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  • Vacuum pumps suck!!!

    Alrighty...give me your thoughts on sizing vacuum pumps. As we all know, vacuum pumps are sized according to how much volume of a gas they will remove per minute (cubic feet per minute or just cfm). This is normally stamped on the nameplate. Vacuum pumps that are too small will take longer to de-gas and dehydrate the system, where as one that is too large will drop internal pressure too fast and may cause moisture to freeze in the system - hence not being able to remove it. I have seen various sizing charts for vacuum pumps that match them up with various tonnages of hvac equipment, but they always differ. I was taught long ago to size a vacuum pump by squaring the cfm. Example - a 3 cfm pump would be good for equipment up to 9 tons. What's your thoughts? Any info would be great.

    Later, jonesy

  • #2
    Re: Vacuum pumps suck!!!

    Originally posted by JONESY View Post
    I was taught long ago to size a vacuum pump by squaring the cfm. Example - a 3 cfm pump would be good for equipment up to 9 tons. What's your thoughts? Any info would be great.

    Later, jonesy
    I was taught the same thing. I use a jb 3cfm platinum pump. I've never had ice freeze ups yet. I remove the cores and use a jb zepplin 4 hose setup. The 3/8 vacuum hose helps out imo and I regularly change out the gaskets. I used to change hoses regularly until I learned about changing the gaskets. If the hoses aren't cracking, try changing the gaskets before you trash the hose. Check out ritchie's super evac system, very fast pumpdown. What kind of micron gauge do you use?
    Buy cheap, buy twice.

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    • #3
      Re: Vacuum pumps suck!!! Bigger is better?

      We have always used 5 cfm and 6 cfm pumps and never had any problems.
      For the cost difference from the smaller ones, I like to have the capacity.
      I don't enjoy standing around looking at a vacuum gauge, waiting for it to tell me good news...

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      • #4
        Re: Vacuum pumps suck!!!

        I have always used a 6cfm pump for pretty much everything without any problems so far. On large systems I have even used a pair of 6 cfm pumps but thats because I have no patients at all.

        Is it considered bad form to bring a chaise lounge when vaccing a system down? How about a cooler full of beer?

        Why don't they make micron gauges with a pager built in so you can have lunch or something?
        sigpic

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        • #5
          Re: Vacuum pumps suck!!!

          Do you guys use solienoid valves on your vacuum pumps in case you lose power? I met one guy who did that and I've seen it in books but have never done so.
          Buy cheap, buy twice.

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          • #6
            Re: Vacuum pumps suck!!!

            Nope, seems like a winner though.
            sigpic

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            • #7
              Re: Vacuum pumps suck!!!

              I have yet to find a good micron gauge that holds up for any length of time. The best one I ever used was an old Robinair analog style that you actually dialed in the micron setting you wanted. I have never used a solenoid valve on my vacuum pump - but I can see where it would be beneficial. Wire it in parallel to the switch on the pump and that would take care of any problems if you had a power loss. At school I use JB and Robinair brand pumps. I have 9 pumps and I have the students change the oil in them once a year and oil the motor bearings when I teach a lesson on evacuation & dehydration. What about the gas ballast feature on pumps? Any of you guys ever open it up and use it?

              Later, Jonesy

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              • #8
                Re: Vacuum pumps suck!!!

                I always open the gas ballast upon intial startup. I use ritchie thermistor style micron gauge. Solid as a rock but I do treat it gingerly based on cost. I used JB's micron gauge once and it broke after 2 uses. Upon further research, I discovered other people found out they're crap too.
                Buy cheap, buy twice.

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                • #9
                  Re: Vacuum pumps suck!!!

                  I'd be lost without my Ritchie analog vacuum gauge. I bought it new on Ebay a couple years ago for $60 and some change. The wholesaler at the time didnt have 1 in stock, but they did have a listing in their computer, and it was $220. My vacuum pump is a 10 year old JB 5 cfm. The oil gets changed when it gets slow. I think doing a nitrogen purge on every system cuts down on the evacuation time anyway.

                  Andy

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