diy solar

diy solar

Paired vs non-paired UL9540 requirement

zanydroid said:
Following up on this a bit.

I was trying to understand what the difference is between ESS and UPS, and what the state of code writing is to disambiguate this (given that ESS is defined expansively enough to include UPS, yet UPS have been installed for much longer and plenty of people still need UPS, including commercial sites that really really care about UPS which one would imagine is a strong forcing function for new code).

Has anyone been following this?
Click to expand...
The definition of ESS in the 2023 NEC includes this informational note to help differentiate between ESS and UPS:

Informational Note No. 2: These systems differ from a stationary standby battery installation where a battery spends the majority of the time on continuous float charge or in a high state of charge, in readiness for a discharge event.​
​
UPS and ESS systems are also listed under different UL standards, the only exception seeming to be UL9540A fire testing for both ESS and UPS lithium batteries.

In implementation, ESSs are deployed more widely and in larger sizes then UPS systems, are cycled more frequently, and can send power back to the grid. While a large permanently installed UPS would typically only be installed in limited commercial locations, not at peoples houses. Now as ESS systems are deployed more widely including residential locations, where they may be subject harsh conditions, daily cycling of batteries, limited temperature control, limited fire protection, and limited maintenance and monitoring.
 
Thanks for the reference.

That note is helpful but it seems like it would be better for the text of the official definition to exclude UPS.

So I wonder how all those data centers with UPS built (whether dedicated or inside another facility) under 2017 and 2020. Engineering supervision/the AHJ trusts the design firms a lot more than they trust residential solar company hack job? Both believable I guess.

I saw a draft, I think from NPFA, of proposed amendments to various codes explicitly saying that UPS installations only need the UPS UL listing and not 9540. I asked here because I wasn’t able to understand the adoption status.
 
Also note even if the exception for UPS listed as UPS were widely adopted, I’m not sure that would allow AIOs listed to inverter listings but not UPS to be installed as UPS. There’s AFAIK very few AIO listed for both 1741 and the UPS one
 
Also don't forget Lead Acid batteries are still also used for UPS as well, and those get large exceptions in the code.
 
Sounds like a system which does not use the batteries to backfeed or time shift would be UPS.
Time shifting consumption and additional local consumption (limiting current drawn from grid), maybe one or the other.
Storage of PV (or grid) power for later backfeed would be ESS.

Lead-acid? I thought exemptions when away when the stringent ESS restrictions were adopted.

My interest of course is lead-acid with Sunny Island, possibly lithium with it in the future. Does not have algorithm for time shifting or backfeed from battery.
 
But you would have a hard time arguing for it as a DIY without engineering license or other pull with AHJ since the definitions don’t clearly exclude UPS

706.2 “one or more components assembled together capable of storing energy and providing electrical energy into the premises wiring system or an electric power production and distribution network.”

R327 (very old version, my google skills aren’t good enough to get 2003 version)

IMG_2818.jpeg

 
Looked through UL9540 Third Edition for some snippets about AC / DC ESS. That was painful to do on the free web viewer.

The points I saw from skimming through the spec are:
  • The sticker has to explicitly say DC ESS, so an AC ESS / UL9540 Second Edition battery probably can't be used as DC ESS.
  • Installation instructions for DC ESS (reviewed as part of certification process) can indeed be written to make the DC ESS compatible with a generic range of UL1741 inverters
(Doh, I had to remove the UL screenshots due to watermark)
 
Last edited:
Seeing as how there’s very little info out there on DC ESS product roadmaps/ability to migrate existing product from general or AC ESS listing, etc, I tried fishing for more on Reddit. Either I’m terrible at writing compelling titles, people don’t get it, or people don’t care…

Where else can I fish for more info?
 
pvgirl said:
Under 9540:2020 Ed 2, anything added to DC bus of the ESS, solar charge controllers, chargers, DC generators, would be in scope of the 9540 listing, and to be completely compliant would need to be included in the listing. On the AC side it's a little different as energy going in to storage has to go thru a charger that is part of the ESS and would not be in scope of 9540. As always the final decision is made by the AHJ

The newly released UL 9540 Ed 3, introduces the concept of a DC ESS, which would allow the listing of a module just includes protection(BMS, etc), and storage(battery), and doesn't necessarily limit use to just a select set of products. Although we will have to see if the market produces these products.

We could see server rack batteries, become listed as DC ESS, and be usable with what ever listed components we want in the future. If these DC ESS, also come with proper 9540A testing, the 20kw and 3ft spacing rules in the IRC can be reduced to more reasonable values.

FYI if you register for an account at https://www.shopulstandards.com/ you can get free access to read the UL standards for yourself.
Click to expand...
The 18kPV - Powerpro ESS now has UL9540 3rd edition Certification it seems, I'm trying to wrap my head around that vs 2nd edition...which is what it seemed was required before. Does 3rd edition do away with the the need for 2nd edition? (for an ESS)
 
damo green said:
The 18kPV - Powerpro ESS now has UL9540 3rd edition Certification it seems, I'm trying to wrap my head around that vs 2nd edition...which is what it seemed was required before. Does 3rd edition do away with the the need for 2nd edition? (for an ESS)
Click to expand...
The 3rd edition supersedes the 2nd, currently products can be certified to either some time soon the 2nd edition will no longer be valid for new listings. Products listed under previous editions are still considered listed and usable, unless there are local regulations that are more strict. I believe California's residential code requires at least ul 9540 2nd edition for ESS installs.
 
I have a related question.

Do solar modules used in off grid systems also need acertain IEC or UL certification to be installed in California?

@pvgirl Thank you for your excellent answers
 
For on grid they do, CEC approved streamlines this further. CEC I believe maintains a list, and PG&E loads this into the application webapp.

If it’s not in the list/application then you’re going to have extra hassle if not outright ban.

For off-grid, it is probably up to your AHJ whether appropriate UL is fine or CEC is required.

I don’t know how non-CEC is frankly coming up. There’s a glut of modules right now.

You’ll still eventually break even on interconnection fee if you go grid tie.
 
Created a new thread for a DC ESS that I found last night:
diysolarforum.com

Finally found a UL9540 DC ESS - SimpliPHI 6.6

Every couple of months I do another round of Googling to see what the progress is on UL9540 Edition 3. I finally found a 48V DC ESS: Haven't had a chance yet to look through the manuals / listing certificate. Here is a screenshot of the press release. /
diysolarforum.com diysolarforum.com
 

Attachments

  • 1715461066185.png
    1715461066185.png
    253.5 KB · Views: 0
You must log in or register to reply here.
Back
Top