The LiftMaster LMPDT24-4W is a 4‑wire photoelectric and thermal smoke detector designed for use with LiftMaster releasing devices and compatible commercial door operator systems. Combining photoelectric smoke sensing for early detection of smoldering fires with an integrated thermal element for heat activation, it is used to trigger the automatic closing of rolling steel fire doors, counter shutters, and other fire-rated closures when smoke or elevated temperature is present. The 4‑wire design separates power from the alarm relay circuit, making it suitable for releasing service inputs on control panels that accept 24 VDC detectors.
Intended for indoor commercial applications, the LMPDT24-4W operates on 24 VDC and is typically ceiling-mounted (or high on a wall) in the area protected by the fire door or shutter. Proper installation requires connection to a supervised releasing/control circuit, resettable power for post-alarm restoration, and adherence to NFPA 72 and local codes; depending on the control equipment, an end-of-line supervision device may be required for 4‑wire detector circuits. Use this unit as a replacement part or upgrade when a 24 V, 4‑wire photoelectric/heat detector is specified for LiftMaster fire door release systems or other compatible releasing panels. Installation and testing should be performed by qualified life-safety professionals, with regular functional testing and maintenance to ensure reliable operation.