To meet the fundamental requirements of performance, longer service life and greater safety under real world conditions, ERICO has developed Transient Discriminating (TD) technology. This quantum leap in technology adds a level of “intelligence to the Surge Protection Device enabling it to discriminate between sustained abnormal over-voltage conditions and true transient or surge events. Not only does this ensure safe operation under practical application, but it also prolongs the life of the protector since permanent disconnects are not required as a means of achieving internal over-voltage protection.

The Core of TD technology: The secret to ERICOs Transient Discriminating Technology is its active frequency discrimination circuit. This patented device can discriminate between a temporary over-voltage (TOV) condition and a very fast transient, which is associated with lightning or switching-induced surges. When the transient frequencies are detected, the patented QuickSwitchTM within TD activates to allow the robust protection to limit the incoming transient. The frequency discriminating circuit that controls the Quick-SwitchTM ensures that the SPD device is immune to the effects of a sustained 50 or 60Hz TOV. This allows the device to keep operating, providing safe and reliable transient protection, even after an abnormal over-voltage condition has occurred.


  • TD Technology with thermal disconnect protection
  • Compact design fits into DIN distribution panel boards and motor control centres
  • Indication flags and voltage-free contacts provide remote status monitoring
  • Separate plug and base design facilitates replacement of a failed surge module
  • 50kA 8/20μs maximum surge rating provides protection suitable for sub-distribution panels and a long operational life



Part Number TDS350TNC277
Article Number 702417
Nominal System Voltage (Un) 240 – 277 VAC
Max Continuous Operating Voltage (Uc) 320/536 VAC
Stand-off Voltage 480/813 VAC
Voltage Protection Rating (VPR) 1,000.0 V @ 3 kA
1,600.0 V @ 20 kA
Nominal Discharge Current (In) 20 kA 8/20 μs
Max Discharge Current (Imax) 50 kA 8/20 μs
Back-Up Overcurrent Protection 125 A
Short Circuit Current Rating (SCCR) 200 kA
Frequency 0 – 100 Hz
Protection Modes L-N
Response Time 5 ns Max
Technology TD technology with thermal disconnect
Connection, Solid 35 mm² Max
Connection, Stranded 25 mm² Max
Mounting 35 mm top hat DIN rail
Enclosure Material UL® 94V-0 Thermoplastic
Enclosure Rating IP 20
Remote Contacts Yes
Status Indication Mechanical flag
Temperature -40 to 80 °C
Module Width 3 M
Depth (D) 68 mm
Height (H) 90 mm
Width (W) 53 mm
Unit Weight 0.36 kg
Certification Details UL® 1449 Edition 4 Type 4CA, 20 kA Mode
Complies With ANSI®/IEEE® C62.41.2-2002 Cat A, Cat B, Cat C
ANSI®/IEEE® C62.41.2-2002 Scenario II, Exposure 2, 50 kA 8/20 μs
IEC® 61643-1 Class II
Replacement Module TDS150M277
Certifications CE
Standard Packaging Quantity 1 pc
UPC 78285658546
EAN-13 8711893046298

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