Getting around 120% rule without line side tap

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ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
Another thing worth pointing out is that a supply-side connection that consists only of installing a new circuit breaker as a service disconnect (in a panel that allows such a thing) would not be modifying the switchgear either.

All of which is besides the fact that this stuff should be the business of the AHJ and not the utility.
In some locations the utility is the AHJ.
 

shortcircuit2

Senior Member
Location
South of Bawstin
A couple further comments...

I have always maintained that one inverter constitutes 'one system' since any inverter is capable of meeting the 690 definition for a system on its own regardless of how many other inverters are installed at a site. Apply this to 705 is a bit tricky because 705 covers other non-solar systems and doesn't have its own definition of those systems, except for the confusing 'Hybrid System', but overall its the best to go on with current code definitions.

The wrinkle to this is micro-inverters and AC modules, which are designed to have multiple inverters connected to the same output conductors and which fit the common sense usage of the word 'system' when installed as such.

In my opinion, the word 'source' in 705.12(D)(1) should be replaced with 'inverter', and the section otherwise reverted back to the 2011 language, while an exception should be added aimed at micro-inverters, along the lines of their being 'identified' for such use. It would clear up the meaning and fit what I believe is the real intent.

Good insight. Thank you.
 

cowboyjwc

Moderator
Staff member
Location
Simi Valley, CA
John, out of curiosity, what do you/your utility consider to be the difference between a "line side tap" and what I proposed in post #10?
Sorry been on vacation since Christmas day. OK there is a difference between a, before the meter tap, and a line side tap. The utility here will only allow one service per address, other than for car charging stations, which are billed at a different rate. According to the panel manufactures that I've spoken to, a line side tap (between the meter and the main) will void their warranty. The manufactures offer a solar ready panel (up to 60 amps on a 200 amp panel), so I don't know why everyone wants to try doing some cutesy hook up to get around the rules.

As for John Wiles. If he wrote the code section and it was approved by the code panel, then it is what it is and it is what he meant it to be. You don't have to agree, but it is the code. As for the definition of one system, if you want to install a system and the size requires two or maybe even three inverters, then it's still "one" system. It's not two or three separate systems. Even if you added a system to a house that had a system installed the code section that we spoke about before would still apply.
 
Sorry been on vacation since Christmas day. OK there is a difference between a, before the meter tap, and a line side tap. The utility here will only allow one service per address, other than for car charging stations, which are billed at a different rate. According to the panel manufactures that I've spoken to, a line side tap (between the meter and the main) will void their warranty. The manufactures offer a solar ready panel (up to 60 amps on a 200 amp panel), so I don't know why everyone wants to try doing some cutesy hook up to get around the rules.

I am still not following. First we are always talking one service. Whether there are multiple sets of service entrance conductors, a line side tap, or tapped service entrance conductors to a second service disconnecting means (which is the exact same thing as the first one - the code makes no distinction on where or if one set of service entrance conductors split into multiple sets). Second, I dont see how a panel manufacturer has any say about what happens outside of the panel board cabinet. I could maybe be persuaded that if they were tapped INSIDE the cabinet but not outside.
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
Sorry been on vacation since Christmas day. OK there is a difference between a, before the meter tap, and a line side tap. The utility here will only allow one service per address, other than for car charging stations, which are billed at a different rate. According to the panel manufactures that I've spoken to, a line side tap (between the meter and the main) will void their warranty.

I have designed several commercial line side interconnections on large MDP's where I landed the PV connection on unused perforations on the input busbars of the main breaker. I have consulted with the MDP manufacturer every time (the AHJ usually wants some kind of documentation saying that it's OK) and without exception they have had no objection or warranty issues. In a residential setting, unless the meter and panel are a single unit, I do not see how mounting a tap box between the meter can and the panel would or should have any effect on the warranty for the panel.

When you say "before the meter" that implies to me that the interconnection would be outside the meter (is that what you mean?) and therefore the PV output would not be registered on the meter. That would only work where there is a feed in tariff (FIT) and it would require separate metering.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
...The manufactures offer a solar ready panel (up to 60 amps on a 200 amp panel), so I don't know why everyone wants to try doing some cutesy hook up to get around the rules.

Because...
a) 60A may not be adequate for a lot of systems
b) doing something 'cutesy' might be a lot cheaper. Not all houses have meter/main combos. (And by the way, line side taps are about following the rules, not getting around them, specifically the 120% rule.. Otherwise we'd just stick higher rating breakers in load centers.)


As for John Wiles. If he wrote the code section and it was approved by the code panel, then it is what it is and it is what he meant it to be. You don't have to agree, but it is the code.

John Wiles did not write the code section. I can see you didn't really read my previous post. I agree that the code is the code, and the code is not whatever John Wiles says.

As for the definition of one system, if you want to install a system and the size requires two or maybe even three inverters, then it's still "one" system. It's not two or three separate systems. Even if you added a system to a house that had a system installed the code section that we spoke about before would still apply.

Give me a logical code reason to agree with you. Read the 690 definition of a system and tell me why one inverter isn't sufficient to call an installation a 'system'. If I install a string inverter on the main house and a micro-inverter system on the detached garage in what manner is it sensible to call all of that 'one system'? If I have a wind-turbine inverter and a solar inverter are they 'one system'? If yes, how are these the same 'source' (the word used by the code)? If not, what possible safety justification is there for treating interconnection differently than multiple solar (or wind) inverters?
 

cowboyjwc

Moderator
Staff member
Location
Simi Valley, CA
I am still not following. First we are always talking one service. Whether there are multiple sets of service entrance conductors, a line side tap, or tapped service entrance conductors to a second service disconnecting means (which is the exact same thing as the first one - the code makes no distinction on where or if one set of service entrance conductors split into multiple sets). Second, I dont see how a panel manufacturer has any say about what happens outside of the panel board cabinet. I could maybe be persuaded that if they were tapped INSIDE the cabinet but not outside.
OK you first. I can only answer for what goes on here. The utility is responsible to the top of the meter, even though that is usually installed by the EC if it's an overhead, if it's underground the utility feeds to the meter. Here we install all in one panels so the only way to do a line side tap would be to do it inside of the panel.
 

cowboyjwc

Moderator
Staff member
Location
Simi Valley, CA
I have designed several commercial line side interconnections on large MDP's where I landed the PV connection on unused perforations on the input busbars of the main breaker. I have consulted with the MDP manufacturer every time (the AHJ usually wants some kind of documentation saying that it's OK) and without exception they have had no objection or warranty issues. In a residential setting, unless the meter and panel are a single unit, I do not see how mounting a tap box between the meter can and the panel would or should have any effect on the warranty for the panel.

When you say "before the meter" that implies to me that the interconnection would be outside the meter (is that what you mean?) and therefore the PV output would not be registered on the meter. That would only work where there is a feed in tariff (FIT) and it would require separate metering.
You next. We're probably talking apples and oranges here. I would allow what you described on a large system, but most of the 20 or so that I look at a week are on houses. All of the panels we set here are all in ones. We don't have separate meter sockets and then disconnects that then go to a panel.
 

cowboyjwc

Moderator
Staff member
Location
Simi Valley, CA
Because...
a) 60A may not be adequate for a lot of systems
b) doing something 'cutesy' might be a lot cheaper. Not all houses have meter/main combos. (And by the way, line side taps are about following the rules, not getting around them, specifically the 120% rule.. Otherwise we'd just stick higher rating breakers in load centers.)

All the houses here have meter main combos. The title of this thread was getting around the 120% rule without line side tap. There is no way around it. You may have to derate the main breaker and depending then the size of your bus will still dictate the amount of solar that can be installed


John Wiles did not write the code section. I can see you didn't really read my previous post. I agree that the code is the code, and the code is not whatever John Wiles says.

I'm guessing that if he didn't write it that he had something to do with it, otherwise why would he be writing articles explaining it?

Give me a logical code reason to agree with you. Read the 690 definition of a system and tell me why one inverter isn't sufficient to call an installation a 'system'. If I install a string inverter on the main house and a micro-inverter system on the detached garage in what manner is it sensible to call all of that 'one system'? If I have a wind-turbine inverter and a solar inverter are they 'one system'? If yes, how are these the same 'source' (the word used by the code)? If not, what possible safety justification is there for treating interconnection differently than multiple solar (or wind) inverters?

If it's on two separate buildings, it is still one system. You are only allowed 120% of the bus rating on to the main service. So you would have to add the house and the detached garage together and that would be you allowed. You could feed into the subpanel at the garage and have one disconnect there and one at the house. We don't do wind here so I don't have an answer for you.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
If it's on two separate buildings, it is still one system. You are only allowed 120% of the bus rating on to the main service. So you would have to add the house and the detached garage together and that would be you allowed. You could feed into the subpanel at the garage and have one disconnect there and one at the house. We don't do wind here so I don't have an answer for you.

Glad we agree that I can feed the subpanel in the garage separately from the main panel in the house. We were having this whole argument because I thought you were saying that I had to combine all the solar sources into one breaker in the main. But now you are saying I can have two breakers in the main that connect interactive sources: one for the solar on the house, and one for the sub in the garage.
 

Smart $

Esteemed Member
Location
Ohio
OK you first. I can only answer for what goes on here. The utility is responsible to the top of the meter, even though that is usually installed by the EC if it's an overhead, if it's underground the utility feeds to the meter. Here we install all in one panels so the only way to do a line side tap would be to do it inside of the panel.
I think you are making the assumption that one would field modify the conductor between meter and disconnect.

They do make meter mains with one supplied main circuit breaker, and the capability of adding a second. If you add the second breaker, making it the PV System line-side 'tap" disconnect, that should neither void the listing nor the warranty.

They also make meter panelboard combos where each breaker is considered service equipment (i.e. normal service disconnecting means or PV System disconnects) with no field modification of the panel, and again should neither void the listing nor the warranty.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
I'm guessing that if [John Wiles] didn't write it that he had something to do with it, otherwise why would he be writing articles explaining it?

If people would publish my interpretations of code articles because of my name and past contributions, I would surely write articles too. You don't necessarily have to have 'something to do with' the code making process to write an article.

(Now if that article had been written by someone on the CMP for chapter 7, I wouldn't be so dismissive.)
 

cowboyjwc

Moderator
Staff member
Location
Simi Valley, CA
Glad we agree that I can feed the subpanel in the garage separately from the main panel in the house. We were having this whole argument because I thought you were saying that I had to combine all the solar sources into one breaker in the main. But now you are saying I can have two breakers in the main that connect interactive sources: one for the solar on the house, and one for the sub in the garage.
Well more because of semantics than any other reason.

Here's my final word on the subject. You can do anything that your AHJ will approve. It's about that simple. Here I don't allow the 120% rule on center fed panels. The next jurisdiction over could care less, but then he climbs on the roof and uses a magnet to check all of the bolts to make sure that they are stainless steel and he checks the UL listing of all the panels. We only require one inspection on solar and one of our other neighboring jurisdictions requires 4 inspections. One jurisdiction doesn't care if you put in a new panel or not, they require you to add two ground rods, a cold water bond and a gas bond, if you install solar. One utility want's a clear front on the AC disconnect to that they can visibly see that it is open. One fire department want's three feet of walkable roof all around the panels. Like I said what ever the jurisdiction you are working in allows, is what's allowed.

Also in the article it talks about the situation that you described and it also says that there is no definition of "PV system" in the cod and that it must be interpreted by the AHJ. That being me here gives you your answer.:happyyes:
 

cowboyjwc

Moderator
Staff member
Location
Simi Valley, CA
I think you are making the assumption that one would field modify the conductor between meter and disconnect.

They do make meter mains with one supplied main circuit breaker, and the capability of adding a second. If you add the second breaker, making it the PV System line-side 'tap" disconnect, that should neither void the listing nor the warranty.

They also make meter panelboard combos where each breaker is considered service equipment (i.e. normal service disconnecting means or PV System disconnects) with no field modification of the panel, and again should neither void the listing nor the warranty.
That I may be.

You are correct it doesn't void anything and is a good way to do it, but you see most of those in the older Zinsco panels that so many claim, on this site, are a major fire hazard and there for must be replaced.

If we're talking about the same thing, those are the ones I already mentioned. They have a dedicated PV spot that comes right off of the meter socket.
 

Smart $

Esteemed Member
Location
Ohio
That I may be.

You are correct it doesn't void anything and is a good way to do it, but you see most of those in the older Zinsco panels that so many claim, on this site, are a major fire hazard and there for must be replaced.

If we're talking about the same thing, those are the ones I already mentioned. They have a dedicated PV spot that comes right off of the meter socket.
The meter mains/panels I had in mind are Milbank and Siemens. I'm quite certain there are others, of which Zinsco was not one that had come to mind. None of the ones I had in mind have a dedicated PV spot.

http://www.milbankmfg.com/metering/...on-sockets/meter-mains-with-load-centers.aspx

https://extranet.w3.siemens.com/us/...Over_Breaker_Section_ contRPSA-MCSA1-0505.pdf
 

cowboyjwc

Moderator
Staff member
Location
Simi Valley, CA
The meter mains/panels I had in mind are Milbank and Siemens. I'm quite certain there are others, of which Zinsco was not one that had come to mind. None of the ones I had in mind have a dedicated PV spot.

http://www.milbankmfg.com/metering/...on-sockets/meter-mains-with-load-centers.aspx

https://extranet.w3.siemens.com/us/...Over_Breaker_Section_ contRPSA-MCSA1-0505.pdf
Zinscos have a main with a space for another main right next to it. we only see the Milbanks when they are used for traffic signals or irrigation meters and such and only then usually the meter pedestals. We don't see any of the one like you show, here.
 

Smart $

Esteemed Member
Location
Ohio
Zinscos have a main with a space for another main right next to it. we only see the Milbanks when they are used for traffic signals or irrigation meters and such and only then usually the meter pedestals. We don't see any of the one like you show, here.
I can't control what equipment choices are made any more than you can. All I can say is the proper equipment is out there and available to everyone in a position to specify such equipment.

And that only applies to meter main/panel combos. Where the meter is separate, the panel manufacturer has no say if the tap is external to their equipment. And IMO, they have no say if tapped internally with no field modification to the panelboard itself. For example, where main circuit breaker has listed option for dual lugs?one hole POCO, the other PV line-side tap?would be completely within the panel listing. Using other tapping means within the enclosure may infringe upon Code required wire-bending space at terminations, but not specifically a listing violation.
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
...he climbs on the roof and uses a magnet to check all of the bolts to make sure that they are stainless steel...
Some stainless steel is magnetic and some is not. Is there a particular SS alloy that they require?
 

cowboyjwc

Moderator
Staff member
Location
Simi Valley, CA
Some stainless steel is magnetic and some is not. Is there a particular SS alloy that they require?
There's this whole big debate that if you use the wrong type of screws when you are bonding to the panels that it will erode. I don't know exactly what he's looking for as it's not something that I concern myself with since the installers have such a long warranty on their installs.
 
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