The Solar-Log PM Box is a dedicated fail-safe power management unit that sits between the PV inverter array and the grid connection point. Unlike the standard Solar-Log data logger — which monitors and controls feed-in during normal operation — the PM Box takes over when the primary controller loses communication, power, or functionality, automatically restricting grid export to the preconfigured percentage limit. This closed-loop protection is mandatory under DNO reverse-power requirements such as G59/3 in the UK and avoids the risk of uncontrolled feed-in during a control system failure.

How does the fail-safe function work?

The PM Box continuously monitors the health of the primary Solar-Log controller via a dedicated communication link. If the controller stops responding — due to power loss, network failure, or hardware fault — the PM Box assumes control within the fail-safe timeout period. It directly signals the inverters to reduce output or disconnect, enforcing the licensed export limit independently of the primary controller. Once the primary controller resumes normal operation, the PM Box returns to standby monitoring mode. This redundant architecture ensures grid code compliance even during worst-case failure scenarios.

What is the difference between PM Box 1200 and PM Box 2000?

The two models share identical hardware, firmware, and fail-safe logic. The difference is the maximum installation capacity they are rated to manage:

• PM Box 1200: Up to 100 kWp — suited for commercial rooftop and small ground-mount installations with up to two inverter manufacturers.
• PM Box 2000: Up to 2 MWp — designed for utility-scale PV farms with up to three inverter manufacturers and up to 100 inverters. The PM Box 2000 also includes a CAN-Bus interface and supports master-slave coupling of up to 10 units for installations exceeding 2 MWp.

Both models operate from a 115–230 VAC supply, draw 3 W, and mount on a wall in an IP20 indoor enclosure measuring 22.5 × 4 × 28.5 cm (W × D × H).