Operating Principles; Ultrasonic Atomisation; Control Principles; Flow-Rate Modulation (Dipswitch 8 Off) - Carel humiSonic User Manual

8.1 Ultrasonic atomisation

Ultrasonic humidifiers atomise water through propagation of a wave
generated by a piezoelectric transducer to the surface of the water.
Droplets of water thus form on the surface, with the smaller ones being
carried in the forced air flow. The quantity of atomised water depends on
the water level, water temperature and distribution in the air. Water level is
kept constant using fill and drain valves, and a level sensor. Demineralised
water is recommended: if using mains water, the scale that builds up over
time will foul the piezoelectric transducer, compromising atomisation. To
avoid excessive scale, the humidifier periodically drains and automatically
refills the water (periodic washing)

8.2 Control principles

The humidifier can be controlled using the following signals:
• Remote ON/OFF;
• External proportional signal (only with auxiliary card);
• Humidity probe;
• Built-in temperature and humidity probe for dew point temperature
control
• Serial.
ON/OFF control
The action is all or nothing, activated by an external contact that
consequently determines the control set point and differential. The
external contact may be a humidistat, whose status determines the
operation of the humidifier:
• contact closed: the humidifier produces atomised water if the remote
ON/OFF contact is closed;
• contact open: atomised water production stops.
Proportional control (only with auxiliary card)
• Atomised water production is proportional to the value of a signal "Y"
from an external device. The type of signal can be selected between
the following standards: 0 to 10 Vdc, 2 to 10 Vdc, 0 to 20 mA, 4 to 20 mA;
• Maximum humidifier production, corresponding to the maximum
value of the external signal, can be set from Pn (default 10%) to 100%
of the rated value of the humidifier (parameter P0).
Minimum production has an activation hysteresis, equal to the value of
P1 (default 2% of the proportional band of external signal "Y").
Atomized water production
P0
P1 P1
Pn
OFF ON
Fig. 8.a
Stand-alone control with humidity probes
The production of humidity is linked to the reading of the connected
relative humidity probe (TH or connection to optional card). The humidifier
will work at maximum capacity if the humidity measured is less than the
set point minus the proportional band, while it will modulate production
inside the proportional band, parameter bP modifiable, default 10%rH).
The minimum production has a fixed activation hysteresis of 10% of the
proportional band amplitude bP.
Production %
P0
Pn
Fig. 8.b

8. OPERATING PRINCIPLES

Y
ON OFF
%rH
10% bP
bP
SP
Stand-alone dew point control
The production of humidity is linked to the reading of the temperature
and humidity probe (TH). The humidifier will work at maximum capacity
if the dew point temperature measured is less than the set point
minus the proportional band, while it will modulate production inside
the proportional band, parameter bP modifiable, default 10%rH). The
minimum production has a fixed activation hysteresis of 10% of the
proportional band amplitude bP.
Production %
P0
Pn
Enable TH probe as humidity/ dew point limit
When the TH probe is connected to the input on the dedicated card
(P/N UU**R*AS*1), the unit can be controlled via ON/OFF contact
(A0=0), external proportional signal or RS485 (A0=1) or external active
probe (A0=2) and the TH probe can be enabled as a humidity limit
probe, setting parameter bH = 1, or a dew point limit probe, setting
parameter bH = 2. When approaching the limit set point (parameter SL,
modifiable, default 70% rH or 10°C/50°F) inside the proportional band
bL, atomisation is increasingly modulated, until stopping at the limit set
point. The hysteresis for reactivation of minimum production is fixed and
equal to 10% of the proportional band amplitude bL.
Production %
P0
Pn
8.3 Flow-rate modulation (dipswitch 8 Off)
Atomised water flow-rate can be varied from 5% to 100% (parameters Pm
and P0) by alternating on-off cycles of the transducers over a set period
(parameter b7, default 1 second). Flow-rate is set based on parameter P0
(default 100%) and the request from the external signal (with optional
card and proportional control).
Transducer
Flow rate 10%
ON
OFF
Period (b7)
17 Direct version for room applic. +0300062EE - rel. 1.4 - 24.09.2020
ENG
ON OFF
°C/°F
10% bP
bP
SP
Fig. 8.c
ON OFF
%rH or °C/°F
10% bL
bL
SL
Fig. 8.d
t
Fig. 8.e