Siemens OH921 Addressable Multi-Criteria Photoelectric Heat Detector

Siemens OH921 – Cerberus PRO addressable multi-criteria fire detector, part number S54320-F6-A2.

It carries a dust-resistant photoelectric smoke chamber and a shock-resistant thermistor in one plug-in head, combining both readings in an onboard neural network to separate smoke signatures from dust, steam and aerosols. The panel selects the profile, and the head can also serve as a heat-only device.

Listed to UL 268 7th Edition, to UL 521 for heat detection and to UL 268A for direct in-duct use
Two alarm sources: combined smoke and heat, with Standard or Duct profiles, plus heat only
Thermal rating fixed at 135°F (57°C) with rate-of-rise detection at 15°F per minute
16 to 30 VDC, 250 µA standby and 410 µA alarm current
Built-in ISOtechnology isolators, up to 252 isolation devices per loop
Mounts on DB-11, DB-11E or DB2-HR bases

The related Siemens heads are the OP921, photoelectric only, and the HI921 heat detector. Siemens states the OH921 may share a loop with the older HFP-11 and HFPT-11 FirePrint devices, an interoperability statement, not a replacement one.