PowerWall installation mess: Need advice on how to get it resolved

[wwhitney]

@wwhitney Thanks for patiently listening to me and providing me with a possible solution.

Good luck with Tesla, do let us know the resolution in the end. Your situation raised some questions that were of interest to me, so you got the benefit of my learning (e.g. how to size feeders for multiple motors/HVAC units). Hopefully I was still able to give you correct answers.

About the torquing the lug nut, thanks for pointing that out. I actually tightened it. Did not realize the electrical screws also need to be torqued appropriately.

Just slightly confused by the phrase "lug nut", from the picture the only connection I see that you undid was the feeder neutral to that subpanel, which uses a slotted set screw in the neutral lug. Were there others?

Anyway, FYI, when tightening a slotted set screw like that, it's important to use a slotted driver that fills or very close to fills the slot. If you use one that's too small, it often can't transfer the required torque and you end up damaging the slot in the set screw instead of tightening it.

Cheers, Wayne

 

[valleydude]

Good luck with Tesla, do let us know the resolution in the end. Your situation raised some questions that were of interest to me, so you got the benefit of my learning (e.g. how to size feeders for multiple motors/HVAC units). Hopefully I was still able to give you correct answers.

@wwhitney , No luck getting through to Tesla . Meanwhile, I went to a friend's place in the neighborhood and checked out his PowerWall and Solar installation. He has a much bigger house than me, which is about 4300 Sq. Ft. I've attached pictures from his installation.

His electrical system also has a split panel, here are some of the details of his system which look very similar to what needs to be done to mine:
- two 200A Circuit breakers in the main panel (I've a 200A and 150A disconnect)
- the distribution section of the main panel has several heavy loads such as AC, SPA, Oven etc.
- Tesla installed a backup load center with a 200A disconnect
- Tesla relocated most of the loads from the main panel to the Tesla installed backup load center panel (200A). This includes one of the ACs !
- Tesla rewired one of the 200 A disconnect from the main panel, that was previously going to a sub-panel in the garage, to the Tesla Gateway.
- Tesla wired the sub-panel in the garage to a 100A breaker in the backup load center

This is a reaffirmation of the design changes you have proposed for my powerwall installation.
I don't why Tesla did not do this in the first place and why they are not willing to make a change now!

Just slightly confused by the phrase "lug nut", from the picture the only connection I see that you undid was the feeder neutral to that subpanel, which uses a slotted set screw in the neutral lug. Were there others?

Sorry for using the wrong terminology. There are 3 screws in all. I opened each of them to look at the cable to see if i can see any markings.

Anyway, FYI, when tightening a slotted set screw like that, it's important to use a slotted driver that fills or very close to fills the slot. If you use one that's too small, it often can't transfer the required torque and you end up damaging the slot in the set screw instead of tightening it.

I've a torque wrench that I use on my cars, but, don't have a torque screw driver.
Any recommendations for an appropriate torque screwdriver to be used with electrical wiring?

Cheers, Wayne

thanks

 

[wwhitney]

I've a torque wrench that I use on my cars, but, don't have a torque screw driver.
Any recommendations for an appropriate torque screwdriver to be used with electrical wiring?

Well, you need to check the torque specification for the 3 lugs (it might be different for the ungrounded lugs than for the grounded (neutral) but I doubt it). Actually, the torque specification may depend on the wire size, so you may need a calipers for determining the wire size. But more likely #4 to #1 will be the same torque, so you won't have to distinguish.

So if the torque rating is, say, 60 lb-in, and your torque wrench will go reliably go as low as 5 lb-ft, then you can just put a 1/4" hex socket on your torque wrench, stick in the correct 1/4" hex driver bit, and torque it. Don't use much of the handle of the wrench (hold it near the head) and stop if you suspect at all that your torque wrench isn't really calibrated at the low lb-ft you need.

Otherwise, get yourself a torque screwdriver, probably one with a 10-50 lb-in range would be best (assuming the lug doesn't call for more than 50 lb-in). Wiha is a good brand; I have one that looks like the Neiko currently available on Amazon, which is a bit less expensive.

Cheers, Wayne

 

[valleydude]

@wwhitney, many thanks for patiently replying to all my questions and the help you provided with the detailed info. Finally, Tesla guys came and fixed my installation. They just relocated all the loads except for the AC from the 200A distribution section on the old panel, to the Tesla Backup Load Center (BLC) inside the garage. They connected the 100A feed from the old panel to the BLC. The panel inside the garage which housed most of the breakers for the loads within the house was then connected to a 70A breaker on the BLC.

Here are the details from the work order from their operations team to the electrician who did the work:
- Scope of Work: add the garage sub panel in backup
1. Use the (E) 100/2P Solo main breaker to feed the backup circuit.
2. Only 1 (E) 90A/2P A/C/ Subpanel feed to remain in the lower busing of the (E) Split 300 MSP after the tie-in.
3.Relocate all other (E) loads to (N)225/100 Back Up Load Center.
4. Re-feed the (E) garage Sub Panel (now fed from 100A/2P Solo Main Breaker) from a new 70A/2P Branch Breaker in the (N) BLC with AWG#4 Conductors.
5. No change to BOS locations.

 

[wwhitney]

I didn't review the entire thread, but did look at your last one line diagram. A one line diagram of the current layout would be helpful.

But if I am understanding correctly, sounds suboptimal. You've gone from having a 300A service pre-Tesla to having everything on a 100A breaker, except for the 90A for the A/Cs (if I recall). A reasonable expectation would be to have a 200A breaker and feeder for the Gateway and all non-A/C loads (backed up), rather than 100A. Seems like they wanted to take the easy way out to provide a poor solution (which in practice may be fine with your existing loads, you just have less headroom for expansion).

Cheers, Wayne