Carel humiSteam UE005 - 12 Advanced Functions; Operating Principle; Control Principles; Supply Water Conductivity

39
“UE BASIC” +08C0042EZ - rel. 1.0 - 16.10.2017
ENG
12. ADVANCED FUNCTIONS
12.1 Operating principle
Immersed electrode humidiers manufacture steam by boiling the
water contained inside the cylinder. The heat required to boil the water
is produced by passing an electrical current through the cylinder. This
is done by applying a voltage to the electrodes immersed in the water.
Initially, when the cylinder is new or has just been cleaned, the current
depends almost exclusively on the type of supply water: the more salts
in the water, the higher the current, and the required steam production
is achieved quicker. Over time the salt deposits in the cylinder increase
(these do not evaporate with the water), helping achieve the rated
production. In steady operation, the level of production required is
maintained automatically by controlling the current input, adjusting the
level of water in the cylinder.
The salts that deposit over time cause the progressive depletion of the
cylinder. To avoid excessive accumulation, the humidier automatically
drains and replenishes a certain quantity of water at set intervals.
12.2 Control principles
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 steam if the remote ON/OFF
contact is also closed;
• contact open: the production of steam ends.
Proportional control
The production of steam 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.
The entire range is indicated as the proportional band. The maximum
production of the humidier, corresponding to the value maximum of
the external signal, can be set from 20% to 100% of the rated value of the
humidier (parameter P0).
The minimum production has an activation hysteresis, hy, equal to 5% of
the proportional band of the external signal “Y”.
Fig. 12.a
Control with humidity probe (see g. 12.b)
The production of steam is related to the reading of the probe and
increases as the relative humidity value read decreases. The production
reaches the maximum when the relative humidity is lower than the set
point (St) by a value at least equal to the proportional band (P1). The
maximum production may be programmed between 20% and 100% of
the rated value of the humidier (and between the 10% and 100% in
series operation). To set the set point and dierential for the main control
probe: “SET” screen > set point and proportional band. The minimum
production has an activation hysteresis, hy, equal to 2% of the range.
Fig. 12.b
Application for steam baths: autonomous control with
temperature transducer (NTC), parameter A0=2 and
A2=5
In applications for steam baths, where the control probe measures
temperature rather than humidity, the same considerations are valid as
described in paragraph Control with humidity probe
, replacing relative
humidity with temperature.
Fig. 12.c
12.3 Supply water conductivity
Conductivity measurement and alarms
The conductivity of the supply water is measured by the conductivity
meter when the ll solenoid valve is opened.
Two programmable alarm thresholds are available:
• b5: warning threshold (signal only without activating the alarm relay,
automatic reset when the condition is no longer present);
• b6: alarm threshold (unit shutdown with activation of the alarm relay).
The alarm is activated when the reading exceeds one of the two
thresholds continuously for 60 minutes, or alternatively instantly if the
value read is 3 times higher than the threshold.
To disable the alarm signal, simply set the thresholds above the maximum
value of the reading.
12.4 Automatic draining
The humidier automatically drains and replaces some of the water
contained in the cylinder, to prevent an excessive concentration of salts
following the evaporation process.
The drain pump is opened for a set time whenever the conductivity
exceeds the maximum limit; this situation is measured indirectly by
evaluating the evaporation speed.
During the automatic draining phase, the electrodes are o, so as to
prevent the drain water from carrying current (the display shows “dr”).