Article 705

[david]

So, how is Load Two getting power?

We are not sure since the OP did not provide enough information. A safe assumption would be that building one is existing and the solar was to supplement the utility supply to building one.

Another safe assumption would be the solar array is away from building one. Or this is a huge facility that would justify the distance in stepping up the voltages.

A third safe assumption would be that the second load is a distance away from the first building and the solar array since the OP wants to go back and tap the stepped up voltage to take the solar supply to the secound load.

My assumptions are that building one and load two are existing loads that the OP wants to supplement solar to the utility supply

 

[badbanano]

The breaker would need a lockout to prevent it from being closed under normal utility operation and the second building must be fed downstream of the breaker.

Sent from my XT1254 using Tapatalk

 

[jaggedben]

...My assumptions are that building one and load two are existing loads that the OP wants to supplement solar to the utility supply

The solar is already supplementing the utility supply. We've no reason to believe that more than one service is involved. It would not be allowed to connect a solar system to two services and anyone trying to do so would be very misguided.

If one is going to make assumptions, it seems most reasonable to assume that the OP is installing new loads, not trying to change the supply to existing ones.

 

[david]

I don't know why you have building two labeled 'utility supplied' and what the red arrows would stand for. The red arrows represent nothing that the OP said.

and what the red arrows would stand for.

To answer your earlier question

 

[david]

The solar is already supplementing the utility supply. We've no reason to believe that more than one service is involved. It would not be allowed to connect a solar system to two services and anyone trying to do so would be very misguided.

If one is going to make assumptions, it seems most reasonable to assume that the OP is installing new loads, not trying to change the supply to existing ones.

I know you see it more likely that the second load is strictly solar supplied.

 

[GoldDigger]

I know you see it more likely that the second load is strictly solar supplied.

Basic problem with your analysis:
there is no way to connect "only" to the inverter output and not to the service.

 

[david]

Basic problem with your analysis:
there is no way to connect "only" to the inverter output and not to the service.

I know that and that is why the blue arrows in the diagram go from building one to load two

 

[david]

We have two utility interactive inverters feeding step up transformer (208p/13.8kw s)

Your voltage seems to be stepped up to 13.8 K and by placing a tap to supply load two you moved the point of connection to the tap location. Looks like you will need some distribution equipment rated at 13.8 K

I’m not sure I see the advantage to making the tap and moving the point of connection.

I realize you would be saving the cost of one additional trans former to step up the voltage from the distribution (service) equipment at building one to feed the second load from building ones service.

I would think there would have to be some trade offs in cost between 13.8k gear and another transformer to step up the voltage from building one.

Point of Connection.
(D) Utility-Interactive Inverters. The output of a utility-interactive inverter shall be permitted to be connected to the load side of the service disconnecting means of the other source(s) at any distribution equipment on the premises. Where distribution equipment including switchboards and panelboards is fed simultaneously by a primary source(s) of electricity and one or more utility-interactive inverters, and where this distribution equipment is capable of supplying multiple branch circuits or feeders or both, the interconnecting provisions for the utility-interactive inverter(s) shall comply with (D)(1) through (D)(7).

• at any distribution equipment on the premise
• Where distribution equipment including switchboards and panelboards is fed simultaneously by a primary source(s) of electricity and one or more utility-interactive inverters

 

[ggunn]

I know you see it more likely that the second load is strictly solar supplied.

Nothing can be strictly solar supplied by a grid tied inverter. It's either operating in parallel with the utility furnishing power to everything that the utility is connected to or it's not operating at all.

 

[david]

He didn't say that. If that is the problem you see (one building supplied by two feeders), then yes there are some code issues pertaining to that and some potential dangers. But he neither said that, nor do such dangers have anything whatsoever to do with the inverters and whether they would shut down.

After carefully re-reading what you had to say i agree with most of what was said.

Nothing can be strictly solar supplied by a grid tied inverter. It's either operating in parallel with the utility furnishing power to everything that the utility is connected to or it's not operating at all.

I appreciate your comment

nor do such dangers have anything whatsoever to do with the inverters and whether they would shut down.

I struggle a little bit with that comment, If the second load was existing code compliant feeder. A second feeder taken to it from the feeder tap he talked about. Load side ( of the current feeder disconnect) connected the second feeder to a back feed breaker thinking the only purpose of that second feeder was to bring solar to that load. I don’t mind that I raised concern.

 

[GoldDigger]

After carefully re-reading what you had to say i agree with most of what was said.
....
I struggle a little bit with that comment, If the second load was existing code compliant feeder. A second feeder taken to it from the feeder tap he talked about. Load side ( of the current feeder disconnect) connected the second feeder to a back feed breaker thinking the only purpose of that second feeder was to bring solar to that load. I don’t mind that I raised concern.

It appears that there may still be a fundamental problem of understanding.

If the second load is in fact connected to a existing compliant feeder, from any source, then the only way to add a connection to the inverter output would be to remove the existing connection first! Or remove any existing connection at the inverter.
Is that what you were trying to describe?

 

[david]

It appears that there may still be a fundamental problem of understanding.

If the second load is in fact connected to a existing compliant feeder, from any source, then the only way to add a connection to the inverter output would be to remove the existing connection first! Or remove any existing connection at the inverter.
Is that what you were trying to describe?

In short the OP defined the point of connection at the first load (building) load side connection (back feed breaker). 705 states the load side point of connection be at distribution equipment. The whole thing would be simplified if distribution equipment was placed ahead of the first transformer. and yes most importantly ensure that the second load is supplied by only one feeder

 

[ggunn]

705 states the load side point of connection be at distribution equipment.

Where does it say that?

 

[ggunn]

I appreciate your comment.

OK, but did you understand it? If a grid tied inverter has no connection to the grid it cannot operate - generally speaking of course. There are situations where some grid tied inverters can operate when AC coupled with battery inverters in the absence of a utility connection, and there are a few smallish GT inverters that can keep operating and power a small isolated AC circuit when the grid goes away, but these cases are far removed from what we are discussing.

 

[david]

Where does it say that?

In the context of this discussion being about load side connections

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

"at any distribution equipment on the premises. Where distribution equipment including switchboards and panelboards is fed simultaneously by a primary source(s) of electricity and one or more utility-interactive inverters"

705.12 Point of Connection.
(D) Utility-Interactive Inverters. The output of a utility-interactive inverter shall be permitted to be connected to the load side of the service disconnecting means of the other source(s) at any distribution equipment on the premises. Where distribution equipment including switchboards and panelboards is fed simultaneously by a primary source(s) of electricity and one or more utility-interactive inverters, and where this distribution equipment is capable of supplying multiple branch circuits or feeders or both, the interconnecting provisions for the utility-interactive inverter(s) shall comply with (D)(1) through (D)(7).

 

[david]

OK, but did you understand it? If a grid tied inverter has no connection to the grid it cannot operate - generally speaking of course. There are situations where some grid tied inverters can operate when AC coupled with battery inverters in the absence of a utility connection, and there are a few smallish GT inverters that can keep operating and power a small isolated AC circuit when the grid goes away, but these cases are far removed from what we are discussing.

Of course I understand it it’s the same concept as unit equipment (EM) in reverse. With emergency lighting the unit sees normal power the EM lights stay off.

With Utility-Interactive Inverters, the inverters utility voltage fells to be present they stop putting out to the grid.

 

[ggunn]

Of course I understand it it’s the same concept as unit equipment (EM) in reverse. With emergency lighting the unit sees normal power the EM lights stay off.

With Utility-Interactive Inverters, the inverters utility voltage fells to be present they stop putting out to the grid.

It's semantics, I guess. Whenever I tell someone that I appreciate their comment, I usually mean that I do not agree but I do not wish to get into an argument over it.

 

[iwire]

With Utility-Interactive Inverters, the inverters utility voltage fells to be present they stop putting out to the grid.

Or if the utility goes overvoltage, or out of frequency or any out of range condition.

You can't even get a utility interactive inverter to come on line with a local generator as the source.

 

[ggunn]

Or if the utility goes overvoltage, or out of frequency or any out of range condition.

You can't even get a utility interactive inverter to come on line with a local generator as the source.

That's not necessarily true. I have gotten a Sunny Boy/Sunny Island system to operate with a generator acting as the grid. You cannot use just a generator, or at least it's not advisable because without a battery buffer to prevent backfeeding of the generator you can blow up the generator, but in the above scenario the Sunny Island can be in paasthrough mode with the Sunny Boy accepting the generator as the grid.

 

[GoldDigger]

That's not necessarily true. I have gotten a Sunny Boy/Sunny Island system to operate with a generator acting as the grid. You cannot use just a generator, or at least it's not advisable because without a battery buffer to prevent backfeeding of the generator you can blow up the generator, but in the above scenario the Sunny Island can be in paasthrough mode with the Sunny Boy accepting the generator as the grid.

Often when a hybrid system has a generator the presence of voltage on that input causes the inverter to relax its standards for "grid" power quality. If same input terminals are used for both, then configuration settings may serve the same purpose.