User manual

54
ENG
“UEX-PLUS” +03U220621 - rel. 1.4 - 04.08.2009
installeruserservice
14. TECHNICAL APPENDIX
ONOFF
hy
hy
hy
Banda Proporzionale/ Proportional Band
Pmax
Pmin
Y
Produzione di vapore
Steam production
hy
Dehum. offs.
P0
Pmin
Dehum. diff.
ST
Produzione di vapore
Production of steam
OFF
DEUMIDIFICAZIONE
DEHUMIDIFICATION
attivata / activated
disattivata / deactivated
ON
ON OFF
% rH
Produzione di vapore
Steam production
Banda Proporzionale/ Proportional Band
2%
Pmin
Pmax
Sonda in
mandata (% rH2)
Limit probe
(% rH2)
Banda proporzionale/Proportional Band
L set point
Limite di produzione %
Production limit %
14.1 Operating principle
Immersed electrode humidiers produce 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 water in 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/
minerals 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 ate set intervals.
14.2 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 (see Fig. 14.1)
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 1 Vdc, 0 to 10 Vdc, 2 to 10 Vdc, 0 to 20 mA, 4 to 20 mA, 0 to 135
Ohm, 135 to 1000 Ohm (installer menu > regulation type > signal type).
The entire range is indicated as proportional band.
The maximum production of the humidier, corresponding to the maximum
value of the external signal, can be set from 20% to 100% of the rated value
of the humidier (“SET” screen> Max. Prod).
In humidiers with two cylinders in “series” operation, the modulation can
be set between 10% and 100% (in “parallel” operation it remains between
20% and 100%).
The minimum production has an activation hysteresis, hy, equal to 5% of the
range of the proportional band BP of the external signal “Y”.
Nota: Operation in parallel sequence or series sequence are
available only in models
UE090...UE130 .
Proportional control with limit probe (see Figs. 14.1 and
14.3)
See “proportional control”, with the addition of a limit probe, generally
installed in the air duct downstream of the humidier.
This type of control is used to reduce steam production if the relative
humidity, downstream of the humidier, is within the proportional band
set for the limit probe. Steam production is stopped if the relative humidity,
downstream of the humidier, reaches the limit set point %rH2.
To set the set point and dierential for the limit probe: “SET” screen> set
point limit and proportional band.
Independent control with relative humidity probe (see Fig.
14.2)
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. 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.
The dehumidication function (if enabled) activates a relay output that
can be connected to a dehumidier, for complete humidity control in the
environment. The dehumidication relay is activated when the relative
humidity measured by the probe, exceeds the set point (St) by a certain
value (Dehum di.) plus an oset (Dehum oset), and is deactivated when
the humidity falls below a value equal to the oset.
To check that the relative humidity measured by the probe is within certain
preset values, two alarm thresholds can be set in independent control:
• highhumidityalarmthreshold;
• lowhumidityalarmthreshold.
When these thresholds are exceeded, an alarm is activated, after a set delay.
Independent control with relative humidity probe and
outlet humidity limit (Figs. 14.2 and 14.3)
See control with main probe, combined with a limit probe, installed in the air
duct downstream of the humidier.
This type of control is used to reduce steam production if the relative
humidity, downstream of the humidier, is within the proportional band
of the limit probe. Steam production is stopped if the relative humidity,
downstream of the humidier, reaches the limit set point %rH2.
Fig. 14.1 Proportional control
Fig. 14.2 Control with main probe Fig. 14.3 Control with limit probe