Carel humiSteam x-plus, Руководство пользователя, Страница: 53 / 60

53
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“UEX-PLUS” +030220621 - rel. 1.4 - 04.08.2009
installer
user
ser
vice
14. TECHNICAL APPENDIX
14.1 Operating principle
Immersed electrode humidifi 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 humidifi 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 diff erential.
The external contact may be a humidistat, whose status determines the
operation of the humidifi er:
contact closed: the humidifi 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 controller. 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 humidifi er, corresponding to the value
maximum of the external signal, can be set from 20% to 100% of the
rated value of the humidifi er (“SET” screen> Max. Prod).
In humidifi 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 humidifi er.
This type of control is used to reduce steam production if the relative
humidity, downstream of the humidifi er, is within the proportional band
set for the limit probe. Steam production is stopped if the relative humidity,
downstream of the humidifi er, reaches the limit set point %rH2.
To set the set point and diff 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 humidifi er (and between the 10% and 100% in
series operation). To set the set point and diff 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 dehumidifi cation function (if enabled) activates a relay output that
can be connected to a dehumidifi er, for complete humidity control in the
environment. The dehumidifi cation relay is activated when the relative
humidity measured by the probe, exceeds the set point (St) by a certain
value (Dehum diff .) plus an off set (Dehum off set), and is deactivated
when the humidity falls below a value equal to the off 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 humidifi er.
This type of control is used to reduce steam production if the relative
humidity, downstream of the humidifi er, is within the proportional band
of the limit probe. Steam production is stopped if the relative humidity,
downstream of the humidifi 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
ON OFF
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 %