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2xPowerwall whole house backup - HVAC sure start problem

af88

Member
Sep 28, 2019
259
49
Cali
Reality bites, this is why relying on specs and speculation doesn't mean anything. Having gone through this process I have a little more know how. I've spend a lot of time on the phone with Tesla engineering and installers engineering sorting out all the issues and options. Frankly it does not surprise me anything I hear when it comes to HVAC and PW. Your hope is that this advertised Tesla energy cap increase will solve your problem. As you can see right now it does not.

The reason it starts is b/c the solar is offsetting what the PW can't support with its ~58-9A cap that is why. It is also why I made the statement I made earlier about having solar in the loop or not to avoid causing confusion. The PV output and day and conditions all make a difference, if your reliance is on solar than you have not designed the system properly as it should work without it if that was your requirement.

In regards to the wiring the HVAC has a longer pull up than PW so it will trip the breaker. Can't compare apples to oranges

---------------- 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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Reality bites, this is why relying on specs and speculation doesn't mean anything. Having gone through this process I have a little more know how. I've spend a lot of time on the phone with Tesla engineering and installers engineering sorting out all the issues and options. Frankly it does not surprise me anything I hear when it comes to HVAC and PW. Your hope is that this advertised Tesla energy cap increase will solve your problem. As you can see right now it does not.
I'm not sure what you mean about the increased LRA rating not working but my Powerwalls are too old for the firmware upgrade (or so I've been told). Tesla proposed using the load shedding terminals using the terminals on the Gateway to keep my compressor from running during an outage. This would prevent me from operating my AC in limp mode like I can now during an outage. However, they wanted to splice into wire between the thermostat and the outside unit. But my thermostat wire doesn't go to the outside unit. It is a Carrier proprietary communicating thermostat that uses data A and data B signals to communicate with the inside unit and then the inside unit uses data signals to communicate with the outside unit. I wanted them to explain exactly how they were going to incorporate load shedding but they pretty much wanted to come out and wing it. After my experience with the last technician leaving with the AC not working, telling me something must be wrong with my AC unit and to call a HVAC repair place, and me having to rewire the system myself per the schematic to get it working again; I'm not going to let them come out without a plan.

What frustrates me is my system has a utility curtailment feature that allows for load shedding. I could then manually control whether or not the compressor runs and at what stage from the wall unit. Tesla would just have to connect to the Gateway load shedding terminals to the utility curtailment terminals of my system. But tesla refuses to incorporate that into a plan.

In regards to the wiring the HVAC has a longer pull up than PW so it will trip the breaker. Can't compare apples to oranges
I disagree that this is apples and oranges. Just like it is acceptable for my HVAC unit to draw more than the 50 amp breaker limit during compressor startup, it would be acceptable to have a Powerwall provide more than 30 amps through a 30 amp breaker during a transient situation. We just don't know how much more and for how long.
 

af88

Member
Sep 28, 2019
259
49
Cali
Wong again, the data is known and easy to measure if you have the proper instrumentation which I have tested and passed the data along to Tesla Engineering and others. I also spend quite a bit time talking to Daniel and Hyperenginering and the developers at Micro about improvement their product to work more seamlessly with Tesla PW.

Again I tried to help you and all you want to do is argue. Your problem is actually relatively easy to fix to with your HVAC issue and not as complicated as you think. You made assumptions about my system and falsely claim 2 PW can work when you have no data to back it up. Lets not mention the code mess that can occur if Tesla pushes a FW update to increases energy cap without installers being made aware like most as is now including Tesla who continue to install using legacy wiring specs.

What frustrates me is people like you who read a spec and spread false information. I'm done trying to help you and I will not be responding to your nonsense any more.


For Others who are considering a PW and HVAC: I'm going to repeat this again from someone who has a lot of experiencing and real world data.

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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