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

18
ENG
“Ultrasound for fancoil” +0300059IE - rel. 1.7 - 24.10.2022
9. OPERATING PRINCIPLES
9.1 Ultrasonic atomisation
Ultrasonic humidiers 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 air by the forced air ow. The quantity of atomised water depends
on water level, water temperature and distribution in the air. Water level is
kept constant using ll and drain valves, and a level sensor. Demineralised
water is recommended: if using mains water, the scale that accumulates
over time will foul the piezoelectric transducer, aecting atomisation. To
avoid excessive scaling, humidier periodically drains and automatically
rells the water (periodical washing).
9.2 Control principles
The humidier can be controlled using the following signals:
• remote ON/OFF;
• TAM (set by dipswitch);
• External proportional signal (only with auxiliary board);
• 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 dierential. The
external contact may be a humidistat, whose status determines the
operation of the humidier:
• contact closed: the humidier produces nebulized water if the remote
ON/OFF contact is also closed;
• contact open: the production of nebulized water ends.
Proportional control (only with auxiliar card)
• The production of nebulized water 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 humidier 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 humidier (parameter P0).
Minimum production has an activation hysteresis, equal to the value of P1
(default 2% of the proportional band of external signal “Y”).
ONOFF
P1P1
P0
Pn
Y
Atomized water production
Fig. 9.a
Autonomous control with humidity probe
Humidity production is controlled based on the reading of the relative
humidity probe (TH or connection via optional card). The humidier 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 modiable, default 10%rH).
The minimum production has a xed activation hysterisis of 10% of the
the proportional band amplitude bP.
%rH
OFFON
Pn
P0
Production %
10% bP
SP
bP
Fig. 9.b
Stand-alone dew point control
The production of humidity is linked to the reading of the temperature
and humidity probe (TH). The humidier 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 modiable, default 3°C/5°F). The
minimum production has a xed activation hysteresis of 10% of the
proportional band amplitude bP.
°C/°F
OFFON
Pn
P0
Production %
10% bP
SP
bP
Fig. 9.c
Enable probe TH as humidity/ dew point temperature limit
When probe TH is connected to the dedicated card input, 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 probe TH can be
enabled as a
humidity limit probe, setting parameter bH = 1. When
approaching the limit set point (parameter SL, modiable, default 70% rH)
o 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 xed and equal to 10% of the
proportional band amplitude bL.
%rH
or °C/°F
OFFON
Pn
P0
Production %
10% bL
SL
bL
Fig. 9.d
9.3 Parallel ow-rate modulation
(dipswitch 8 O)
Atomised water ow-rate can be varied from 5% to 100% (parameters Pm
and P0) by alternating on-o 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).