Page 1 of 2 12 LastLast
Results 1 to 13 of 18
  1. #1
    Join Date
    Feb 2010
    Posts
    6

    Angry how to fix over sized unit with banging customer

    I responded to a call where the evaporator and the condenser the evap is 3 tons and the condenser is 5 ton how can I correct this problem with out changing what's there and costing the owner crazy money.
    I have three years in the trade one in school. Mostly walk ins and reach in units in time
    The three ton unit. Have a txv for three ton. As well would a bigger txv hurt or just flood the evaporator. Or could I add a nother evap on to take away some refrigerant from the other but keep the regular condenser.

  2. #2
    Join Date
    Aug 2009
    Location
    Jurupa Valley, CA
    Posts
    1,781
    Is it actually causing a problem? I'm thinking an oversized condenser shouldn't really be a problem.. Perhaps you may have to get more water flow through it, but I'd doubt even that.

  3. #3
    Join Date
    Mar 2003
    Posts
    7,326
    compressor is probably moving more gas out of the evap than necessary, causing low pressure condition in low load? there are ways to skin that cat none of which is easy.

  4. #4
    Hot Gas by-pass valve with 3ton txv

  5. #5
    Join Date
    Sep 2005
    Location
    Texas
    Posts
    2,793
    If you polish a turd, at the end of the day you end up with a polished turd


    ...do it right

  6. #6
    Join Date
    Dec 2005
    Posts
    1,918
    Quote Originally Posted by will173 View Post
    I responded to a call where the evaporator and the condenser the evap is 3 tons and the condenser is 5 ton how can I correct this problem with out changing what's there and costing the owner crazy money.
    I have three years in the trade one in school. Mostly walk ins and reach in units in time
    The three ton unit. Have a txv for three ton. As well would a bigger txv hurt or just flood the evaporator. Or could I add a nother evap on to take away some refrigerant from the other but keep the regular condenser.
    If the building load is 3 tons then change OD unit to 3 tons.

    If building load is 5 tons then make sure the ducts can handler at least 1800 CFM, and power is large enough, then change the ID unit to 5 tons.

    If the owner said he does not want to change any equipment, then tell him "I ain't no miracle worker and good luck"

  7. #7
    Join Date
    Nov 2004
    Location
    Oxnard, CA
    Posts
    35
    The problem with the "marriage" of a 5T compressor to a 3T evaporator is that the evap cannot produce as much vapor as the compressor can pull, resulting in a lower-than-normal suction temp. A compressor operating at a low suction pressure will consume more kw/ton. If the mis-match is severe, the suction pressure can be so that the saturation temp that corresponds to the evap pressure is below freezing, which can cause the condensate on the evap to freeze up, blocking airflow completely. You can fix that problem by installing an EPR (evaporator pressure regulator) between the evap and the compressor. It will sense the upstream pressure, and modulate closed (creating a pressure drop) to prevent the evap from getting below freezing temp. But you will still be stuck with an inefficient compressor because of the low suction pressure after the EPR.

  8. #8
    Join Date
    Jul 2009
    Location
    In a mechanical room....
    Posts
    1,888
    So which is sized improperly the evap or the condenser?
    Who makes the equipment?
    How many cfm's are you moving? Fan in evap set to hi.
    If the evap is the correct size and the condenser is the improperly sized component I would pick up the extra sub-cooling/ efficiency and install a smaller compressor in the existing condensing unit.
    “It takes courage to grow up and turn out to be who you really are.”

    - E.E. Cummings

  9. #9
    Join Date
    Apr 2007
    Location
    Pa
    Posts
    758
    Sometimes this is done on purpose i.e. dehumidification. What is the reason you got called to the job? What part of the country do you live in? 5 ton with a 3 ton is a bit different compared to what I have run across.

  10. #10
    Join Date
    Jul 2010
    Location
    Edmonton
    Posts
    92
    Quote Originally Posted by will173 View Post
    I responded to a call where the evaporator and the condenser the evap is 3 tons and the condenser is 5 ton how can I correct this problem with out changing what's there and costing the owner crazy money.
    I have three years in the trade one in school. Mostly walk ins and reach in units in time
    The three ton unit. Have a txv for three ton. As well would a bigger txv hurt or just flood the evaporator. Or could I add a nother evap on to take away some refrigerant from the other but keep the regular condenser.
    Measure pressure drop across and entering liquid temp of the TXV. Work backwards from there to size a TXV for 3 ton capacity.

    You can also bring up the liquid temp entering TXV to decrease capacity. Sometimes that's insulating the liquid line, sometimes it involves blocking off some of the condenser.

    HTH
    I came upon this pile of junk, the torch has been passed. I take ownership of things shaped before me, it is now my responsibility.
    But what are you suppose to do when you see yourself in that pile of junk?

  11. #11
    Join Date
    May 2008
    Posts
    6

    Thumbs up Correct

    Quote Originally Posted by just_opinion View Post
    If the building load is 3 tons then change OD unit to 3 tons.

    If building load is 5 tons then make sure the ducts can handler at least 1800 CFM, and power is large enough, then change the ID unit to 5 tons.

    If the owner said he does not want to change any equipment, then tell him "I ain't no miracle worker and good luck"
    This only correct 3and 3, 5and 5 it's the only and right way it's always best not to half step...

  12. #12
    Join Date
    Aug 2009
    Posts
    2,459
    Technically I don't see why an oversized condenser is all that terrible.

    As long as the compressor, evaporator and TXV all match, the oversized condenser is simply going to be able to shed more heat more easily or at a lower fan speed. You will of course need more refrigerant to fill the larger circuit but in the end you could probably run the condenser fans at a lower speed thus reducing both noise and cost.

    What type of compressor(s) are involved? Any issues with keeping enough oil in the system?

  13. #13
    Join Date
    Mar 2009
    Location
    VB
    Posts
    319
    how to fix over sized unit with banging customer
    So this customer is hot!!!!!!!

    Or is she
    Code:
    BANGING
    If I would of killed my wife when I first met her, I'd be out of jail by now!

    GET SOME!!

Page 1 of 2 12 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event