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2xPowerwall whole house backup - HVAC sure start problem

Discussion in 'Tesla Energy' started by af88, Jan 2, 2020.

  1. af88

    af88 Member

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    I don't know if my solar company made a promise they can't keep. They told me 2 PW will support whole house with HVAC.

    House is already very energy efficient, lets say just a couple of small electronics on during the day and AC running. I want the AC to work so they recommended a sure start be installed, they installed it but not correctly compressor fan would only run at half speed. Contacted Hyper Engineering and they confirmed it is wired correctly now.

    What happens is the compressor (Carrier 3 ton 134LRA single stage scroll compressor) outside runs than after 2-3 mins just shuts off than starts again a 2-5 mins later. There is no fault code on the sure start (SS1B16-32SN). The fan in the house continues to run while the compressor has shut off. I called a dozen HVAC experts and none of them are familiar with sure start modules. Hyper Engineering thinks it is a compatibility issue with inherent controls of the AC unit and suggested calling an HVAC expert.

    Has anyone had success with 2 PW and a sure start on their HVAC working properly?

    Any tips or advice is appreciated.
     
  2. Lloyd

    Lloyd Well-Known Member

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    I have a three ton unit that works properly. I had my electrician install it. Also two PW's, but not carrier AC units.
     
  3. af88

    af88 Member

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    Curious do you know what the LRA is on your compressor and did they install a sure start? is it the same model sure start?
     
  4. diverbelow72

    diverbelow72 Member

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    Yes, but had issues.

    When I had my 2x PW's installed last March, Tesla also installed the SureStart (SS1B08-16SN) device to protect the PW's, when the AC kicked on. If I had 4 or more PW's installed SureStart is not needed.

    When it was getting warmer in southern WA, the AC fan kicked on but the compressor stayed off.

    The Tesla electricians did not wire my SureStart correctly. I did called Tesla Customer Care of they had no paperwork of me having 2x PW's and a SureStart.

    I had my HVAC person stop by and look at the SureStart and I found the instructions and the schematic, came to find out the wiring was wrong according to the schematic. He wired the SureStart according to the schematic and I had no more issues since.
     
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  5. af88

    af88 Member

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    Unbelievable they miss wired it but that is also my case. I actually checked the wiring and moved and made the correction and it is wired properly now but the system is behaving in the same manner as your before it was working. By any chance do you have pictures of your wiring, if not no problem, just want to do a sanity check.
     
  6. mongo

    mongo Well-Known Member

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    Just to be sure: this problem is happening while you are connected to the grid? If so, the Powerwalls have nothing to do with it.

    It sounds like the compressor is overheating, which could indicate an issue with the capacitors or the wiring for the start winding. The initial slow fan could indicate either a bad connection or they swapped the fan capacitor with one of the motor ones.

    Likely not a controls compatibility issue as the fan keeps running.
     
  7. JayClark

    JayClark Member

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    #7 JayClark, Jan 2, 2020
    Last edited: Jan 2, 2020
    The Tesla tech had to come out and replace one of the surestarts on my smaller AC unit. Evidently there are different models (capacities?) of sure-starts for different AC tonnage, and the first one was Spec’d in theory to handle my smaller AC unit, but the compressor would not spin up correctly until they placed a higher spec sure-start unit on the AC - as best I understood the situation, that was what he explained to me.

    I have four PWs, and my AC behavior sounded very similar to yours until the tech made the change, and I don’t think the PWs themselves had anything to do with the problem, purely caused by the sure-start (soft start?) units. In fact I verified this by running on only home power and the ac unit still wouldn’t start after the soft start units were installed.
     
  8. af88

    af88 Member

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    Thanks for the feedback guys, I had an HVAC expert come out and they removed the sure start and replaced it with an OEM Carrier Soft start kit made for this compressor. They also discovered since the sure start was not wired properly the Run Capacitor 7uF side was burnt out due to miss wiring so they replaced it and all is working with 2 PW with the AC running on a single test shutting off shore power the compressor continued to run on the PW. Will test again tomorrow with the compressor off and on battery power to see if it fires up. I suspect it will but will test to confirm.


    This guys has been doing this for a long time and said the sure start is a generic module not compatible with all compressors. Coincidentally hyper engineering (maker of sure start) said it could be a compatibility issues with the logic board which could have been the issue as well.

    Long story short without the sure start b/c of the 134 LRA there is no way the compressor would work switching to the batteries. But I will do a test tomorrow with the compressor off initially than go to battery and than turn the compressor on to see what happens.
     
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  9. mongo

    mongo Well-Known Member

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    Thanks for the update! Glad to hear things are working now.
     
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  10. af88

    af88 Member

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    Thanks, I'm glad it is working as well. Tomorrow will be another true test to see if the compressor will turn on after it goes to battery backup. I learned a lot more about the AC system than I thought I would from this experience. Good to be informed.

    Another thing i learned is if the Powerwall is fully charged the Solar Edge inverter will not allow the solar to operate until the capacity on the battery goes down a bit. This was a surprise to me b/c i expected it to be on but apparently the PW sends a signal to shut it off initially to prevent back flow into the grid but it also only allows it to turn back on once the capacity is reduced to a point where the solar production can be used either by the home or the battery to charge itself because the PV system can't just produce as the power has to go somewhere. Very interesting.
     
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  11. mongo

    mongo Well-Known Member

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    That is the way it works when the grid is down. Unless they started adding extra wires, the PW will not impact Solar Edge operation when connected to the grid.
     
  12. af88

    af88 Member

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    I was expecting the solar edge inverter to remain on to charge the battery and be used for what ever power the home needs. It still works this way apparently but according to the solar tech if the PW is fully charged the inverter will remain offline until it needs to be charged and there is an algorithm which checks capacity every 2% to determine if it should send the proper AC signal to the Solar edge inverter to make it run again.

    I honestly didn't expect it to behave this way. I would have wanted the solar to remain on and keep the battery charged and topped off while allowing the home to use solar but it doesn't work this way as I found out.

    Is this how you understand it?
     
  13. mongo

    mongo Well-Known Member

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    When off grid and near full, the Powerwall will start shifting the line frequency higher than the normal 60 Hz. This causes the solar inverters to reduce their output or disable themselves, depending on the model. Ideally this occurs in a gradual fashion which allows the house to use as much solar as possible.
     
    • Informative x 2
  14. af88

    af88 Member

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    Thanks for the confirmation and clarification. I guess this is expected behavior. I guess the battery capacity is only part of the equation on when the inverter kicks back on. How much power the home is consuming and the size of the PV all play a role i guess for when the PW changes the line frequency back to 60Hz to allow the inverter to turn back on.
     
  15. bob_p

    bob_p Active Member

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    When planning our recently installed solar/PowerWall system, we reviewed the potential need for "soft start" modifications to our 3 HVAC systems.

    We installed 44 350W solar panels with 4 PowerWalls and have 3 HVAC systems. After reviewing the configuration, the electricians believed we shouldn't need to add soft start.

    And after performing a stress test of the system while off grid and operating off the 4 PowerWalls, it appears the 3 air conditioning units will successfully start and that the PowerWalls have sufficient power for the 3 HVAC units plus our pool pumps - and everything else running in the house (except the electric ovens).

    At least with 4 PowerWalls, there appears to be sufficient capacity to provide power for the spike consumption when the air conditioners kick in.
     
    • Informative x 1
  16. af88

    af88 Member

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    You must have a very large home with that many HVAC units.
     
  17. af88

    af88 Member

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    Sure enough after the test today the Compressor does not run when it is off and tries to start in battery backup. Very upset about this and I'm holing the Solar company responsible for telling me it can run with 2 PW. Waiting to see how they want to rectify the problem.
     
  18. power.saver

    power.saver Supporting Member

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    My 4 ton 128 LRA Carrier unit with SureStart will not start from 2 PWs with the grid down. Too much current draw shuts off the PWs briefly, and the compressor stops.
     
    • Informative x 1
  19. af88

    af88 Member

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    That sounds right. I think everytime the compressor was trying to start the UPS in the house would sound an alarm for a second indicating the PW was probably for a ms shutting off
     
  20. mongo

    mongo Well-Known Member

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    This would only help slightly, but if they could stagger the fan and the compressor startup, that would improve things (soft start may do that already).
     

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