User Manual

CM1N1513E / 02.1999 Siemens Building Technologies

2/4 Landis & Staefa Division

r.h. Relative humidity in %

S1 Microswitch

1−2 Humidification

1−4 Dehumidification

w Setpoint

x Actual value

Switching differential

If the relative humidity exceeds the adjusted setpoint, the potential-free contact of the

microswitch will change over from 1−2 to 1−4. If the relative humidity falls by the amount

of the fixed switching differential X

, the contact will return to the position 1−2.

The hygrostat is designed for wall mounting. It can be fitted to most commercially avail-

able recessed conduit boxes. The cables can be introduced from the rear (concealed

wiring) or from above (surface-run wires) through knockout openings.

The unit consists of base and cover. Both snap together and can be detached again.

The base accommodates a printed circuit board which carries the humidity sensing

element (plastic texture strip), the setpoint adjusting element with the spindle, scale,

microswitch, and connection terminals.

The cover houses the detachable setpoint knob with the setting scale and a concealed

mechanical setpoint limitation facility.

Same design as the QFA81, but with a cover with no setpoint knob and no setpoint

limitation facility. The setpoint can be adjusted only when the cover is removed.

Using the setpoint knob, the setpoint can be adjusted in the range 30…100 % r.h.

After removal of the setpoint knob, the setpoint can be mechanically limited to a mini-

mum or maximum value by appropriate setting of the tongues.

1 Tongue for minimum limitation of setpoint

2 Tongue for maximum limitation of setpoint

The setpoint can only be changed with the spindle after removal of the cover.

Function diagram

r. h.

[%]

1513D01E

Mechanical design

QFA81

QFA81.1

Setting elements

QFA81

Setpoint knob

Setpoint limitation

% rH

1513Z01

QFA81.1

Setpoint spindle