The Ideal suction AIr Flow numbers for a Vacuum

[gregvacs28]

Has anyone/entity put together what the ideal suction range is for vacuuming?


 


What is the least (not good) and what is TOO MUCH (also not good) 


 


Obviously those old canister vacuums from the 70s with a meager 1/4 or 1/2 h.p. motor were just not adequate. 


 


But then the Hoover Celebritys from the 70s with the 3.7 h.p. proved to be too much.


 


I seriously found a Sears Central Vacuum from the late 60s with a 1 h.p. motor in it.  That seems laughable.  almost impossible.


 


Also, different vacuum systems need different motor requirements.  


 


A bot, an upright, a stick, a canister, a carpet cleaner, a shop vac, a central vac.


 


Basically, the shorter the distance from the cleaning surface to the dirt container the less powerful the need for a motor. it would seem.


 


Too much suction and one ends up with air lock with using attachments, possible damage to flooring and surfaces, tools and hoses wearing out prematurely, burst bags, excess dust getting blown around, and possibly excess noise pollution.  Plus wasted electricity.


 


Too little and well, we know how bad that is.

 

[crazykirbydude]

Anything under 80 CFM is not great. I think the upper limit would be when the vacuum is so strong that it becomes extremely hard to move.

 

[mike811]

Everything over 80 cfm from the nozzle is good in my opinion.
But when the number starts to go near 90 cfm from the nozzle that causes hard to push problems.
Here is list of my canisters nozzle airflow numbers.
Lux Royal D790, Nilfisk GM80 and Miele C3 are pushing the limits what my Sebo ET1 powerhead can handle on my big medium pile living room rug.
My Kirby G6 with 126 cfm is easy to push due to the self propelled feature, but my 100 cfm Vorwerk VK135 is very hard to push. Thankfully it has 3-speed motor so I always use the medium power.
And my canister suction numbers vary (from the hose end) from 78 - 104" of water lift. Not nearly as important than airflow.

 

[vaclab]

After Testing And Logging Numbers For A Few Years...

I have some general answers. As usual, your mileage may vary but assuming fairly typical scenarios, here we go:

For non-power assisted uprights with average size nozzles (say 12" x 2")
90 CFM paired with 30"-40" of suction

For non-power assisted canister PN's with average size nozzles (say 12" x 2")
80 CFM paired with 30" of suction

For power assisted uprights, essentially anything that makes the PN reasonable to push. For example, a Kirby can easily handle pile carpet with 150 CFM paired with 30"-ish suction.

CFM density is also important.
If you have a density larger than 4 CFM per square inch (without a power drive), be prepared to exert yourself greatly unless your brushroll is so aggressive that it can pull the vacuum along all by itself (Royal).

WHAT DOESN'T WORK IS THIS:
Anything with higher suction than airflow (measured at the nozzle). For example: a stick vac with 50 CFM and 110" of suction. The pile clamping effect is too high, the air speed is too low and the PN can easily stall.

Little tiny motors with 1" fans usually produce a ton of suction, but poor airflow. If you want to move the dirty air, you need a fan of some size, say 5" or larger.

Bill

 

[vaclab]

HP Ratings Are Also Mostly False

If anyone claims more than 2 HP (for US machines, unless they specify a dedicated circuit is required).

1 HP = 746 Watts
2 HP = 1492 Watts

Standard 15 Amp circuit @ 120 Volts = 1875 Watts

You said you saw 70's canister vacs that were rated at 1/4 or 1/2 HP. That would mean 187 Watts and 373 Watts respectively. I've personally never heard of an under 200 watt canister vacuum sold in the 1970's.

A Hoover Celebrity couldn't run at 3.7 HP because that would mean 3.7 A x 120 V = 2760 Watts, which would require a 23 Amp 120 Volt circuit. Any rating more than 2 HP (continuous load) is based on what can be called "peak surge current", which is a very short (a few milliseconds) turn on power spike.

Shop-Vac and other companies have insane false ratings like "6.5 Amps" but if you look closely, they are required by the FTC to publish the actual continuous load rating which is MUCH lower and reflects the true running power of the vacuum.

https://www.shopvac.com/product/sho...uum-with-svx2-motor-technology-catnum:5801611

That ShopVac is rated 6.5 HP** with a REAL power usage of you guessed it, 12 Amps or 1440 Watts, which is 1.93 HP.

Bill

 

[vacfan1982]

It's not high suction and low airflow and it's not high airflow and low suction. A balance of airflow and suction will give the best performance.
Airflow picks up the dirt and suction keeps the airflow strong through the resistance of the carpet.

 

[vaclab]

Mark, That Would Be An Incorrect Assumption

Equal airflow and suction at the PN is a disaster. I have a plethora of tests easily proving this.

Once the airflow has arrived at the PN, the suction almost doesn't matter at all. For example take my Kirby DS80, sporting a whopping 125 CFM paired with a minuscule 12" of lift. Result: 76% baking soda pickup on medium pile carpet.



Now compare that to the Dyson DC65 at 40% pickup although the Ball Animal 2 head increases that score to 62% pickup. The Dyson DC65 is a more "balanced" machine with about 60 CFM and 60" of lift.

Of course what seals the usable carpet airflow deal are these two videos:

The Kirby Avalir pulls about 57 CFM


The Dyson DC65 pulls about 26 CFM


And then there's my countless "flour under the carpet tests" showing that lower CFM, higher suction bagless machines mostly fail miserably when attempting to pull anything through the carpet pile.

Manufacturers realized long ago that attempting to put something like 80 CFM and 80" of lift at the PN would create non-pushable PN. Blackheart measured a Lux Guardian Platinum and found the hose suction dropped from 100" down to 32" at the PN. That's almost a 70" loss. This was intentional because with 81 CFM, the PN is difficult enough to push.

Bill

 

[vacfan1982]

I didn't say equal.What I mean is the maximum amount of suction to avoid clamping but to keep the airflow strong through the resistance of the carpet. (Carpet on the floor not on top of a box with a hole in) Putting a piece of carpet on top of a box is not the same as the carpet on the floor. You don't have a gaping hole in your floor do you, (if you do you need to call the builders in ) so there's more resistance on your flooring. You need suction to overcome the resistance and to keep the airflow strong.

Your tests are fun to watch I enjoy them but as to their accuracy that is debatable [this post was last edited: 3/4/2020-23:50]

 

[vaclab]

To Quote Your Previous Statement

You said:

"It's not high suction and low airflow and it's not high airflow and low suction. A balance of airflow and suction will give the best performance."

Since you said neither high nor low AND neither low nor high, the only ratio left to consider would be a "balance", which can be interpreted as "equal". If you meant some specific ratio, like one third, two thirds, one quarter, etc., you should have been more specific.

The only way to measure resistance through a carpet is the way I measure it. When carpet installed on the floor, there is no way to measure it. If you are unable to place a measuring device directly below the carpet, there would be no way to take any readings through the carpet.

The numbers I've previously mentioned give the general ratio (high CFM to low suction) of around 4:1 or 5:1 for flow through medium pile carpets. More dense carpet may indeed require less suction to avoid clamping.

So broadly speaking, my medium pile starts to become annoying around 30". I have several PNs that have around 40" and they become quite "sticky", especially when the CFM density becomes too high. A newer Kirby is actually un-pushable with 30" if the Tech Drive is off, so that would mean you would have to lower the CFM by about 30 and/or lower the suction to 20" if you wanted to use it in neutral.

And I've also been very happy seeing other YouTubers performing similar tests with different carpets and I can see a general scaling up or down of the results, which proves my points quite readily.

Bill

 

[vacfan1982]

Yes you're correct you can't test the resistance with the carpet on the floor. That is my point. You're tests cannot be truly accurate as you are not able to test in the way the cleaner is actually used.

If you used the Kirby on non porous carpet you would get different results.
Non porous carpet is becoming more and more popular at least here in the UK where you rarely see anyone using a Kirby.

Alex ( Performance Reviews) gave his carpet a good going over with his Kirby he then followed with his central vac and picked up a LARGE amount that the Kirby left behind.

You love your Kirby's they work for you and I'm very happy for you. [this post was last edited: 3/5/2020-02:33]

 

[vaclab]

Still Believing Last Vacuum Wins Comparos?

Remember this video I made a few years ago? I can take ANY two vacuums and claim "last vacuum wins." Watch a cheap $30 Bissell beat a Kirby here:



Obviously, a last vacuum wins test cannot give meaningful results. Here's how the Math works, especially when proper measurements aren't taken.

Z = Amount of Carpet Dirt
X = Vacuum #1 Pickup (First Vacuum)
Y = Vacuum #2 Pickup (Last Vacuum)
R = Any Remnant Dirt That Can't Be Pickup Up

We also need to remember that no vacuum picks up 100%, even with an insane number of passes as this video shows:



To make things simpler, let's ignore the "R" variable for now to make the Math more recognizable, but realize "R" can still be a significant amount.

So X + Y = Z. The reason why non-measured tests are false is because even if you weighed (or merely showed) a bunch of dirt pickup from Vacuum #2 (Variable Y), the other two variables (X & Z) remain unknown.

How do you solve this equation X + (30 grams from Y) = Z? This is unsolvable and therefore invalid. You must know at least two out of three variables.

As a degreed Mathematician who has taught in High School and College, probability, statistics and proper testing/proof methods are my strong suit. I started my YouTube channel to properly debunk various so-called "tests", especially when no measurements are taken.

Bill

 

[vacfan1982]

Very good explanation but...... I expect it to pick up some dirt after the Kirby but the amount was huge! How do you explain that?
My explanation is you need suction to keep the airflow high through the resistance of the carpet.

We aren't going to agree on this subject are we so let's just agree to disagree

PS I have degrees too but I don't like to blow my own trumpet like some people. [this post was last edited: 3/5/2020-11:45]

 

[vacfan1982]

Even if you could prove beyond doubt that the Kirby could pick up a few more percentages of dirt than other high end cleaners I'd sacrifice that for the ease of use of my central vac and my fabulous Vorwerk VK150 which has become my all time favourite upright. A truly fantastic cleaner [this post was last edited: 3/5/2020-11:53]

 

[vaclab]

You Said...

"My explanation is you need suction to keep the airflow high through the resistance of the carpet."

I've never disagreed with that and in fact, I've made several videos proving that. Some have used bagless cyclones to as proof and one even used hose length as proof.



You may be confusing absolute value with a ratio. In my Dyson DC65 example above, that machine lost 58-26=32 CFM or 55%. The Kirby Avalir lost 150-57=93 CFM or 62%. Since the Kirby has less nozzle suction, it lost a higher percentage (ratio) of airflow than the Dyson. BUT, the remaining airflow is still much higher (57 vs. 26).

The higher remaining airflow through the carpet wins. Most direct air machines start out with very high airflow, lose a high percentage of it, but still come out on top with the remaining absolute value.

Have a nice day!

Bill

 

[vacfan1982]

Maybe you're correct and I've got it wrong but I still stick to what I said in reply #12.

You have a nice day too

 

[vacfan1982]

Bill your testing shows how well the Kirby cleans on porous carpet, I would like to see you test the kirby with a non porous carpet as these carpets are becoming more popular.

Modern carpets have a protective membrane.

SpillStop provides a specialty backing that prevents moisture from reaching the subfloor, protecting it from any mold. SpillStop works by keeping liquids sitting on the surface of the carpet’s backing where it can easily be soaked up.[this post was last edited: 3/7/2020-01:05]

 

[tolivac]

You can use the Kirby on sealed carpet-You have to adjust it differently-The nozzle has to ride slightly higher than on unsealed carpets.Just enough where the brush can touch the carpet---that's it!IE adjust to where you hear the brush hitting and no more-unlike the one step lower with unsealed carpets.

 

[vacfan1982]

Oh yes it will work but the performance will not be as good as on porous carpet.

I'd like to see Bill carry out tests so we can compare the results and compare it to other cleaners on non porous carpet.

 

[mike811]

Well my sand in the carpet test shows that G6 with the stiff oblique brushroll
performs fantastically on the sealed rug.
Pick up was 90% and with only two passes
Other machines performed like this:

Kärcher CV36/2...........94%
Sebo Felix.....................79%
Vorwerk VK135............77%
Shark NV500................73%
Shark NV340................67%
Electrolux Precision.....56%
Dyson DC40 MKII.......36%