REFRIGERANTS
HUMIDITY CONTROL
Resistive humidifi er vs electrode boiler humidifi er: what’s the diff erence?
One of the fi rst decisions you’ll likely have to make when choosing a steam humidifi er for a commercial or industrial application is whether to select a resistive or electrode humidifi er. Both units diff er from one another in several key areas as John Barker of Humidity Solutions explains.
W
hen it comes selecting a steam humidifi er, there are several key diff erences between a resistive or electrode humidifi er that you will need to take
into account according to the application, including:
■The method of Heating water to produce steam. ■The level of close control required. ■Maintenance requirements ■Water quality of the site’s location ■Importance of capital or consumable costs.
What is an electrode humidifi er? Electrode steam humidifi ers heat water by transmitting
an alternating current between electrodes within a plastic cylinder, using the ions dissolved (minerals) in the water for conduction. Mains water (which contains minerals) will conduct electricity between the electrodes with signifi cant resistance, heating the water to boiling point and producing steam.
The capacity of the unit is determined by the size of the cylinder, the surface area of the electrodes in contact with the water, and the humidifi er’s rated power (kW). It’s method of regulating
the steam output involves changing the level of water inside the cylinder. The more of the electrode surface that is submerged the more current will fl ow between them which increases the amount of power used and increases the overall steam generation. Lowering the water level will result in a decrease in steam production.
As the mains water turns into steam within the boiling chamber, all of the water supply ions left behind within the tank will eventually form as scale. Periodic cylinder cleaning will reduce the build-up, but over time the scale will build up to a point where the electrodes get worn and coated and are unable to provide maximum capacity. At this point, the cylinder needs to be exchanged, which is quick and easy to do but is a consumable item.
What is a resistive humidifi er? Resistive humidifi ers diff er by generating its steam
production within a stainless-steel evaporation chamber and use self-cleaning heating elements to heat water to boiling point using electricity. Regardless of the water’s ion concentration, this radiant heating will elevate the temperature of the water inside the evaporation chamber to boiling point, enabling equal performance. Unlike the electrode boiler, not having reliance on the minerals in the water to generate heat means that the resistive humidifi er can operate off a purifi ed reverse osmosis water supply which can reduce maintenance. The accumulation of scale inside an evaporation chamber
is reduced in resistive humidifi er installations as they can perform regular fl ush cycles to help expel the minerals left behind. Without water treatment the humidifi er will require regular cleaning of the evaporation chamber. As the chamber / cylinder is made of stainless steel consumables are less but labour time may be greater.
30 September 2023 •
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