couldn't, you would experience voltage drop. And the 200 amp OCP at the service is for the service panel, there is another breaker feeding the 70 amp panel. So now you made conclusions about systems you didn't have facts about.


The only concept that I can dope from Rap2's word salad runs along the notion that electric power can race in from two directions at the same time...

Which he takes to mean that electricity is racing right past itself within the same conductors... in opposed directions.

The only spot in such inter-tied systems where one is at hazard is when you've managed to attain full PV output -- while the panel is massively loaded -- say by air conditioning loads. It is for such situations that the Code demands a robust bus.

Rap2's concerns don't make sense in the other system elements -- as they will always be either pure load or pure up-the-line power -- and protected by properly sized OCPD.

This would be much more evident with a circuit diagram. :thumbsup:

*Kirchhoff's laws* would clear up the confusion,... I hope. :laughing:


----------



## backstay (Feb 3, 2011)

telsa said:


> The only concept that I can dope from Rap2's word salad runs along the notion that electric power can race in from two directions at the same time...
> 
> Which he takes to mean that electricity is racing right past itself within the same conductors... in opposed directions.
> 
> ...


An OCPD is going to trip if you exceed its limits. You can't force more through it(for long) than it's designed for. Fault currents aside.


----------



## macmikeman (Jan 23, 2007)

backstay said:


> An OCPD is going to trip if you exceed its limits. You can't force more through it(for long) than it's designed for. Fault currents aside.


In the past 3 weeks I have had to change out no less than 4 services that had melted down 100 amp breakers that had load side connections to a sub panel along with insuleator taps to pv systems. In every case the connected strings of solar generating panels wattage exceeded the 20% of the feeder overcurrent device they were load tied onto. The breakers did not ''trip'' but instead melted down , caught fire in two situations and the internals got consumed enough that an open resulted in one of the phases in each case, resulting in customers telling me only half the house worked. The plastic insulating material behind the plug in busbars was melted beyond any further use in all cases I came across. So far in the last 5 years, I think it is about thirty times all told I had to do this same repair for the same reasons. Truly, I have zero respect for the quality of work that most all of the electrical contractors in my area doing pv jobs have shown me. They are all fast and good at turning a buck though. 
I'm not so hot at Kirchoff's laws but I do believe a loaded up feeder, coupled with a pv supplying more than 20% of the breaker for the feeder is the cause of the issue most of the time. The other cause sometimes I find is loose connections at the load terminals of the breaker because of sloppy work probably due to trying to go too fast due to management pressure.


----------



## Rap2 (Dec 17, 2010)

backstay said:


> No I don't have 60 amps of PV in the panel. There is 50 amps. Your first mistake. You are pulling parts of code out of context. You don't understand what you are talking about. You say the utility can supply more power than the system is rated for, but the utility can provide more power to a service on any system, PV connected or not. If they couldn't, you would experience voltage drop. And the 200 amp OCP at the service is for the service panel, there is another breaker feeding the 70 amp panel. So now you made conclusions about systems you didn't have facts about.


The size of your PV does not matter. It is the size of the OCP you chose to protect it. Please read it carefully I will post it again below.

Therefore the over current devices feeding the 70 amp panel from the PV system is 60 amps. You have yet to mention the size of the breaker feeding that panel from the 200 amp service panel I am going to assume that it is at least 60 amps a conclusion I am forced to make as I do not have the facts.

That is a violation.



705.12(D)(2)
(2) Bus or Conductor Rating. The sum of the ampere ratings
of overcurrent devices in circuits supplying power to a
busbar or conductor shall not exceed 120 percent of the rating
of the busbar or conductor.


----------



## Rap2 (Dec 17, 2010)

Big John said:


> You keep saying this. I haven't seen anything in this thread where that appears to actually be true.
> 
> I don't do much solar, but I know _Backstay _does a ton: I don't see the code violation you claim he's created. If you're including the panel main in your calculations, that's incorrect for the reasons already explained. The utility tie breaker is not a "power production source."


The code I am talking about does not mention "power production source".

This is what it says:

NEC2011,705.12(D)(2)
(2) Bus or Conductor Rating. The sum of the ampere ratings
of overcurrent devices in circuits supplying power to a
busbar or conductor shall not exceed 120 percent of the rating
of the busbar or conductor. 


Say you have a giant 200 amp panel with only 2 breakers in it.

One is 200 amp and the other is 60 amp.

If you connect the utility to the 200 amp breaker and PV to the 60 amp breaker the "The sum of the ampere ratings of overcurrent devices in circuits supplying power" are 260 amps. This exceeds the amperage rating of the bus in your 200 amp panel by 130%, you are only allowed to exceed it by 120%.

It does not matter what the size of the service is or the size of the PV.

It does not matter that there are only 51 amps passing through the bus from the PV to the service.


----------



## Rap2 (Dec 17, 2010)

Just to be clear to those who say the PV in my fore-mentioned example is only back feeding the utility at 51 amps, no argument that is exactly what is happening but still a violation.

Lets say you have a third breaker in the panel drawing a 100 amps of load.

An amp meter should show something like 49 amps coming from the utility and 51 amps coming from the PV to total that of the 100 amps of power being consumed by the load, neither the utility or the PV account for the power being used on their own, this is because the load is drawing power from 2 sources not one.

The PV and Utility are separate sources of power and when they both tie into a bus or conductor via over current protection to that bus or conductor, they are rated by the sum of the size of over current devices they are connected with, not the amount of power they pass or where the power is intended to go.


----------



## Rap2 (Dec 17, 2010)

macmikeman said:


> In the past 3 weeks I have had to change out no less than 4 services that had melted down 100 amp breakers that had load side connections to a sub panel along with insuleator taps to pv systems. In every case the connected strings of solar generating panels wattage exceeded the 20% of the feeder overcurrent device they were load tied onto. The breakers did not ''trip'' but instead melted down , caught fire in two situations and the internals got consumed enough that an open resulted in one of the phases in each case, resulting in customers telling me only half the house worked. The plastic insulating material behind the plug in busbars was melted beyond any further use in all cases I came across. So far in the last 5 years, I think it is about thirty times all told I had to do this same repair for the same reasons. Truly, I have zero respect for the quality of work that most all of the electrical contractors in my area doing pv jobs have shown me. They are all fast and good at turning a buck though.
> I'm not so hot at Kirchoff's laws but I do believe a loaded up feeder, coupled with a pv supplying more than 20% of the breaker for the feeder is the cause of the issue most of the time. The other cause sometimes I find is loose connections at the load terminals of the breaker because of sloppy work probably due to trying to go too fast due to management pressure.


Wow that is allot!

A single phase 240 volt service is 24kw and a PV system that is 20% larger is 28.8kw... are you saying the PV was larger than that?

Sorry if I didnt understand....


----------



## Rap2 (Dec 17, 2010)

Were not under NEC2014 here yet But wow did 705.12D2 change....

All the panels talked about in this thread are still in violation but maybe not so much the conductors or busses that cant have anything else installed on them.... 

I have to go out and buy 2014 now.... But here is what I found on the web...


(NEC 2014)
*705.12(D)(2), “Bus or Conductor Rating.”* Where distribution equipment is capable of supplying multiple branch circuits or feeders, the sum of the ampere rating of the inverter OCPDs and panelboard OCPD must not exceed 120% of the panelboard bus ampere rating. This is commonly referred to as “the 120% rule,” and it allows a PV system to interconnect to a panelboard that has busbars rated at the same ampere value as the panelboard’s overcurrent protection.
This concept is best illustrated with an example. What is the maximum ampere rating of the dedicated inverter overcurrent device when connecting to a 200 A bus panelboard that is capable of supplying multiple branch circuits or feeders supplied by 4/0 AWG aluminum rated 180 A?
The formula to answer this question is:
maximum inverter OCPD
= panelboard bus ampere x 1.20 – panelboard OCPD
To properly answer the question, you need to know the rating of the main OCPD. If that OCPD is rated at 200 A, which is very common in residential applications, the way to determine the maximum inverter OCPD is:
maximum inverter OCPD
= 200 A x 1.20 – 200 A
maximum inverter OCPD
= 240 A – 200 A
maximum inverter OCPD
= 40 A
If that panelboard is protected by a 150 A main OCPD, the calculation results in a different maximum inverter OCPD:
maximum inverter OCPD
= 200 A x 1.20 – 150 A
maximum inverter OCPD
= 240 A – 150 A
maximum inverter OCPD
= 90 A
The sum of the OCPDs supplying power to the busbar or conductor is what determines if the busbar is in compliance. This means you may have more than one dedicated inverter OCPD within a panelboard, as long as you meet the 120% requirement. Section 705.12(D)(2) applies only to distribution equipment that is capable of supplying multiple branch circuits or feeders, or both. For example, a 200 A bus panelboard protected by a 200 A main circuit breaker could have four 50 A inverter OCPDs, if those breakers fill all spots in the panelboard.


----------



## backstay (Feb 3, 2011)

So I went back and looked at my system. 70 amp panel has a max OCPD of 30. It has two, but the code section states the max not the combination. This leaves the MLO panel and connects to a 200 amp panel that has feed through lugs. No breaker other than the main. Which in hind site might be a violation. 

705.12(D)(2)(3) Panelboard Busbar Amper Rating. The ampacity of the Panelboard Busbar must comply with *one* of the following. 

(c) A panel board is permitted to have any number of circuit breakers as long as the total ampere ratings of all of the circuit breakers, *excluding* the rating of the over current device protecting the Busbar, don't exceed the ampere rating of the busbar.

There are four ways to determine busbar rating. You took one and laid it over all systems. You have to use all of the code section. Not just the part that fits your narrative.


----------



## Rap2 (Dec 17, 2010)

backstay said:


> So I went back and looked at my system. 70 amp panel has a max OCPD of 30. It has two, but the code section states the max not the combination. This leaves the MLO panel and connects to a 200 amp panel that has feed through lugs. No breaker other than the main. Which in hind site might be a violation.
> 
> 705.12(D)(2)(3) Panelboard Busbar Amper Rating. The ampacity of the Panelboard Busbar must comply with *one* of the following.
> 
> ...



The over current devices protecting the bus bar is all you have in the 70 amp panel. Even though it is main lug you must include the size of the breaker in the 200 amp panel feeding the 70 amp bus. You have yet to mention its size.

Still a violation. Even 2014.


----------



## Rap2 (Dec 17, 2010)

Backstay if you want to make the system you installed code compliant this is what I suggest you do.

First off you need to change the 70 amp panel to 100 amp. You need to ensure the OCP feeding it from the 200 amp service is 60 amps and there are no more than the 2 30 amp breakers of PV feeding the panel in combination with the 60 from service.

However we are not done, you must make the 200 amp compliant as well.

In order to do this you could remove the PV from the panel all together and change the panel from main lug and install a 200 amp main breaker.

At this point you could tap the wires going between the 200 amp breaker now in the panel and the 200 amp service breaker using a 100 amp fused disconnect with 60 amp fuses to feed the 100 amp panel with the PV.

From what I just read this may make you compliant with 2014 and your done. 

If not there are a few more things you need to check.

The wire size between the 200 amp breakers must be sized to to handle 260 amps and not be over feed by more than 120%. The same holds true for the wire going to and from the disconnect. If the tap is within 10 feet of where you tied into the wires between the load side of the service and line side of the 200 amp panel. then a rating of 100 amps for those wires is fine, but it needs to be on both sides and include the run to the 100 amp panel connecting to the PV.

Hope that's clear, sorry if its not.


----------



## backstay (Feb 3, 2011)

Rap2 said:


> The over current devices protecting the bus bar is all you have in the 70 amp panel. Even though it is main lug you must include the size of the breaker in the 200 amp panel feeding the 70 amp bus. You have yet to mention its size.
> 
> Still a violation. Even 2014.


You need to read it again. There are 4 ways to rate the busbar. You are only using one. I don't know how else to explain that to you. You really need to look at 705.12 again. 

Option three, 705.12(D)(2)(3)(c) First, the sum of the ampere ratings of all OCPD’s on the panelboard, both load and supply devices, excluding the rating of the OCPD protecting the busbar, shall not exceed the ampacity of the busbar. In this method, we are simply adding the face value of the OCPD’s in the panelboard excluding the main. Second, the rating of the OCPD protecting the busbar shall not exceed the rating of the busbar. If this method is used then there is no restriction on where the backfed PV breaker must be located in the panelboard.


----------



## Rap2 (Dec 17, 2010)

backstay said:


> You need to read it again. There are 4 ways to rate the busbar. You are only using one. I don't know how else to explain that to you. You really need to look at 705.12 again.
> 
> Option three, 705.12(D)(2)(3)(c) First, the sum of the ampere ratings of all OCPD’s on the panelboard, both load and supply devices, excluding the rating of the OCPD protecting the busbar, shall not exceed the ampacity of the busbar. In this method, we are simply adding the face value of the OCPD’s in the panelboard excluding the main. Second, the rating of the OCPD protecting the busbar shall not exceed the rating of the busbar. If this method is used then there is no restriction on where the backfed PV breaker must be located in the panelboard.


"the rating of the [COLOR=blue !important][COLOR=blue ! important]OCPD[/COLOR][/COLOR] protecting the busbar" 

Thats the violation once again, nothing to do with what you are saying about putting breakers in a panel. 

You have 2x30 amp breakers plus whatever connects your 70 amp panel to the 200 amp.

I assure you that is a violation.


----------



## backstay (Feb 3, 2011)

Rap2 said:


> "the rating of the [COLOR=blue !important][COLOR=blue ! important]OCPD[/COLOR][/COLOR] protecting the busbar"
> 
> Thats the violation once again, nothing to do with what you are saying about putting breakers in a panel.
> 
> ...


I can assure its not. I guess with your vast knowledge you should be able to put MH out of business.


----------



## Rap2 (Dec 17, 2010)

backstay said:


> I can assure its not. I guess with your vast knowledge you should be able to put MH out of business.



NEC is not a faith based initiative you dont have to just believe what I am saying but you should present a reasonable argument instead if calling my qualifications into it.

I believe the problem at this point is that you do not agree that the 2x30 amp breakers and the breaker connecting that connects your 70 amp panel to the 200 amp panel are protecting the 70 amp bus and fall under NEC 2011 705.12D2.

Is that right?



https://www.google.com/search?safe=...ChMIzpTXi4X6yAIViyuICh3BFgXj&biw=1246&bih=741


----------



## Rap2 (Dec 17, 2010)

Sorry for the bad english I cant type and read at the same time from my cell phone...


----------



## Rap2 (Dec 17, 2010)

Ill try again.

Are you saying the OCP in the 200 amp panel feeding the 70 amp panel is the only OCP protecing its bus?


----------

