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A high-water float switch prevents water carry-over into the duct due to an excessive water level in the
tank. When the high water limit is reached the HIGH WATER light comes on and the fill valve is
blocked until some water is boiled away and the water level drops. This is common during startup. If
the high water light comes on and the water level is in the lower half of the steam generator, contact
the factory for assistance. This is due to high static pressure. Installation of fill cup extension kit could
be required.
If an overcurrent situation is detected, the overcurrent protection circuit will drain water from the tank
to reduce current flow. If the overcurrent persists, the contactor will be de-energized to stop all current
flow.
The Series EHU-700 patented automatic capacity adjustment feature eliminates manual adjustment
and improves humidity control. This feature automatically adjusts maximum output up or down
depending on the humidity demand history. When the unit is first turned on the maximum output is
40%. If the demand stays high, the unit automatically steps up the maximum output and will reach
100% maximum output after one hour. For test purposes, or for special operating situations, this fea-
ture can be easily over-ridden by changing the position of jumper BJ1 on the printed circuit board from
pins 1 and 2 to pins 2 and 3.
An automatic drain cycle blows down mineral-laden water to increase steam generator life and reduce
maintenance requirements. The frequency and duration of the drain cycle will vary with supply water
conductivity, steam output, and humidistat demand history. When it is initiated automatically, the drain
valve cycle occurs at the beginning of a fill cycle. The incoming cold water tempers the drain water to
less than 160ºF after 72 hours of no demand, the unit will initiate an "End-of-Season" drain to remove
stagnant water.
OPERA
TIONAL GUIDELINES
This section describes the conditions and indications you should expect to find in a normally operating
humidifier.
Tank Contactor Operation:
The microcontroller will de-energize the contactor, turning off the current to the electrodes if ANY of
the following occur:
1. The control humidistat demand signal is less tan 25%.
2. The fan interlock circuit is open.
3. The high limit humidistat circuit is open.
4. The tank current is greater than the over-current limit.
Conversely, the microcontroller will energize the contactor, turning on the current to the electrodes,
only if ALL of the following occur:
1. The control humidistat demand signal is greater than 35%.
2. The fan interlock circuit is closed.
3. The high limit humidistat circuit is closed.
There is a time delay of fifteen seconds in the contactor operating circuitry to prevent it from cycling
too rapidly after it has been turned off.
Monitoring Stat Demand:
Indicates the demand for humidity in relationship to the control range of the humidistat. 0% indicates
that the humidity requirement has been exceeded. 100% indicates that the humidistat is calling for full
humidifier output. In general, a reading of around 50% indicates that the set point has been met.
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