Hand dryer selection
At AirtowelHygiene Systems , we believe in value for money and products that do the job that the item implies. There are too many hand dryers that are light weight, inefficient and over priced. Whilst the appearance of a hand dryer is important to an architect, it should not be at the expense of the function and efficiency of the hand dryer.
The heart of hand dryers or air towels is the motor and there are basically two types used; the universal armature brush style (used by Airtowel Hygiene Systems), which should have EMC approval to prevent radio interference (which we do). The brushes, through arcing (corona discharge), create a small amount of ozone. Ozone is nature’s own way of killing odours and bacteria and is not a disadvantage but an advantage.
There is a lot of nonsense about brushes having to be replaced regularly and this is not our experience at all. The benefits of this style of motor far outweigh any suggested brush related problem. The universal motor has around 70% to 90% efficiency and runs between 6000 rpm to 7000rpm, making it a powerful, effective motor. Dryers set up with universal motors will generally go close to the 2400watts, 10amps (total unit draw) maximum for a standard plug in the wall socket, giving high air velocity and high air volume, which relates to quick dry times. In other words, you don’t walk away wiping your hands on your clothes!
Induction motors, on the other hand, are very cheap to manufacture but are not very efficient (around 50% or less), draw a massive starting current and/or both and are large in size for the output watts. Standard induction motors want to turn at a constant speed of around 1500rpm, based on a four pole motor (source NSW University Physics Resources). They can be slightly altered to increase the revolutions per minute along with power consumption.
Hand dryers with induction motors have poor air velocity, low air volume and, unlike the universal motors, will overheat if used too many times in succession They are fitted with a heat overload switch to shut the unit down. These units can only be used in light usage areas. If you do not know the usage, you should specify heavy duty universal armature motor type dryers.
9-Jun-2006