Honeywell Home 5821 Wireless Temperature and Flood Sensor

The Honeywell Home 5821 is a configurable environmental transmitter for basements, laundry rooms, kitchens, mechanical areas, food storage, and other spaces where a temperature swing or water leak could become expensive. Its internal sensor supports cold, warm, and hot thresholds at 45 F, 75 F, and 95 F, and selected modes can monitor two programmed conditions at the same time.

Flood sensing requires an FP280 or 470PB probe, while refrigerator and freezer monitoring requires a T280R temperature probe; those probes are separate accessories and are not built into the 5821. With the T280R, the unit can report refrigerator temperatures above 42 F or freezer temperatures above 10 F after the specified 30-minute delay. One separate 5821 is required for each external probe, and the probe wiring is supervised for opens and shorts.

The compact transmitter uses one CR123A battery with up to ten years of listed service, operates from 14 to 104 F, and reports cover tamper and low-battery conditions to a compatible 5800-series receiver.