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Growatt Error 120: HCT Current Sensor Failure

Updated June 2026 · Reviewed for technical accuracy · ~2 min read

Error 120 is an HCT (Hall current sensor) failure. The HCT is the component the Growatt uses to measure current accurately. If it reports a fault, the inverter cannot trust its current readings, so it stops. This is an internal hardware item, so beyond a single restart it is a job for a technician.

What it usually means

  • A transient sensor glitch a restart can clear.
  • A genuine fault in the current sensor or its circuit on the inverter's board.

What to do

  1. Restart the inverter once. AC breaker off, then the DC isolator, wait 5 minutes, restart. A one-off Error 120 may clear.
  2. If it returns, stop. The current sensor is internal; you cannot adjust it from the outside.
  3. Contact your installer or Growatt for board-level service.
When to bring in a professional A persistent Error 120 is an internal sensor or board fault. Don't keep power-cycling; have it serviced.

Related Growatt codes

Error 100, Voltage failure Error 404, DC bus sampling Error 405, Relay failure

Helpful guides

Error codes explained How to safely restart your inverter

Sources

  • Growatt inverter user manual and error-code reference (Error 120 = HCT failure; restart, request maintenance if it persists).
  • Growatt installer documentation.
⚠️ Safety disclaimer. Solar inverters carry lethal DC and AC voltage even when "off". This guide covers a single safe power cycle only. Internal sensor and board faults must be handled by a licensed installer or Growatt technician.