Implementing a whole hose backup and welcome comments

[agarg]

Folks:

My wife and I got tired of PG&E enforced outages in Sonoma county (California) and I initially started to search for California approved 3 x 1 KW boxes for each of our refrigerators and the internet router + phone. It looked like a $4K spend when suddenly a company liquidation event gave me an opportunity to purchase SMA ABU 200 Amps + SMA Storage inverter 6KW + BYD 10.2 KW. It was more expensive and more involving, but it offered a pathway to complete energy independence. And, as engineers, we love to make things complicated!!

Using these units, I have come up with an energy independence plan that looks like the line diagram of the proposal (attached).

I will also post real pictures of the stuff soon.

 

[Ampster]

One of the key issues could be the UL certification of that particular unit. I saw that it was UL1741 compliant but the current spec is UL1741SA which also means CA Rule 21 compliance. I believe that today UL1741SA (CA Rule 21) is required but one way to make sure is to visit the CEC site and see if that model is listed. I do not know if that is a Building Code issue or a utility issue or both. It is worth finding out before you submit anything official to avoid having it rejected on the basis that it does not conform to CA Rule 21 which has been in existence for at least five years.

 

[zanydroid]

Is Rule 21 required if the storage inverter is only set up for local consumption and not export?

Similar question too but for off-grid. I don’t think POCO can say anything about storage inverter whose output is not paralleled to grid.

(Well, for really large scale customers I believe PG&E requires a review of when the load will be shifted to, to confirm that is OK)

 

[Ampster]

Is Rule 21 required if the storage inverter is only set up for local consumption and not export?

I do not believe so, but in the diagram submitted by the OP it is shown as connected though the main panel to the grid. My comment was trying to be helpful to @agarg so that he does not submit something that would be rejected on its face.

Similar question too but for off-grid. I don’t think POCO can say anything about storage inverter whose output is not paralleled to grid.

I absolutely agree and in that context I have a SolArk installed behind the meter and not part of the NEM 2.0 agreement for my 7.9kW GT system. That might be an option for the OP to apply for a simple GT system to get in before the deadline. Then later install the battery system aft.er he gets his NEM 2.0 PTO.

 

[Hedges]

Looks to me like it is all on CEC list, so UL-1741-SA Rule 21.

On CEC website I do find:

"

Altenergy Power System Inc.

DS3-L [240V]

768 VA, 240 Vac Grid Support Utility Interactive Microinverter, Rack mounted

"

Solar Equipment List - CA Energy Commission

solarequipment.energy.ca.gov

Also,

"

SMA America

SBS6.0-US-10 [240V]

6.0 kW, 240 Vac, 1-phase, Sunny Boy Storage- Permanently-connected, Transformerless Multimode - Grid Support Utility Interactive and Standalone functionality - Inverter

"

Solar Equipment List - CA Energy Commission

solarequipment.energy.ca.gov

So seems to me like the system should be accepted for permitting, and as PV with battery storage by utility.

Microinverters are UL-1741-SA, so they may work fine with SBS frequency shift when grid is down. But no guarantees. People are having mixed results with other microinverters and other high-frequency battery inverters.

I would recommend Sunny Boy string inverter instead, and compatible RSD boxes if required.
If you're already got the microinverters, I guess get permitted and installed with them. Then test their operation off-grid, see if they play nice. If necessary, "upgrade" to SMA string inverters. Current -41 model is also compliant. Older models work but are not grid-support. May also require separate RSD transmitter.

I would also backfeed from sub panel to interlocked "generator" breaker on main panel, allowing manual switching to power any loads.

 

[agarg]

Folks,

I live in wildlife urban interface (wui) area and ESS required a clearance from fire department and they are very deligent now about what they approve.

For fire, sprinklers, heat rise alarms come into play. And, I can explain and upload documents related to that.

I already have an approved ess hooked to grid as shown in the single line minus the upstream of Solar PV connection. Essentially, I am now working on SMA PV input to Rapid Shutdown to combiner box to the arrays with micro.

Once I have anchored this down, I will file an amendment application and that should be quick.

 

[zanydroid]

Weird that it's called a Rapid Shutdown in the diagram. It should just be a knife disconnect? This is a microinverter string.

Probably just a typo, unless I misunderstand how this is supposed to be configured/represented.

 

[agarg]

You are right. All the micros are grid following and so a knife disconnect is also rapid shutdown. The reason I used this terminology as it removes ambiguity from the mind of first responder about the function of this knife disconnect. There are other disconnects adjacent to it on the same wall (one for Sma storage and the second is BYD battery disconnect rated at 600v DC).

 

[zanydroid]

Sounds good that they're all knife disconnects, I believe the disconnects are required to be grouped together, hopefully they know to throw all of them.

 

[Hedges]

My plan is to use a 3-pole knife switch, with two poles isolating grid (make PG&E lineman happy), 3rd pole carrying power to keep-alive circuit for RSD.

One switch for everything. (Another switch inside to bypass RSD for debug purposes. Breaker in main panel can shut off grid/export without tripping RSD, but I also want to be able to re-enable from inside, if anybody outside pulls the switch.)


My RSD keep-alive for panels is separate from inverter. My switch will also shut off AC to inverter to trigger its discharge of input capacitance, part of RSD system.

I thought some switches could take a signaling switch (handle position), but I'm not finding that now.

 

[agarg]

bypass RSD for debug purposes

why do you need that? The primary RDS also belongs to you and you can use it to debug when in need.

 

[Hedges]

One handle for fireman or lineman shuts off possible backfeed, also performs RSD and disconnects battery backup AC in house. Main breaker in addition would be required to turn off grid AC to house.

I could have separate RSD button next to knife switch, but thought I would combine the functions. That way, same operation for fireman as shutting down GT PV (which is how RSD is usually triggered.)

If I want to open the knife switch and lock it off, that triggers RSD, so I'll have a bypass. If anyone shuts off my power when I'm inside, I could turn my system back on.

 

[Shimmy]

I could have separate RSD button next to knife switch, but thought I would combine the functions. That way, same operation for fireman as shutting down GT PV (which is how RSD is usually triggered.)

It's a good idea... especially the bypass switch. Keep it simple for the person that would use it, but also make it so it is workable for you. I used to have a bunch of DIN link switches that we used for bypasses. It was nice becasue the function wasn't obvious to the person inspecting it...

 

[agarg]

When I was reading code and they always say lockable, it gave me a uncomfortable feeling as someone exercising undue control on my property. I thought, with all the wires concealed, I can easily develop a hidden hack to take control of my home back in my own hands. Even though, it may never get exercised but intrusive control in someone else's hand is very disconcerting.

 

[Hedges]

Like someone cuts the phone line and turns off power. We have PV/battery, but don't want the controls out of reach in that situation.

Lockable visible-blade disconnect lets utility ensure you don't backfeed while lineman is working. Optional now; they can yank the meter. Backup system, we can keep powering our house.

My RSD keep-alive transmitter has 120VAC power supply, and I'll put a relay on input of step-up transformer (for 480V 3-phase inverter) to save power at night. Those two would perform RSD at PV panel and cut power to inverter so it discharges input caps. Inverter has an "error" status output; if that will switch for things like arc-fault but not normal things like "no AC" or "no PV", then I may be able to have arc-fault perform RSD (to be more thorough.)

Presumably you won't connect your equipment to the web. Unless through a gateway/firewall of your own design, passing what you want but immune to intrusion.

 

[zanydroid]

If your inside bypass overrides the outside (in the sense that it can force the RSD to be active despite the outside switch state), how would the first responders know that the RSD did not trigger? Is there an indicator light?

 

[agarg]

how would the first responders know that the RSD did not trigger?

Despite my aversion to the lockable nature of giving control to someone else, I think to defeat the purpose of disconnects is not recommended. There may be other ways to fight if it came to a pass.

 

[Hedges]

Same way first responders would know if they sprayed water or used a pickaxe on a house that had the system replaced without connecting RSD

Proper way might be to put a "Lock ON tag ON" warning on that switch while doing my work. Most of the time I would just switch off the breaker, leave 3 pole switch closed, so the shutoff would be functional. But I might want to work on the switch while leaving system running. Guess my bypass switch could make the 3rd pole cold for my comfort and safety.

Being able to restore power in dead of the night would be useful if a prowler switched it off.

"Lockable" just means a padlock can hold the lever in the off position.

Have you seen whether code addresses shutoff of battery backup systems?

 

[Shimmy]

When I was reading code and they always say lockable, it gave me a uncomfortable feeling as someone exercising undue control on my property.

The reason for lockable switches is so when you are working on it you can properly Lock-out/Tag-out the switch in accordance with NFPA and OSHA requirements. The alternative to lockable was always "in sight of".

 

[Hedges]

Can be done with individual breakers too.
Switches only used for some things.

In our training, "line of sight" isn't good enough, except for an unplugged cord. (and there are hasps for cords, too.)