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  1. #1
    Join Date
    Jun 2009
    Posts
    20

    A-coil freezes only at night.

    I live in a 1200 sq. ft. mobile home in South Texas - HOT and HUMID. Last month I had my condenser and evaporator coils replaced. The compressor was shot. Since it was an 18 y/o 10 SEER Coleman I had both replaced. The original system was a 3.5 ton unit. The replacement is a 3.5 ton unit (13 SEER) and the evaporator coil is rated 10 SEER with a TXV. I replaced the thermostat with a digital one.

    The previous unit had to strain to keep the house at 85 when the temp passed 95. We get broadside sun from 3:00 pm on.

    The new unit works great. It has been over 100 for 2 weeks straight and will keep the temp around 76 (unless my wife is cooking and then the temp goes to 85 - way better than the old unit). It runs long enough to dehumidify well. I have a digital weather center and the indoor humidity is usually around 25 - 30 %.

    The e-coils have been freezing most nights around 3 am. The technician has been out 3 times to check everything out. The last time (last Friday) I probed for answers harder than usual. He said the condenser split was good and the pressures are right where they should be (thus the TXV was working). The temp right where the air enters the blower read 74 and the nearest vent read 56. This was when my wife cooking. The digital thermostat read 83. His digital thermometer read 78 when placed next to the thermostat. It was pretty uncomfortable because the humidity was up from cooking (open floor plan where kitchen and living room are open). He said the air flow was good and the ducts are not restricting air flow. He said trying to get to 70 degrees at night is the issue. Since there is no load on the system because of the cooler night temp, the e-coils freeze the condensate instead of the water draining into the pain.

    He suggested setting the thermostat to 74 and see if that solved the issue. Tonight the temp was 74 and the coils froze again.

    This technician has serviced my a/c for over 5 years and is extremely honest. He is also spoke at several conferences, so he's knowledgeable. During the last visit he did mention servicing mobile homes isn't his main source of business so he was going to talk to the regional experts. I haven't heard back, but I will definitely be talking to him today.

    Could this be because the e-coils are rated for 10 SEER instead of 13 SEER? Does all of this ice put a strain on the new condenser (Ruud 13AJA R22)

    I know I've rambled, but getting up at 3 am kind of fogs my brain and I've been doing it a lot lately.

    I'm not a DIYer. I can't afford to have everything done twice. I do software, not a/c.

    Thanks for your help and opinions.

  2. #2
    Join Date
    Jun 2007
    Location
    Round Rock
    Posts
    3,559
    Hard to say without anybody being there to inspect. Hopefully the evaporator coil is clean and the filter is clean. Unfortunately, this is one of the problems when people try the mix and match thing. It is best to replace everything at once. When people opt out of matching systems, I write it on the service ticket that it is highly recommended and charge them for a service call everytime I have to go out for issues related to this and I tell them I will upfront and write it on the service ticket as well. After the 2nd call, they usually finish the job.
    I like DIY'ers. They pay better to fix.

  3. #3
    Join Date
    Jun 2007
    Location
    The Twilight Zone
    Posts
    2,964
    Quote Originally Posted by bmathews View Post
    It is best to replace everything at once.
    He did replace both the evap coil and condenser, but used a 10 SEER evap coil on a 13 SEER condenser. Not sure why he didn't match the new coil with the new condenser.

  4. #4
    Join Date
    Jun 2009
    Posts
    20
    Thanks for responding.

    He said he couldn't get a 13 SEER coil the same size as the old one (to fit an Intertherm furnace) and the regional experts supply house gave him a 10 SEER and said to use a TXV and it would be fine. I looked at the manufacturer's web site and they have an ARI matched coil the same size. The one he installed is ARI rated for a 3 ton 13 SEER. Sounds twisted.

  5. #5
    Join Date
    Jun 2008
    Location
    South,Tx
    Posts
    331
    Mobile home coils are smaller becuase of space restriction, but still there is an coil that can fit the sitation you in , as long it fits the cabinet, just need to do the match up , if not already done.Probaly for you're situation on frezzing up the coil not enough air coming in , or air filters plug up ,even the motor might be going off by chance.
    Matt 7:12 The Golden Rule
    "Do for others what you would like them to do for you. This summary of all is taught in the law and the prophets.

  6. #6
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,427
    Raise the t-stat a couple more degrees at nite. Regards TB
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  7. #7
    Join Date
    Jun 2009
    Posts
    20
    derbysr,

    I have been awake when the coils started to freeze (insomnia). The blower is going just as hard as during the day. My technician said the blower is moving enough air.

    teddy bear,

    It's freezing at 74 degrees. I don't believe that's normal or acceptable for a new system.

    Thanks for the help, I really appreciate it. He's stumped bad on this one. He's going to replaced the TXV in case it's not working. Kind of shooting in the dark right now. I never had this problem with the previous unit. That Coleman could get to 65. I know because my wife thinks turning it lower will make it cool faster and she would forget to turn the thermostat setting to a normal temp. I have a digital theromostat now and she's afraid to mess with it.

    PeteTx

  8. #8
    Join Date
    May 2002
    Location
    Houston Texas
    Posts
    6,323
    Quote Originally Posted by PeteTx View Post
    derbysr,

    I have been awake when the coils started to freeze (insomnia). The blower is going just as hard as during the day. My technician said the blower is moving enough air.

    teddy bear,

    It's freezing at 74 degrees. I don't believe that's normal or acceptable for a new system.

    Thanks for the help, I really appreciate it. He's stumped bad on this one. He's going to replaced the TXV in case it's not working. Kind of shooting in the dark right now. I never had this problem with the previous unit. That Coleman could get to 65. I know because my wife thinks turning it lower will make it cool faster and she would forget to turn the thermostat setting to a normal temp. I have a digital theromostat now and she's afraid to mess with it.

    PeteTx
    Teddy Bear is right turn the t'stat up and it probably will not freeze.

    There is no such thing as a 10 SEER or 13 SEER coil, a coil will affect the SHR of a system and it will affect the SEER/EER of a system but evaporator coils do not have SEER ratings PERIOD!

    There are three reasons a coil will freeze up, low on refrigerant charge, insufficient airflow across the coil or a bad or restricted metering device.

    You may have confidence in your tech but he is missing something buy I doubt it is the coil. How is he measuring the airflow, is he just testing with his hand or is he using an instrument. As he tested the static pressure of the system, is the blower wheel dirty, is the return duct collapsing.

  9. #9
    Hello
    The problem sound like the thermostatic expansion valve [TXV] maybe the wrong size or need ajustment.

  10. #10
    Join Date
    Jun 2009
    Posts
    20
    classical and teddy bear,

    I meant no offense. I'm thinking a normal functional system would not freeze when the room temp is 74.

    The return duct is the vented furnace door and it's clear, the filters are new every 2 weeks and are the blue fiberglass type, the blower assembly was just cleaned during the down time waiting for the new system to be installed. The ductwork is metal, square (12" X 18" and there are 8 vents (5" X 12").

    As far as I know, the air flow was determined by the temp split between the nearest vent and just outside the blower wheel in the furnace cabinet. The old unit was 18 years old but the blower motor was replaced about 2 years ago. Should the new coil require more cfm than the old one? As for the SEER rating, pardon me. I should have said, Mortex documents only show an ARI certified SEER rating when the ne coils are matched with a Ruud 13AJA-36. Mortex says I need 1 more row of coils and different fins to get the ARI certification for a Ruud 13AJA-42.

    Thanks again for your help.

    PeteTx

  11. #11
    Join Date
    Jan 2008
    Posts
    95
    Post a picture of the a/h and evap coil.

  12. #12
    Join Date
    Jan 2007
    Location
    Vancouver Island, B.C.
    Posts
    2,471
    Quote Originally Posted by PeteTx View Post
    I live in a 1200 sq. ft. mobile home in South Texas - HOT and HUMID. Last month I had my condenser and evaporator coils replaced. The compressor was shot. Since it was an 18 y/o 10 SEER Coleman I had both replaced. The original system was a 3.5 ton unit. The replacement is a 3.5 ton unit (13 SEER) and the evaporator coil is rated 10 SEER with a TXV. I replaced the thermostat with a digital one.

    The previous unit had to strain to keep the house at 85 when the temp passed 95. We get broadside sun from 3:00 pm on.

    The new unit works great. It has been over 100 for 2 weeks straight and will keep the temp around 76 (unless my wife is cooking and then the temp goes to 85 - way better than the old unit). It runs long enough to dehumidify well. I have a digital weather center and the indoor humidity is usually around 25 - 30 %.



    The e-coils have been freezing most nights around 3 am. The technician has been out 3 times to check everything out. The last time (last Friday) I probed for answers harder than usual. He said the condenser split was good and the pressures are right where they should be (thus the TXV was working). The temp right where the air enters the blower read 74 and the nearest vent read 56. This was when my wife cooking. The digital thermostat read 83. His digital thermometer read 78 when placed next to the thermostat. It was pretty uncomfortable because the humidity was up from cooking (open floor plan where kitchen and living room are open). He said the air flow was good and the ducts are not restricting air flow. He said trying to get to 70 degrees at night is the issue. Since there is no load on the system because of the cooler night temp, the e-coils freeze the condensate instead of the water draining into the pain.

    He suggested setting the thermostat to 74 and see if that solved the issue. Tonight the temp was 74 and the coils froze again.

    This technician has serviced my a/c for over 5 years and is extremely honest. He is also spoke at several conferences, so he's knowledgeable. During the last visit he did mention servicing mobile homes isn't his main source of business so he was going to talk to the regional experts. I haven't heard back, but I will definitely be talking to him today.

    Could this be because the e-coils are rated for 10 SEER instead of 13 SEER? Does all of this ice put a strain on the new condenser (Ruud 13AJA R22)

    I know I've rambled, but getting up at 3 am kind of fogs my brain and I've been doing it a lot lately.

    I'm not a DIYer. I can't afford to have everything done twice. I do software, not a/c.

    Thanks for your help and opinions.
    DON'T match a 10 SEER DX coil with a 13 SEER outdoor unit plus it is illegal to put anything in below 13 SEER......If your guy is speaking at HVAC/R engagements, he of all people should know that.....bottom line....you got a set of 6" wide tires on a dragster....too much horsepower....not enough method to place it to the ground (air), plus Mobile Homes are notoriously bad for too small of ductwork....IMHO...
    "The quality you deserve is not expensive---it's priceless"

  13. #13
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,427
    Quote Originally Posted by PeteTx View Post
    derbysr,

    I have been awake when the coils started to freeze (insomnia). The blower is going just as hard as during the day. My technician said the blower is moving enough air.

    teddy bear,

    It's freezing at 74 degrees. I don't believe that's normal or acceptable for a new system.

    Thanks for the help, I really appreciate it. He's stumped bad on this one. He's going to replaced the TXV in case it's not working. Kind of shooting in the dark right now. I never had this problem with the previous unit. That Coleman could get to 65. I know because my wife thinks turning it lower will make it cool faster and she would forget to turn the thermostat setting to a normal temp. I have a digital theromostat now and she's afraid to mess with it.

    PeteTx
    Systems that are have the air flow slowed to max the moisture removal have very cold coils. As the outside air temp drops in the evening, the capacity of the outdoor condenser increases. Add to this that you are able to get the house cooler and the indoor coil temp goes lower-bingo freezing. After you figure out how to increase the air flow, increasing the indoor coil temperature gets you less dehumidification. Sometimes is a fine line between good dehumidification and a freezing coil. Raise the inside temp until you do not have a freezing coil. Then decide if you want less dehumidification by raising the air flow which warms the coil temperature. Small coils freeze up easy but do a good job of dehumidifying. 76^F is with low humidity might be ok. Regards TB
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

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