Macurco (GBC-24-4) Gas boiler controller – 4 relays

The Macurco GBC-24-4 is a gas boiler shutdown controller with four relays. Specifically, it monitors up to four Macurco gas detection heads. Therefore, it can drive multi-zone or multi-stage boiler interlocks.

First, the controller accepts 24 VAC or 24 VDC supply power. Then, it provides four of up to eight 10A SPDT relays for boiler, valve, blower, and notification outputs. In addition, a 24 VDC, 250 mA output drives one remote horn or strobe appliance.

Macurco GBC-24-4 enclosure and indicators

The GBC-24-4 ships in an opaque polycarbonate NEMA 4X / 6P (IP66 / IP68) enclosure. As a result, it tolerates wet, washdown, or temporarily submerged mechanical rooms. Also, the front panel carries a green power LED, a red alarm LED, an audible buzzer, and a boiler reset button.

Verified specifications

• Power input: 24 VAC or 24 VDC
• Relays: 4 of up to 8 SPDT outputs, 10 A contact rating
• Detector inputs: up to 4 Macurco gas detector heads
• Horn / strobe output: 24 VDC, 250 mA max
• Enclosure: opaque polycarbonate, NEMA 4X / 6P (IP66 / IP68)
• Enclosure size: approximately 9.8″ H × 8″ W × 4.5″ D
• Expansion: supports up to 4 expansion relay boards for 8 total outputs

Installation guidance

First, mount the NEMA 4X enclosure in the boiler or mechanical room. Then, wire 24V supply, detector inputs, and the relay outputs at the boiler controls. Finally, follow the Macurco GBC manual (Rev 1.4) for relay assignments and reset behavior.

For smaller installations, the GBC-24-2 offers two relays in the same family. Alternatively, the line-voltage GBC-120 variants run on 120 VAC.

For more information, contact the Life Safety Consultants team at (888) 557-0558, or email us at: sales@lifesafetycom.com