Yes
Yes, although:
Is an unknown to me
On top or in front? I don't think front to back as the glass front panel is the access point. Vertically, maybe if your code allows it.
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Discussion: Powerwall 3 [Speculation / Discussion etc]
- Thread starter n.one.one
- Start date
I think this situation with an electrical service consisting of 2 phases of the 3-phase system in Australia will turn out to be very much like a 400A service in North America.
Each 240VAC phase will:
This is really not ideal, but to my knowledge, Tesla does not have a mechanism to net out the meter between the two systems. In North America this is because the Gateway can only handle 200A and a 400A service must have two Gateways to handle all loads being backed up. In international markets where 3-phase is common in Residential electrical service, last I heard they just don't have a way to provide coordinated backup of multiple phases. I seem to recall that a three phase service can be metered to be self powered while only one phase is backed up and equipped with solar. However, I don't know if this can work with two Gateways and two phases backed up. I also don't know if it will balance Powerwall in/out with a 3-phase solar inverter. A 3-phase solar inverter also won't generate when the grid is down and only one phase is backed up. It would be super clever if you could have one multi-phase remote metering device feeding data to both Gateways, but I think it's unlikely to work at all or work well unless Tesla put effort into making it work properly. I would not hold my breath on that. If Tesla cared about 3-phase markets, they would have developed a native 3-phase Powerwall.
Each 240VAC phase will:
- Require its own Gateway
- Appear on a separate page in the Tesla app
- Balance its own consumption and generation without coordination with the other "system" on the other phase.
This is really not ideal, but to my knowledge, Tesla does not have a mechanism to net out the meter between the two systems. In North America this is because the Gateway can only handle 200A and a 400A service must have two Gateways to handle all loads being backed up. In international markets where 3-phase is common in Residential electrical service, last I heard they just don't have a way to provide coordinated backup of multiple phases. I seem to recall that a three phase service can be metered to be self powered while only one phase is backed up and equipped with solar. However, I don't know if this can work with two Gateways and two phases backed up. I also don't know if it will balance Powerwall in/out with a 3-phase solar inverter. A 3-phase solar inverter also won't generate when the grid is down and only one phase is backed up. It would be super clever if you could have one multi-phase remote metering device feeding data to both Gateways, but I think it's unlikely to work at all or work well unless Tesla put effort into making it work properly. I would not hold my breath on that. If Tesla cared about 3-phase markets, they would have developed a native 3-phase Powerwall.
Yeah.
They can net zero a three phase system with PW on one one phase (within power limits of course), but that's with only one Gatway.
There are conflicting reports of two powerwalls on a three phase system in the UK where the two phases are backed up on a single gateway. Bear in mind most three phase residential deployments in the UK and Australia (as far as I am familiar with them) tend not to have that many devices that use all three phases. Many of those Powerwall installations are for a single power for TOU reasons, not for backup reasons. So the systems resemble the typical US "one phase" system but at 240V(50Hz) with three supplies. Since the gateway can and does monitor all three phases to net consumption, it has some of the necessary tools for controlling three phase. Whether it can sync three different phases on a single control bus (CANbus) is, I think an open question.
(I personally think that the US phase nomenclature is skew whiff; the US norm has two 120V supplies 180 degrees out of phase. But that is neither here nor there. Any electrical engineer would describe that as "two phase". Single phase systems exist with only one 120V supply. So why is the provision of two, different 120V phases still "one phase"? That is a different discussion, and not likely to change established jargon, though that does not make it accurate in my opinion. For the record, three phase is power supply lines 120 degrees out of phase (120=360/3, just as 180=360/2). Don't get me started on all the three phase variants kicking around in the US.)
All the best,
BG
It's called single phase because it comes from a single winding in the transformer. Although there is a center tap for the neutral which splits the single phase into two legs (A & B) it is not "two phase" because both the A and B legs are derived from the same source. It's also commonly called "split phase" power for this reason. To get true two phase power, you need two transformer windings, similar to how three phase power comes from three transformer windings.
No, that's not correct. A phase is a collection of possible voltage waveforms that are scalar multiples of each other. If I give you a 2-wire supply, with an autotransformer (a coil with multiple taps along its length) you can get as many different voltage waveforms as you like, but they will all be in phase with each other, so they are a single phase.
Cheers, Wayne
Marktm250
Member
Wayne;
My understanding is that my (US) home is fed by a ~700 VAC single phase wire (no ground wire). The "transformer" at the pole I have assumed is center tapped wire coils made specifically to produce ~240 split phase to my utility meter/disconnect/home panel. I understand that this "split phase" is actually two 120 VAC wave forms that are opposite in voltage to each other - and on a "60 cycle" or 60 split phase waveforms per minute (180 degrees appart).
Is this description correct?
Not sure about this part, it varies, but I would be surprised if it is as low as 700 VAC on the primary side of the first transformer upstream of your house. I would think 2.4 kV would be a more likely minimum. But my familiarity with this part of the utility network is limited.
Basically yes. If we call the 3 wires on the transformer secondary A-N-B, where N is the neutral wire (the wire whose potential is always between the potential of wires A and B), then you can say that the voltage N-A and the voltage N-B are opposite to each other, or that they are 180 degrees apart. I think the "opposite each other" description is more apt, i.e. they differ by a multiple of -1.
Note also that if you look at the voltages A-N and N-B, those are identical (in theory, other than voltage drop, etc), so certainly in phase. And the voltages A-N and A-B differ by a factor of two, so also in phase with each other. There is only one phase present in this configuration, and any two voltages you can measure are in phase with each other.
Basically in a suitable sense 180 degrees apart is the same as 0 degrees apart, when just considering "phase".
Cheers, Wayne
Yes. That is exactly how the situation will turn out here I'd reckon. Thanks for the clear description so I can understand everything.
I really appreciate the explanations, advice and replies everyone. If Tesla won't combine/summate data from two gateways in their app, no problem. I'll do it in Home assistant. I've had that HA platform going now 2 years anyway, am very familiar with it and pretty much use it exclusively for energy monitoring etc anyway. Cheers for all the help 
Wayne, I have to disagree on the above statement. That is not the general description of phase. A signal or frequency is in phase when the peaks are zero degrees offset at all times. A harmonic may be in phase as a multiple of the base frequency, and in periodic alignment. 180 degrees off is completely out of phase and not the same as a zero degree offset, except at the zero voltage crossing point.
All the bets,
BG
I will agree that you would call the two waveforms 180 degrees out of phase, or negative, or something equivalent.
But my point is that those two waveforms only form one "phase". Otherwise, you'd never have single phase, as if I give you two wires A and B, the voltage waveforms A-B and B-A will be 180 degrees out of phase.
So a phase is something like a 1 dimensional subspace of the two dimensional vector space of sine-waves of a given frequency. The space spanned by v and the space spanned by -v are the same subspace.
Likewise, the space spanned by v and by the space spanned by 2v are the same subspace. Three wire split-phase is still single phase.
Cheers, Wayne
OK, I agree that the sentence I wrote "There is only one phase present in this configuration, and any two voltages you can measure are in phase with each other" is not standard usage. Rather I should have said "any two voltages you can measure are scalar multiples of each other." Generally "in phase" would mean a positive scalar multiple in common usage. I think that's the only adjustment required to the post you quoted.
But then "in phase" and "form the same phase" are slightly different in meaning--the former implying a positive scalar multiple, the latter allowing any scalar multiple.
Cheers, Wayne
It's only 180 out of phase if you flip the wires.
When L1 to L2 is 240V (which we all know is not the peak voltage)
L1 to N is 120V and N to L2 is 120V
L2 to N (mirrored) would be -120V
Or in Wayne's description a factor of 1/2 or -1/2. Wheras no real multiple will time shift the waveform to a different phasing.
Marktm250
Member
Quoting Wayne
"Not sure about this part, it varies, but I would be surprised if it is as low as 700 VAC on the primary side of the first transformer upstream of your house. I would think 2.4 kV would be a more likely minimum. But my familiarity with this part of the utility network is limited."
Yes, I was surprised but that's what my electrical cooperative has stated. This is a rural, single line transmission line to a few houses along a private road. They may have transformed the main transmission line voltage along the county road for some reason - I'm going to check - simply out of interest
"Not sure about this part, it varies, but I would be surprised if it is as low as 700 VAC on the primary side of the first transformer upstream of your house. I would think 2.4 kV would be a more likely minimum. But my familiarity with this part of the utility network is limited."
Yes, I was surprised but that's what my electrical cooperative has stated. This is a rural, single line transmission line to a few houses along a private road. They may have transformed the main transmission line voltage along the county road for some reason - I'm going to check - simply out of interest
If you actually have Single Wire Earth Return, that's pretty rare these days. Hopefully the distribution in your area will be updated some day.
Cheers, Wayne
I was puzzled by the electrical service at my cousin's rural Ohio farm. It had a single bare high voltage line that ran up the property from the road, came to the top of a pole with a transformer and some insulated wires ran down to a box with the meter, then back up to an overhead wire that ran 25 feet to the house. I was wondering how they could provision service with a single high voltage wire, but Single Wire Earth Return sounds like a good description of what I saw.
Marktm250
Member
My guess is this is fairly common for relatively short dead end runs (~1 mile) in rural coop type installs. I have two solar systems and voltages are always above 240 VAC. The earth ground is at the meter pole. I was actually surprised at the reasonable cost to install, especially with all the tree grinding required.
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