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SD
Optimizing Cylinder Life on the SD 2000 Electrode Steam Humidifier
11.1.
The normal life of a steam cylinder ranges anywhere from 500 to 4,000 hours depending on the water quality
and use profile. Generally we seek to see around 2,000 hours of life.
If the steam cylinder is experiencing less than normal life, the following items should be checked:
•
Spent cylinder color is a very good indicator of correct or incorrect operating conditions. A cylinder that has seen
its normal life usually contains some mineral that is mostly white to light tan in color. If the mineral in the cylinder
appears more as a black sludge (and particularly if putting a magnet in the sludge pulls up iron filings), then more
than likely there is an operational problem either with the water or the proper filling and draining of the humidifier.
•
Improper filling and draining of the SD humidifier can be caused by:
o
(75% cause) Steam hoses sagging or kinked collect condensate which creates a back pressure on the steam
cylinder and forces fresh fill water to flow to the drain instead of into the cylinder. Refer to the guidelines on
steam hose piping on page 13 in this manual.
o
(10% cause) Short cycling of the humidifier due to oversizing. The SD must hit 5 fill cycles before it will decide
to activate drain cycles. Correction to this is to limit the maximum production of the unit to match the load.
o
(5% cause) Plugged fill valve screen or defective fill valve, filling too slowly (more than 5 minutes to full).
o
(5% cause) Plugged or defective drain valve, draining too slowly (more than 5 minutes) or not at all.
o
(5% cause) Plugged drain screen in the bottom of the cylinder, draining too slowly (more than 5 minutes) or
not at all.
•
The optimum water conductivity for the SD humidifier is from 150 to 350 micromhos. Water with conductivity
higher than this progressively shortens the cylinder life, so at 1700 micromhos the cylinder will last no longer than
500 hours. If the water conductivity is too high, the only solution is to mix demineralized water with the raw water
to get closer to the optimum conductivity range.
•
Softened water can be used, but only when the water conductivity is below 250 micromhos, and even then, its
benefits are questionable. Softened water contains Sodium which tends to stay in solution longer and will not
plate out on the electrodes as quickly. However, when the resulting conductivity is in excess of 250 micromhos
the water pH will generally go very basic and the water then becomes very corrosive to the electrodes. Water
foaming also occurs, which can create conductive mineral traces between the electrodes promoting arcing. Long
term arcing will damage not only the electrodes, but also the power contactors. Highly softened water usually
results in a short cylinder life where the electrodes have disintegrated.
•
Drain the unit during long periods of nonuse The water can lay in the cylinder on the electrodes and slowly
deteriorate them. It is good practice to manually drain the unit over the Summer or over long periods of inactivity.
•
Water analysis should be done and check for Silica, Nitrates, Phosphates, Iron and pH. Water containing large
amounts of Nitrates or Iron can be handled by installing a water filter containing activated charcoal (referred to as
a taste and odor filter). Water containing large amounts of Silica is best handled with a 1 micron particulate filter.
Phosphates are often used by municipalities and some buildings to coat and protect old piping (or lead pipes) to
prevent corrosion. However, this protective coating action works against the SD 2000 by coating the electrodes
rapidly and insulating them from the water and thus they can no longer pass current and produce steam.
Buildings with Phosphate feeders should bypass these and give the raw, untreated water to the humidifier. If the
Phosphates are coming from the local water source, then again a water filter with activated charcoal will be of
some help.
•
Drain timer can be used in cases where the water is high in mineral content or where the water contains some
unidentifiable component causing problems. The timer connects to the back of the SD controller and forces a
complete drain down every few hours. This eliminates the possibility of building up any concentration of the
unknown agent. This is usually a last resort when all the above fails.
23
Carel USA
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