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  1. #1
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    Default Compressr Upgrade Help...

    I have a 3hp, 60 gal, 2 stage, Kobalt compressor. The next compressor up the Kobalt line is a 5 HP, 80gal, 2 stage. I looked up the specs on both machines and found that they use the same pump for both. If, in the future, I decide I want to upgrade my unit, can I swap the 3hp motor for the 5hp motor, with appropriate pulley and will that increase my cfm?

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    Yes, and wear out your pump that much faster.

    The old cast iron, slow rpm pumps like Quincy, Saylor Beall, Kellogg lasted forever if you changed the oil.

    New aluminum higher rpms pumps wear out quickly and get tossed.

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    What is actual pump?

    Was not impressed with anything retail as most are built to price.

    Our 7.5 hp champion has intercooler as well as auto tank drain and cost at mom and pop industrial supply was maybe $100.00 max more than the 7.5 hp unit at TSC.

    your unit as is should last fair time but increasing to larger motor w/o increase cost to operate and decrease life span.

    Review the outputs of both before spending the money as the difference may not be that much for the investment

    Sent from my SAMSUNG-SM-G930A using Tapatalk

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    Quote Originally Posted by darita View Post
    If, in the future, I decide I want to upgrade my unit, can I swap the 3hp motor for the 5hp motor, with appropriate pulley and will that increase my cfm?
    I think if you swapped the motor from 3hp to 5 hp you would not get more CFM. You would get less motor heating if you had long sustained periods of motor on time,
    which means that you are demanding more air from such a small tank like in using it to operate a sand/bead blast booth.

    Something I did some research. Have used the formula myself. Any corrections welcome. Always learning.

    Compressor CFM Calculation
    --------------------------
    1. Drain tank
    2. Record number of seconds to fill tank.

    CFM = G x 0.536 x PSIG / S

    CFM = Cubic Feet per Minute of Compressor
    G = Tank capacity in gallons
    PSIG = Gauge pressure reading on tank
    S = Seconds to fill tank

    example:

    Time to fill tank = 11 minutes and 11 seconds
    PSIG = 155
    G = 120

    CFM = 120 x 0.536 x 155 / ((11 x 60) + 11) = 14.85

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    Quote Originally Posted by Doug W View Post
    Yes, and wear out your pump that much faster.

    The old cast iron, slow rpm pumps like Quincy, Saylor Beall, Kellogg lasted forever if you changed the oil.

    New aluminum higher rpms pumps wear out quickly and get tossed.
    You need to compare the factory pump RPM difference between the 3 H.P. and the 5 H.P. if in fact the pump is run faster on the 5 H.P then yes what ever RPM difference there is will increase CFM proportionately.
    Although Doug W is correct these Home depo type pumps are not commercial pumps and will only wear out faster and there is probably an operational duty cycle before it fails due to heat.

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    Even Ingersoll Rand does the same thing with some of their cheap stuff too. Run the same pump on a larger motor at a higher RPM to increase the output. There is no free lunch, it just puts more wear on the pump, but it will get you more airflow. Also if you look at the amp draw on those big box "5hp" compressor motors, they usually are not actually 5hp anyways.

    You could maybe just bump the pulley size up a bit now, and run it that way until the smaller motor gives out. I wouldn't invest much money into one of them, as those pumps don't have a very long life to begin with in my experience.


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