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  1. #14
    Join Date
    Dec 2007
    Location
    Ohio
    Posts
    2,876
    Quote Originally Posted by chewreck View Post
    I know that he used nitrogen and did a pressure check at 150 psi and then charged the refrigerant. I would've thought the line would be sweating at this point as well, and that was the point of my original question. I realize the house is hot and will take time to cool down, but I thought the refrigerant line would be sweating by now.
    Based on what you have told me....I would say you should call your installer back tomorrow and see what they say. I am sure that the unit will get things cooled off tonight and satisfy the thermostat. I would keep an eye on it tomorrow and see how long it runs and whether or not it can hold the temperature in your house like it did before the compressor was changed out.

    Just for your own information: "Charging" up the unit from completely empty should be done by weighing in the charge that is depicted on the data plate...HOWEVER...that is nothing more than a starting point. The system then needs to be run and the proper charge needs to be verified using superheat and sub cooling measurements.
    I need a new signature.....

  2. #15
    Join Date
    Mar 2006
    Posts
    254
    It could also be the way your house retains heat (downtime while unit was being recharged).

    It might be well worth it to buy 2 very cheap inexpensive Radio Shack Indoor/Outdoor digital thermometers

    Place one of those with the probe at the register in a "smaller room", with the other recording the ambient room temp.

    Note the difference in ambient room temp from what the register temp reads.
    That will tell you if your entire system is under performing.

    It's something you can do on your own and doesn't cost much.

    It's also something physical you can show him.

    They sell them everywhere and cost just a bit more than a couple of meals at McDonalds.

  3. #16
    Join Date
    Jul 2008
    Posts
    8
    Quote Originally Posted by I_bend_metal View Post
    Based on what you have told me....I would say you should call your installer back tomorrow and see what they say. I am sure that the unit will get things cooled off tonight and satisfy the thermostat. I would keep an eye on it tomorrow and see how long it runs and whether or not it can hold the temperature in your house like it did before the compressor was changed out.

    Just for your own information: "Charging" up the unit from completely empty should be done by weighing in the charge that is depicted on the data plate...HOWEVER...that is nothing more than a starting point. The system then needs to be run and the proper charge needs to be verified using superheat and sub cooling measurements.

    Thanks for the information. It'd be too late to get him back out here tonight anyway. When he charged the system, he purged and pressure tested with nitrogen as I mentioned, and then he charged it with refrigerant. Once it was full, he asked me what the inside temperature was at the time, but he didn't mention superheat or sub cooling. He didn't appear to measure any temperature on the unit itself.

    I'll wait it out tonight to see what happens, but what you've said makes sense, and I'd bet that it's not fully charged. Thanks again for your help.

  4. #17
    Join Date
    Dec 2007
    Location
    Ohio
    Posts
    2,876
    Keep us posted and let us know how it works out for you
    I need a new signature.....

  5. #18
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    5,025

    The thermodynamics of refrigerants'

    Quote Originally Posted by chewreck View Post
    Yes, he was there, and everything checked out ok after he installed it and recharged the system.
    He should have checked the indoor CFM airflow before attempting to charge the system. Then, if he did not use superheat & subcooling procedures to accurately charge the system, it may not be properly charged.
    I just wanted to know how long it should reasonably take for the refrigerant line to get cold when recharged with warm refrigerant.
    Warm refrigerant has nothing to do with the suction line getting cold.
    The refrigerant has to get cold prior to cooling the house down, correct?
    NO, no, the thermodynamics of refrigerants' does not work that way.

    A 'fixed orifice metering device' (-the example used here) causes a pressure drop in the evaporator coil & the hot air with its condensing moisture causes the liquid refrigerant to boil/vaporize. Heat vaporizes liquid refrigerant without additive heat it won't boil/vaporize. Vaporizing refrigerant absorbs the heat & transfers the heat to the condenser where it is discharged. (This is not a total explanation of the process.)

    Due to the extremely hot, & perhaps rather humid air, when passing through the evaporator fins, that represents an extreme heatload that will boil off the refrigerant "well before" it gets near the end of the coil.

    Therefore, with a fixed metering device the vapor gets Super-Heated before it leaves the evaporator coil. Therefore, until the load is finally reduced Superheat will be high & the suction line will NOT be very cold.

    The suction line could be very cold, but if the condenser is not ejecting a normal temp split - the evaporator is not properly loaded.

    Additionally, the design of the higher EER & SEER units operate with higher ratio pressure/temperatures in relationship to a specific heat-load. - udarrell

  6. #19
    Join Date
    May 2007
    Location
    DC Metro Area (MD)
    Posts
    3,371
    Just for clarification Chewreck: the insulated line that sweats is not taking the refrigerant into the home in A/C mode. See what others have said above regarding proper refrigerant charging procedure.

  7. #20
    Join Date
    Jul 2006
    Location
    memphis
    Posts
    81

    Hmm sounds like a mischarge to me

    Pretty far off the mark too.....should be getting colder with those temps faster than that.

  8. #21
    Join Date
    May 2007
    Location
    DC Metro Area (MD)
    Posts
    3,371
    2 degrees in 2 hours doesn't sound too unreasonable to me if the latent and sensible heat loads are high.

  9. #22
    Join Date
    Mar 2006
    Posts
    254
    Quote Originally Posted by udarrell View Post
    He should have checked the indoor CFM airflow before attempting to charge the system. Then, if he did not use superheat & subcooling procedures to accurately charge the system, it may not be properly charged.

    Warm refrigerant has nothing to do with the suction line getting cold.
    NO, no, the thermodynamics of refrigerants' does not work that way.

    A 'fixed orifice metering device' (-the example used here) causes a pressure drop in the evaporator coil & the hot air with its condensing moisture causes the liquid refrigerant to boil/vaporize. Heat vaporizes liquid refrigerant without additive heat it won't boil/vaporize. Vaporizing refrigerant absorbs the heat & transfers the heat to the condenser where it is discharged. (This is not a total explanation of the process.)

    Due to the extremely hot, & perhaps rather humid air, when passing through the evaporator fins, that represents an extreme heatload that will boil off the refrigerant "well before" it gets near the end of the coil.

    Therefore, with a fixed metering device the vapor gets Super-Heated before it leaves the evaporator coil. Therefore, until the load is finally reduced Superheat will be high & the suction line will NOT be very cold.

    The suction line could be very cold, but if the condenser is not ejecting a normal temp split - the evaporator is not properly loaded.

    Additionally, the design of the higher EER & SEER units operate with higher ratio pressure/temperatures in relationship to a specific heat-load. - udarrell

    Ya see, that just doesn't happen in the real world, tho it should. Man you are technical!
    Wait while I beam you over to my place...stand by...Energizing.

  10. #23
    Join Date
    May 2004
    Location
    Rapid City, SD
    Posts
    7,415
    I'm not all that great with geography, but I'm assuming it's rather humid in your neck of the woods? (this coming from a guy when it's way humid out, it's in the 40% range lol).

    2 degree's might not sound like a whole heck of a lot, but like others have said, there's likely a lot of mass to cool down (house and everything in it), not to mention if your house is pretty humid a lot of "cooling" is being used to remove that humidity before you'll start noticing the temp drop.

    My guess, 2 deg in the 1st couple hours is not too far off... and likely by tonight (with the help of it cooling off outside) the inside will start to drop faster. Personally I'd think that if by morning or mid morning you're still not at the set temp, you've got a problem. If it's down to what you have the stat set at, it's fine.

    I'm kinda shocked with the replies saying the line should be sweating. Maybe it should be, maybe it won't... just because it's sweating (or not) isn't a very good determining factor if it's charged properly or not.

    I (and everyone else here) will keep our fingers crossed that you're just worried over nothing and it'll be nice and cool in your house tomorrow.
    "If you call that hard work, a koala’s life would look heroic."

  11. #24
    Join Date
    Jul 2006
    Location
    Virginia
    Posts
    4,812
    Prior to the compressor failure, the refrigerant line would be very cold to the touch and have a lot of condensation on it. .


    maybe that is why the compressor failed in the first place possibly over charged or other problems

  12. #25
    Join Date
    Jul 2002
    Location
    Zelienople, Pa
    Posts
    2,965

    Caslon, step away from the keyboard...

    You are not qualified to give advice.

    Stick with your Radio Shack toys and don't confuse the homeowners here...

    Cotty Gee...
    How tall are you Private???!!!!

  13. #26
    Join Date
    Mar 2006
    Posts
    254
    Quote Originally Posted by Gunnery Sergeant Hartman View Post
    You are not qualified to give advice.

    Stick with your Radio Shack toys and don't confuse the homeowners here...

    Cotty Gee...
    Mr. emotional equity in love with yourself...NOTED.

    I mean your character is... noted.

    Actually a simple Radio Shack digital thermometer with a probe at register...and then some other form of thermometer that reads the ambient room temp was of use...to me.

    Your dirt weasle snipe was of no real use to anyone. Was it? Talk about a pinhead elite.

    I also approached a reply here by first off saying I am not a super pro.

    From you.... take a hike?

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