The Siemens 3NJ6900-4HD22 is a bimetal analogue panel ammeter for the SENTRON 3NJ6 series of in-line switch disconnectors with fuses. It provides thermal-response current indication on a 100 A scale via a 100/5 A current transformer input — the combination of the highest current rating in the 3NJ6900 pluggable ammeter range, the overload-tolerant bimetal mechanism, and the universally compatible 5 A secondary interface.

The All-Round 100 A Choice

This variant occupies a pragmatic sweet spot in the 3NJ6900 matrix: 100 A covers the majority of sub-distribution and larger branch circuit ratings; the bimetal mechanism handles the diverse inrush characteristics of mixed-load feeders; and the 5 A secondary ensures compatibility with the CTs most commonly stocked and specified in industrial practice. For a 100 A fused switch disconnector feeding a mix of motors, HVAC equipment, and general-purpose loads, the 4HD22 provides reliable local current indication with minimal engineering overhead.

Decision Parameters