One phase is reading zero, or the meter is under-reading

If two phases read normally and one reads zero, the problem is on the metering connection for that phase, not the platform. The three usual causes are a blown fuse on that phase's voltage reference, a current transformer that has shifted or been damaged, or a loose terminal at the meter.

What you will see

• The load balance chart shows one phase flat at zero.
• Augos disagrees with a solar installer's or another system's readings.
• A large variance against the utility bill, always in the same direction.
• The phase went down at a specific moment, usually a site power event.

Why it happens

A three phase meter needs a voltage reference and a current signal from each phase. Lose either one on a phase and that phase stops contributing, so the meter under-reads by roughly the share of load carried by that phase. It keeps working otherwise, which is why nobody notices until a bill is compared.

The three causes, in the order worth checking:

1. A blown fuse or tripped breaker on the circuit feeding the meter or the current transformer for that phase.
2. A current transformer that shifted, disconnected or was damaged when power was restored after an outage.
3. A loose or failed connection at the meter terminal for that phase.

What to do

Have a qualified electrician check, at the metering point:

1. Whether the phase is actually live and carrying load.
2. Whether there is an obvious sign at the meter: a discoloured or burnt terminal, a tripped or blown fuse on the voltage reference for that phase.
3. The physical condition and connection of the current transformer on that phase.
4. With a multimeter, the voltage directly at the busbar, then trace the voltage sense wiring back to the meter terminal.

Augos can be on the phone while your electrician is on site, and can watch the platform live as they work so you get confirmation before they pack up. Ask for this. It shortens the loop considerably.

What Augos will do

Support pins the loss to a timestamp from the interval data, which tells your electrician whether the fault is continuous or intermittent. A fault that has been continuous since a named date is reproducible on site, and that is worth saying up front. Support will also offer a quoted technician visit.

Good to know

• Fuses have been found blown more than once on the same job. If replacing one does not fix it, check the others before concluding the meter is faulty.
• A bill verification can still balance with one phase down, if the loss started part way through the period or the site's total is dominated by the other phases. A balanced verification is not proof that all three phases are healthy.
• Fitting a current transformer rated below the panel's rating risks damaging it. See Current transformers explained.
• If the fault follows the meter when you move it to another point, the meter is faulty. If it stays with the point, it is the installation. See Is the meter faulty.

Still stuck

Email support@augos.io with the point path, which phase, when you first noticed it, and any photographs of the metering point and the current transformers.