Conventional Fire Detection Systems

What Is a Conventional Fire Detection System?

Each zone is connected to the panel by a separate pair of cables. Multiple detectors and manual call points are connected to a zone line in parallel . A end of line resistor is placed at the end of the line; the panel continuously monitors line continuity through this resistor.

When a detector goes into alarm, it reduces the line resistance, current increases, and the panel reads this as an alarm. The panel indicates which zone is in alarm — not which device .

For this reason, zone size is limited: according to TS CEN/TS 54-14 guidance, a zone should typically cover a single storey, a single fire compartment, and a limited area. Otherwise, locating the fire becomes practically impossible.

Zone Logic and End of Line Resistor

The end of line resistor (End of Line Resistor — EOL) is the conventional system's self-monitoring mechanism:

• Normal condition — The panel reads a low and steady current across the EOL resistor.
• Alarm condition — The detector reduces resistance, current increases significantly.
• Fault (line break) — Current drops to zero, the panel issues a fault.

Typical EOL values are 4K7 or 10K; the value is determined by the panel manufacturer. The EOL resistor must be installed at the last device at the physical end of the line, not at the panel. If this rule is not followed, line supervision becomes meaningless — the panel cannot detect a broken line.

Wiring: 2-wire, 4-wire, and NAC Lines

• 2-wire line — Power and alarm signal share the same pair. This is the classic detector line.
• 4-wire line — Separate power + separate alarm contact. Beam, flame, aspirating, and gas detectors typically operate this way.
• NAC lines — Sirens and flashers are fed from the panel's siren output on separate lines, independent of detector lines. This is where the largest wiring load of a conventional system originates. Topology is radial. There is no ring. If a line breaks at any point, all devices downstream of the break are disabled. This is a structural limitation of conventional architecture and must be accepted in design.

Conventional Panel Types Conventional panel types, capacities, and typical applications

Type

or parallel display panel may additionally be added to the system. The panel and power supply must comply with ZQX0ZQX and ZQX1ZQX. Details: Conventional Fire Alarm Panels Detectors Used in Conventional Systems Conventional architecture is not more restricted than addressable architecture in terms of detector type.

All of the following devices can operate in a conventional system:

— optical, ionization, dual-sensor (ZQX0ZQX) — fixed temperature, rate-of-rise (RoR), combined (ZQX0ZQX) Beam detectors

• Smoke detectors — alarm and fault relays in the control unit are connected to the zone line (EN 54-7)
• Heat detectors — virtually all industrial flame detectors ship from the factory as conventional: alarm relay, fault relay, pre-alarm relay, and 4–20 mA analog output (EN 54-5)
• — sensor control unit relay output is connected to the zone line (ZQX0ZQX / ZQX1ZQX) Aspirating detectors
• Flame detectors — warning, pre-alarm, alarm, and fault relays can be connected to separate zones (EN 54-10)
• Linear heat sensing cable Manual call points
• (ZQX0ZQX) Sirens and flashers
• — from separate ZQX2ZQX lines (ZQX0ZQX / ZQX1ZQX) In summary:
• A flame detector or beam detector being "conventional" does not mean the device is simpler. The device is the same; it is only connected to the panel via a relay. The same device can be integrated into an addressable system by adding a monitoring module

. Semi-Addressable Intermediate Solution Some manufacturers offer an intermediate solution with an address module mounted on conventional detectors, allowing device-level discrimination. Its cost falls between conventional and addressable. It is not preferred in new institutional projects; however, it is a practical option in retrofit

projects where existing conventional wiring must be preserved.

Advantages and Disadvantages of Conventional Systems Low initial investment cost No device-level identification — zone resolution only

Advantages and disadvantages of the addressable system

Transformer, generator, and panel rooms

Small gaseous suppression areas (single area protection)

• Budget-constrained retrofit projects
• As a
• field layer
• of an addressable system — in Ex zones and industrial areas as a sub-system connected to the addressable loop via a zone monitoring module
• A conventional system is insufficient for:

high-rise buildings (addressable is mandatory per BYKHY),campuses multi-storey car parks tunnels hotelshistoric buildings Shopping Mallshistoric buildings ,factories ,historic buildings .historic buildings Converting a Conventional System to Addressable and It is possible to migrate an existing conventional system to addressable without completely removing it.A zone monitoring module connects an entire conventional detector line to the addressable loop. Critical areas are renewed with addressable devices while secondary zones continue to operate with their existing wiring. This provides significant cost advantage in capacity upgrade and renovation projects.

Conventional or Addressable?

For comparative assessment: For comparative evaluation:Linear heat detection cable, often confused with ZQX0ZQX, is a different technology: the cable alarms at a threshold temperature and does not measure temperature meter-by-meter. For comparison, see the

linear heat detection (ZQX0ZQX)

page. Addressable Fire Detection Systems

DTS is frequently confused with linear heat detection cable a different technology: the cable alarms at a threshold temperature, it does not measure temperature on a per-meter basis. For a comparison of the two, linear heat detection (LHD) page.