The Crowcon Gasflag is an entry-level single-channel gas detection control panel designed for light industrial and commercial applications — LPG monitoring on garage forecourts, chlorine detection in swimming pool dosing rooms, and methane monitoring in boiler houses. Note: The Gasflag was discontinued in February 2024 due to component obsolescence; spare parts are no longer available.

What gas detectors are compatible with the Gasflag?

The Gasflag accepts any 4–20 mA analogue detector — flammable, toxic, or oxygen — in sink or source configuration, connected via 2 or 3-wire screened cable. The panel supplies 24 VDC to the detector and monitors for fault conditions: < 3 mA (open circuit) and > 23.5 mA (over-range). Internal PCB test points output 40–200 mV proportional to the 4–20 mA loop for service diagnostics with a standard DVM. The Gasflag itself is for safe area use only; connected detectors may be installed in hazardous zones provided they carry appropriate certification.

How are the alarm relays and levels configured?

Two independent alarm levels are adjustable via potentiometers on the PCB, with configurable rising or falling alarm direction and latched or non-latched operation. Each alarm drives a dedicated SPDT relay (1 A @ 30 VDC) with volt-free contacts, selectable as normally de-energised or failsafe (energised). A third SPDT relay handles fault indication. Alarm hysteresis is ~0.5 mA with a sub-1-second response time. The internal 80 dB sounder can be enabled or disabled via an internal link. Front-panel LEDs — green (Power), amber (Fault), and two red (Alarm 1 / Alarm 2) — provide at-a-glance system status.

What replacement options exist after discontinuation?

Crowcon recommends two migration paths: the Sensitron PL4+ (4–8 channels, IP65, 100–230 VAC) for multi-channel expansion, or the Gasmaster (1–4 channels, IP65, aluminium/ABS) in a 1-channel configuration for direct Gasflag replacement. Both offer higher ingress protection (IP65 vs. IP20), graphical displays, and expanded I/O — at the cost of larger enclosure dimensions and higher weight. For existing Gasflag installations, the DC power supply wiring and 4–20 mA detector cabling can be reused with either replacement, reducing migration effort.