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WATER QUALITY AND TREATMENT FOR EHU SERIES HUMIDIFIERS
GENERAL
Series EHU 700 electronic humidifiers use ordinary tap water in their operation. The quality of this
water affects both the operation and the maintenance of the humidifier.
How the EHU works:
The EHU is an electrode boiler. When no water is present, the electrodes are separated by air, an
insulator, so no current flows. When tap water contacts the electrodes it conducts current between the
electrodes, heating the water.
How much current passes between the electrodes is dependent on the conductivity of the water, which
is measured in micromhos/cm (μMhos/cm). EHUs can operate effectively with water conductivity in the
range of 50 (low) to 800 (high) μMhos. For conductivity greater than 800 μMhos, please consult facto-
ry. The optimum incoming water conductivity level is 200-400 μMhos/cm. the greater the conductivity
of the water, the lower its level will be in the tank in order to draw a given current. In general, the EHU-
700 Series will adjust its drain cycle to maintain the water level around 1/3-1/2 full in the tank.
What affects conductivity?
The minerals (mainly calcium) dissolved in the water. Pure water is NOT conductive and can't be used
exclusively in an EHU without special procedures. This includes distilled, de-ionized and reverse
osmosis diffusion treated water. Most tap water is conductive however, so it will work in an EHU. If tap
water is not available, consult with the factory.
How does this affect maintenance?
Figure 23-1. Tank filled with mineral buildup.
Generally, the more conductive the water is, the more
minerals there are dissolved or suspended in it. As the
water is boiled away these minerals can be left as a
deposit on the electrodes, tank, and fittings. Any
deposits that build up can block valves, diminish the
internal volume of the tank, and form an insulating barrier
on the electrodes (Figure 23-1).
The EHU automatic drain cycle:
All Series EHU humidifiers have a built in blow down
circuit to intermittently purge excess mineral accumulations from the water. The drain cycle should
automatically adjust for variations in water quality. Eventually, however, minerals will accumulate in
the steam generator, and have to be removed (see tank cleaning in the maintenance section of
this manual).
Water treatment guidelines for the EHU:
Generally, the EHU will work with any potable water source. If you are experiencing problems with
your installation, however, the following suggestions may be helpful in identifying and rectifying your
difficulty.
WHEN W
ATER CONDUCTIVITY IS TOO LOW
Indicators:
-Unable to reach humidity set point in space.
-High water level in tank
-Low current draw and low % power reading even though the stat demand remains at 100%.
-Consistent drain cycles of two seconds or less.
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