3ft between energy storage system

[Designer101]

AHJ is not convinced that ESS system marked for use in residential dwelling units are exempt from R327.3 ( CALIRORNIA RESIDENTIAL CODE 2019)

the requirement is 3ft between the energy storage units.

We asked for an exception but he said that basically the fire code (CFC1206.11.2.1) trumps the California Residential Code (CRC327.3.1) so they are unable to accept our exception request.
He said if we wanted to do this, we have to Prove a smaller separation is sufficient through UL9540A.

Are Tesla Powerwall UL9540A certified.
I cannot find them online,

if you guys deal with similar issue with AHJ how did you deal it??

 

[wwhitney]

AHJ is not convinced that ESS system marked for use in residential dwelling units

I'm not aware of any such that exist. That requires passing the cell level test of UL 9540A, which basically means the testing agency can't get an individual cell to go into thermal runaway.

are exempt from R327.3 ( CALIRORNIA RESIDENTIAL CODE 2019)

the requirement is 3ft between the energy storage units.

Yes, R328.3.1 (CA adopted a new version of its codes on January 1, so numbering could have changed).

https://up.codes/viewer/california/ca-residential-code-2022/chapter/3/building-planning#R328.3.1

We asked for an exception but he said that basically the fire code (CFC1206.11.2.1) trumps the California Residential Code (CRC327.3.1) so they are unable to accept our exception request.

I wouldn't necessarily say that's broadly true. The Fire Code spells out what parts of it apply to structures governed by the Residential Code:

Chapter 1 Scope and Administration: Scope and Administration, California Fire Code 2022 | UpCodes

UpCodes offers a consolidated resource of construction and building code grouped by jurisdiction

up.codes

But R328.3.1 specifically references 1207.1.5 of the Fire Code, so that would be the standard you need to comply with, as the AHJ told you.

Are Tesla Powerwall UL9540A certified.
I cannot find them online,

Yes, the spec sheet reference UL9540A testing, IIRC. But they haven't publicly released the test results, you have to contact Tesla to get the testing and find out what reduced separation passed the UL9540A unit level testing.

Cheers, Wayne

 

[jaggedben]

Wayne pretty much nailed it.

I have dealt with this with a few AHJs (not with Tesla, but with other equipment) and they have all handled it differently. I have not had the UL9540A test report rejected outright anywhere, but in some places it has been more trouble than it's worth trying to get less than 3ft approved. I've heard from others that some AHJs just don't listen and enforce 3ft.

 

[pv_n00b]

AHJs want simple to evaluate and apply rules, like installing batteries 3' apart. The codes and standards for BESS are complex with a lot of "if you have X then you can ignore Y and do Z" in them and a lot of AHJs choose not to deal with it. I can't blame them, right now it's very hard to navigate the rules. I can't really fault an AHJ for just saying I want them 3' apart and I'm not evaluating all these exceptions.

 

[jaggedben]

On the other hand, for installations under the residential code, if the datasheet says UL9540A and the submittal includes the mfr instructions ... that's not a serious plan review burden. Then it really just comes down to whether the jurisdiction wants to be pro or anti battery.

 

[Designer101]

On the other hand, for installations under the residential code, if the datasheet says UL9540A and the submittal includes the mfr instructions ... that's not a serious plan review burden. Then it really just comes down to whether the jurisdiction wants to be pro or anti battery.

 

[Designer101]

I'm not aware of any such that exist. That requires passing the cell level test of UL 9540A, which basically means the testing agency can't get an individual cell to go into thermal runaway.

Yes, R328.3.1 (CA adopted a new version of its codes on January 1, so numbering could have changed).

https://up.codes/viewer/california/ca-residential-code-2022/chapter/3/building-planning#R328.3.1

I wouldn't necessarily say that's broadly true. The Fire Code spells out what parts of it apply to structures governed by the Residential Code:

Chapter 1 Scope and Administration: Scope and Administration, California Fire Code 2022 | UpCodes

UpCodes offers a consolidated resource of construction and building code grouped by jurisdiction

up.codes

But R328.3.1 specifically references 1207.1.5 of the Fire Code, so that would be the standard you need to comply with, as the AHJ told you.


Yes, the spec sheet reference UL9540A testing, IIRC. But they haven't publicly released the test results, you have to contact Tesla to get the testing and find out what reduced separation passed the UL9540A unit level testing.

Cheers, Wayne

specs sheets says only UL 9540, It doesn't say UL9540A , do you have updated specs sheets, i cant find in their web site

 

[wwhitney]

specs sheets says only UL 9540, It doesn't say UL9540A , do you have updated specs sheets, i cant find in their web site

Look at https://www.tesla.com/support/energy/powerwall/documents/documents

That has a link to the latest spec sheet, among other things. That sheet is dated "2021-10-28" and says "Fire Testing: Meets the unit level performance criteria of UL 9540A"

Cheers, Wayne

 

[gadfly56]

I assume that the reason for the separation is that if one battery catches on fire, it reduces the chance that adjacent batteries will go up. Wouldn't a fire-resistant barrier between the batteries be just as effective? This is the solution if you have a deep fryer next to a range top. You add a stainless steel barrier and it's all good, otherwise you have to have 18" between the fryer and the open flame appliance.

 

[wwhitney]

I assume that the reason for the separation is that if one battery catches on fire, it reduces the chance that adjacent batteries will go up. Wouldn't a fire-resistant barrier between the batteries be just as effective?

Such an arrangement would require full scale fire testing under UL 9540A to be accepted. Because of the novelty of the fire danger presented by lithium ion batteries (or unreasonable fear, depending on your point of view).

Cheers, Wayne

 

[gadfly56]

Such an arrangement would require full scale fire testing under UL 9540A to be accepted. Because of the novelty of the fire danger presented by lithium ion batteries (or unreasonable fear, depending on your point of view).

Cheers, Wayne

I went to the UL site and there are some very interesting requirements. Not only must there be 3 feet between units, but they also have to be 3 feet from any wall. For residential applications, an individual unit may not exceed 20kW-hr of storage, and no more than 80kW-hr total. Tesla Powerwall II's have a capacity of 13.5 kW-hr at a discharge rate of 3.3 kW. The maximum number of Powerwall II's you can install then is 5 for a total of 67.5 kW-hr. At my winter rate of ~30 kW-hr/day, that's a smidge over 2 days. I can probably stretch that to 4-5 days with strict enforcement of the general "TURN IT OFF!" policy. The only thing that really has to run is the furnace fan. Well, and the fridges.

 

[ggunn]

I went to the UL site and there are some very interesting requirements. Not only must there be 3 feet between units, but they also have to be 3 feet from any wall. For residential applications, an individual unit may not exceed 20kW-hr of storage, and no more than 80kW-hr total. Tesla Powerwall II's have a capacity of 13.5 kW-hr at a discharge rate of 3.3 kW. The maximum number of Powerwall II's you can install then is 5 for a total of 67.5 kW-hr. At my winter rate of ~30 kW-hr/day, that's a smidge over 2 days. I can probably stretch that to 4-5 days with strict enforcement of the general "TURN IT OFF!" policy. The only thing that really has to run is the furnace fan. Well, and the fridges.

Powerwalls are designed to stack in groups of three a couple inches apart and to mount on a wall.

 

[gadfly56]

Powerwalls are designed to stack in groups of three a couple inches apart and to mount on a wall.

I only know what I read.

UL 9540A Test Method

UL 9540A was developed to address safety concerns identified by the building codes and the fire service in the United States.

www.ul.com

 

[jaggedben]

I went to the UL site and there are some very interesting requirements. Not only must there be 3 feet between units, but they also have to be 3 feet from any wall. For residential applications, an individual unit may not exceed 20kW-hr of storage, and no more than 80kW-hr total. ...

Not sure what you're quoting but that is not entirely accurate. I don't know where you got the '3ft from any wall' idea or how wall mounted ESS could be listed if that were the case. Also the 80kWh limit is per certain locations in the resi code, not for a whole property.

EDIT: I see now what you're quoting but at least in California that was never in effect. Perhaps because changes including UL9540A were agreed upon before Cali's version of the 2021 IFC went into effect.

 

[BobKresek]

I currently have two Powerwalls outside of my house and wanted to add a third, until I found out that Santa Clara County (and cities that they serve) will not allow stacking of Powerwalls. I have had no success in getting Tesla to provide needed testing. Here is what Santa Clara County Fire said:

You are correct that SCCFD does not allow stacking of Powerwalls. The California Fire Code (CFC) and California Residential Code (CRC) requires 3 feet of spacing between units, unless smaller separation distances are approved through large scale fire testing in accordance with UL9540A (CRC R328.3.1). SCCFD has not approved smaller separation distances for Powerwalls. If at such time SCCFD approves the Powerwall large scale fire testing report, we would change spacing requirements to align with the test report.

 

[jaggedben]

It may not be possible for Tesla to provide a satisfactory report. The UL9540A test involves deliberately overheating a cell within the battery back, and seeing successively whether it catches the whole unit on fire, and whether the fire then spreads from one unit to the next. It's certainly not a given that stacked powerwalls will not catch each other on fire, especially given the cell chemistry they use.

 

[wwhitney]

Tesla has a UL9540A report that says stacked power walls pass at the unit level. For some reason it is not publicly available, but they will provide it to AHJs. Some AHJs choose not to accept Tesla's UL9540A report on the basis that they don't include the (non-passing) cell level and module level results.

Cheers, Wayne

 

[pv_n00b]

If at such time SCCFD approves the Powerwall large scale fire testing report, we would change spacing requirements to align with the test report.

Here is the key statement. Tesla has done the testing and has made the report available, SCCFD has not approved it and may choose not to. Which they can do, it's their ball and bat.

 

[BobKresek]

It is a shame that Tesla does not share with us the report they supposably provide to AHJs. We could be an advocate for reasonable decision making if we knew what was in it.

My fear is that Tesla is putting all of their efforts into the rumored new Powerwall 3, and does not want to invest any effort in the older Powerwall 2, which leaves people with the Powerwall 2 hanging.

 

[ggunn]

When SolarEdge first came out with their white paper that said that they don't need string fusing when three strings are combined, one AHJ we deal with said that since the document came from the same company as the product they would not accept it.