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2xPowerwall whole house backup - HVAC sure start problem

Merrill

Merrill
Jan 23, 2013
4,179
1,650
Sonoma, California
No alcohol for me. Recovered alcoholic. Don't crave it anymore, don't even like it any more. Actually, I don't think I ever liked it. I drank because I was depressed and alcohol just made me more depressed. Cardio pretty much cured my depression. And living on Maui it's not an issue.
Maui no ka oi




That's because you met the ones who left. :)



It is expensive. It's bound to be when everything but pineapples and mangoes has to be shipped or flown in from 2,500 miles way.
 
The HVAC people I called said I'd need to have an electrician do it. The electrician said I'd have to have an HVAC person do it. So I gave up. I'll have to make do with the ceiling fans during an outage. Too bad, because my solar powers the A/C easily except for the start. The cost of a new A/C isn't worth it. A/C here isn't a life-or-death essential.

It shouldn't be complicated. My soft-start was only complicated because of a Daikin heat pump with unusual wiring. Premier Components Supply sells the soft starts online for about $250, and their employee Jeffrey Solak was very helpful identifying which unit I would need.
Sure-Start Products
 
Just wanted to share my experiences with install the Hyper Engineering SureStart, following the advice from YouTube, this forum and Reddit :)

I installed the SureStart SS1B16-32SN for my Carrier Comfort 15 AC and it brought the inrush current from 110 amps down to 39 amps.

The first run brought it down to 56.2 amps. The second run brought it down to 46.8 amps. The third run brought it down to 41.8 amps. The fourth run brought it down to 39.4 amps. The fifth run brought it down to 33.7 amps. The sixth run brought it back to 39.3 amps. The seventh run brought it down again to 34.1 amps. The eighth run brought it back up to 39 amps.

For the 8 AWG red wire that is provided, I bought this ring terminal from Home Depot: 8 AWG 1/4 in. Tab Ring Terminal, Vinyl Red.

For the small green terminal screws, you will need to have a small flat head screwdriver like from a small screw driver set.

For mounting the plastic bracket, that holds the SureStart, to the sheet metal, I used four hex sheet metal fasteners. The size is 8x1/2 which is perfect because the hex head doesn't jut out much and allows for the SureStart unit to snap into the plastic bracket.

To install the plastic bracket, I used blue tape to dry fit the plastic bracket first on the sheet metal. Then I used a drill to pre-drill holes for the hex screws. Then I just screw on the sheet metal fasteners by hand.

Now my two Tesla Powerwall 2s can start the AC when disconnected from PG&E!
 

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af88

Member
Sep 28, 2019
259
49
Cali
Surestart does not work on all systems the same. On my Carrier 5-ton scroll compressor it only reduced the 134 LRA down to 70A which was not enough for 2 PW to start with no other load at all. In my case I got a 3rd PW and a different soft starter and it all works fine now.

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.

Good luck
 
Surestart does not work on all systems the same. On my Carrier 5-ton scroll compressor it only reduced the 134 LRA down to 70A which was not enough for 2 PW to start with no other load at all. In my case I got a 3rd PW and a different soft starter and it all works fine now.

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.

Good luck
Looks like I got lucky. I did see Tesla claim two PWs can support LRA <139 but looks like it varies. For me 39 amp start up with my other typical electrical loads seems to be working. However I did not test with the fridge compressor cycling on. I wonder what the inrush current is for my fridge. Maybe that could cause an issue in the case both the AC and fridge compressors are started at the same time.
 

af88

Member
Sep 28, 2019
259
49
Cali
It won't be that that much, you should be fine, most fridge are energy efficient. The biggest problem with whole house backup is people don't understand simple math and rely too much on sales people. I should caveat, daytime and nighttime with and without solar is also different.

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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It won't be that that much, you should be fine, most fridge are energy efficient. The biggest problem with whole house backup is people don't understand simple math and rely too much on sales people. I should caveat, daytime and nighttime with and without solar is also different.

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.
Forgot to ask. What soft starter did you end up using?
 

af88

Member
Sep 28, 2019
259
49
Cali
MicroAir EasyStart, works well, actually much better than surestart unit but also costs more.

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.
 
MicroAir EasyStart, works well, actually much better than surestart unit but also costs more.

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.
Ok nice. I was looking at that as well. Do you happen to know what percentage reduction in inrush amps you achieved with the MicroAir? With SureStart I was able to reduce by 64.5%.
 

af88

Member
Sep 28, 2019
259
49
Cali
If the surestart is working with your compressor stick to it. I know on my system it worked better, but again it all depends on the compressor. That is why each company provides a range and not a static value in reduction.

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.
 
If the surestart is working with your compressor stick to it. I know on my system it worked better, but again it all depends on the compressor. That is why each company provides a range and not a static value in reduction.

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.
Yeaup makes sense. At least for the future I know the other options. On a side note I bragged to my wife about reducing inrush current and she eyerolled me. She’ll thank me later next time PG&E does a PSPS and it’s 100F outside 😂
 

af88

Member
Sep 28, 2019
259
49
Cali
glad it worked out for 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
4,599
Kihei, HI
I've never been able to find an electrician or A/C contractor willing to install a soft-start device on my A/C. Either they're afraid of damaging the A/C or they just don't know how and are (wisely and responsibly) unwilling to accept a job they're not confident of being able to do properly.

Fortunately, I can live without A/C. if I open my windows and turn on the ceiling fans it will be uncomfortably humid, but not dangerously hot.
 
I've never been able to find an electrician or A/C contractor willing to install a soft-start device on my A/C. Either they're afraid of damaging the A/C or they just don't know how and are (wisely and responsibly) unwilling to accept a job they're not confident of being able to do properly.

Fortunately, I can live without A/C. if I open my windows and turn on the ceiling fans it will be uncomfortably humid, but not dangerously hot.
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.
 
If the surestart is working with your compressor stick to it. I know on my system it worked better, but again it all depends on the compressor. That is why each company provides a range and not a static value in reduction.

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.
The updated Powerwall 2s have a LRA rating of 106 amps per Powerwall:

2 of the new Powerwall 2s shouldn't have a problem starting AC compressors and shouldn't need a sorf start device.
 

af88

Member
Sep 28, 2019
259
49
Cali
I have PW2 and that is not accurate.if that was the case Tesla themselves would not be installing a soft start!

I speak from experience not what a spec says on a piece of paper. I'm not going to debate you either. Do as you wish but you have been warned.

The sure start spec says it also works with any scroll compressor it does not.
The spec also claims operating frequency is delta 1, that is also not true with the default PW gateway cutoff being higher it works.

---------------- 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.
 
I have PW2 and that is not accurate.if that was the case Tesla themselves would not be installing a soft start!

I speak from experience not what a spec says on a piece of paper. I'm not going to debate you either. Do as you wish but you have been warned.

The sure start spec says it also works with any scroll compressor it does not.
The spec also claims operating frequency is delta 1, that is also not true with the default PW gateway cutoff being higher it works.

---------------- 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 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.
 
Last edited:

af88

Member
Sep 28, 2019
259
49
Cali
Again i speak from experience.

I have these "newer" PW and it makes no difference with the FW upgrade they claim. It still required the 3rd PW and soft starter. Not to mention what they claim is already what they have been doing to some degree already but instead they increased it. Even with 2 of the newer PW it behaves the same.
 

af88

Member
Sep 28, 2019
259
49
Cali
---------------- 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.
 
Again i speak from experience.

I have these "newer" PW and it makes no difference with the FW upgrade they claim. It still required the 3rd PW and soft starter. Not to mention what they claim is already what they have been doing to some degree already but instead they increased it. Even with 2 of the newer PW it behaves the same.
You started this thread in January of 2020 and already had your Powerwalls installed. The updated weren't being shipped until November of 2020 so you don't have the newer Powerwalls.

Again, if you go to Tesla's website and navigate to Powerwalls you will see this:
1627838203099.png
 

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