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  1. #14
    Join Date
    Feb 2004
    Posts
    2,597
    piston metering devices are charged by superheat.

    airflow could be an issue, what is the duct size, including all branch ducts?

    also wet bulb temps?

    i do not see your credentials listed, that would help also.


  2. #15
    Join Date
    Sep 2002
    Location
    South Dakota
    Posts
    6,579
    Originally posted by NormChris



    I goofed up. Will repost.

    Norm

  3. #16
    Join Date
    Jun 2005
    Location
    PA
    Posts
    16
    Originally posted by billva
    i do not see your credentials listed, that would help also.
    Just updated....did not see that it was germane to my query for advice but I'm happy to provide that info. ;-)

  4. #17
    Join Date
    Aug 2002
    Posts
    490
    I agree with the over charge now with the new readings also from the first readings I think you may have had a restriction in the refigerant lines etc.
    but u can check see the condenser coil needs cleaning

    here is what you can do now
    to much refrigerant remove by recovery, some of the refrigerant and check the superheat.
    if the superheat is low remove more refrigerant and if the superheat is high add refrigerant.
    also note high efficient expansion valve systems may require charging by a factory subcooling chart.
    you can also get amp rating for compressor and take amp draw to while chargeing on name plate good backup.

    superheat example not trying to be funny just help
    take low side pressure say 68 psig convert to temp 40f
    now that = temp of line going into evap.
    now take temp of line coming out of evap say 48f that =8f
    superheat

  5. #18
    Join Date
    Jun 2005
    Location
    Manitoba, Canada
    Posts
    94
    It sounds like you have a restriction due to too small of an orfice. You stated the evaporator came factory installed with a #84 orfice, could it be that it's a universal 4-ton coil and need to match the orfice more closely with the condenser capacity? I've seen systems set up like this that work half-decent for quite a while until conditions in house or system change and this problem shows up.

    [Edited by bmc on 06-25-2005 at 12:50 AM]

  6. #19
    Join Date
    Feb 2003
    Posts
    538
    Origonally you had a partial restriction. Now you have a gross overcharge w/ a partial restriction. Fix it by finding the restriction and removing it.

  7. #20
    Join Date
    Jun 2005
    Location
    PA
    Posts
    16
    Originally posted by bmc
    It sounds like you have a restriction due to too small of an orfice. You stated the evaporator came factory installed with a #84 orfice, could it be that it's a universal 4-ton coil and need to match the orfice more closely with the condenser capacity? I've seen systems set up like this that work half-decent for quite a while until conditions in house or system change and this problem shows up.

    [Edited by bmc on 06-25-2005 at 12:50 AM]
    Assuming there is a partial restriction and #84 orifice is too small, what would be the best way to determine what the size of the orifice should be? I spoke to RUUD customer support yesterday and they stated they had no way of determining how to evaluate if a carrier coil is properly matched to a RUUD condensing unit. This system was installed eight years ago when the home was newly constructed.

    I am able to resolve the overcharge but want to be able to address the possible restriction and undersized piston at the same time.

    It appeared NormChris was going to post a reply but has not done so yet.

  8. #21
    Join Date
    Dec 2002
    Location
    Houston,Tx.
    Posts
    15,850
    Originally posted by pehanlon
    I spoke to RUUD customer support yesterday and they stated they had no way of determining how to evaluate if a carrier coil is properly matched to a RUUD condensing unit.
    This is some of the best advise you will ever hear so jot that down give that Ruud tech. support a gold star.
    __________________________________________________ _______________________
    “Experience is a hard teacher because she gives the test first, the lesson afterwards". - Vernon Law

    "Never let success go to your head, and never let failure go to your heart". - Unknown

  9. #22
    Join Date
    Jun 2005
    Location
    Manitoba, Canada
    Posts
    94
    You must have spoke to the wrong person there, I mainly install Lennox and our tech support have charts that match condenser model numbers to proper orfice size. Surely Ruud has the same? The charts were made so they could sell you any make of coil and you could orfice it for exact match. Because of pressures stated and no evidence of frost, I think this is a possibility worthwhile checking into.

  10. #23
    Join Date
    Jun 2003
    Location
    Florida
    Posts
    9,548
    RUUD could tell you what size piston came with that factory condenser.....if they can't chop it out and install a txv. Your problem is right there anyways......You now have an overcharge with a restricted metering device. There's no way around it....you have to open the system up. Adding freon is just going to fill your condenser up more.....good old mis-matches.
    If everything was always done "by the book"....the book would never change.

  11. #24
    Join Date
    May 2004
    Posts
    53
    Just forget the piston and install an adjustable TXV. Just tweaked my superheat. 92 deg here, good day to fine tune!

  12. #25
    Join Date
    Mar 2005
    Location
    Suppy NC
    Posts
    4,513
    why is refrigerant always the blame for a cooling problem
    is the evape ciol clean or dirty. is the condensor coil dirty. what does the blower look like and is the blower motor working properly and at the correct speed. did the return flex if you have it clalasp. look at the entire system and do so checking. tunel vision will just cause more problems. now you may be over charged and when you lower it you will be back where you started and with the same question. check the entire system out and look for anything that may be causing this

  13. #26
    Join Date
    Jun 2004
    Posts
    247
    May I suggest you calculate the BTU/hr the system is currently delivering. Here's a site that can supply all the data with minimal data input http://www.connel.com/freeware/psychart.shtml

    If it's rated for 4 tons but delivering 2 tons of cooling, then a restriction/wrong piston seems likely. But if it's delivering 4 tons of cooling with only a 15 degree air temp difference, then maybe the system is undersized. The behavior would be similar.

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