On 11/28/2014 9:07 PM, wrote:
there is no water running through it.


From: http://www.aprilaire.com/docs/defaul...s.pdf?sfvrsn=6

The Aprilaire Humidifier is installed to operate in conjunction with the
furnace blower. When the Aprilaire Humidifier Control calls for humidity
and the blower is operating, water flows to the distribution tray located at
the top of the unit. The water is uniformly distributed across the width of
the tray and through a scientifically designed system of outlets. It flows
by gravity over the Water Panel®
evaporator, the heart of the unit. Dry, hot
air is moved through the moisture-laden Water Panel evaporator where
natural evaporation takes place. The now humidified air carrying moisture
in vapor form (nature’s own way) is circulated throughout the home.
The correct water flow is determined by an orifice equipped with
each drain type unit. When the unit is operating, there will be a small,
steady stream of water to drain, which flushes away most of the
trouble-causing minerals. Do not use the saddle valve to regulate the
water flow. It is designed to be completely opened or closed. The minerals
and solid residue not trapped by the replaceable Water Panel evaporator are
flushed down the drain in the Models 550, 600 and 700. This is the most
effective and least expensive method to dispose of trouble-causing minerals.
The drain also eliminates the problems caused by stagnant water.