QFA81, QFA81.1 are room hygrostat from Siemens. They can be used to control humidification equipment, dehumidification equipment, monitor humidity
The QFA81 room hygrostat is an on/off device with a microswitch and a plastic‑texture humidity sensor. It monitors and controls relative humidity in ventilation and air‑conditioning plants within a setpoint range of 30 % to 100 % r.h., with an approximate 4 % r.h. fixed switching differential. The unit can be mounted directly on a wall or in recessed conduit boxes and supplies a potential‑free contact output to drive humidification or dehumidification equipment.
The manual details mechanical design, mounting instructions, and technical data. Mounting should be on an inner wall about 1.5 m above the floor, at least 0.5 m from other walls, with natural air circulation and no direct solar exposure. Technical specifications include contact ratings, ambient temperature limits, degree of protection (IP30), weight (≈0.06 kg), and material information.
| Contact rating (humidification) | 5 A (0.2 A), AC 250 V, 100 mA, AC 24 V |
|---|---|
| Contact rating (dehumidification) | 3 A (0.2 A), AC 250 V, 100 mA, AC 24 V |
| Degree of protection | IP30 |
| Weight | ≈ 0.06 kg |
| Sensing element | Plastic texture strip (ABS) |
The setpoint is adjusted with the detachable setpoint knob on the cover, allowing a range of 30 % to 100 % r.h.; after removing the knob, the setpoint can be mechanically limited with tongues.
It should be wall‑mounted on an inner wall about 1.5 m above the floor, at least 0.5 m from the next wall, with natural air circulation and no direct solar radiation.
Humidification contacts are rated 5 A (0.2 A), AC 250 V, 100 mA, AC 24 V; dehumidification contacts are rated 3 A (0.2 A), AC 250 V, 100 mA, AC 24 V.