8.5 Humidifier Maintenance during Extended Shutdown
WARNING! Risk of electric shock. Can cause equipment damage, injury or death. Open all local
and remote electric power supply disconnect switches and verify with a voltmeter that power is
off before working within any electric connection enclosures. Service and maintenance work
must be performed only by properly trained and qualified personnel and in accordance with
applicable regulations and manufacturers’ specifications. Opening or removing the covers to
any equipment may expose personnel to lethal voltages within the unit even when it is
apparently not operating and the input wiring is disconnected from the electrical source.
Always drain the cylinder before disconnecting power to the humidifier for a period of extended
shutdown. Otherwise, the electrodes are subject to harmful corrosion, which drastically shortens the
cylinder life. Do not leave the switch in the DRAIN position indefinitely because the drain coil could burn
out. Leave the switch in the Off position and open the main external fused disconnect to stop power to
the humidifier. Close the shutoff valve in the water supply line feeding the humidifier.
8.5.1 Humidifier Troubleshooting
Terms Used in Humidifier Troubleshooting:
• FLA (Full Load Amps) are amps listed on the humidifier specification label.
• Short cycling occurs when the humidifier’s “On time” is less than 10 minutes upon a call for
humidity. To correct short cycling, all humidifiers have a capacity adjustment that allows the
output of the humidifier to be reduced to as low as 20% of rated output, thus extending the “on
time” required to maintain output.
• Foaming can occur when the impurities already in water reach an excess concentration as a
result of boiling away water and continued boiling agitates the contained water. The humidifier
electronics are designed to prevent foaming, although in extreme cases water will foam with
little concentration, making it necessary to increase the drain time of the water contained in
the cylinder. Foaming is normally caused by short cycling, a restricted drain or back pressure.
The foam generated in these instances is conductive and may lead to false full-cylinder
indication if the level of the foam approaches the top of the cylinder.
• Back pressure is the restriction of steam flow caused by long steam runs, improperly sloped
steam lines, elbows changing the direction of steam flow from horizontal to vertical without a
drain leg, any plumbing detail allowing the accumulation of condensate, undersized steam line,
improper steam distributor, downward air flow onto the distributor causing excess static
pressure at the steam outlets, or high static pressure ducts (not probable). To overcome
excess static pressure in the duct, use a fill cup extension kit. In downflow applications, a
downflow distributor should be used, but in some cases the fill cup extension will also be
required.
• Reset unit (humidifier): To reset the humidifier, switch the auto On/Off/Drain switch at the
front of the humidifier to the Off position for at least five seconds, then switch it back to the On
position.
• Monitored leg is the primary wire to the cylinder that loops through the current sensing device
of the main PCB. This wire ends at the red cylinder plug at the cylinder.
Vertiv | Liebert CRV Installer/User Guide | 87
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