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4. The modulation signal must increase from
minimum toward maximum as sensed RH
(actual RH) drops below desired RH (%RH
setpoint). In response, humidifier's steam
output will increase from minimum toward
maximum. When humidifier's steam output
(lbs/hr) matches humidification load (lbs/hr),
modulation signal will stabilize.
5. Field-wiring connections for modulation control
are to be made to external side of terminals 30
and 32 on humidifier's control terminal strip.
Always refer to the external control's wiring
diagram factory supplied with each Liebert
modulation control option.
6. Varying dc Voltage Modulation Signal
Powered by Others: SGH humidifier can be
factory configured to accept the following vdc
signals: 0-10 vdc, or 2-10 vdc. Wire
according to Liebert supplied external wiring
diagram that comes with each modulation
option. To share the signal with more than
one humidifier, wire in parallel to each
humidifier. If a different signal is desired
consult factory.
7. Varying dc milliAmp (mA) Modulation
Signal Powered by Others: SGH humidifier
can be factory-configured to accept a standard
dc mA signal, if pre-specified. Wire according
to Liebert supplied external wiring diagram
that comes with each modulation option.
Choose from 0-20 dc mA or 4-20 dc mA. To
share the signal with more than one humidifier
consult factory.
OPTIONAL MODULATION (CONTINUOUS
CONTROL) PACKAGES BY LIEBERT
Modulation (continuous control) "packages" are
offered as accessories by Liebert.
OPERATION
INTRODUCTION
When the humidifier is first turned on, the
controller starts with a self test procedure, which takes
about 10 seconds. The test consists of activating for a
short time the drain valve, fill valve, and power relays.
The sound of the working solenoids is an indication of
valves operation. Green and yellow lights flash during
this time.
If there is no call for humidity, the humidifier is
standing by and green light flashes. When control loop
is closed ( Figure #13), the green light is steady on
and the humidifier starts its operation. The controller
waits 10 seconds before energizing the on-board
relays. When the relays energize, heating voltage is
delivered to the cylinder. After a 30 second delay, the
fill valve is activated (if the output from the cylinder is
below 100 %). If controller detects increase of
amperage above allowed range, the unit will activate
drain valve for 2 seconds.
During operation, the controller measures the rate
at which water is converted to steam and thus the
mineral content of water inside the cylinder. When this
rate exceeds the design optimum, a drain of the
cylinder takes place. The amount of water drained is
just enough to keep the contained water at design
levels.
During start up, when mineral content in the water
is low, water will reach the top of the cylinder at which
point the yellow indicator light will come on. This is
normal operation with a fresh cylinder. After a period of
time the water level will drop and the yellow light will
turn off.
High water level in the cylinder also indicates that
the cylinder is near the end of its service life as
electrodes become coated with minerals. The yellow
light coming on more often would be the first indication
of approaching the end of the cylinder life.
SGH OPERATION
END OF CYLINDER LIFE
When the cylinder is used up and water level can
no longer stabilize below full cylinder (due to fully
coated electrodes), the yellow light will flash in 4 pulse
cycles. At this time the control board interrupts steam
production and switches the green indicator lamp off.
The disposable cylinder must be replaced.
It is wise to keep a new replacement cylinder on
hand to avoid downtime when it becomes time to
change the disposable cylinder.
MANUAL CAPACITY ADJUSTMENT
On/Off Controls
The SGH humidifier is rated in lbs/hr of steam
output capacity. Set to 100%, it will operate at full
output until the humidistat has sensed that the
humidity has reached setpoint. Then it will stop the
humidifier by breaking control circuit 8-10.
If the humidifier is oversized, the humidistat will be
quickly satisfied and stop the humidifier. As humidity
level drops the humidistat calls again. It is quickly
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