Carel heaterSteam UR Series, User Manual

Page: 67 / 72

67
ENG
“heaterSteam” +0300075EN - rel. 1.2 - 29.09.2015
13. ADVANCED FUNCTIONS
13.1 Operating principle
HeaterSteam is an isothermal humidifi er with steam produced by
heating the heaters completely immersed in a tank fi lled with water.
This can be tap water or completely demineralised water. The heat
generated by the heaters increases water temperature up to about 100 °
C. The use of demineralized water ensures long service life of the cylinder
and the heaters because virtually no lime deposits can form and grow
gradually. Instead, when using tap water, a part of the minerals dissolved
in water accumulates in the cylinder as solids of various composition. To
prevent this phenomenon, when the water conductivity of the cylinder
exceeds a certain value, a part of the water is drained and reintroduced
periodically to obtain the necessary dilution. For the specifi c models, the
drain water is mixed with tap water to avoid exceeding the maximum
temperature specifi ed by the applicable local and national regulations
(drain tempering function). The steam generated has a temperature of
about 100 ° C and minimum positive pressure (steam without pressure).
It is virtually demineralized and germ-free.
Steam production is regulated with ON / OFF logic or by continuous
modulation of the nominal power (from 0% to 100%), by means of solid
state relays (SSR); the control logic is of PWM type (pulse length variation)
with programmable time base.
13.2 Regulation principles
The appliance is fi tted with solid-state relays and steam production can
be controlled continuously as a function of the required quantity, in one
of the following modes.
13.2.1 ON/OFF regulation (parameter A0=0)
The action is of all or nothing type and it is activated by an external
contact connected to terminals 4I, 5I (see chap. 4), with the setpoint and
the control diff erential determined by parameters St and P1, respectively.
In case of command from external variable (Analog 52: A52), steam
production is enabled/disabled according to the fi gure.
ON
OFF
A52 variable
Steam_Pr
70.0 30.0
A0=0
Fig. 13.a
13.2.2 Slave control, with signal from an external
regulator (parameter A0 = 1)
Steam production is proportional to the value of an external signal Y,
(selected by programming one of the following standards: 0 to 1Vdc; 0
to 10Vdc; 2 to 10Vdc; 0 to 20mA; 4 to 20mA) the entire range of which
is indicated by BP (proportional band). The maximum output Pmax
(parameter P0), corresponding to the maximum value of the external
signal Y can be programmed between 10% and 100% of the nominal
value of the humidifi er. The minimum production Pmin (parameter
Pm) can be set between 0% and 10% (default 4%) of the humidifi er’s
rated value. The activation hysteresis hy is based on the value of Pmin
(parameter Pm), however referring to the external signal Y (e.g.: Pmin =
4%, hy = 2%). If enabled, the pre-heating function overlaps the control
diagram, and is activated when the external signal Y is lower than the
activation point for steam production by a quantity b2.
P0
Steam_Pr
Pm
A52 variable
Pre_heat
hy hy
Bp
0%
OFF
ON
A0=1
Fig. 13.b
Key window
Steam_pr Steam production Pre_heat Pre-heating
P0 Max production hy Activtion hysteresis
Pm Min production b2 Pre-heating start off set
Y External signal Bp Proportional band
13.2.3 Independent control with relative humidity
transducer (parameter A0 = 2)
Steam production is linked to the measurement of % rH, performed by the
relative humidity transducer connected to the regulator, and increases as
the distance from the set point St increases. The maximum production
Pmax (parameter P0), which occurs when the relative humidity is less that
the set point by a value P1, can be programmed between 10% and 100%
of the rated value of the humidifi er.
The minimum production Pmin (parameter Pm) can be programmed
between 0% and 10% (default 4%) of the nominal value of the humidifi er,
with an activation hysteresis (hy) equal to 10% of P1. The pre-heating
function, if enabled, overlaps the control diagram and is activated when
the relative humidity % rH, measured by the transducer, is higher than
St by a programmable quantity b2. To check that the relative humidity
measured by the transducer is within the pre-set values, the control
module with autonomous control allows two alarm thresholds to be
programmed:
•
high relative humidity alarm threshold P2;
•
low relative humidity alarm threshold P3.
When these thresholds are exceeded, after a programmable delay
P4, an alarm state is activated, with the closing of the contact of the
corresponding relay on the main control board. With independent
control (parameter A0=2) it is also possible to have an ON/OFF action,
as represented in the graph, by disabling power modulation (setting
parameter b0=0).
St
Pm
P0
Steam_Pr
P1
hy A52 variable
Fig. 13.c
Key window
Steam_pr Steam production %rH Humidity measurement
P0 Max production hy Activtion hysteresis
Pm Min production