Results 1 to 14 of 14
  1. #1
    Join Date
    Feb 2010
    Location
    England
    Posts
    32
    Rep Power
    0

    A friend of mine told me...



    ...that I could build a vacpump using a domestic fridge compressor. My questions are:

    1) True or false
    2) Good idea or not. If not, why?

    Any other points you wish to raise, please do. I am learning all the time here & find these early stages of my refrigeration life challenging but very interesting so please be gentle with me.



  2. #2
    Join Date
    Apr 2001
    Location
    New Port Richey, Florida - USA
    Age
    78
    Posts
    5,072
    Rep Power
    34

    Re: A friend of mine told me...

    1. True
    2. Better than nothing, not nearly as good as a real vacuum pump.

  3. #3
    Join Date
    Feb 2010
    Location
    England
    Posts
    32
    Rep Power
    0

    Re: A friend of mine told me...

    Hi Gary.

    I was just reading your refrigeration 11 thread & find your post easy to understand & informative. Keep up the good work.

    If I were to try to build one using a compressor, I assume that I would need one to use on R134a & another for R600a or would that not be strictly required?

    Also, any idea what sort of vacuum this method would achieve or is this like asking how long is a piece of string?

    Many thanks.

    Bobby.

  4. #4
    Join Date
    May 2008
    Location
    U.K.
    Age
    62
    Posts
    73
    Rep Power
    16

    Re: A friend of mine told me...

    Surely a vacuum is a vacuum? But hey, I've heard that the old compressor can be used as a vac pump. You'll also need a gauge to measure the vacuum and tightness of the system. Good luck.

  5. #5
    Join Date
    Apr 2001
    Location
    New Port Richey, Florida - USA
    Age
    78
    Posts
    5,072
    Rep Power
    34

    Re: A friend of mine told me...

    Quote Originally Posted by Bobby Drake View Post
    Hi Gary.

    I was just reading your refrigeration 11 thread & find your post easy to understand & informative. Keep up the good work.

    If I were to try to build one using a compressor, I assume that I would need one to use on R134a & another for R600a or would that not be strictly required?

    Also, any idea what sort of vacuum this method would achieve or is this like asking how long is a piece of string?

    Many thanks.

    Bobby.
    I have never worked with R600a, so I'm not certain if that would be different.

    A compressor might get to 15-20 inches of vacuum, whereas a real vacuum pump will get well over 29 inches, down into the microns. There is really no comparison... but as I said, it is better than nothing.

    Way back before vacuum pumps were common, we used fridge compressors and did triple evacuations. It worked reasonably well... on the other hand, as soon as vacuum pumps became readily available, everyone ran out and bought one.

  6. #6
    Join Date
    Feb 2010
    Location
    England
    Posts
    32
    Rep Power
    0

    Re: A friend of mine told me...

    Hi Gary.

    The only reason I asked about different compressors for different refrigerents is to avoid any potential contamination of the system being vacced, say the system being repaired is R134a & if you are using an R600a compressor or vice versa. Or am I worrying over nothing?

  7. #7
    Join Date
    Apr 2001
    Location
    New Port Richey, Florida - USA
    Age
    78
    Posts
    5,072
    Rep Power
    34

    Re: A friend of mine told me...

    Quote Originally Posted by Bobby Drake View Post
    Hi Gary.

    The only reason I asked about different compressors for different refrigerents is to avoid any potential contamination of the system being vacced, say the system being repaired is R134a & if you are using an R600a compressor or vice versa. Or am I worrying over nothing?
    I wouldn't think that would make any difference. As soon as you start vacuuming, the system refrigerant vapor flushes through the compressor.

  8. #8
    Brian_UK's Avatar
    Brian_UK is offline Moderator I am starting to push the Mods: of RE Site Moderator : and general nice guy
    Join Date
    Mar 2001
    Location
    Dorset
    Age
    76
    Posts
    11,192
    Rep Power
    60

    Re: A friend of mine told me...

    Quote Originally Posted by Bobby Drake View Post
    Hi Gary.

    The only reason I asked about different compressors for different refrigerents is to avoid any potential contamination of the system being vacced, say the system being repaired is R134a & if you are using an R600a compressor or vice versa. Or am I worrying over nothing?
    Think of which way the molecules are being drawn, from the system via the pump to atmosphere.

    Backwards contamination should not occur unless you have a power failure and do not have a non-return valve in the line.
    Brian - Newton Abbot, Devon, UK
    Retired March 2015

  9. #9
    Join Date
    May 2007
    Location
    Scotland
    Posts
    327
    Rep Power
    17

    Re: A friend of mine told me...

    You should change the oil regularly in any vac pump, this may be tricky of you are using a small hermetic compressor.

    Hydrocarbons require a special safe handling certificate here in the UK and I think i'm right in saying you should be using dedicated equipment only.

  10. #10
    Join Date
    Aug 2006
    Location
    england
    Age
    49
    Posts
    3,874
    Rep Power
    46

    Re: A friend of mine told me...

    Get a proper vac pump if you are working for other people, they rightly expect things to be done correctly when calling in a professional.
    If its some project for yourself then maybe a compressor would do but personally i'd still use a vac pump, especially on capiliary systems.

    Jon

  11. #11
    Join Date
    Jul 2008
    Location
    wet coast B. C.
    Age
    76
    Posts
    123
    Rep Power
    16

    Re: A friend of mine told me...

    The first refridgeration tech. I worked with had used a fridge comp. as a vaccumn. pump. He told me that the comp. did not last very long in this service. I would think that the comp. probably would overheat. Thus leading to its failure. C.D.
    NH3 for me

  12. #12
    Join Date
    Feb 2010
    Location
    England
    Posts
    32
    Rep Power
    0

    Re: A friend of mine told me...

    Thanks for the replies guys. I was pondering wheather to make one up just as a project really. I probably won't bother as it is probably a load of aggro for little benefit.

  13. #13
    Join Date
    Feb 2001
    Location
    Doncaster, England
    Posts
    199
    Rep Power
    25

    Re: A friend of mine told me...

    'If you use a compressor as a vac pump, - hermetic compressors are piston type compressors and there will always be a gap at the top of the cylinder, even when the piston is at top dead centre. So this gas will never be pumped out of the compressor.

    Therefore you can never achieve a vacuum with a low enough pressure to boil off any water in the system.

    Typically water does not start to boil until you get down below 20 Torr (that is the pressure required to get water to boil at 20°C).

    If the temperature is lower then the pressure has to be lower.

    So get a vac pump!!!!!!!
    Tony

  14. #14
    Join Date
    Feb 2010
    Location
    England
    Posts
    32
    Rep Power
    0

    Re: A friend of mine told me...

    Quote Originally Posted by Tony View Post
    Typically water does not start to boil until you get down below 20 Torr (that is the pressure required to get water to boil at 20°C).

    If the temperature is lower then the pressure has to be lower.
    I have learned someting new there. Thanks for the info.

    Quote Originally Posted by Tony View Post
    So get a vac pump!!!!!!!
    I think I just might. Cheers.

Similar Threads

  1. Advice needed for a friend
    By marc5180 in forum Training
    Replies: 10
    Last Post: 10-06-2009, 10:56 PM
  2. From me and the mine, to you and the yours...
    By The Viking in forum Chit Chat & Service Stories
    Replies: 6
    Last Post: 23-12-2008, 12:47 PM
  3. finding the net friend: lala
    By Crystal-426 in forum New Technologies
    Replies: 5
    Last Post: 20-06-2008, 02:55 AM
  4. Trying to help a friend out ident system
    By The MG Pony in forum Air Conditioning
    Replies: 1
    Last Post: 09-04-2007, 08:37 PM
  5. Your new friend
    By S.K.VARDE in forum New to RE
    Replies: 4
    Last Post: 21-06-2006, 09:07 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •