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  1. #1
    Join Date
    Jul 2007
    Posts
    12

    What is happening to my AC?

    Ok - I noticed my HVAC wasn't cooling like it used to.

    10 year old York 4 ton unit.

    The symptom is, it will cool GREAT, then sometimes, it wont get lower than 70 degrees at the register.

    Had a tech come out - he said someone put too much freon in.... let some out to get the pressure right.

    Now.... it still does the same thing. When it works, it works great.... (even better than before) and puts out 55 degrees at the register with a 78 internal temp (23 degree drop). Outstanding.

    Other times, when it cycles on - the register will not drop below 70 degrees.

    This means, I know it is cooling.... because it is cooler than ambient at the register, but it isnt cooling where it should.

    Filter is always changed, it isnt freezing up inside or out (checked), and gas is good (same problem before tech let some out to be optimal)

    Compressor is running as is outside and inside fans.... all coils are clean.


    Help! What can cause a system to run great sometimes, and then other times hardly at all?

  2. #2
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,376
    You sure compressor never stops running? Next time you experience bad performance, go outside and listen for the familiar buzz of the compressor above the fan noise. If it ain't there, then that might give your next service call some focus.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  3. #3
    Join Date
    Feb 2007
    Location
    pa outside philly
    Posts
    30
    there is no way to tell you what is going on with this system with out looking at the system. Call a good service company.

  4. #4
    Join Date
    Jul 2007
    Location
    Jacksonville, Fl
    Posts
    219
    When the system is doing poorly push the thermostat to all the way down to keep the system running in cool. This will hopefully keep the system running in its poor performance condition.
    Call the Service company to come out fast so they can see what is happening when the system is not cooling. If they can't come out fast call a service company that can.

  5. #5
    Join Date
    Dec 2006
    Location
    New Jersey
    Posts
    747
    Quote Originally Posted by ClassicDave View Post
    When the system is doing poorly push the thermostat to all the way down to keep the system running in cool. This will hopefully keep the system running in its poor performance condition.
    Call the Service company to come out fast so they can see what is happening when the system is not cooling. If they can't come out fast call a service company that can.
    this is the dumbest idea i heard. a system not working right should be turned off. how do you know its not frosting up on the evap coil? I get there its frozen im packing my tools and the jobs getting rescheduled. i have to many calls to sit there till the fan melts your coil down. the compressor may be getting weak have the tech test out your pump next time he is out.

  6. #6
    Join Date
    Jul 2007
    Posts
    12
    Quote Originally Posted by acmech13 View Post
    this is the dumbest idea i heard. a system not working right should be turned off. how do you know its not frosting up on the evap coil? I get there its frozen im packing my tools and the jobs getting rescheduled. i have to many calls to sit there till the fan melts your coil down. the compressor may be getting weak have the tech test out your pump next time he is out.
    Actually - it sounds like a good idea.... because when the tech was out here last, it was working perfectly. He checked amperage at the compressor on both legs, and said it looked really good.

    What does test out your pump mean? What is involved in that?

    I know the evap coil is not frozen... I am pretty familiar with these things... and I pulled the cover from the evap unit on the A-coil and checked it out to ensure it wasnt freezing up.... it isnt. My coils are very clean, inside and out, and with the gas pressure set correctly, and proper airflow - it aint gonna freeze.... and it doesnt.

    When it will only pump 70 degrees at the register - airflow is not restricted - it has great flow. The evap coil is just not running as cool.

    I checked the outside compressor when it isnt cooling well - and yes - it is running. It just seems to not be compressing enough. Also - at the condensing unit - when it is cooling well - you can feel the heat being pulled off by the fan - the air being drawn out of the unit is very warm. When it isnt cooling well, the outside unit air feels like ambient temperature.

    When the tech came out last - he measured the pressures... and found it was a bit high on gas - so he reduced that. Now when it is working correctly, it cools much colder at the register. However... when it isnt working correctly... it still just sits there at 70 degrees. I keep my house at 78 degrees... so I know it is cooling a little. It's almost like a 2 stage compressor, stuck on the first stage. However, this isnt a 2 stage compressor that I know of.... it is an older unit. (10 years)


    All other things aside - can a scroll compressor do this? Are their internals where they dont run right sometimes, but run fine at other times?

  7. #7
    Join Date
    Jun 2004
    Location
    Howell, Michigan
    Posts
    16,184
    Quote Originally Posted by ClassicDave View Post
    When the system is doing poorly push the thermostat to all the way down to keep the system running in cool. This will hopefully keep the system running in its poor performance condition.
    Call the Service company to come out fast so they can see what is happening when the system is not cooling. If they can't come out fast call a service company that can.
    Shut it off..............call ONE competent service company and get on their schedule.

    You are promoting the........................

    "Hey put me on your schedule and the first guy that gets here gets the job I don't care if there are three service trucks in my driveway at the same time I am only gonna pay the first guy that pulls into my driveway attitude."

  8. #8
    Join Date
    May 2006
    Location
    Dallas,tx
    Posts
    319
    Quote Originally Posted by igotdoo View Post
    Actually - it sounds like a good idea.... because when the tech was out here last, it was working perfectly. He checked amperage at the compressor on both legs, and said it looked really good.

    What does test out your pump mean? What is involved in that?

    I know the evap coil is not frozen... I am pretty familiar with these things... and I pulled the cover from the evap unit on the A-coil and checked it out to ensure it wasnt freezing up.... it isnt. My coils are very clean, inside and out, and with the gas pressure set correctly, and proper airflow - it aint gonna freeze.... and it doesnt.

    When it will only pump 70 degrees at the register - airflow is not restricted - it has great flow. The evap coil is just not running as cool.

    I checked the outside compressor when it isnt cooling well - and yes - it is running. It just seems to not be compressing enough. Also - at the condensing unit - when it is cooling well - you can feel the heat being pulled off by the fan - the air being drawn out of the unit is very warm. When it isnt cooling well, the outside unit air feels like ambient temperature.

    When the tech came out last - he measured the pressures... and found it was a bit high on gas - so he reduced that. Now when it is working correctly, it cools much colder at the register. However... when it isnt working correctly... it still just sits there at 70 degrees. I keep my house at 78 degrees... so I know it is cooling a little. It's almost like a 2 stage compressor, stuck on the first stage. However, this isnt a 2 stage compressor that I know of.... it is an older unit. (10 years)


    All other things aside - can a scroll compressor do this? Are their internals where they dont run right sometimes, but run fine at other times?
    is a TXV on the E.COIL?

  9. #9
    Join Date
    Jun 2007
    Location
    Greenwood Indiana (Indianapolis)
    Posts
    420

    Wink

    hears what it sounds like to me. I've seen this problem many times. I bet the outdoor unit has a time delay relay and it works most of the time but occasionally it doesn't. have the tech by-pass the time delay relay and get a digital thermostat that has time delay built into it and is way more accurate.

  10. #10
    Join Date
    Jul 2004
    Location
    Massachusetts
    Posts
    6,841
    Igotdoo didn't say how the home is heated. Is this a heat pump or straight AC? If it's a heat pump, he could have a 4-way valve that's sticking occassionaly. Or it could be the TDR or it could be a weak compressor or it could be something else entirely. How about trying to figure out if there is some way you can duplicate the problem. Such as does this happen after a long run or a long dwell time or a short cycle or only during the heat of the day. If you can come up with some scheme that will duplicate the problem for the tech, you've got a much better chance of getting the problem properly resolved as the least cost.
    If YOU want change, YOU have to first change.

    If you are waiting for the 'other guy' to change first, just remember, you're the 'other guy's' other guy. To continue to expect real change when you keep acting the same way as always, is folly. Won't happen. Real change will only happen when a majority of the people change the way they vote!

  11. #11
    Join Date
    Oct 2002
    Location
    Yo.... Here!, I'm right here..
    Posts
    6,236
    Quote Originally Posted by igotdoo View Post
    Ok - I noticed my HVAC wasn't cooling like it used to.

    10 year old York 4 ton unit.

    The symptom is, it will cool GREAT, then sometimes, it wont get lower than 70 degrees at the register.

    Had a tech come out - he said someone put too much freon in.... let some out to get the pressure right.

    Now.... it still does the same thing. When it works, it works great.... (even better than before) and puts out 55 degrees at the register with a 78 internal temp (23 degree drop). Outstanding.

    Other times, when it cycles on - the register will not drop below 70 degrees.

    This means, I know it is cooling.... because it is cooler than ambient at the register, but it isnt cooling where it should.

    Filter is always changed, it isnt freezing up inside or out (checked), and gas is good (same problem before tech let some out to be optimal)

    Compressor is running as is outside and inside fans.... all coils are clean.


    Help! What can cause a system to run great sometimes, and then other times hardly at all?
    You are trying to measure something you have no idea about what it should be doing and it couldn't be answered here any way.

    Call an HVAC contractor and have it checked.......it's that simple.......

  12. #12
    Join Date
    Oct 2003
    Location
    34.8n 102.4w
    Posts
    3,244
    Should'a got a Coleman.....
    Life goes on long after the thrill of living is gone.

  13. #13
    Join Date
    Jun 2003
    Location
    Florida
    Posts
    9,548
    Possible heaters on.....call for service.
    If everything was always done "by the book"....the book would never change.

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