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  1. #1
    Join Date
    Jan 2012
    Location
    Oregon
    Posts
    101

    I need to charge a r408 system

    I have a r 408 system that is low on charge. High superheat, low sub cooling, low head pressure and pretty close to normal low side pressure. Is it best to charge by sub cooling or by the sight glass? Thanks Rusty

  2. #2
    Join Date
    Jan 2010
    Posts
    6,298
    Don't worry about sub cooling on a refrigeration system. The sight glass needs to be full. Don't rush it though, let the box pull down some first.

  3. #3
    Join Date
    Jan 2012
    Location
    Oregon
    Posts
    101
    So sub cooling isn't a factor?

  4. #4
    Join Date
    Jan 2010
    Posts
    6,298
    Not really, it kinda is what it is. Now the super heat is where you need to be concerned.

  5. #5
    Join Date
    Jan 2012
    Location
    Oregon
    Posts
    101
    Ok will do thanks.

  6. #6
    Join Date
    Jan 2010
    Posts
    6,298
    What's the possibility of converting it to R404a ? It's a whole lot cheaper then R408. What size system ?

  7. #7
    Join Date
    Jan 2012
    Location
    Oregon
    Posts
    101
    I will get the specs tomorrow and let you know.

  8. #8
    Join Date
    Jun 2013
    Location
    Montana
    Posts
    73
    I don't know if you can convert r408 to 404. But 408 is a replacement for 502

  9. #9
    Join Date
    Oct 2011
    Location
    Chicagoland Area
    Posts
    4,620
    Did you repair the leak?

    MontanaJon, you can convert it. New oil, drier, suction filter, and figure in a changeout of the drier, filter, and cleaning the txv screen after a week of runtime.
    Officially, Down for the count

    YOU HAVE TO GET OFF YOUR ASS TO GET ON YOUR FEET

    I know enough to know, I don't know enough
    Liberalism-Ideas so good they mandate them

  10. #10
    Join Date
    Jun 2013
    Location
    Montana
    Posts
    73
    2sac- just a question but would the condenser be able to handle the load. I have seen old 502 condensers that would handle a negative evap but not if it was 22. Maybe I am not think all the way. *But I did have a concern about the condensing unit.

  11. #11
    Join Date
    Oct 2011
    Location
    Chicagoland Area
    Posts
    4,620
    I have read that 404 will increase capacity when replacing 502 @ low temp but have done a number of retrofits, nothing larger than 5hp, without issue.
    Officially, Down for the count

    YOU HAVE TO GET OFF YOUR ASS TO GET ON YOUR FEET

    I know enough to know, I don't know enough
    Liberalism-Ideas so good they mandate them

  12. #12
    Join Date
    Jun 2013
    Location
    Montana
    Posts
    73
    Thanks for the info 2sac. I will keep that in mind.

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