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Question for Donald (Expert advise needed)

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  • Question for Donald (Expert advise needed)

    Donald, i've been reading your blogs for a few years now, and I must confess, I learned pretty much everything I know about vacuum calculations right from your own blogs, so I want to thank you for indirectly educating me. Now, heres my quere, and I think I might already know the answer but wanted to run it by those who are much better schooled in vacuum characteristics than I am. Ok, I have 4 brand new lamb 117500-12 vac motors. all are the large 7.2" 3 stages motors. Each motors specs out at 145.9" H20 and 102.5 CFM, and 530 air watts. Now after doing the calculations for 2 series pairs in parellel I get 240.7" H2o lift(or 17.8" Hg) and 184.5 CFM for a total of 44,409 total vac units. Now, if I put all 4 motors in air parellel, I get 145.9" H2o lift (or 10.8" Hg) and 410 Cfm for a total of 59,819 total vac units. Thats an increase of 15,410 vac units above the series/parellel set up. Now I know that this should perform better in theory, but my question here is, would 145.9" of water lift be enough to run 200' of hose? By the way, if I run all 4 in air parallel, then only 3 motors will be in the truck and the fourth motor will be used as a booster down line behind the wand. Will I have enough lift at the wand, even at the actual .75" oriface? Any thoughts and helpful comments are appreciated. I've already been told by one distributer from another board that the way to go is in series parallel because of some graph that lamb uses to chart the system in series parallel. But I can't ignore the fact that there is a distinct increase of total vac units with the system piped in air parallel. So his answer to my question goes against everything i've learned here about vacuum theory and i'm very confused now. Please shed some light on this for me. Thanks.

  • #2
    Vacuum systems

    First of all four vacuum motors, no mater how they are configured with operate 200 ft of 2" hose. I mention 2" hose because the maximum CFM you can operate on 1.5" ID hose is 200 cfm. You also have to remember that once you are cleaning, the carpet wand on the carpet will reduce the cfm by half and the inches of lift by half. What we are really looking for is the best inches of lift and CFM in the head of the wand durring cleaning. With that said, as you ask for more CFM to be pulled through the head and around the lip of the wand this naturally increases the inches of lift in the head of the wand. (Read this previous sentence again) I believe that a all parallel configuration would probably dry carpets slightly faster than series/parallel. In conclusion, I agree with you.