I realize I'm late to the game, but if the PW couldn't do frequency shifting to signal the solar inverters to reduced output, you would have a problem anytime the solar exceeds the house load in a backup situation. Once the PW is full, there is nowhere for the solar generation to go. Either the frequency or voltage limit would trip the solar inverters...
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Is Telsa proposing the right thing for my Powerwall installation?
- Thread starter Jeff P
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I realize I'm late to the game, but if the PW couldn't do frequency shifting to signal the solar inverters to reduced output, you would have a problem anytime the solar exceeds the house load in a backup situation. Once the PW is full, there is nowhere for the solar generation to go. Either the frequency or voltage limit would trip the solar inverters...
Frankman60
Member
Thanks for all of that great information. I am going to discuss it with my Powerwall contractor and see how their calculations come out and whether the service panel can support the 4p breaker you mentioned.
I have a Powerwall question that I need help answering. I was told by Tesla that current powerwall owners have been having issues whereby their sump pumps have been tripping the breaker and therefore turning off the power wall during power outages and therefore we were told that we now need 2 powerwalls instead of one powerwall to use as a partial backup system. We were originally told that a single powerwall would meet our needs for ensuring that our sump pump remain functional during power outages. Is this accurate, have people been having issues with their sump pump turning off their powerwall during power outages and do we actually require a 2 powerwall system or is Tesla trying to get us to needlessly purchase an additional powerwall? Thank you!
Can you provide details on your sump pump? What kind of outlet does it plug into? Do you know the Volts and Amps it uses?
Sump pumps are absolutely a potential issue, and in fact any kind of electric motor has a high start up requirement. Even more so, because they are critical to the function of a building, so customers expect them to work 100%
This is typically defined as Locked Rotor Amps (LRA), or startup amps. Its similar to the issue that happens with an AC unit, but slightly less common as the pumps tend to be smaller than the AC compressor motor.
Typically LRA can be approximated 3x the running current. Powerwall has the ability to generate 500W continuously, or 7000W of draw for 10 seconds. In our experience this is a problem that we also address with customers, and they have similar questions.
This problem is made worse when the house sees an outage. Since the sudden loss of power makes every piece of equipment that was on before the power outage come back at the same time. So not only do you need enough headroom for the pump, but the pump plus all the other stuff that is typically on the backup system. This can sometimes overload a single Powerwall.
Some pumps are worse than others, so some data on the pump will help us understand the depth of the issue.
This is typically defined as Locked Rotor Amps (LRA), or startup amps. Its similar to the issue that happens with an AC unit, but slightly less common as the pumps tend to be smaller than the AC compressor motor.
Typically LRA can be approximated 3x the running current. Powerwall has the ability to generate 500W continuously, or 7000W of draw for 10 seconds. In our experience this is a problem that we also address with customers, and they have similar questions.
This problem is made worse when the house sees an outage. Since the sudden loss of power makes every piece of equipment that was on before the power outage come back at the same time. So not only do you need enough headroom for the pump, but the pump plus all the other stuff that is typically on the backup system. This can sometimes overload a single Powerwall.
Some pumps are worse than others, so some data on the pump will help us understand the depth of the issue.
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It is a 1/3 hp Zoeller sump pump. 115 V 9.7 amps (per spec sheet). I believe it uses a 20 amp outlet.
could you install a capacitor on the motor to reduce startup amps used? Can do this for AC units to reduce number of powerwalls needed. hard start/soft start kit or something like that
nwdiver
Well-Known Member
You could try a VFD. It's soft-start so there's no current surge.
Cheaper than adding a powerwall...
If that's the case, wouldn't it be a lot cheaper to upgrade to a 240V sump pump instead of adding a second Powerwall?
Or add a 12V backup sump pump with the 12V battery charger fed from the powerwall?
Could also use a 240V to 120V step down transformer.
I have confirmed that only about half of the 5 kW of continuous power is available per phase. So some strategy would be needed to reduce the startup amps.
Sure start is one option, but is more designed for AC compressors Hyper Engineering | Single Phase
For a more advanced user the VFD option would work too.
Native 1/3 HP pump @240VAC would work, though would require reworking the wiring.
I probably wouldn't hack together a 12V pump, that's going the wrong way imho.
Of course another Powerwall might not be a bad idea, but cost sounds like it might be an object here.
Sure start is one option, but is more designed for AC compressors Hyper Engineering | Single Phase
For a more advanced user the VFD option would work too.
Native 1/3 HP pump @240VAC would work, though would require reworking the wiring.
I probably wouldn't hack together a 12V pump, that's going the wrong way imho.
Of course another Powerwall might not be a bad idea, but cost sounds like it might be an object here.
Could you clarify this? The spec sheet (https://www.tesla.com/sites/default.../Powerwall 2_AC_Datasheet_en_northamerica.pdf) says that the imbalance for split-phase loads is 100%. I thought this meant that the full power could go to either phase. Is that incorrect?
That means you can have 100% of the available 120V load on one phase of 120V with no load on the other. However each phase breaker is only 30A, which lines up with 50% of the 7kW max.
So the 100% imbalance would be 0W on one phase and 3,600 Watts max on the other. Steady state, 0W, 2,900 Watts.
If full power could be delivered to either phase, then the wiring and breaker would need to be sized accordingly.
5000w/120vac=42A. This would be beyond the design of the wire or the 30A breaker. I agree it is confusing that they worded it this way, and points to how important it is to balance the L1 and L2 phases on a Powerwall system.
5000w/120vac=42A. This would be beyond the design of the wire or the 30A breaker. I agree it is confusing that they worded it this way, and points to how important it is to balance the L1 and L2 phases on a Powerwall system.
Thank you for the info. For our back up system the only things we were planning on having on the single powerwall originally was the sump pump and our wireless router. Even with just these two items, there would still be too much inrush of electricity for a single powerwall. If we puchased a different sump pump, would this alleviate the demand on the powerwalk?
