CARNES HBGH Installation, Operation And Maintenance Manual page 18

The Control humidistat, which provides the Control Demand, is
normally the humidistat in the room being humidified. It is either
installed in the room itself or the return air duct. The High-Limit
humidistat, which provides the Hi-Limit Demand, is a safe-guard
humidistat installed in the supply duct roughly 10-15 feet past the
distribution tube. This humidistat is usually set to a high level (80-
90%), and will shut down the humidifier if the humidity gets too
high in the supply duct. Without a High-Limit humidistat properly
installed, the supply duct could reach a humidity level where any
steam entering the duct would readily condense.
Both Control humidistats and High-Limit humidistats are wired in
the same way, only Control humidistats are wired to port J16 of
the circuit board and High-Limit humidistats are wired to port J17.
Both ports have the same number of pins and connection layout.
When using an on/off humidistat, the percentage should be
either 100% or below 20%. In this case the control is either calling
for full output or no output. On-Off humidistats are dry-contact
switches. They will have two wires; each connected to pins 2 and
4 (in no particular order/polarity).
For a proportional humidistat, any percentage value is possi-
ble between 0% and 100%. In this case the humidifier can be
modified to output any fraction of its max output. If the propor-
tional control falls to 20% or below, the humidifier is shut off. The
input signal of a proportional humidistat must be of the 0-10V DC
variety. Proportional humidistats will have three wires, with 'power'
going to pin 1, 'signal' to pin 3, and 'ground' to pin 4.
In lieu of a humidistat, a DDC signal from a building
management system may also be used. Here, the 'signal' should
be connected to pin 3, and 'ground' to pin 4. In this case, 'power'
can be ignored. A DDC signal must be of a 0-10V DC variety,
though a 4-20 mA control signal can be converted to a 0-10V
signal by adding a 470 Ohm resistor between the 'signal' (pin 3)
and 'ground' (pin 4).
"COMPONENT ACTIVITY" PAGE
The Component Activity page lists all internal components that
can switch on and off during operation. This includes the Fill
Valve, Drain Valve, Contactor, and High Water Sensor. Each
orange button in the component list is accompanied by a colored
indicator representing whether or not the component is currently
'on'. Green indicates that the component is 'on', whereas gray
indicates the component is 'off'. The Fill Valve is on when the unit
is either filling or draining the cylinder. The Drain Valve is on when
the humidifier is draining the cylinder. The Contactor is on when
the humidifier is producing steam. The High Water Sensor is on
when the humidifier has identified a high water situation. When in
a high water situation, the fill valve is disabled for 5 minutes. At
the end of 5 minutes the high water sensor light will go out, the
fill valve will open, if there is a call for more humidity, and unit will
continue normal operation. High water sensors can be cumulative
depending on the condition of the water.
The other item present on this screen is the Communication
button. The Communication button has a rotating indicator that
represents whether the True Touchscreen controller on the circuit
board is properly communicating with the microcontroller. If this
icon is not rotating and has a red 'X' through it, the information on
the screen is invalid and you should contact the factory.
"SETPOINTS" PAGE
The Setpoints page displays the setpoints (the target steam
output of the humidifier) associated with the unit. There are three
different setpoints, but only one setpoint is active at any given
time. Each setpoint is accompanied by the current value of the
setpoint to the right, and an indicator that represents its status.
For all setpoints, the following colors represent the status of the
setpoints:
Gray – The setpoint is inactive because it is not currently
necessary.
Green – The setpoint is active, and the humidifier is producing
steam at or above the setpoint value.
Yellow – The setpoint is active, but the humidifier is producing
steam below the setpoint value.
Yellow/Black X – The setpoint is inactive because it is being over-
ridden by a setpoint with a higher priority.
The three different types of setpoint are as follows: The Max
Setpoint is the user-specified setpoint active when no external
controls or internal reduction is taking place. The Max Setpoint
is always modifiable via the "Max Output Adjust" within the set-
tings menu. The Controlled Setpoint is the setpoint when a
humidistat (Control or High Limit), reduces the target output of
the humidifier due to changing room requirements. The Reduced
Setpoint is active when the unit requires a reduction in output due
to a high water situation.
The setpoints have the following priorities: The Reduced Setpoint
has the highest priority and always overrides the Controlled
Setpoint and the Max Setpoint when active. The Controlled
Setpoint has the next highest priority, and always overrides the
Max Setpoint. It should be noted that the Reduced Setpoint is
always lower than or equal to the Max Setpoint (or Controlled
Setpoint, if active), and the Controlled Setpoint is always lower or
equal to the Max Setpoint.
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