The Siemens 3NJ6900-4HE11 is a moving-iron analogue panel ammeter for the SENTRON 3NJ6 series of in-line switch disconnectors with fuses. It provides true RMS current indication on a 150 A scale via a 150/1 A current transformer input, with Class 1 accuracy and a low 0.6 VA burden. The plug-in design enables fast retrofit onto existing switch disconnectors.

150 A Rating for Mid-Range Feeders

The 150 A scale serves a common intermediate rating in low-voltage distribution — larger than the 100 A branch circuits, smaller than the 200 A main feeders. Typical applications include dedicated equipment supplies (large HVAC units, compressor banks, pumping stations) and sub-distribution panels where the operator needs local visual confirmation of load current. The moving-iron mechanism ensures true RMS response regardless of waveform distortion.

1 A Secondary for Extended Wiring

The 1 A secondary input reduces CT secondary loop losses to 4% of the equivalent 5 A circuit — significant when the instrument panel is located at a distance from the switch disconnector. This variant is the correct choice for centralized monitoring rooms, remote feeder pillars, and any installation where the CT-to-instrument cable run exceeds 10-20 meters.

Decision Parameters