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lennox xc14 410a 2 ton condensor 2.5 ton evap subcooling question

Mcro1986
Mcro1986 Member Posts: 8
in A-C, Heat Pumps & Refrigeration
when i look on the chart it tells me i need 3 degrees of subcooling, started i had a 35 degree SH, 80OAT 77inside air temp, and a 6 degree subcool. got my SH to 25 degrees and a subcool of 16degrees, the delta air temp across the evap is now 15degrees indoor temp dropped 5 degrees in an hour, been 2 hours and still running. is there chart correct with a 3 degree subcooling? or am i reading it wrong?

i haven't messed with the txv but added about two pounds of 410a (linset is only 25 feet and i figured the system was undercharged when it was changed a year ago and the install crew didn't add any at start up an knowing from the install manual you have to add 6 oz for every foot over 15 feet of lineset)

Comments

  • Techman
    Techman Member Posts: 2,144
    The "charging chart" or the unit nametag spec'ed 3* SC? 16* SC is kinda high for a 25' line set.If you charge the system under "pulldown loads" then that would explain the high 16* SC under a more "normal load". Got pressurers ? That 6oz per foot, is that w/ a 5/16 LL and 5/8 SL or on a 1/2 LL and a 1 1/8 SL?
  • unclejohn
    unclejohn Member Posts: 1,833
    Stick with 8 to 12 sub cool and you should be ok. I have never seen a Lennox unit list sub cooling any where. It should be on the name plate if they use that for charging. Let the unit run at least 15 mins before you adjust the charge. What is the fan speed. Try a lower speed and get the delta T closer to 20.
    Ironman
  • John Mills_5
    John Mills_5 Member Posts: 952
    The chart I found says 10SC at 65 ambient and 8 for temps warmer than that. Are you running no more than 800 CFM per ton? Most installers just leave the furnace on high and never look at having excess airflow.
  • Techman
    Techman Member Posts: 2,144
    Morning John Mills, I've read you enough to say that your Type Error of 800CFM /T should be 400CFM/T. HA! Most installers don't know their elbow from their butt about Service nor do they care .I KindaSorta understand/agree w/ the installer ,also. But I'm a 1% installer ,99% Service so I am VERY biased.
  • Empire_2
    Empire_2 Member Posts: 2,340
    Testing, testing........
  • Empire_2
    Empire_2 Member Posts: 2,340
    Yea, sub cooling on most of the units I have seen range from 10 to 14* sub cooling.
  • Empire_2
    Empire_2 Member Posts: 2,340
    10-12* S/C is usually on most name plates. S/C is constant designed temps regardless of loads unless it is outside of designed parameters. Add ref to lower LL temp remove to raise LL temp. Your half ton over sized coil will give you warmer S/H, but will aid in dehumidification.
  • John Mills_5
    John Mills_5 Member Posts: 952
    Ooops, got a little carried away on that airflow, didn't I? :o
  • Techman
    Techman Member Posts: 2,144
    John Mills, Type Error, my friend.
  • Mcro1986
    Mcro1986 Member Posts: 8
    Sorry for the late response, been a bit hectic at work. thankfully this was my AC at home haha. checked the airflow and found it set to 1200cfm! reduced it down to 900 cfm and the system is working great! sc is 13 sh is 25 and the delta t across the coil is 20. the condensate is pissin out the drain like an open faucet

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