Multi-sensor smoke detector using ASAtechnology signal processing: two optical sensors plus two heat sensors on the C-NET bus.
The detector is built to shrug off the things that cause nuisance alarms. Siemens lists resistance to dust, fibres, insects, humidity, extreme temperatures, electromagnetic interference, corrosive vapours, vibration, synthetic aerosols and atypical fire phenomena, alongside insensitivity to impact and tamper protection.
Underneath that sits a redundant, high-quality sensor system with sophisticated sensor and electronics surveillance, protected electronics and high immunity to power-electronic disturbance. The alarm indicator is centred in the detector and visible at 360°, so no alignment is needed at install.
| Item | OOH740 | OOHC740 |
|---|---|---|
| Designation | Multi-sensor smoke detector, ASA | Fire and CO detector, neural ASA |
| Part number | S54320-F7-A3 | S54320-F8-A3 |
| Sensing | 2 optical + 2 heat | 2 optical + 2 heat + CO cell |
| Operating voltage (modulated) | DC 12 … 33 V | DC 12 … 33 V |
| Operating current (quiescent) | ~170 … 250 µA | ~300 … 380 µA |
| Operating temperature | −25 … +55 °C | −10 … +50 °C |
| Storage temperature | −30 … +70 °C | −20 … +55 °C |
| Humidity | 95% rel. | 15 … 95% rel. |
| Communication | C-NET, collective or conventional | C-NET |
| External alarm indicators | 2 | 2 |
| Protection category | IP40 (IP44 with RS720 base seal) | IP40 (IP44 with RS720 base seal) |
| Permissible air speed | max. 5 m/s | max. 5 m/s |
| Weight | 0.100 kg | 0.100 kg |
| Colour | White, ~RAL 9010 | White, ~RAL 9010 |
| Item | OOH740 | OOHC740 |
|---|---|---|
| Standards | CEA 4021, EN 54-5, EN 54-7, EN 54-17:2005 | CEA 4021, EN 54-5, EN 54-7, EN 54-17:2005, VdS 2806 |
| VdS approval | G211070 | G211047 |
| LPCB approval | 126ba/01 | 126ba/02 |
| Marine (MED) | 59 825-13 HH | n/a |
| Marine (Germanischer Lloyd) | 20 207-11 HH | n/a |
| System compatibility | C-NET FS720; collective FC10 | C-NET FS720 |
Rather than being a fixed device, the OOH740’s behaviour is chosen with parameter sets (pre-engineered algorithm profiles matched to an application). On the addressed C-NET line the detector offers seven parameter sets; in collective/conventional mode three are available, selected physically via the detector base or a parameter-set resistor. Representative sets:
| Parameter set | Mode | Typical use |
|---|---|---|
| Standard Plus (PS1) | Collective + addressed | General-purpose balanced detection for most standard rooms and areas |
| Suppression (PS5) | Collective + addressed | Reliable triggering for extinguishing/suppression release applications |
| High Sensitive Fast (PS9) | Collective + addressed | Fastest, most sensitive response for critical areas (e.g. data centres) |
| Additional sets (addressed) | Addressed C-NET only | Further profiles for deceptive-phenomena and specific process environments (7 total) |
Parameter-set availability and behaviour depend on line type, product version and configuration in the Cerberus tools. In collective mode, sets are chosen via base type (e.g. DB110/DB721D) or resistors PSR720-1 (33 kΩ = PS1) / PSR720-2 (68 kΩ = PS2).
For Australian fire professionals, point-type smoke and multi-sensor detectors are covered by the AS 7240 series (Australia’s adoption of ISO 7240 / EN 54), notably AS 7240.7 (point smoke detectors) and AS 7240.8 (CO fire detectors, relevant to the OOHC740). System design falls under AS 1670.1 and maintenance under AS 1851. The OOH740’s EN 54-5/7/17 certification generally underpins local acceptance; confirm the current Australian product listing before specifying. Practical AS 1851 servicing notes for the OOH740:
Confirm the current edition of each standard and the applicable Australian approval with Siemens or an authorised partner before finalising design or maintenance.
Using a base with a loop contact means the detector line is not interrupted even when no detector is fitted, which matters during construction and detector exchange. Detectors can be turned into the base by hand or with the DX791 detector exchanger and its FDUD491 adapter.
Figures on this page are the manufacturer’s published specifications, taken from the Siemens OOH740 / OOHC740 Cerberus PRO datasheet, document A6V10284161_h_en (Manual FD720, Section 2, edition 03.2013). They are reproduced for reference and are not design, compliance or engineering advice. Siemens notes that data and design are subject to change without notice, so confirm every figure against the current datasheet, and design to the standards that apply in your jurisdiction. Australian installations are designed to AS 1670.1 and serviced to AS 1851.
Two optical sensors working on the scattered-light principle (forward and backward scattering), plus two heat sensors. The heat sensors are there to raise immunity to deceptive phenomena rather than to act as the primary detection method. The OOHC740 variant adds a carbon monoxide cell.
Siemens’ term for Advanced Signal Analysis: signal processing where detection behaviour is time- and process-dependent rather than a fixed threshold, tuned through application-specific ASA parameter sets. On the OOH740 the parameter set can be selected in software, or in the field by fitting a PSR-1 (33k) or PSR-2 (68k) resistor into a DB110 or DB721D base.
Not quite. The datasheet lists the OOH740 as "multi-sensor smoke detector, ASA" and the OOHC740 as "fire and CO detector, neural ASA". The neural designation goes with the CO-sensing OOHC740, which analyses smoke, heat and gas together.
Yes. The software can set the head to work as a multi-sensor smoke detector, as a smoke detector, or as a heat detector, so a single part number covers several situations. It also runs addressable on C-NET or in collective / conventional mode.
Yes, an integrated short-circuit isolator that locates the defective part of the detector bus and isolates between two detectors. There is also a built-in alarm indicator visible through 360°, and up to two external alarm indicators can be connected per detector.
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