Solar Backfeed Issue

[jaggedben]

The concern is not really about the PV, it's the round-about way they went about adding 40 amps of solar to a 100 amp service. I hope the drawing helps, I left out the grounds and neutrals so it would be less confusing.

The general concept of what they did was completely valid. In fact I almost posted an initial reply to this thread to say "They did nothing wrong!" And if you leave out the grounds, neutrals and bonding, then you don't see what's wrong. But when you look at those details they really screwed the pooch. Most of it comes back to the fact that they tried to reconfigure a meter main combo which is not meant to be reconfigured in such a fashion. If this house had possessed separate meter and service panel enclosures, they could have made it work.

The most difficult issue I see with fixing what they have done now is isolating the neutral bar in the original panel. It would need to be isolated from the neutral lugs in the meter base and it's probably manufactured with a busbar that connects straight through. Modifying that would be a much more serious violation of the listing than removing the factory conductors to the original main breaker. (By the way, we haven't mentioned it yet, but the neutrals and grounds in the original panel would also need to be separated to different terminal bars.)

It's not a good situation now.

I think you're dealing with someone who knows their solar code pretty well but does not have a background as an electrician. There's no 690 or 705 problems here, but glaring violations of key parts of 230, 250.6, and 300.

 

[david]

The panel on the right is the service panel now, and the solar is connected as supply side connections, and therefore not subject to the 120% rule. Read the 120% rule again carefully; it refers to the sum of solar and the breaker protecting the busbar. The 100A breaker is NOT protecting the busbar; it is protecting the feeder to the original panel and everything beyond that.

i agree since the smaller panel is main lug feed from the utility there is no main breaker ahead of the buss in that panel, however all the load current is subject to the over load protection of the 100 amp breaker in that panel
a main lug panel could have up to six over current devices serving to make up the service disconnect.

i believe in this installation being discussed you would have to include the 100 amp breaker plus the two 20 amp breakers (140) amps. from my reading of these sections you have a choice of a line side of the service disconnecting means or the load side of the service disconnecting means

What disconnects this service from the utility

 

[jaggedben]

i believe in this installation being discussed you would have to include the 100 amp breaker plus the two 20 amp breakers (140) amps.

Include them in what?

The solar is not a load so it is not added to the calculated load. See 230.90 Exception 3.

 

[ggunn]

i agree since the smaller panel is main lug feed from the utility there is no main breaker ahead of the buss in that panel, however all the load current is subject to the over load protection of the 100 amp breaker in that panel
a main lug panel could have up to six over current devices serving to make up the service disconnect.

i believe in this installation being discussed you would have to include the 100 amp breaker plus the two 20 amp breakers (140) amps. from my reading of these sections you have a choice of a line side of the service disconnecting means or the load side of the service disconnecting means

What disconnects this service from the utility

Nothing. It seems to me that this panel would need to be listed as service equipment to be used this way, and two interconnection points for solar is a no-no in many jurisdictions.

 

[david]

Include them in what?

The solar is not a load so it is not added to the calculated load. See 230.90 Exception 3.

i was not looking at them (2 ea 20 amp two pole breakers) as a load and i was not looking at hem as having anything to do with 230 90 exception three i would have considered that section in regards to the (100 amp breaker), service disconnect breakers

(B) Load Side. The output of a utility-interactive inverted shall be permitted to be connected to the load side of the service disconnecting means of the other source(s)

if the connection point is allowed to a main lug ("service disconnect") distribution panel and you are defining that as a load side connection point. than you would have to consider any breakers disconnecting the service equipment from the utility as service disconnects in that panel.

The distribution equipment, panelboard is fed simultaneously by a primary source(s) of electricity and one or more utility-interactive inverters in this thread two utility-interactive inverters

This distribution equipment is capable of supplying multiple branch circuits or feeders, or both
Buss rating consideration 120%

100 amp plus 20 amp plus 20 amp 140 amps toward the buss rating for consideration.

 

[david]

Nothing. It seems to me that this panel would need to be listed as service equipment to be used this way, and two interconnection points for solar is a no-no in many jurisdictions.

Nothing. It seems to me that this panel would need to be listed as service equipment to be used this way

i agree

and two interconnection points for solar is a no-no in many jurisdictions.

what code section do they point to for that would you know?

i said in and earlier thread it would seem that the service equipment should have been left alone.

they could have come out of the 100 amp service panel with a feeder supplying a 150 amp or a 200 amp sub panel. it would have looked odd but that may have been a solution for a connection point for the inverters.

 

[david]

Include them in what?

The solar is not a load so it is not added to the calculated load. See 230.90 Exception 3.

Solar is certainly not a load but it is connected to the line side or the load side of a service disconnect

I’m having difficulty agreeing with you that this can be defined as a connection point ahead of a service disconnect when the panel is a service disconnect at least up to six breakers in that panel would have to be defined that way

Second if your connected ahead of a service disconnect you would be connected ahead of any distribution panels that distributes the load throughout a facility

Someone mentioned that this is a hybrid somewhere between a line side and a load side connection.
I contend there is no such animal it has to be defined as one or the other.

(Disconnecting Means. A device, or group of devices, or other means by which the conductors of a circuit can be disconnected from their source of supply.)

If I was to add a twenty amp branch circuit breaker to the main lug panel in discussion say for a sump pump I would not need the permission of 230.82 (6) before doing so because it would not be a line side (supply side) connection of that branch circuit. The only thing that I would have done was add a second breaker in the total of the allowable six throws to disconnect the building from the utility

((A) Supply Side. The output of a utility-interactive inverter shall be permitted to be connected to the supply side of the service disconnecting means as permitted in 230.82(6).)

 

[david]

Nothing. It seems to me that this panel would need to be listed as service equipment to be used this way, and two interconnection points for solar is a no-no in many jurisdictions.

it has been mentioned here that a panel of this type, set up with a main lug not being supplied through a main breaker is most likely being used as a non service rated panel and such use of the panel as service equipment has added to the confusion in applying the NEC to this distribution system .

 

[curt swartz]

I'm not a PV expert but would never have done the installation this way. The idea works but it creates so many other issues.

My first suggestion would have been to replace the service panel. Without seeing the job and knowing the AHJ requirements there may be a really good reason this was avoided.

The other thought I had is what about installing a 200 or 225 amp panel next to the existing service as they did.
Feed the new panel from a new 100 amp breaker in the existing service.
Install a 2" nipple at the bottom side between both panels.
Extend the new feeder and all existing branch conductors into the new panel.
This would leave the existing panel empty except for the 100 amp main and 100 amp feeder breakers.
The 40 amps of PV could be installed in the new panel without exceeding the 120% buss rating.

As I said above I'm not very strong on PV requirements but the suggestion above should work correct?

 

[ggunn]

I'm not a PV expert but would never have done the installation this way. The idea works but it creates so many other issues.

My first suggestion would have been to replace the service panel. Without seeing the job and knowing the AHJ requirements there may be a really good reason this was avoided.

The other thought I had is what about installing a 200 or 225 amp panel next to the existing service as they did.
Feed the new panel from a new 100 amp breaker in the existing service.
Install a 2" nipple at the bottom side between both panels.
Extend the new feeder and all existing branch conductors into the new panel.
This would leave the existing panel empty except for the 100 amp main and 100 amp feeder breakers.
The 40 amps of PV could be installed in the new panel without exceeding the 120% buss rating.

As I said above I'm not very strong on PV requirements but the suggestion above should work correct?

No, not if I correctly understand what you are proposing. The contribution to the 120% rule by the PV counts in every successive panel all the way back to the service.

 

[ggunn]

what code section do they point to for that would you know?

It doesn't have to be in the NEC for it (only one PV interconnection point allowed) to be the policy of the AHJ for PV interconnection, and it is in many jurisdictions. One thing they could point to, however, is the requirement that the PV backfed breaker must be at the opposite end of the busbar from the main breaker to fit into the 120% rule provision of the code. With two backfed breakers they cannot both be at the opposite end from the main.

 

[david]

It doesn't have to be in the NEC for it (only one PV interconnection point allowed) to be the policy of the AHJ for PV interconnection, and it is in many jurisdictions. One thing they could point to, however, is the requirement that the PV backfed breaker must be at the opposite end of the busbar from the main breaker to fit into the 120% rule provision of the code. With two backfed breakers they cannot both be at the opposite end from the main.

690.64 Point of Connection.
(B) Load Side.
………………………at any distribution equipment on the premises………………………………fed simultaneously by a primary source(s) of electricity and one or more utility-interactive inverters,-----------------------

I wasn’t being critical of your statement I just look at the NEC specifically allowing more than one connection to the distribution equipment, just wondering if there was a code section perhaps that stated something different.

edit why couldn't they both be, one on the left and one on the right side

 

[david]

No, not if I correctly understand what you are proposing. The contribution to the 120% rule by the PV counts in every successive panel all the way back to the service.

i wasn't aware of that if that is true than than i need to look into that because i had a similar statement just my arrangement was different

 

[jaggedben]

(B) Load Side. The output of a utility-interactive inverted shall be permitted to be connected to the load side of the service disconnecting means of the other source(s)

if the connection point is allowed to a main lug ("service disconnect") distribution panel and you are defining that as a load side connection point. than you would have to consider any breakers disconnecting the service equipment from the utility as service disconnects in that panel.

I'm certainly not defining the solar connections as load side in the OP's picture. I've said exactly the opposite. Your last sentence is correct in my opinion, although some would debate whether the solar breakers count as 'service disconnects'. They are, at any rate, not on the load side of a service disconnecting means, so none of the load side rules apply, including the 120% rule.

The distribution equipment, panelboard is fed simultaneously by a primary source(s) of electricity and one or more utility-interactive inverters in this thread two utility-interactive inverters

This distribution equipment is capable of supplying multiple branch circuits or feeders, or both
Buss rating consideration 120%

100 amp plus 20 amp plus 20 amp 140 amps toward the buss rating for consideration.

All of that applies only to the load side of the service disconnecting means. It does NOT apply to a busbar that is on the utility side of all disconnecting means.

I’m having difficulty agreeing with you that this can be defined as a connection point ahead of a service disconnect when the panel is a service disconnect at least up to six breakers in that panel would have to be defined that way. Second if your connected ahead of a service disconnect you would be connected ahead of any distribution panels that distributes the load throughout a facility

The code does not say 'ahead of'. It refers to the 'supply side' or 'load side'. That it no way implies that a supply side connection can't be in the same enclosure as the normal service disconnecting means. It's not about location.

I'm not a PV expert but would never have done the installation this way. The idea works but it creates so many other issues.

My first suggestion would have been to replace the service panel. Without seeing the job and knowing the AHJ requirements there may be a really good reason this was avoided.

The other thought I had is what about installing a 200 or 225 amp panel next to the existing service as they did.
...
As I said above I'm not very strong on PV requirements but the suggestion above should work correct?

Replacing the original service panel on the left would have been the way to go, and still is. All they need is a meter/main combo panel with a 125A busbar and 100A breaker. Then the load-side 120% rule would allow 50amps of solar.

There's no need to upgrade the amperage of the service conductors or service here. It can remain a 100A service if that's all the customer wants or needs.

...With two backfed breakers they cannot both be at the opposite end from the main.

Sure they can. A residential load center busbar typically has two stabs at the opposite end. Many panelboards can accept up to four two pole circuits on those stabs, using quad breakers on both sides. There's no sense in which the connections to those stabs for all four circuits aren't at the opposite end; they are all paralleled to the same point on the busbar.

With single column panels or a double-sided 3-phase panel you'd be limited to 2. With connections above 50A your contention is more likely to be correct.

 

[david]

I'm
The code does not say 'ahead of'. It refers to the 'supply side' or 'load side'. That it no way implies that a supply side connection can't be in the same enclosure as the normal service disconnecting means. It's not about location.

(A) Supply Side. The output of a utility-interactive inverter shall be permitted to be connected to the supply side of the service disconnecting means as permitted in 230.82(6).

It is certainly about location both locations are allowed but you have to be one or the other.

It doesn’t say supply side it says supply side of the service disconnecting means and goes on to say that connection is allowable in compliance with 230.82 (6) as I already said any connection that does not need the permission of 230.82 (6) could not be defined as a supply side connection.

For the purpose of discussing this in relationship to these thread. Load distribution cannot happen prior to a service disconnect. The most that one could claim it is happening at the service disconnecting means since the 100 amp feeder breaker and the service disconnect are in fact the same breakers in this panel along with the additional five allowable service disconnects that would make up the six service disconnect for this building.

In other word lets add the six breakers that would make up the allowable service disconnect to this building it no longer has one 100 amp disconnect. It now has six 50 amp breakers making up the service disconnect. The panel still has space to allow connection of the two 20 amp solar breakers your position is the two solar breakers would be a line side connection of the six service disconnects as far as 230 is concerned this panel is the service disconnect for the building a line side connection to the service entrance ahead of the service equipment (disconnect) would be allowed 230.82 (6)

From your comments you want to add the two 20 amp solar breakers to the buss of this panel and give no consideration of the 120% because you define that as a line side connection

 

[david]

to be honest I"m still struggling with the main lug panel when you look at dedicated source disconnect rule shouldn't the utility source interconnect through a single circuit breaker

( Dedicated Overcurrent and Disconnect. Each source interconnection shall be made at a dedicated circuit breaker or fusible disconnecting means.)

 

[ggunn]

Sure they can. A residential load center busbar typically has two stabs at the opposite end. Many panelboards can accept up to four two pole circuits on those stabs, using quad breakers on both sides. There's no sense in which the connections to those stabs for all four circuits aren't at the opposite end; they are all paralleled to the same point on the busbar.

With single column panels or a double-sided 3-phase panel you'd be limited to 2. With connections above 50A your contention is more likely to be correct.

I wasn't trying to say that the AHJ would be necessarily justified, only that they might point to that as a justification of their position. Whatever the reasoning behind it, in many jurisdictions you can only interconnect PV at a single point. If you have more than one inverter you must combine their output before interconnecting the system to the service. It's not necessarily code backed but it's in their interconnection rules. As we all know, the AHJ can add to or subtract from the NEC for local enforcement.

 

[jaggedben]

(A) Supply Side. The output of a utility-interactive inverter shall be permitted to be connected to the supply side of the service disconnecting means as permitted in 230.82(6).

It is certainly about location both locations are allowed but you have to be one or the other.

It's really simple. If you're connecting to a busbar or conductor that has no means which disconnects it from the utility, it's a supply side connection. If not, it's a load side connection. Whether any other connections happen in the same enclosure is irrelevant. Whatever else is connected to the same busbar or conductor is irrelevant.

Each connection is certainly one or the other, but you could have both types in series.

... In other word lets add the six breakers that would make up the allowable service disconnect to this building it no longer has one 100 amp disconnect. It now has six 50 amp breakers making up the service disconnect. The panel still has space to allow connection of the two 20 amp solar breakers your position is the two solar breakers would be a line side connection of the six service disconnects as far as 230 is concerned this panel is the service disconnect for the building a line side connection to the service entrance ahead of the service equipment (disconnect) would be allowed 230.82 (6)

From your comments you want to add the two 20 amp solar breakers to the buss of this panel and give no consideration of the 120% because you define that as a line side connection

There's no question that the last part is a correct interpretation. Any busbar or conductor that cannot be disconnected from the utility is not subject to any of the rules in 705.12(D). Period. It's not load side of a service disconnecting means. I realize lots of people have wrong ideas about this, or take a while to understand, but that's just because they haven't gone back to the code and carefully read what it clearly says.

Whether the two solar handles count towards the six handle for service disconnects is a more open question. People have argued for many pages on this forum about whether the solar breakers would count as service disconnecting means.

to be honest I"m still struggling with the main lug panel when you look at dedicated source disconnect rule shouldn't the utility source interconnect through a single circuit breaker

( Dedicated Overcurrent and Disconnect. Each source interconnection shall be made at a dedicated circuit breaker or fusible disconnecting means.)

The word 'source' probably needs clarification in this section, but it is not intended to refer to the utility. This section should be be re-written, in my opinion. The intent is that (non-utility) sources don't share the same overcurrent protection with loads.

Also, the section you quote is another one of the load side rules. Breakers or switches connected directly to the service do not have to follow it. But per article 230 all the normal (non 230.82) loads need to be connected to the same (six) service disconnecting handle(s).

 

[jaggedben]

I wasn't trying to say that the AHJ would be necessarily justified, only that they might point to that as a justification of their position. Whatever the reasoning behind it, in many jurisdictions you can only interconnect PV at a single point. If you have more than one inverter you must combine their output before interconnecting the system to the service. It's not necessarily code backed but it's in their interconnection rules. As we all know, the AHJ can add to or subtract from the NEC for local enforcement.

Points taken. If the utility requires a single disconnect, or that it all run through a single meter, then what the NEC says on that is moot.

With that said, it seems like a lot of AHJs and utilities put unwritten restrictions on things for no good reason, and it may not have the force of law. It just has the force of 'it's too expensive for most people to sue us about it.'

 

[ggunn]

Points taken. If the utility requires a single disconnect, or that it all run through a single meter, then what the NEC says on that is moot.

With that said, it seems like a lot of AHJs and utilities put unwritten restrictions on things for no good reason, and it may not have the force of law. It just has the force of 'it's too expensive for most people to sue us about it.'

The point is moot. If you want to play in their sandbox you have to play by their rules. It's also been my experience that if you want to prevail in a disagreement with an AHJ, your chances are much better if you have the discussion before the system is built and they have failed you on your inspection. A client of mine recently learned that lesson the hard way. They ultimately won out but it cost them time and money.