There are two kinds of "two-phase" supply, and they need different setups.
| Two phases from a three-phase network | Split phase | |
|---|---|---|
| Voltage between actives | 400V (sometimes written 415V) | 480V (240-0-240V) |
| Angle between phases | 120° | 180° |
| Where you'll find it | Urban and suburban homes | Mostly rural properties |
| Phase netting with myenergi | ✅ Supported | ❌ Not supported, see below |
Two-phase vs split-phase supplies
"Two phase" is used for two quite different supplies. They can look the same at the switchboard: two actives and a neutral. But myenergi devices can only net energy across one of them.
Genuine two phase
A genuine two-phase supply is two of the three phases from a normal three-phase network. The street transformer produces three phases, A, B and C, each 120° apart, and the property is connected to two of them.
- Each active is about 230V to neutral.
- The two actives are 120° apart.
- The voltage between the two actives is about 400V (sometimes written 415V).
This is the setup myenergi devices are designed for, and phase netting works normally.
Split phase
A split-phase supply comes from a single-phase transformer whose winding is centre-tapped. The centre tap becomes the neutral, and each end of the winding becomes an active. You'll mostly find these on rural properties, often fed from SWER (single wire earth return) lines.
- Each active is about 240V to neutral.
- The two actives are 180° apart, exact mirror images of each other.
- The voltage between the two actives is about 480V.
Strictly speaking, a split-phase supply is a single phase split in half, not two separate phases.
How to tell which one you have
Measure the voltage between the two actives:
| Reading between actives | Supply type |
|---|---|
| About 400–415V | Genuine two phase |
| About 460–480V | Split phase |
If you're unsure, ask the network provider or check the transformer that feeds the property. A single-phase pole transformer on a SWER line almost always means split phase.
Why it matters for myenergi devices
A myenergi device only measures voltage on the phase it's connected to. To work out the power on another phase, it takes its own voltage and assumes the other phase is 120° behind, as it would be on a three-phase network.
On a split-phase supply the other phase is really 180° away. The device's calculation is off by 60°, so power on the second phase is reported inaccurately. For a typical load it can read as little as half the real figure. The device then makes diverting decisions on the wrong numbers. For example, it might think there's surplus solar when the property is actually importing from the grid.
Charging and diverting on a two-phase supply
Very few EVs or EV chargers can charge across two phases. For most installs, the zappi, eddi or libbi is connected to one phase and charges or diverts on that phase only.
The device can still monitor both phases and work out the total solar surplus across them. This is called 'netting' phases. It means you can use solar from a single-phase inverter on one phase without paying for grid energy imported on the other phase.
⚠️ Phase 'netting' happens on your bill, not in the wiring. The phase without solar still draws its power from the grid. The solar exported on the other phase only cancels that out if your meter nets across phases. Most Australian smart meters do, however it is uncommon in New Zealand. Check with your energy retailer or metering provider if you are unsure.
eddi, zappi and libbi support phase netting and have Net Phases turned on by default.
GLO doesn't support phase netting. It only sees the phase it's connected to.
Wiring the CT clamps
A myenergi device measures power using the voltage on the phase it's connected to. That means:
- A CT clamp hardwired into a device can only measure that device's phase.
- If the device is connected on one phase, CT clamps on the other phases must connect to either:
- a harvi, or
- a myenergi device that is connected three phase and set as the controller (formerly 'master')
You can't hardwire CT clamps for other phases into a single-phase device and expect it to net them.
Tell the device which phase it's on
Every myenergi device on a two- or three-phase supply needs to know which phase it's connected to.
- Go to Installer Settings > Supply Grid > Device > Phase.
- Choose the phase the device is connected to.
ℹ️ 1, 2 and 3 are phase names, not a count of phases. They mean phase A, B or C, the phase this device is connected to. They don't mean how many phases the property has. A zappi on phase B of a two-phase home should be set to 2.