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  1. #1
    Join Date
    Jul 2008
    Location
    Dorval, Quebec, Canada
    Posts
    8

    Return duct size and frost on coil.

    Had a NEW electric furnace and heat pump installed a month ago. Installer suggested I should increase the size of my return air ducts. The house is a 1950s bungalow, 1000 sq. ft. plus a basement.

    I removed the grates off the returns and measured the openings going to the ducts. There were only 3 return openings measuring a combined total of 108 sq. in.

    Everything worked fine until a couple of days ago. The A/C stopped cooling and when I looked the line going into the coil was covered in thick frost. Not the insulated line. The non-insulated one. I called the service people and they wanted to know if I had increased the return duct size. I had not. This they claim could be causing the problem.

    Worked all day Sat. installing another return grate and ducting to add another 52 sq. in. bringing the total to 160 sq. in. Still getting frost to the extent I have to shut the A/C off every few hours.

    The duct size going into the bottom of the furnace is 210 sq. in. Do I have to further increase my return ducts by another 50 sq. in to match this or am I completely off base. I am no HVAC pro by a long shot.

    To give the A/C additional return air I opened the cleaning port in the return duct and left the filter door off. Still getting frost.

    I think I have more than a return air problem. Any comments or suggestions welcome. Should I increase the return ducts some more or is it likely I have another problem. The service guy is coming back this week but I dont think I can accept if he claims this is all due to duct sizing.

    Thanks in advance.

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,765
    If the little line was freezing, its not caused by your return being to small.
    You got another problem.

    Call them back, and remind them, the liquid line will not freeze because of an undersized return.
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    How many times must one fix something before it is fixed?

  3. #3
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Tell me you didn't tell them,which line was icing!

  4. #4
    Join Date
    Mar 2001
    Location
    North Carolina
    Posts
    428
    small line frosting going into air handler sounds like partially clogged piston or bad expansion valve. probably a Goodman air handler piston is right at the door and would be more noticeable than an expansion valve as far as seeing it outside the cabinet.

  5. #5
    Join Date
    Jul 2008
    Location
    Dorval, Quebec, Canada
    Posts
    8

    Ice on line

    I'm trying to attach a photo of the ice to see if it helps identify the problem. Not sure if I did it right or not.
    Attached Images Attached Images  
    Last edited by tomntina; 07-08-2008 at 12:12 AM. Reason: To add photo

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,765
    It didn't work.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  7. #7
    Join Date
    Jul 2008
    Location
    Pittsburgh PA
    Posts
    37
    Quote Originally Posted by tomntina View Post
    Had a NEW electric furnace and heat pump installed a month ago. Installer suggested I should increase the size of my return air ducts. The house is a 1950s bungalow, 1000 sq. ft. plus a basement.

    I removed the grates off the returns and measured the openings going to the ducts. There were only 3 return openings measuring a combined total of 108 sq. in.

    Everything worked fine until a couple of days ago. The A/C stopped cooling and when I looked the line going into the coil was covered in thick frost. Not the insulated line. The non-insulated one. I called the service people and they wanted to know if I had increased the return duct size. I had not. This they claim could be causing the problem.

    Worked all day Sat. installing another return grate and ducting to add another 52 sq. in. bringing the total to 160 sq. in. Still getting frost to the extent I have to shut the A/C off every few hours.

    The duct size going into the bottom of the furnace is 210 sq. in. Do I have to further increase my return ducts by another 50 sq. in to match this or am I completely off base. I am no HVAC pro by a long shot.

    To give the A/C additional return air I opened the cleaning port in the return duct and left the filter door off. Still getting frost.

    I think I have more than a return air problem. Any comments or suggestions welcome. Should I increase the return ducts some more or is it likely I have another problem. The service guy is coming back this week but I dont think I can accept if he claims this is all due to duct sizing.

    Thanks in advance.
    Could be a restriction in the liquid line. I found one after a compressor failure. Copper dryer/strainer acting like a metering device.
    What was I thinking??? I never do that again!!!

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