Page 2 of 2 FirstFirst 12
Results 14 to 21 of 21
  1. #14
    Join Date
    Mar 2018
    Location
    USA, PA
    Posts
    16
    Post Likes
    Thread Starter
    Quote Originally Posted by crazzycajun View Post
    If all the company did was pay for your epa card that’s not training. They set you up for failure you have a butt load of learning ahead of you. The fact that they have a guy that knows the equipment but aren’t willing to pay for his knowledge tells me a lot about this company run forest run
    VERY VERY TRUE! this operation is a **** show. if it wasn't for me they would have wasted thousands of dollars on dum ****.
    we got bought out twice now. management is fleeing. i got no worries finding another job so ill take what experience i can.

  2. Likes crazzycajun liked this post
  3. #15
    Join Date
    Dec 2015
    Location
    Michigan
    Posts
    28
    Post Likes
    Quote Originally Posted by JohninJoliet View Post
    I recommend referring it to a contractor with retrofit experience. There's a lot going on here. From the OEM set up, the cap length and diameter may or may not have changed. You are never going to achieve OEM specification as 408A requires more volume in the condenser to reject heat than 502. As you have seen, it gets close, though.

    The condition you describe indicates a loss of refrigerant with fractionation occurring. The solution is to recover the charge and then pressurize the system to 200 PSIG with Nitrogen. Grab your leak soap and rags and go looking, especially at the compressor discharge line, access valves, flare fittings, and cap tubes. Insulation usually needs to be removed.

    After the leak is repaired - if repairable, the filter drier needs replacement, all of which requires Nitrogen purge. Re-pressurize to 200 PSIG which must be held for 2 hours. Evacuate the system to 350 microns, must hold and not rise over 600 microns (this can take several evacuations broken with Nitrogen) over 10 minutes. This is critical on low temp cap tube machines, as molecular water vapor will freeze in and restrict the cap tubes.

    The system volume needs to be calculated as closely as possible to get the correct charge weight from 502 to 408A.

    The system will need to be reinsulated with attention to detail before evacuating and charging as exposed metal will build frost quickly.

    Good Luck!
    Very sound advice! I would also look into how old that compressor is. The
    date of manf. is on the tag. Hermetic compressors used in extended medium temp.
    can go 10+ years of use but tend to just fade in performance as time goes by.

    Amp the compressor out on a pull down. If you have similar units to compare
    your results with then you can judge if your in the ballpark.

    R-408a? Who uses that stuff. R-404a and R-507 with poe oil is the logical option.
    Been retrofitting R-502 equipment from 1994 ish days. Lean towards R-507 in the
    future. R404a has R-134a blend at 5% and can cause a hemorrhoid in the earth's
    atmosphere and has been deemed unsafe for humans.

    Anyone else notice the new classes of refrigerants coming out. Vendors are
    not happy! Changing refrigerant every 20 years is all about the money folks.

    R-11
    R-12
    R-22
    R-502
    Mineral oil
    These covered about 90% of refer or A/C stuff
    The good old days.

    12 years to retirement tick tock........

  4. #16
    Join Date
    Jan 2010
    Posts
    13,385
    Post Likes
    The temperature glide on R408a is 1 therefore fractionation is moot.

  5. #17
    Join Date
    Aug 2006
    Location
    Mixing oil and fire with a big spoon.
    Posts
    6,307
    Post Likes
    Quote Originally Posted by VTP99 View Post
    The temperature glide on R408a is 1 therefore fractionation is moot.
    It isn’t moot if it is sitting around and not operating.
    Don't step on my favorite part of the Constitution just to point out your favorite part.

    Political Correctness is forced on you because you have forgotten decency.

    Technically speaking, they are all heat pumps.

  6. #18
    Join Date
    Jan 2010
    Posts
    13,385
    Post Likes
    Quote Originally Posted by dart289 View Post
    hello all,

    so i have a unit that seems to be running as good as the others under normal conditions. but is close to being out of spec (2c set point, 8c max temp). for testing i run the unit at full speed and max cool. normally i can get -10c or more. this unit only gets me -5 !
    Doesn't sound like it's been sitting around idle.
    I'll add this for a good read.
    Attached Images Attached Images
    Last edited by VTP99; 04-03-2018 at 11:46 AM.

  7. #19
    Join Date
    Mar 2018
    Location
    USA, PA
    Posts
    16
    Post Likes
    Thread Starter
    Quote Originally Posted by SumZero View Post
    Very sound advice! I would also look into how old that compressor is. The
    date of manf. is on the tag. Hermetic compressors used in extended medium temp.
    can go 10+ years of use but tend to just fade in performance as time goes by.

    Amp the compressor out on a pull down. If you have similar units to compare
    your results with then you can judge if your in the ballpark.

    R-408a? Who uses that stuff. R-404a and R-507 with poe oil is the logical option.
    Been retrofitting R-502 equipment from 1994 ish days. Lean towards R-507 in the
    future. R404a has R-134a blend at 5% and can cause a hemorrhoid in the earth's
    atmosphere and has been deemed unsafe for humans.

    Anyone else notice the new classes of refrigerants coming out. Vendors are
    not happy! Changing refrigerant every 20 years is all about the money folks.

    R-11
    R-12
    R-22
    R-502
    Mineral oil
    These covered about 90% of refer or A/C stuff
    The good old days.

    12 years to retirement tick tock........
    Thanks for the info!

    the why behind 408A one it was recommended. and two it seems to do a better job under max load. but i never played with 404A so it could have been the other guy trying to make more on mark up? i heard its better and they are very willing to pay for it sooo why not?

    you also made a good point with the compressor im fairly sure it checked good. i have a print out on the compressor but theirs no data tag other then the model

    as of now i have it back together and its got another issue wont stay running (not hvac related). so now i gota go over the computer boards kinda got it on the back burner working on other units.

    thanks again!

  8. #20
    Join Date
    Mar 2018
    Location
    USA, PA
    Posts
    16
    Post Likes
    Thread Starter
    Quote Originally Posted by jayguy View Post
    It isn’t moot if it is sitting around and not operating.
    units run 5 days a week on ave 17 hours a day.

    59 units with several tonns of hvac cooling the room

  9. #21
    Join Date
    Mar 2008
    Location
    kansas
    Posts
    633
    Post Likes
    Quote Originally Posted by dart289 View Post
    Thanks for the info!

    the why behind 408A one it was recommended. and two it seems to do a better job under max load. but i never played with 404A so it could have been the other guy trying to make more on mark up? i heard its better and they are very willing to pay for it sooo why not?

    you also made a good point with the compressor im fairly sure it checked good. i have a print out on the compressor but theirs no data tag other then the model

    as of now i have it back together and its got another issue wont stay running (not hvac related). so now i gota go over the computer boards kinda got it on the back burner working on other units.

    thanks again!
    the reason 408a was used is them days 404a retrofit was more time consuming hence exspense. You recovered the refer changed driers evacuated and charged with 80% of the charge and dialed it in from there hence cheaper. That was when r22 was cheap a major component of 408.
    Honeywell you can buy better but you cant pay more

    I told my wife when i die to sell my fishing stuff for what its worth not what i told her i paid for it

Page 2 of 2 FirstFirst 12

Tags for this Thread

Posting Permissions

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

Related Forums

Plumbing Talks | Contractor MagazineThe place where Electrical professionals meet.