Specifications

CAREL gaSteam
55
16. Operating Principle and Other Functions
16.1 Operating Principle
In a gas humidifier the production of humidity is generated when water inside a boiler is heated to and then held
at boiling temperature. The heat required to boil the water is provided by a heat exchanger heated by a type
pre-mix, modulating, room-sealed gas burner (standards compliant). This burner takes in air from and
discharges the flue gas to the outside through suitable piping. This machine is therefore suitable for rooms
where there is not sufficient fresh air.
The operation of the burner is completely automatic and does not use a pilot flame. All the operating phases of
the burner are controlled by an electronic board, which also constantly checks the presence of the flame by
ionization. The output of the burner continuously responds to the request for heat, according to an ample
modulation ratio.
The variable speed fan, managed by the control board, together with the proportional gas valve, allows the
output to be modulated (the flow-rate of gas is proportional to that of the air needed for combustion).
The water that evaporates over time is automatically replaced with water from the mains supply.
In stable operating conditions, the level of production required is automatically controlled by adjusting the
thermal output of the burner.
The salts introduced by the automatic refilling of the water are partly deposited as lime scale inside the cylinder,
contributing to the progressive build up of minerals on the cylinder, and partly remain dissolved in the water.
To avoid excessive accumulation of salts, a quantity of water is periodically and automatically drained and then
replaced with fresh water.
16.2 Other Functions
16.2.1 Measurement of the Conductivity of the Supply Water
– Alarm Thresholds
To optimize the operation of the humidifier, by suitably spacing the automatic draining cycles (see Automatic
draining), when the fill solenoid valve opens, the conductivity of the water is measured using special
conductivity measuring electrodes.
Two high conductivity thresholds can be set for activating, respectively, a pre-alarm and an alarm event
(shutting down the appliance) when such thresholds are exceeded for at least 60 minutes, or alternatively
instantly if the value measured is three times greater than these.
16.2.2 Automatic Draining
Automatic draining is managed by the control module: part of the water contained in the cylinder is drained
automatically, and replaced with fresh water to prevent an excessive concentration of salts following the
process of evaporation.
The electric drain pump is opened for a set time at varying intervals, according to the production of steam and
the concentration of solids dissolved in the supply water, measured using the conductivity electrodes.
Apart from the salt concentration in the supply water, at least one drain cycle will be performed within a
maximum period, based on the quantity of steam produced; this is also valid for supply using demineralized
water.
16.2.3 Anti-Foam Procedure
The level of the water inside the cylinder is maintained by the level control at a minimum pre-set distance from
the top of the cylinder. Therefore, when the high level electrodes detect water, a foam detection event occurs.
A draining procedure is then automatically started, which is then repeated until the problem disappears, or, in
the event of multiple activations, an alarm is signaled.