120% or 125% NEC backfeed rules as of 2014 code ?

[inetdog]

We are not on it yet here. Less restrictive I am not so sure about. Only a few system designs I know of that will meet the code.
Next code cycle only one right now.

Yes, what I should have said is that it made some of the restrictions from previous code cycles less restrictive and more rational, but added several major new requirements, such as DC AFCI and Rapid Shutdown.
And other than the fact that they increase the cost substantially and require equipment that is not being manufactured yet, the new restrictions are well thought out.

[Naptown]

And, uncharacteristically for the NEC, it actually both clarifies some points about PV and makes the rules less restrictive and arbitrary!

We are not on it yet here. Less restrictive I am not so sure about. Only a few system designs I know of that will meet the code.
Next code cycle only one right now.

[inetdog]

The 2014 code just came out.
little discussion about it.

And, uncharacteristically for the NEC, it actually both clarifies some points about PV and makes the rules less restrictive and arbitrary!

[Naptown]

These points are nothing new - they have been discussed and explained every couple of weeks so the informing others isn't too valid.

The 2014 code just came out.
little discussion about it.

[Naptown]

On the other hand, the fine points involved in PV backfeed are subtle enough that even electricians and inspectors (especially inspectors) have very lively discussions about
1. What they really say and
2. Whether what they say makes any sense from a safety point of view.

So although I would be less than thrilled to hear advice and interpretations from someone who just started reading the NEC, I would definitely like to hear about peoples experiences with their local AHJ and the hoops they may have had to jump through as a result.
(e.g. this post from Naptown.)

That cost was actually each of two panels
double the cost to get the result

[inetdog]

These points are nothing new - they have been discussed and explained every couple of weeks so the informing others isn't too valid.

On the other hand, the fine points involved in PV backfeed are subtle enough that even electricians and inspectors (especially inspectors) have very lively discussions about
1. What they really say and
2. Whether what they say makes any sense from a safety point of view.

So although I would be less than thrilled to hear advice and interpretations from someone who just started reading the NEC, I would definitely like to hear about peoples experiences with their local AHJ and the hoops they may have had to jump through as a result.
(e.g. this post from Naptown.)

[wanabefree]

dont take this personal

These points are nothing new - they have been discussed and explained every couple of weeks so the informing others isn't too valid.

I think that many of the long time well informed and educate folks on this forum take for granted that everyone will just accept the wise and sage knowledge from you guys.

I would argue that the many new and less educated posters will always ask questions and not just accept any advise until they are educated and have built up a trust in the person or persons providing such advice.

I am one of them and instead of being curt and saying things that discourage them/'me to go elsewhere bear with us. I am a low voltage electrician by trade myself and understand most of the stuff being discussed here but I admit I have a lot to learn about Solar PV systems. I always question blanket remarks or posts as facts until I can be satisfied that it is from a credible source.

The same questions will get asked over and over and to the educated they seem just a waist of time but I am pretty sure the next new guy here will appreciate the discussion if not chastised or told to just accept the facts and move one.

This is not intended to flame or discount all the good advice available here just to ask for a little more patience and understanding when we post about things that seem redundant to the long time posters but fresh and important to the newcomers.

[russ]

Sage advice, Easier said than done.

However My main reason for posting about it here is to inform others with similar situations and to journal my process while educating myself and others in the process.

These points are nothing new - they have been discussed and explained every couple of weeks so the informing others isn't too valid.

[Sunking]

However My main reason for posting about it here is to inform others with similar situations and to journal my process while educating myself and others in the process.

I understand and in the biz. This is why I would never recommend as a DIY project. Even pros have troubles jumping through the code hoops and stand no chance when code interpretation issues come up. If you DIY you own the problem and will not pass inspection or get connected until resolved. When you have a pro contractor doing the work takes you off the hook and the contractor must resolve before he collects a check and he will correct it to minimize any losses they might incur.

Secondly not every jurisdiction is working off 2014 code cycle. Many are still working off of 2011, 2008, and even some 2005 out there. Very few jurisdiction s adopt new code cycle when released. With each code cycle comes extra expense from lessons learned and manufactures pressure to adopt thier new and improved product lines.

One big fight that is still not resolved is AFCI breakers. Very expensive and still many jurisdictions do not require them. However with solar many dangers are coming into focus. They are dangerous and present significant fire dangers and FD's and insurance companies have a large loud voice with a large vote percentage in NFPA who writes the electrical codes under NEC division.

[wanabefree]

Two rules apply with Inspectors and all you have to know.

1. Inspector is always right.
2. When Inspector is incorrect refer to rule 1.

What it boils down to is it is not your problem to solve or worry about. It is your contractors problem to fix. You have a contract and he owns the responsibility on his dime. So relax.

Sage advice, Easier said than done.

However My main reason for posting about it here is to inform others with similar situations and to journal my process while educating myself and others in the process.

[Sunking]

Two rules apply with Inspectors and all you have to know.

1. Inspector is always right.
2. When Inspector is incorrect refer to rule 1.

What it boils down to is it is not your problem to solve or worry about. It is your contractors problem to fix. You have a contract and he owns the responsibility on his dime. So relax.

[bcroe]

That rule is a belt-and-suspenders requirement. The issue is the main input
and the solar feed will add up to more current on the bus. It's assumes your
bus can handle 20% more current than the box rating, so that is the feed limit.

But then it Is specified the 2 feed points must be at opposite ends of the bus.
So no matter how you arrange the loads in between, its IMPOSSIBLE for the
2 feed currents to add up on any segment of the bus.

[inetdog]

I just wanted to be at least a little informed in the process.

You qualify for that anyway.

If there were some way of guaranteeing that the load above the main never changed from the initially installed 40A and 30A 240V breakers, it would be theoretically safe, but the NEC does not deal in that level of installation-dependent decisions except in a few specific areas like calculating circuit and service loading.

Look at the full cost of the options that you are offered.
In some cases (like LADWP) you will not be allowed to put in a 150 or 200 panel without paying for an upgrade of your utility service to a matching level, even if you still put a 100A main in the new panel.

[wanabefree]

Still trying to understand

Nope. If it is center fed, you get the 100% of bus rating rule, and nothing else. The 120% rule requires opposite ends and the 125% rule just covers how you calculate the backfeed in the first place.

The idea is that if you put more than 100A of breakers (load) on the far side of the center feed from the PV backfeed the bus will be forced to carry more than 100A and no breakers will blow. No way around that.

So it sounds like in my case there is no way the center fed panel is going to work at all. By the way it is actual not center fed exactly it just has a 40 amp AC & 30amp Dryer breaker above the 100amp main breaker there are six or so 20 & 15 amp breakers below with a 30 amp solar breaker at the bottom. I am pretty sure that is still considered a center fed main.

I guess i just have to wait and see what they come up with. I just wanted to be at least a little informed in the process.

[inetdog]

Evan if that is true Since it is center fed I believe that at best they could use a 25 amp solar feed breaker and comply with the 120% rule. If I am reading your answer correctly in order to use the 125% rule the main breaker must be at the top of the bus and the solar back feed breaker at the bottom. then they may be able to justify a 30 amp feed breaker.

Nope. If it is center fed, you get the 100% of bus rating rule, and nothing else. The 120% rule requires opposite ends and the 125% rule just covers how you calculate the backfeed in the first place.

The idea is that if you put more than 100A of breakers (load) on the far side of the center feed from the PV backfeed the bus will be forced to carry more than 100A and no breakers will blow. No way around that.