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2xPowerwall whole house backup - HVAC sure start problem

af88

Member
Sep 28, 2019
259
49
Cali
This is why you should not make assumptions about other people's installs. I had my PW changed to the newer models a few weeks ago with the latest and newest Tesla PW stock. Even if I have the old ones they are planning on doing a software update to bring them up to the same spec, it is not a hardware change!

You can keep arguing until you're blue in the face it is not going to change the facts!

---------------- I'm going to repeat this again for others: Bottom line, if you have an AC requirement, and are being told by the installer it works fine with just 2 PW, you are rolling the dice, be prepared to purchase a 3rd PW. Lastly you should do your own math and due diligence, the PW is rated at 30A each but realistically it only provides about 28.5-29.5A for inrush startup, assuming you have absolutely no other load (lights, fridge, etc..) which is unrealistic, keep these factors in mind when calculating startup amperage needed without AC before making assumptions how well the soft starter will work and aggregate amperage and what 2 PW will support.
 
This is why you should not make assumptions about other people's installs. I had my PW changed to the newer models a few weeks ago with the latest and newest Tesla PW stock. Even if I have the old ones they are planning on doing a software update to bring them up to the same spec, it is not a hardware change!

You can keep arguing until you're blue in the face it is not going to change the facts!

---------------- I'm going to repeat this again for others: Bottom line, if you have an AC requirement, and are being told by the installer it works fine with just 2 PW, you are rolling the dice, be prepared to purchase a 3rd PW. Lastly you should do your own math and due diligence, the PW is rated at 30A each but realistically it only provides about 28.5-29.5A for inrush startup, assuming you have absolutely no other load (lights, fridge, etc..) which is unrealistic, keep these factors in mind when calculating startup amperage needed without AC before making assumptions how well the soft starter will work and aggregate amperage and what 2 PW will support.
It would have been helpful if you had posted that you had changed out the Powerwalls a few weeks ago with the newer version. You had never mentioned this previously in this thread.

All that I can say is that it isn't an installer that is claiming that each Powerwall is rated for 106 LRA, it is Tesla. Tesla should back that up.
 

af88

Member
Sep 28, 2019
259
49
Cali
Fair enough, I had not followed this thread or updated it in quite some time. My point is Tesla makes a lot of claims, don't believe everything you read. They claimed the original PW could support 2 AC and it clearly can't for everyone. Even the newer one touts this increased capacity will help but it makes no real world difference.

This is why I state to do your own due diligence and be prepared to fork out some money for an additional PW

Cheers
 
Fair enough, I had not followed this thread or updated it in quite some time. My point is Tesla makes a lot of claims, don't believe everything you read. They claimed the original PW could support 2 AC and it clearly can't for everyone. Even the newer one touts this increased capacity will help but it makes no real world difference.

This is why I state to do your own due diligence and be prepared to fork out some money for an additional PW

Cheers
How were you able to swap out the old PW2s with the newer ones? For the 3rd one, was this a separate job with separate permit, SGIP, etc?
 

af88

Member
Sep 28, 2019
259
49
Cali
Yep all separate, new permit and wiring

---------------- I'm going to repeat this again for others: Bottom line, if you have an AC requirement, and are being told by the installer it works fine with just 2 PW, you are rolling the dice, be prepared to purchase a 3rd PW. Lastly you should do your own math and due diligence, the PW is rated at 30A each but realistically it only provides about 28.5-29.5A for inrush startup, assuming you have absolutely no other load (lights, fridge, etc..) which is unrealistic, keep these factors in mind when calculating startup amperage needed without AC before making assumptions how well the soft starter will work and aggregate amperage and what 2 PW will support.
 
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Yep all separate, new permit and wiring

---------------- I'm going to repeat this again for others: Bottom line, if you have an AC requirement, and are being told by the installer it works fine with just 2 PW, you are rolling the dice, be prepared to purchase a 3rd PW. Lastly you should do your own math and due diligence, the PW is rated at 30A each but realistically it only provides about 28.5-29.5A for inrush startup, assuming you have absolutely no other load (lights, fridge, etc..) which is unrealistic, keep these factors in mind when calculating startup amperage needed without AC before making assumptions how well the soft starter will work and aggregate amperage and what 2 PW will support.
That’s great. You got patience to go through all of that. I wish I had thought more about how much energy I actually needed to go off grid with AC. I run my AC alot off of the PW2s and it can last for say 5 hours till it cools down at night. In hindsight I should’ve gotten four or more.
 

af88

Member
Sep 28, 2019
259
49
Cali
You have no idea. Been a very frustrating process which is why I keep cautioning others


---------------- I'm going to repeat this again for others: Bottom line, if you have an AC requirement, and are being told by the installer it works fine with just 2 PW, you are rolling the dice, be prepared to purchase a 3rd PW. Lastly you should do your own math and due diligence, the PW is rated at 30A each but realistically it only provides about 28.5-29.5A for inrush startup, assuming you have absolutely no other load (lights, fridge, etc..) which is unrealistic, keep these factors in mind when calculating startup amperage needed without AC before making assumptions how well the soft starter will work and aggregate amperage and what 2 PW will support.
 
You have no idea. Been a very frustrating process which is why I keep cautioning others


---------------- I'm going to repeat this again for others: Bottom line, if you have an AC requirement, and are being told by the installer it works fine with just 2 PW, you are rolling the dice, be prepared to purchase a 3rd PW. Lastly you should do your own math and due diligence, the PW is rated at 30A each but realistically it only provides about 28.5-29.5A for inrush startup, assuming you have absolutely no other load (lights, fridge, etc..) which is unrealistic, keep these factors in mind when calculating startup amperage needed without AC before making assumptions how well the soft starter will work and aggregate amperage and what 2 PW will support.
Yeah totally understand. I had my own share of hiccups. Just for my two PWs end to end took from Dec ‘19 to Apr 2021 due to everything and alot of miscommunication with my 3rd party installer. I had to upgrade my main panel late in the game (alot more $$$) and one of the PW2s arrived late due to low stock. Due to the delays I had to extend the CA SGIP rebate funds otherwise I’d lose them. Additionally Tesla sets the solar inverter shutoff to 65 Hz and I kept having to call them to switch it to 62.5 Hz which they finally did. Then I found out my old SMA solar inverter from 2016 only shuts off at 65 Hz so the PW2s kept resetting during my outage testing. So then I had to chase my solar installer support and SMA support to get admin access to change my inverter settings to 62 Hz. And then of course finding out that the AC doesn’t start let me to this thread and SureStart. Hoping this is it 🤞🏻
 

af88

Member
Sep 28, 2019
259
49
Cali
Typical PW nightmare scenario. Here is how you can identify the model like my new 2.1
 

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Typical PW nightmare scenario. Here is how you can identify the model like my new 2.1
Ok right I remember reading on some other thread about that. Because of the delay in getting the 2nd PW2, one of my units is the newer one based on the TPN. I’m not sure how this benefits me if it was installed assuming 30 amps though. Maybe it can help with providing more surge power for startup of AC?
 

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h2ofun

Active Member
Aug 11, 2020
3,288
748
auburn, ca
That is not a white paper, that is the specification for the current Powerwall 2. There was a whole thread on Powerwall 2s that started shipping in November that could be updated with a firmware update:

Also, the current Powerwall 2 are now listed as having a 106 LRA rating on their website:

I think Tesla refers to them as Powerwall 2, Series 3 (not Powerwall 3) internally.
There still is NO facts from Tesla in writing about any changes. Just lots of gossip
 

h2ofun

Active Member
Aug 11, 2020
3,288
748
auburn, ca
This is why you should not make assumptions about other people's installs. I had my PW changed to the newer models a few weeks ago with the latest and newest Tesla PW stock. Even if I have the old ones they are planning on doing a software update to bring them up to the same spec, it is not a hardware change!

You can keep arguing until you're blue in the face it is not going to change the facts!

---------------- I'm going to repeat this again for others: Bottom line, if you have an AC requirement, and are being told by the installer it works fine with just 2 PW, you are rolling the dice, be prepared to purchase a 3rd PW. Lastly you should do your own math and due diligence, the PW is rated at 30A each but realistically it only provides about 28.5-29.5A for inrush startup, assuming you have absolutely no other load (lights, fridge, etc..) which is unrealistic, keep these factors in mind when calculating startup amperage needed without AC before making assumptions how well the soft starter will work and aggregate amperage and what 2 PW will support.
WOW, how did you get your PW's changed?
 
There still is NO facts from Tesla in writing about any changes. Just lots of gossip
If you're talking about the firmware update to increase the surge capacity on the newer existing Powerwalls with regards to which powerwalls can be updated and what the update will do then I agree.

However, I don't know how much more information in writing should be expected about the Powerwalls currently shipping.

Tesla has updated the Powerwall specification sheet to reflect the 106 LRA rating:
https://tesla-cdn.thron.com/static/SV2UDQ_powerwall-2-ac-datasheet-en-na_BJ1HWK.pdf?xseo=&response-content-disposition=inline;filename="powerwall-2-ac-datasheet-en-na.pdf"

Tesla has updated their website to reflect the 106 LRA rating:
1627845367120.png


Tesla has updated their FAQs to reflect the number of Powerwalls required to run AC equipment:
1627845547915.png


If Tesla installs a whole house backup system that complies with the above requirements and the AC doesn't start then my position would be that it is up to Tesla to correct the problem.
 
Last edited:

af88

Member
Sep 28, 2019
259
49
Cali
They have had similar HVAC ratings with the older PW2.0 and this is what the installers used that got them in trouble. I have the 2.1 tested and in the real world does not work with 2 PW. Lets assume the FW is not upgraded yet, there is one big piece people keep missing which is the ambient temp required for those operational requirements.

Telsa just installed a new system with 2.1 still using 30A and 10AWG on a new home with softstarter. What does that tell you!


---------------- I'm going to repeat this again for others:

Bottom line, if you have an AC requirement, and are being told by the installer it works fine with just 2 PW, you are rolling the dice, be prepared to purchase a 3rd PW.

Lastly you should do your own math and due diligence, the PW is rated at 30A each but realistically it only provides about 28.5-29.5A for inrush startup, assuming you have absolutely no other load (lights, fridge, etc..) which is unrealistic, keep these factors in mind when calculating startup amperage needed without AC before making assumptions how well the soft starter will work and aggregate amperage and what 2 PW will support.
 

daniel

Well-Known Member
May 7, 2009
5,250
4,601
Kihei, HI
I also had no idea about my air conditioner, what each part was for and which wire was connected to what. After watching a Youtube video about the SureStart install and reading the component/wire diagram inside the AC panel, I finally got familiar with it all. The instructions for the SureStart are pretty good. They provide step-by-step instructions with pictures. They also provided a before and after set of wiring diagrams which I felt answered any lingering questions I had.

It would not be the least bit surprising if you are an order of magnitude or two more capable with this kind of stuff than I am. I can solder, and that's the end of my capability with electronics.

Also, not all A/C compressors are the same. The soft-start device that worked with yours might not work with mine. I think it is significant that I cannot find an electrician willing to take on the job even after I made it clear that I would not hold them responsible if the device damaged the compressor. I'm usually inclined to listen to experts.

I pondered the idea of buying a new compressor designed for soft start, and the idea of getting a third Powerwall. I decided it wasn't worth it, given the rarity of power failures here and the fact that lack of A/C is only a moderate discomfort here.
 
Telsa just installed a new system with 2.1 still using 30A and 10AWG on a new home with softstarter. What does that tell you!
Not much about the LRA capability, there was a discussion about this. A 30 amp breaker and 10 gage wire can handle a lot more than 30 amps in a transient situation (like the inrush current of a motor starting). If my wiring for my AC unit had been sized to handle my 126 LRA rating then it would have 1 AWG wire ran to it and a 130 amp breaker. It doesn't.
 

af88

Member
Sep 28, 2019
259
49
Cali
You are wrong, the 10AWG can can handle higher ampacity for inrush only without potential for meltdown and fire at given ambient temp, but the breaker will pop b/c the AC compressor inrush has a higher mS duration than what the breaker is rated for. If you wire to NEC and follow the rules you will be out of compliance just popping a larger breaker on the 10AWG rated wiring.

Didn't you also post your AC system does not work with your two new PWs and are hoping this fix will solve your problem.

Real world experience sucks when you learn the hard way doesn't it!

---------------- I'm going to repeat this again for others:

Bottom line, if you have an AC requirement, and are being told by the installer it works fine with just 2 PW, you are rolling the dice, be prepared to purchase a 3rd PW.

Lastly you should do your own math and due diligence, the PW is rated at 30A each but realistically it only provides about 28.5-29.5A for inrush startup, assuming you have absolutely no other load (lights, fridge, etc..) which is unrealistic, keep these factors in mind when calculating startup amperage needed without AC before making assumptions how well the soft starter will work and aggregate amperage and what 2 PW will support.
 
You are wrong, the 10AWG can can handle higher ampacity for inrush only without potential for meltdown and fire at given ambient temp, but the breaker will pop b/c the AC compressor inrush has a higher mS duration than what the breaker is rated for. If you wire to NEC and follow the rules you will be out of compliance just popping a larger breaker on the 10AWG rated wiring.
Does that mean my AC's 50 amp breaker and a lot smaller than 1 AWG wire is out of code since my AC compressor has a 126 amp LRA rating?
Didn't you also post your AC system does not work with your two new PWs and are hoping this fix will solve your problem.

Real world experience sucks when you learn the hard way doesn't it!
Yes, I'm in a battle with Tesla right now. The SureStart device isn't compatible with my reverse run compressor. Tesla looked up the wrong revision of my outside unit's specification when they designed the system, although I'm not sure they would have caught that it would have caused a problem even if they did look up the correct specification. Soft start devices quite commonly are used in industrial applications so this isn't new technology. What is unique about SureStart (and other microprocessor controlled soft start devices) is they have learning capability. Industrial units have to be custom set to each device. There are industrial soft start devices that work with reversing motors and there are units sized for my compressor. However, Tesla only uses SureStart by Hyper Engineering and refuses to install anything else.

My AC will start when the grid is down as long as the solar is producing even without a soft start device. However, there is such a small window between when the Gateway commands the solar on and when the Powerwalls have been charged enough for the Gateway to command the solar back off that the Powerwalls invariably get tripped.
 

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