VACUUM CLEANER SPECIFICATIONS
Harold BrochmannThere is just as much nonsense and misleading information supplied to vacuum cleaner buyers as there is to mattress buyers.
The most commonly supplied specifications for vacuum cleaners are: Amps, Watts, HP, Airwatts, Miles per hour What you should be concerned with is the volume of air per minute drawn into the intake when it is unobstructed; the suction (vacuum) produced when the intake is closed; the noise the thing makes.
Amps is short for ampére which is the unit of electric current flow. The current in a 100 watt light bulb is just a little less than 1 amp. The current in a toaster is around 10 amps. Vacuum cleaners have current ratings running from 5 amps to 12 amps.
Watts. Multiply the current rating by 110 (volts) and you get the power in watts. 5 amps is equivalent to 550 watts, and so on.
These two measurements are really not very meaningful in absolute terms; though they may be of limited use for purposes of comparing one machine with another. They describe how much electricity the machine uses. The implications is that the higher the 'power rating' the better is the machine. It's like emphasizing that your car uses a lot of gasoline without telling you how fast it goes or how much it can carry.
HP- or horse power tells you how powerful the motor is supposed to be. Provided that the motor is 100% efficient - which no motors are - there are theoretically (800 watts*) in 1 HP. Here is a sample calculation: An 8 amp motor uses 880 watts. So 880/746 * 90% [assumed efficiency] = 1 HP.
There are two components to the suction-producing mechanism in a vacuum cleaner: the motor and the fan. So far we have dealt with the electricity consumption and assumed power of the motor. Next we talk about the efficiency of the fan.
Rather than having blades such as an ordinary table fan has, fans used in vacuum cleaners are centrifugal. Compared to blade fans, centrifugal fans are characterized by the fact that they can produce greater suction, but need a higher speed (rpm)... which means that they are inherently considerably noisier.
There are two kinds of fan arrangements. In dry vacuums the air is drawn through the motor so as to cool it. This means that if you suck water with it the motor stator, rotor and bearings get wet and they will rust and generally muck things up. Not a good idea. In wet/dry vacuums the air flow bypasses the motor and a separate air flow cools it.
The through-motor air flow arrangement is more efficient in that a greater flow of air can be obtained with the same power. The by-pass arrangement is inherently noisier and less efficient in terms of airflow rate.
The bottom line here is that electricity consumption in amps or watts, or motor power is all very interesting, but not informative unless one also considers fan efficiency.
Another unit sometimes encountered is the airwatt.
Airwatts = (cubic feet per minute) x (inches of water suction) / 8.5
Overall efficiency = airwatts / input watts.
So there. Now we know.
Miles per Hour refers to the speed of the air. Airflow speed is different in different parts of the machine. Airflow speed in the fan, at the exhaust port, through the filter, through the hose and through the tool attachment are all different - and are all dependent on each other. For example, if you take the tool off, the airflow speed through the hose will increase. Take the hose off and the airflow speed out the exhaust port will increase. What is also true is that other things being kept constant, the airflow through a narrow opening is greater than through a larger one. So a tool with a small opening will have greater flow through that opening than through a larger one. All of this matters because it is the speed of the air through the tool when in contact with the surface to be cleaned which determines 'cleaning power' for lack of a better term. The problem with using airflow speed (in miles per hour) is that you aren't saying where in the system and under what conditions this speed is attained.
The majority of vacuum cleaner distributors do not provide meaningful specifications because it makes it possible to make informed comparisons with their competitors' products. Providing poorly understood or irrelevant specifications is a marketing technique which is used to blatantly manipulate the unsophisticated buyer. The vast majority of retail sales people don't know better either. Demand to be treated like an intelligent person.
Don't get sucked in!
The volume of air drawn through an unobstructed intake, when considered in conjunction with closed intake vacuum are the only meaningful and useful units of comparison between vacuum cleaners. The units used are cubic feet (or litres) per minute and inches (or centimetres) water that can be 'lifted'.
The other factor that should be considered is noise level. Many vacuum cleaners are notoriously noisy. This is not the place to discuss the many unpleasant effects that high noise levels can have on people's health and general well being. Suffice it to say that you should be prepared to pay a premium for a really quiet vacuum cleaner.
Noise levels are measured in decibels. Decibel levels in excess of, let's say 70dB or so, are not only unpleasant; they can hurt you, and they are unnecessary.
MY VACUUM CLEANERThe specifications for the vacuum cleaner I bought in the fall of 1997 are: 120 cubic feet of air per minute 2.25 square inch cross section of hose (most have 1.6 square inches). This 40% greater size increases airflow and reduces noise. 90 inches water lift. 49 dB noise level.
The deciding factor for me was the fact that this machine is very quiet. It is perfectly possible to carry out a normal conversation or make a phone call in the same room that is being cleaned.I would be very interested in hearing from anyone who knows of a machine with better or comparable specs.
I intent, as the spirit moves me, and as readers pass on useful information, to improve/extend this page. An obvious topic is the questions filter types and effectiveness.
This page is not an advertisement for a particular brand of vacuum cleaner. However, if you want to know the brand name and maker of the machine I bought, it is NUMATIC model NVQ402. Numatic manufactures in England, but export all over the world. They have a website that will point you to the distributor nearest you.