Aprilaire 1150 Installation, Operation And Maintenance Manual page 9

SEQUENCE Of OPERATIONS
Note: Sequence is for normal operation, starting with an empty Steam Chamber .
Model 1160 humidifier is connected to: 240 VAC, single phase input power; Model 57 modulating Automatic Steam Humidifier
Control (ASHC); Airflow Proving Switch and High Humidity Limit Switch . Water supply is turned on, steam distribution and drain
connections are made .
Model 1180 humidifier is connected to: 240 VAC, three-phase input power; Model 57 modulating Automatic Steam Humidifier
Control (ASHC); Airflow Proving Switch and High Humidity Limit Switch . Water supply is turned on, steam distribution and drain
connections are made .
TAblE 3 – Sequence of operation for Model 1160 and 1180
Operation
Humidifier power turned on .
Fill Sequence:
Water level probe will sense an empty chamber and turn on
the fill valve .
Demand for humidity from control circuit:
(ASHC is calling for humidity and airflow is present.)
As water is boiled off, the water level drops and the water
level probe will sense a need for more water in the chamber .
Pre-heating of water .
Demand for humidity is satisfied .
After a predetermined amount of run time (element energized),
an Autodrain sequence is performed . The control will initiate
Autodrain during a period of inactivity when the water in the
chamber is cool .
• Internal Controller (LW420) powered up.
• LEDs blink - On/Off LED stays on.
• +24 VDC available at terminal #30 on humidifier referenced to C.
• After a few second delay, the Fill LED will turn on and the fill valve will open. The Fill
LED will remain lit as long as the fill valve is open .
• Water will flow into steam chamber. Note: It takes approximately 7 minutes to fill the
Model 1160 chamber and 12 minutes to fill the Model 1180 chamber .
• Water level probe will sense a properly filled chamber and Fill LED will turn off .
• Fill valve will close.
• ASHC will send a DC signal from H+ to terminal #1 on humidifier. The signal will
range from 1 to 10 Volts DC depending on the difference between the ASHC set-point
and the actual RH .
• The Fan Relay will energize in a few seconds.
• The LW420 will check for a closed 'enable' circuit between terminal #2 and C (Airflow
Proving and High Humidity Limit check) .
• If 'enable' circuit is closed, Steam LED will turn on and remain on as long as the call
for humidity is present .
• The Steam LED will stay on unless the 'enable' circuit opens or the ASHC signal drops
below 1 VDC .
• After a 15 second delay, the Contactor will close, energizing the heating elements.
• After about ten minutes, the water will boil and steam will be generated and forced
out of chamber, up through hose and dispersion tube into the duct .
• CAUTION: Steam chamber and hose will be very hot .
• NOTE: During the initial start-up, steam hose may emit an odor .
• See Fill Sequence listed above .
• During normal operation, in the case of a re-fill cycle or a period of no demand for
humidity, the controller will recognize that the tank has cooled down . The heaters will
energize for an appropriate amount of time to bring water close to boiling temperature .
Preheat only occurs when there is a demand for humidity .
• Steam LED will turn off.
• The contactor will open after 15 seconds and the heating elements will be
de-energized .
• The Fan Relay will be de-energized after 5 minutes.
• The Drain LED will turn on and the drain valve will open allowing water to drain from
the bottom of the chamber .
• The drain valve will remain open for 12 minutes after the water level in the chamber
drops below the lower probe .
• The Fill LED will turn on and the Fill valve will open.
• The Fill valve will remain open until the water in the chamber reaches the upper probe,
at which point the fill valve will close and the Fill LED will turn off .
• NOTE: When the water in the chamber reaches the lower probe, if there is a demand
for humidity, the heating element will be energized .
Expected Results
continued on next page . . .
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