Generation disconnect location

[CrazyRabbit]

Why am I see many installations with the generation disconnect between the gateway and service? Instead of between the generation panel and the gateway. If I’m waiting for PTO, the switch shall remain open and I don’t have power to the house. Well I guess you could open the breakers to all generation components, but if the utility saw the switch closed they my get angry.
Result is, if the disconnect is thrown the house is running on batteries. If grid is down, and the disconnect is between generation panel and gateway, there will not be any power to the house..

what is best, not cheapest?

bigger question has anyone ever seen the power company ever use the disconnect?

 

[Ampster]

has anyone ever seen the power company ever use the disconnect?

I think the disconnect is for the safety of firefighters. Fortunately i have not seen them have to use mine.

 

[CrazyRabbit]

If that is the sole reason, them opening the disconnect, if disconnect is between the gateway and service entrance, would not remove power from house as the PW would be powering house. And if that was the sole reason then wouldn’t it be required on all houses without solar.
I don’t know if the fire department will open the meter base and remove the meter to disconnect power.

 

[SoCal Dave]

If that is the sole reason, them opening the disconnect, if disconnect is between the gateway and service entrance, would not remove power from house as the PW would be powering house. And if that was the sole reason then wouldn’t it be required on all houses.
I don’t know if the fire department will open the meter base and remove the meter.

The fire department shouldn't be removing the meter as stated in this demo:

My understanding of the rapid shutdown requirements is that there should be an ability to shut down the solar panels from an accessible location. If the disconnect only turns off power to the grid, but the house goes into an off-grid mode, that isn't sufficient.

I've been looking at adding a second inverter and the Outback Skybox. I would be adding a disconnect which shuts down power to my grid tie inverter (which causes a rapid shutdown) and signals the Skybox to shut down as well. It would be right next to the panel and a single place for the fire department to shut everything down.

 

[SMAlset]

We have a 8.16kW PV + 3 PWs system. Looking at our latest 3-line diagram the solar array goes to the Inverter then to the Disconnect and then to the NGOM (which we had waived and removed and no longer required officially I think) and then to the main panel and ESS (energy storage system).

I will add that our earlier diagrams were for a 7.56kW PV + 3 PWs system (Tesla changed out our 315Ws for the newer 340Ws which generated the above mentioned diagrams) and on this 3-line diagram we had no NGOM or Disconnect listed. The solar array went to the Inverter and then to the main panel and ESS. Have no idea why the second set of diagrams triggered the NGOM and Disconnect addition (maybe a AHJ requirement for the Disconnect?) but our waiver with PG&E was for the NGOM only. The wiring for the Disconnect was drilled through our garage wall on the first install day so if it was no longer needed for whatever reason it would have left a hole in the wall that would have needed repair. We have noticed that on other solar systems in our neighborhood we've seen the Disconnect boxes so it might be a local requirement really not sure.

 

[SoCal Dave]

We have a 8.16kW PV + 3 PWs system. Looking at our latest 3-line diagram the solar array goes to the Inverter then to the Disconnect and then to the NGOM (which we had waived and removed and no longer required officially I think) and then to the main panel and ESS (energy storage system).

That makes sense as turning off the disconnect would de-engergize the inverter which would trigger the optimizers to shutdown.

 

[CrazyRabbit]

Reading code suggests requirement is to protect utility workers and electrician.
Fort Worth required disconnect outside as well as inside with enphase combiner wired stright to meter base.
If I were fire department, I wouldn’t want to mess with a live 400v dc system with the sun out. That is where enphase and solar edge have the advantage.

 

[wjgjr]

I think the disconnect is for the safety of firefighters. Fortunately i have not seen them have to use mine.

That is what I was told is the purpose of ours - the installers even referred to it as the fireman's disconnect. And ours sits between the generation panel and the gateway, so throwing the switch only kills the solar and the PWs. The grid will continue to power the house.

Ours, too, has not been used other than initial testing. Even prior to PTO, that was left in the "on" position. The only thing left off by our installers was the inverter, so the PWs could in principle provide backup power if needed. (Of course, if I didn't go off-grid and use solar to charge them, the batteries would have been drained well before PTO.)

The only switch that can kill all circuits in our home is the 200A breaker Tesla installed between the gateway and the main panel. I believe they did this at least partly for code reasons as our main panel is a split bus design with no main breaker, and I think at some point in the past, somebody went beyond 6 main breakers in the panel.

 

[CrazyRabbit]

If you have a string inverter you will still have high voltage on the roof, with the exception of soar edge. Which really doesn’t protect fireman as you still have dc voltage on the roof and house still has grid.

 

[wjgjr]

If you have a string inverter you will still have high voltage on the roof, with the exception of soar edge. Which really doesn’t protect fireman as you still have dc voltage on the roof and house still has grid.

Rapid shutdown devices address this and are part of the NEC (though recent enough that not all locations may have adopted the relevant code.) That addresses the DC voltage issue. The grid is still active, but the fireman's disconnect essentially makes the house no different from a "normal" house as far as power goes.

 

[CrazyRabbit]

Even though the inverter shuts down dc lines are still hot

this thread has digressed. where dose the generation disconnect belong on a powerwall/solar installation?

 

[SMAlset]

No idea when this was published and put on the Pennsyvania State PUC's website but you guys might find this Abstract of interest. "Interconnected PV - The Utility Accessible External Disconnect Switch". Possibly from SunEdison?

http://www.puc.state.pa.us/electric/pdf/nmic_sunedison_comments_att2.pdf

From PG&E's Greenbook "Disconnect Switch Requirements for Distributed Genertion Customers" (8/15/17)

https://www.pge.com/includes/docs/p...lity/electrictransmission/handbook/060559.pdf

Given the section "Exemption to the Disconnect Switch Installation Requirement" I believe we met all of those conditions that were required, having a Smart Meter (FM2S) installed sometime ago, unless there was a later dated revision to this that changed the requirements. Oh well it's on our outer wall now. We only asked for a waiver on the NGOM.

 

[Vines]

Even though the inverter shuts down dc lines are still hot

this thread has digressed. where dose the generation disconnect belong on a powerwall/solar installation?

The correct answer is a utility disconnect can either between the gateway and generation sources, or between the gateway and the main service panel. Either is acceptable when done correctly, but the concerns of all the AHJ must be met.

If you put the disco between the gateway and the PV and Powerwall sources, then you can turn off the power most swiftly to the whole system in case of emergency. It's also the least amount of equipment on the exterior wall. Downside is that if the utility were to lock that in the open position for grid upgrades, your backup system is locked off. A customer who got notice to turn off the PV for grid upgrades can just turn off the PV or Main breakers instead.

If the disco is between the Gateway and the grid, then opening it will only trigger a grid outage, and cause the system to go into backup mode. Some other method would need to be outside and accessible which initiates rapid shutdown. However the utility locking the disconnect would do nothing to the Powerwall and PV system, except send the house into off grid mode.

With the Gateway 2 you have a new option of the remote battery disconnect switch.

 

[Vines]

No idea when this was published and put on the Pennsyvania State PUC's website but you guys might find this Abstract of interest. "Interconnected PV - The Utility Accessible External Disconnect Switch". Possibly from SunEdison?

http://www.puc.state.pa.us/electric/pdf/nmic_sunedison_comments_att2.pdf

From PG&E's Greenbook "Disconnect Switch Requirements for Distributed Genertion Customers" (8/15/17)

https://www.pge.com/includes/docs/p...lity/electrictransmission/handbook/060559.pdf

Given the section "Exemption to the Disconnect Switch Installation Requirement" I believe we met all of those conditions that were required, having a Smart Meter (FM2S) installed sometime ago, unless there was a later dated revision to this that changed the requirements. Oh well it's on our outer wall now. We only asked for a waiver on the NGOM.

A bladed AC disconnect switch is not required for most services in PGE territory when installing PV or Powerwalls
It is required if your meter is larger than a CL 320 or a Current transformer type (CL 10, 20 or 30)
It is required on services larger than 400A or 3 phase
It is required if the meter is a bolt on type
It is required if the generation connection is a line side tap.

 

[aesculus]

When the fire department shows up to deal with a structure fire in your buildings they will disconnect every switch they can find. It's all about safety. They don't want any energized circuits period.

 

[SMAlset]

A bladed AC disconnect switch is not required for most services in PGE territory when installing PV or Powerwalls
It is required if your meter is larger than a CL 320 or a Current transformer type (CL 10, 20 or 30)
It is required on services larger than 400A or 3 phase
It is required if the meter is a bolt on type
It is required if the generation connection is a line side tap.

lol had to watch a video to see what a line side tap was and verify from install photos that we didn’t have that. All good, and learning.

 

[Vines]

lol had to watch a video to see what a line side tap was and verify from install photos that we didn’t have that. All good, and learning.

Powerwall systems aren't allowed to be on any line side taps just FYI.

 

[bob_p]

Our system was installed with a generation master disconnect (a giant throw switch, which disconnects the PowerWalls and solar panels) plus a grid disconnect (inside the gateway panel, which disconnects the gateway from the grid).

Both switches were likely required by local code.

 

[CrazyRabbit]

There is nothing wrong with line side taps, it is how all tall buildings are wired. Matter fact, they are better then your standard “pinch” style circuit breaker distribution panel. I would rather have a bolted connection any day then a spring clamp.

Tesla will not allow wire piercing taps...

line taps can be done with bus bars in a gutter.. supper clean, and one thousand times better then a standard circuit panel.