Thread Number: 15831
What are suction and airflow, and how are they related?
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Post# 168629   2/6/2012 at 22:55 (2,976 days old) by Sanifan ()        

I'm trying to wrap my head around these concepts but am kinda confused. What exactly are suction and airflow, and how are they related?

I can picture a vacuum wand the diameter of a drinking straw. I could see how it could generate a lot of localized suction, but very little airflow.

On the other hand, I can picture a vacuum wand the diameter of a 4" duct. I could see how it could generate a lot of airflow, but very little suction.

How are they related? Can you make a vacuum cleaner that has a LOT of suction and a LOT of airflow, or do you have to sacrifice one to get more of the other?


Post# 168647 , Reply# 1   2/7/2012 at 04:25 (2,976 days old) by jmurray01 (Scotland)        

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You could have a Vacuum Cleaner with a lot of air flow (large hose diameter) and a lot of suction, but the motor would have to be well designed to get immense suction power.

Post# 168666 , Reply# 2   2/7/2012 at 07:19 (2,975 days old) by sebo_fan (Scotland, UK, member AKA ukvacfan, & Nar2)        

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I'll try and answer the best I can here.

You're getting confused easily with the name and I can see why - Air Flow has little to do with the size of the hose - but more to the point of how air moves through a vacuum cleaner quite literally- therefore even the best vacuum in the world could claim to have the strongest air flow - but it depends on how the vac is built to contain the air flow without leaking air - and well before the hose is affected.

Suction is related because full suction could weaken if there's a leak in the system so therefore it is affected and could lose strength.

Post# 168670 , Reply# 3   2/7/2012 at 07:23 (2,975 days old) by sebo_fan (Scotland, UK, member AKA ukvacfan, & Nar2)        

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So, moving on from that - airflow will only be maintained well if a vacuum cleaner has excellent sealed suction. The Germans know best about this!

Clean air vacs AND Dirty fan vacs can suffer from leaking air, but not all - I recall my Turbopower Total suffered from leaking air, usually from the hose converter door at the side of the vacuum cleaner - you could also feel various points of suction air coming from the vacuum rather than the hose and the floor head.

Brands who make a play on the Air Flow idea confuse buyers because they are hyping up an effect that really isn't required to be promoted - unless it links with allergy sufferers if dust in the escaping impending air leaks - and if the machine is claimed to offer sealed suction.

Post# 168679 , Reply# 4   2/7/2012 at 09:59 (2,975 days old) by eurekaprince (Montreal, Canada)        

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Consumer Reports rates vacuums on "airflow through the hose for tool use". I think "airflow" is a much better indicator of how well a vacuum can clean because it gives you an idea of how strong the "wind" is coming out of the hose. The faster the wind, the more it can pull dirt and move dirt. You can have strong suction in a machine, but if the design of the airpaths from "fan to finish" does not allow fast moving air, the vacuum won't clean well.

Just think of what happens to the upholstery nozzle on the end of the hose of a 12amp Hoover WindTunnel upright - the suction is very very strong, but that nozzle has no holes in it to allow the air to get moving, and so it does a "suction lock" on any fabric it's cleaning.

I guess airflow/airspeed could be measured in volume per second (kind of like car traffic - 200 cars per hour), whereas suction would be measured in how many pounds could be lifted by the end of the hose - like those bowling balls in the Oreck commercials!

Post# 168689 , Reply# 5   2/7/2012 at 13:16 (2,975 days old) by kirbfan94 ()        

Airflow helps the vacuum from getting cloged in the first place, a lot of suction will clear it out when you put you hand on the hose, but it will clog again due to the lack of airflow when its not locked onto something. Suction dosent clean, airflow does.

Post# 168693 , Reply# 6   2/7/2012 at 14:13 (2,975 days old) by twocvbloke ()        

Airflow and Suction are partners when it comes to cleaning, Airflow is what makes the dirt travel from the carpeting or whatever you're cleaning into the bag/bin, and suction is what gives you the lifting action which holds the carpet or sofa covers to the nozzle... :)

So, if you have lots of one, but not the other, you don't get a good performing vacuum, you have to have the right balance to get a vacuum cleaner that works well... :)

You can get water-lift gauges and airflow gauges to measure such things, so, if you're really that curious you should have a look into them... :)

Post# 168711 , Reply# 7   2/7/2012 at 17:15 (2,975 days old) by sanitaire (anchorage, alaska)        

the ways of measuring vacuum performance in commerical world is CFM (cubic feet per minute) and inches of water lift. you can buy a gauge that you put on the end of a hose and it will show the inches of water lift.

Post# 168713 , Reply# 8   2/7/2012 at 17:27 (2,975 days old) by Rolls_rapide (-)        

I seem to remember that brochures for the UK Hoover Alpina cylinder cleaner in the 1990s had a 2 dimensional graph diagram of the relationship between suction power and airflow.

Something like suction on one axis, versus airflow on the other, created a curved "hill". Too little suction = lesser airflow. Too much suction power also meant lesser airflow. There was a "sweet spot" at the brow of the "hill", if you get my drift, where you got optimum suction and airflow.

Post# 168717 , Reply# 9   2/7/2012 at 18:30 (2,975 days old) by vintagerepairer (England)        

In all of this though, no where have I ever read anything which said how much suction or airflow was needed to clean carpets. I do wonder if the people who make vacuum cleaners even know.

Post# 168720 , Reply# 10   2/7/2012 at 19:20 (2,975 days old) by eurekaprince (Montreal, Canada)        

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In truth, the ability to clean carpets depends as much, if not more, on nozzle and brush design, than on suction or airflow.

You can have the most powerful suction or "windy" airflow, but if the powerhead, or attachment or tool is designed poorly, the sucking power is really irrelevant.

Take my Hoover WindTunnel example from above. Consumer Reports has consistently rated the "air-flow through the hose" on all top-rated versions of the Hoover Self-Propelled WindTunnel as "excellent" - a score that is rarely given to uprights or canisters. But this powerful airflow is useless for upholstery or drapes using the upholstery nozzle provided. There is no suction relief valve, and the design of the plastic tool is so cheap that it constantly causes suction lock on anything you are trying to clean - the plastic edges are so sharp that it actually "scrapes" the fabric and can damage it.

Another example is any Eureka Dial-A-Nap F&G Bag Fan First Upright. Many of these Eurekas are excellent at deep carpet cleaning. But if you attach the optional hose for above-the-floor cleaning, the suction and airflow are very, very weak. Therefore, these Eurekas are cleaning the carpets well because of the brush and nozzle and air passage design through the main unit, not because of the level of suction or airflow provided.

Post# 168742 , Reply# 11   2/7/2012 at 21:08 (2,975 days old) by Sanifan ()        
Sort of getting it....

Good info, guys. I'm still wrapping my head around it.

I guess it would help if there was a formula that described the relationship between suction and airflow.

I mean, I can see how a 4" dia hose could support a lot of airflow. In order to also get a lot of suction from this hose the motor would have to move a LOT of air (I mean, although a lot of air moves through a big duct, unless a lot of air is being moved there will not be enough air velocity generated to pick up debris).

Compare that to a 1" dia hose. In order to get the same volume of air moving through as the 4" dia hose (same amount of airflow), the air would have to move at a much higher velocity through the smaller hose. Does that increased velocity equal more suction?

So for an equal amount of airflow, would a smaller diameter hose generate more suction because of the increased air velocity? Is that the relationship? It seems there should be an equation that describes the relationship between the hose diameter, the volume of air being moved (airflow), the velocity of the air, and the amount of suction generated (pressure?).

I'm sure all this is basic to an engineer or physicist, but for us lay folks, it takes some thinking.

Also, can suction be described in terms of pressure (negative pressure)?

Anyway, just thinking out loud.

Yes, I agree with the excecution of the tools. Suction lock kills whatever good is happening with the machine.

Post# 168743 , Reply# 12   2/7/2012 at 21:14 (2,975 days old) by kenkart ()        
The best all around!

Was either the Apex Strato Cleaner or the Dual Deluxe Sunbeam, these used a large single fan shaped like a flying saucer, being one fan, there was much less restriction for maximum airflow, and having the fan tapered to the edges, it was able to produce more sealed suction than two fan machines, the result being, a Baird Airflow Meter indicator would be pulled all the way to the very end, while a Electrolux or Filter Queen would pull it about half way, with a suction gauge the Sunbeam will pull over 80 inches and the apex close to 90, unbeatable by most machines today, but in the late 50s,no contest! Consumer Reports said that the Strato Cleaner had the highest suction ever seen on any vacuum any time they reported on it.

Post# 168783 , Reply# 13   2/8/2012 at 01:05 (2,975 days old) by pr-21 (Middletown, OH)        
Aerus has the same airflow problem

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When I bought the new Aerus Guardian Ultra with the more powerful motor, it seals the tools to drapes, upholstery, etc. The suction relief vent was usless for that much suction power making the airflow unusable. If you were only using it on carpet that would be a different story....I ended up giving it to my nephew. Hopefully Aerus will correct this and then I will get a new one. Very frustrating......



Bud Mattingly


Post# 168789 , Reply# 14   2/8/2012 at 04:15 (2,975 days old) by beerad (Beautiful Vancouver BC)        
my filter queens..pull

between 85 and 90.

Post# 365234 , Reply# 15   1/17/2017 at 12:31 (1,169 days old) by ronni (USA)        

Better late than never! Here's a link that explains the science behind vacuum cleaner suction and airflow in an understandable way:

Company Info.: Cana-Vac Systems Inc. was founded by Leonard Budd in 1970. It is Canada's largest central vacuum manufacturer with a combined manufacturing space totaling over 3.5 football fields.

Post# 365236 , Reply# 16   1/17/2017 at 13:03 (1,169 days old) by Kirbysthebest (Wichita, KS)        
Thank you for posting

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Very good information.

Post# 365240 , Reply# 17   1/17/2017 at 14:31 (1,169 days old) by ronni (USA)        

You're welcome.

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