Maximum height for Powerwall? Tesla wants to cancel!

[Notadog]

Tesla will not work as hard as other smaller installations to do things out of the box, or difficult. They are looking to fill the area under the curve, so if your job is being too difficult, they can sell those Powerwalls elsewhere easily.

It sounds like the plan checker who checked your plans was different than the one that checked Tesla plans. They didn't give the same comments, so the installation has different requirements. Also your neighbors house may be at a different elevation or location due to level of danger in the floodplain.

The inspectors are also not the plan checkers and typically have different skill sets. You would have limited success talking to one about why you have a flood issue and your neighbor does not. It might negatively affect your neighbors installation.

Also, if you have 2 or more PW and your neighbor just one, there is sometimes a different review process for 20 kWh and more, vs under that limit.

Our company is dealing with this currently with County of Santa Clara. They are requiring us to put them 48" above grade, or prove that the floodwaters are lower than that with an engineer.

Thanks for the advice. I'm also in Santa Clara County. My neighbor's house is right next to mine so we are definitely at the same elevation.

The installation by Clean Solar seemed pretty straight forward to me. They just mounted the Powerwall inside the garage, elevated about 3ft above the floor. That's why I'm just baffled at why Tesla isn't capable of doing the same thing.

 

[BGbreeder]

Thanks for the advice. I'm also in Santa Clara County. My neighbor's house is right next to mine so we are definitely at the same elevation.

The installation by Clean Solar seemed pretty straight forward to me. They just mounted the Powerwall inside the garage, elevated about 3ft above the floor. That's why I'm just baffled at why Tesla isn't capable of doing the same thing.

Tesla appears to want cookie cutter. If Clean Solar did a good job on your neighbor's why not go with them?

 

[holeydonut]

Tesla appears to want cookie cutter. If Clean Solar did a good job on your neighbor's why not go with them?

It's probably cost and timing.

It's a 40% premium to find a company that can deal with non-cookie-cutter... and then you're going to the back of the line which means you may not get Powerwalls by the end of NEM 2.0.

Tesla is undercutting the market like crazy and knee-capping a lot of companies. Great for the consumer I guess if it works, but sucks for any consumer that is sold on the project by Tesla, but then needs to find another vendor.

 

[wwhitney]

I vote for waiting to see if the neighbor's project passes, and getting clarity on flood level. It sounds like the neighbor's project shouldn't pass, because it's below the flood level.

Cheers, Wayne

 

[holeydonut]

I vote for waiting to see if the neighbor's project passes, and getting clarity on flood level. It sounds like the neighbor's project shouldn't pass, because it's below the flood level.

Cheers, Wayne

Yep, go on the FEMA site and punch in your addresses. Get your 1% or greater year flooding BFE elevation. Since your home is in a flood zone, the county may have an elevation certificate on file. This should tell you how high up your lower-level wall that BFE will reach.

I'm in Contra Costa County with a house that has a flooding risk in my garage that rises up 2 inches. Total CRAP.

My Powerwalls are mounted 4 inches above the garage slab (2 inches above the BFE for the area my garage is in).

https://msc.fema.gov/portal/search?AddressQuery=

 

[BGbreeder]

Databases have been know to have errors before...just sayin...

 

[wwhitney]

Yep, go on the FEMA site and punch in your addresses. Get your 1% or greater year flooding BFE elevation. Since your home is in a flood zone, the county may have an elevation certificate on file. This should tell you how high up your lower-level wall that BFE will reach.

Can you explain what reference the Base Flood Elevation will be specified against, and how to determine the elevation of a point on your property with respect to that reference?

Cheers, Wayne

 

[holeydonut]

Can you explain what reference the Base Flood Elevation will be specified against, and how to determine the elevation of a point on your property with respect to that reference?

Cheers, Wayne

Yeah I guess what I wrote doesn't make much sense lol.

Ok so let's try that FEMA website with this address (some random address; no clue who lives there).
548 Southbay Dr, San Jose, CA 95134

This is what the FEMA / FIRM map shows.

The blue-shaded side on the front of the house is in a 12 feet above sea level base flood elevation (BFE). But the back of the house technically is not. My house looks similar where the garage is in a 800 feet high BFE (stupid stupid stupid), while the back of the house is not.

For Contra Costa County, I had to get my garage-mounted Powerwalls up a few inches... since my elevation certificate indicates that only the finished garage slab is just below 800 ft, while the other parts of the house are slightly over 800 ft.

Technically if my batteries were mounted on the back of the house, they could be on grade since the back of the house is not in a blue-shaded AE flood BFE.

TBH all this paperwork is the worst. I don't know why my install got hit with every single stupid-doopid issue. Like. ugh. I had totally forgotten about this BFE crap since it was surprisingly easy for me to overcome. Just had to get the PW's up a few inches.

 

[wwhitney]

The blue-shaded side on the front of the house is in a 12 feet above sea level base flood elevation (BFE).

OK, so it tells you that BFE is 12 feet above sea level. For some definition of sea level you could look up.

Now is, say, GPS accurate enough that you could get a device that you can put on the ground and have it tell you the elevation? Possibly along with a formula to adjust the GPS number if the GPS notion of 0 elevation does not match the FIRM map notion of sea level.

Cheers, Wayne

 

[holeydonut]

OK, so it tells you that BFE is 12 feet above sea level. For some definition of sea level you could look up.

Now is, say, GPS accurate enough that you could get a device that you can put on the ground and have it tell you the elevation? Possibly along with a formula to adjust the GPS number if the GPS notion of 0 elevation does not match the FIRM map notion of sea level.

Cheers, Wayne

I think the more conventional way is to pay a few hundred bucks for a surveyor to show up with that weird tripod of theirs and a yellow reflective vest, and they'd produce an elevation certificate for whatever zone/area you're wanting to install those cool-azz Powerwalls.

Then in a perfect world, you'd include this certificate with your building permit. If the planned installed height of the Powerwalls is above the BFE for the area the PW's are going, I would assume you'd be ok.

But maybe Santa Clara County requires 48" above the BFE, which would be ... wacky. I wonder if you put your Powerwalls 4 feet up, if then they'd require 8 feet tall bollards

 

[wwhitney]

I think the more conventional way is to pay a few hundred bucks for a surveyor to show up with that weird tripod of theirs and a yellow reflective vest, and they'd produce an elevation certificate for whatever zone/area you're wanting to install those cool-azz Powerwalls.

Likely required in practice for regulatory reasons. But technically, do you know how the surveyor does it?

Cheers, Wayne

 

[miimura]

Likely required in practice for regulatory reasons. But technically, do you know how the surveyor does it?

Cheers, Wayne

They would reference a nearby monument that has known coordinates in all 3 dimensions. When I had my house built, it did not have a valid tract map since the plot was so old. I hired a surveyor and he placed a marker at the edge of the roadway on my property that had a known offset from the nearby county monuments. The Monuments are under little 8" cast iron "manhole" covers along the road centerline. From that marker he produced the map and placed corner markers for the lot. He also placed a reference marker in the back yard so that the guys doing the grading and concrete work had an accurate elevation to work from on my sloped lot.

 

[holeydonut]

Likely required in practice for regulatory reasons. But technically, do you know how the surveyor does it?

Cheers, Wayne

I guess this is the catch-22.

They normally use a local contour map and measure up to your location from the lower contour and down from another contour. Since they measure the angle and distance with that fancy tripod of theirs, they can produce the elevation of your house.

But, if you believe your local contour maps are wrong or someone has re-graded and not updated the elevation then who the hell knows...

I'm still 100% pissed I can live 800 ft above sea level on the side of a hill and have some stupid azz FEMA map put 2 square feet of a 1% BFE into my driveway and put me into a goddamn flood zone.

Edit: or as miimura says, they could establish a trig point then use that as a new basis for estimating elevation points.

 

[BGbreeder]

@wwhitney I think that you would need kinematic GPS to get that level of height accuracy, and that tends to lead you off into what model for the earth's surface is considered valid in your locale. The earth being somewhat pear shaped has defined sea levels that aren't the same distance to the earth's center. The accurate answer is usually a surveyor using kinematic GPS, located at one or more of this fancy subterranean monuments, and moving around the points of interest.

To make things worse, a number (most?) of consumer level GPS units used to trade improved (x,y) accuracy for reduced height accuracy. GPS units aimed at backpackers and climbers tend not to do that, but I would want to verify any particular unit myself.

@holeydonut it sure sounds like you bumped into the full range of regulations!

Stay safe out there...

BG