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  1. #1
    Join Date
    Apr 2004
    Location
    MN
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    1,799

    Another heat pump question

    What would cause ice to form on the fan blades of the outdoor unit in the heating mode? Unit is not being dripped on from overhead. There are no exhaust vents nearby. It is a 6 year old Bryant that has done this since day one. It only happens a couple times a year and only when it rains or snows. It ends up throwing the blade out of balance and the unit shakes like a cat sh!tt!ng tacks. The HO has to pull the disconnect and melt the ice with a hair dryer. There have been no other problems with the unit. Original fan and blade. I have not seen this unit. The owner is one of my students grandfather. Thanks for any insight.
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  2. #2
    Join Date
    Nov 2001
    Location
    Seattle, WA
    Posts
    7,748
    Perhaps the defrost mode is producing steam/water vapors that rise up across the blades then the system goes out of defrost which freezes the moisture to the blades...keeping in mind during defrost the coil get hot enought to melt the ice but the fan is already cold and stays that way through defrost.

    I'd go searching into a too short, too long defrost mode myself.
    "The American Republic will endure until the day Congress discovers it can bribe the public with the public's own money.
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  3. #3
    Join Date
    Jul 2010
    Location
    nebraska
    Posts
    1,629
    Just when it rains or snows... Suggest waxing the fan blades or a spray on teflon. Guessing the rain is just above freezing and the blades will be several degrees cooler in heating mode.Doesn't take much ice build up to throw them off balance.

  4. #4
    Join Date
    Mar 2013
    Location
    Joplin,Missouri
    Posts
    310
    I have had the same problem with the XP17 lennox heat pumps during snow and ice or cold rain at near freezing temps the fan blades were accumulating ice sometimes even freezing to the shroud is the defrost termination temp adjustable on that model our solution was to change the termination temp from 50 to 80 degrees it seems to have taken care of the problem on those units we just got alot of snow and havent had a call on any since we made the change

  5. #5
    Join Date
    Dec 2005
    Location
    Cincinnati, Oh
    Posts
    4,926
    Quote Originally Posted by doc havoc View Post
    What would cause ice to form on the fan blades of the outdoor unit in the heating mode? Unit is not being dripped on from overhead. There are no exhaust vents nearby. It is a 6 year old Bryant that has done this since day one. It only happens a couple times a year and only when it rains or snows. It ends up throwing the blade out of balance and the unit shakes like a cat sh!tt!ng tacks. The HO has to pull the disconnect and melt the ice with a hair dryer. There have been no other problems with the unit. Original fan and blade. I have not seen this unit. The owner is one of my students grandfather. Thanks for any insight.
    I've had this happen on 3 different units on new installations.

    All 3 times, were heat pump/gas furnace installs.
    All 3 times, we had snow/freezing rain at some point during the installations.

    Go to startup the units, they rocked like crazy, had to knock off the ice.


    Something is preventing that unit from running for a long enough period of time to allow the snow to thaw/freeze, or long enough to have freezing rain stick to it.

    Tell me they have a oil/gas furnace and are using duel fuel also.
    "Better tell the sandman to stay away, because we're gonna be workin on this one all night."

    "Dude, you need more than 2 wires to a condenser to run a 2 stage heatpump."

    "Just get it done son."

    Dad adjusted

  6. #6
    Join Date
    Dec 2007
    Posts
    4,670
    What unit?

    I, too, have the plastic blade freeze up on Lennox units.

    The accumulation is on the shroud mostly and the noise is like a woodpecker 6" from your head.

    Lennox revamped their boards to cycle the fan for a time if off more than a certain time below a certain temp.
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  7. #7
    Join Date
    Apr 2004
    Location
    MN
    Posts
    1,799
    It is a Bryant heat pump. Not sure what the air handler is. I'll get back on that. As mentioned, I have not seen the job. This is one of my students grandparents equipment and it has done this since day one. The original installer has not been able to figure it out, although, I have no idea what has been tried. I'll ask some more questions and get back to you all. Thanks!
    A Veteran is a person, who at some point in their life, wrote a blank check payable to the United States of America for payment up to and including their life.
    Gene Castagnetti-Director of the National Memorial Cemetery of the Pacific in Hawaii

  8. #8
    Join Date
    Jan 2010
    Location
    Central Texas
    Posts
    156
    I like the idea of waxing the cond fan blades.

    I'd expect that the unit is in an exposed area, that is getting enough wind to prevent the warm air of the defrosting coil from sticking around in the cond unit. That would keep the Cond Fan blade below freezing and allow the steam from the defrosting coil to condense onto the Cond Fan Blade. Given enough defrost cycles, the Cond Fan Blade could lose part of the accumalated ice, or break off a piece. Causing the out of balance Cond Fan Blade.

    So waxing the Cond Fan Blade may keep the condensation from accumalating or atleast cause the ice to fall off before it accumalated to much to matter.

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