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Thread: Vacuum pump CFM, does it matter?

  1. #121
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    I've had too many bad experiences drilling out a bigger hole in soft metal. Is that really worth the effort? Seems like splitting hairs. If going through the trouble on a unit I could see adding a larger dedicated evac port on a system.

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  3. #122
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    Quote Originally Posted by skwoodwiva2 View Post
    my Daddy's is bigger than.....

    More flow.
    Plus if you drill the unit access too you get even more.
    Put a access Tee on top when done
    Have you ever figured the conductance speed of those little hoses?
    With those big pumps you have drilling out any fittings is of little significance compaired to the small hoses attached to them IMO

    A 6ft ¾" ID hose will allow for 2.75cfm at 100 microns

    A 6ft 1¼" ID hose will allow 21cfm at 100 microns

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  5. #123
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    Quote Originally Posted by itsiceman View Post
    Have you ever figured the conductance speed of those little hoses?
    With those big pumps you have drilling out any fittings is of little significance compaired to the small hoses attached to them IMO

    A 6ft ¾" ID hose will allow for 2.75cfm at 100 microns

    A 6ft 1¼" ID hose will allow 21cfm at 100 microns
    Do you actually use those spiral hoses in the field or are they just for bench testing? Looking for a faster way to pull down big units 20+ tons

  6. #124
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    It's faster for any size units. I use these on systems that hold ozs.

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  8. #125
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    It's faster for any size units. I use these on systems that hold ozs.[/QUOTE]

    Those are bad azz. Do you have a post on here about how to make those? I've search a little off my phone but haven't found like a full process on them. Thanks

  9. #126
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  11. #127
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    Thank you

  12. #128
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    Had to replace a worn gasket. Here's without the gasket or knurled cap.



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  14. #129
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    so, stupid question, but I’ve always assumed I’d be better off with a 3/8 hose going into a 3/8 access when possible over my 1/2” hose going into a 1/4 access. Thoughts?

  15. #130
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    That's not stupid.

    As with anything; good flow results from lower restriction to flow. So, as far as larger fittings and hoses are less restrictive; they are 'better'.

    What do you mean when you say "I'd be better off" ? What would be better? Faster? Lower? More impressive? <g>

    I have long speculated about pump CFM ratings being almost meaningless at anything below about 25". I have a shelf of big vacuum pumps but 99% of the time I use a little one that is rated at 2 CFM. <g> I haven't weighed it but I would guess it weighs about 5 lbs.

    I always do the piping first and set up the vacuum pump then. All you should be pumping out is fresh dry nitrogen. Then by the time I'm ready-to-start the micron gauge is down. If not; it's always break time anyway. <g>

    PHM
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    Quote Originally Posted by Shreadhead View Post
    so, stupid question, but I’ve always assumed I’d be better off with a 3/8 hose going into a 3/8 access when possible over my 1/2” hose going into a 1/4 access. Thoughts?
    PHM
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    The conventional view serves to protect us from the painful job of thinking.

  16. #131
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    I would use more pumps.

    PHM
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    Quote Originally Posted by Nelsonj22 View Post
    Do you actually use those spiral hoses in the field or are they just for bench testing? Looking for a faster way to pull down big units 20+ tons
    PHM
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    The conventional view serves to protect us from the painful job of thinking.

  17. #132
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    That is what Trenton does on their condensing units.

    PHM
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    Quote Originally Posted by itsiceman View Post
    I've had too many bad experiences drilling out a bigger hole in soft metal. Is that really worth the effort? Seems like splitting hairs.

    If going through the trouble on a unit I could see adding a larger dedicated evac port on a system.

    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  18. #133
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    Quote Originally Posted by Poodle Head Mikey View Post
    That is what Trenton does on their condensing units.

    PHM
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    I started seeing those. Very cool.

  19. #134
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    Quote Originally Posted by Shreadhead View Post
    so, stupid question, but I’ve always assumed I’d be better off with a 3/8 hose going into a 3/8 access when possible over my 1/2” hose going into a 1/4 access. Thoughts?
    Assuming similar hose length the ½" hose would be better if you want less time to a lower vacuum level.
    Appion had a chart that showed times pulling a tank down for ¼, ⅜ and ½ hoses of the same length. All the hoses had ¼ connections at both ends to show the only difference was the diameter of hose.

  20. #135
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    Interesting. Looks like all the photobucket pics are back up.

  21. #136
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    Quote Originally Posted by Poodle Head Mikey View Post
    I would use more pumps.

    PHM
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    Wait what...
    I though CFM didn't matter <g>

  22. #137
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    Well; that's somewhat out of context. <g>

    CFM should, of course, be relative to system size. A 1HP packaged reach-in as versus a 500HP field-piped DX system for radical example. A 100 CFM pump on one would be as silly as a 3 CFM pump would be on the other. <g>

    Let's put it into the perspective of what most people work on - which is almost certainly 5HP or less. For me the time saved by using a larger pump doesn't pay enough for me to haul around a 25 lb. pump, especially up and down ladders or stairs, or to pull and replace schrader cores, or use larger than 1/4" hoses. And most of those things consume at least some time - which of course has to be subtracted from the original savings.

    If my job was to get to a unit, evacuate it, and then leave - sure; then speed would matter to me. But because the evac. is only a smallish portion of my total work, and with efficient tasking I can let the pump run while I am doing something else, I'm just not seeing any real advantage for me. And I sure do like using a vacuum pump that weighs only 5 lb. or so. <g>

    I'm all for everybody accomplishing the job well. If they like big pumps, big hoses, and all the rest: I am all for it too. For Them. For me: three 3 CFM pumps is better all around than is one 10 CFM pump. Especially when working without a helper. <g>

    PHM
    -------



    Quote Originally Posted by itsiceman View Post
    Wait what...
    I though CFM didn't matter <g>
    PHM
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    The conventional view serves to protect us from the painful job of thinking.

  23. #138
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    Oh that reminds me: earlier this week I was digging around in the shop for R-12 and came across two 50' gauge hoses. We used to use them, joined together, with a ball valve at the top end, to evacuate and charge rooftops. Park next to the wall and leave the vacuum pump and refrigerant cylinders right in the truck. <g>

    I've also used them to charge 1500+ lbs. of R-22 into chillers. Left the skid of 125's out in the truck and just ran the hose into the mechanical room. <g>

    Maybe the evacuations went slower than they could have but I don't remember much sitting around waiting on those small jobs. <g>
    PHM
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    The conventional view serves to protect us from the painful job of thinking.

  24. #139
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    Yes I mean which one will pull down to any given micron reading faster

  25. #140
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    .

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