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  1. #1
    Join Date
    Jan 2010
    Location
    Toronto,Ontario Canada
    Posts
    355

    Walk-in freezer Fans wtf.

    Ok i got a call friday night saying their walk-in freezer is not working properly.
    -Coil all iced up de-iced coil.
    -Its skipping the defrost cycle.
    -replaced defrost clock
    -found a leak in system capillary tube off a low pressue switch ok replace that.

    -had system running for a bit then noticed my suction pressure shot down to 15psig thinking it might have sprung a leak (checked for other leaks, didnt find any) checked out evaporator (having 2 fans... only one is spinning normally) luckly i got one in the truck replaced that no luck new motor does the same thing. thinking its a little odd switch motor with the other one, same thing is happening ok this is odd. checked power going into fans 208volts odd. i unplugged one when it was running noticed one fan speeds up plugs the other one in one slows down and the other one runs normal. checked wiring any loose connections, crimped new connectors on any loose wiring no luck. i checked the connection of the fan at the panel of the evap a little loose ok pulled it out and ensured a tight connection turned it on no luck phoned my boss he said have you checked the pitch of the fan blades does th blades match and is it matched up. yes! my boss tells me change the other fan. Have to go back monday before i left suction line to compressor frosting up. Kinda worried might turn into a sunday service call.

    I HONESTLY DONT WANT TO GO BACK!!!Thinking this would be better for someone else to look at it instead of me! . standing 6 hrs in front of the customer isnt fun! oh ya did i mention when i came home discovered my car was broken into and car stereo was gone! might have been thursday night. What a day! #^&#@&*@#*(@#^ Eactly!

    My Boss told me also that i cannot book for the 6 hrs because its after hrs. ( time and a half ) the freezer is kinda keeping temp sitting at -5c

    Any ideas im fkn stumped
    Dont have info on model of evaporator Looks old
    Get er Done!

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  2. #2
    Join Date
    Jan 2010
    Location
    Toronto,Ontario Canada
    Posts
    355
    When i was checking the wiring connections i also looked if the fans were wired in parallel it doesnt seem like anyone touched the connectors maybe thats the issue voltage drop somewhere!

    Any ideas/ oh well let someone else take this call.
    Get er Done!

    Do what has to be done
    when it has to be done
    as well as it has to be done
    And doing it all the time.

  3. #3
    Join Date
    Oct 2009
    Location
    Raleigh, NC
    Posts
    794
    Is there a baffle between the fans inside the unit cooler? In other words, if you were to stop one fan while the other is running, will the still-running fan pull air through the non-operating fan?

  4. #4
    Join Date
    Jan 2010
    Location
    Toronto,Ontario Canada
    Posts
    355
    not sure if its pulling air in. the fans blow air out on this model. If i disconnect one fan the disconnected fan spins bckwards on its own. Umm that makes sense. because now the fan is being pulled backwards and out on the one that is working.
    Get er Done!

    Do what has to be done
    when it has to be done
    as well as it has to be done
    And doing it all the time.

  5. #5
    Join Date
    Oct 2009
    Location
    Raleigh, NC
    Posts
    794
    If you stop one fan and the stopped fan spins backwards with any appreciable speed on its own due to the airflow from the running fan, then the fans must have a common plenum. If this is the case, then one fan having a different pitch or cfm capability, or running at a different speed due to slower or weaker motor on one fan, then you might have the issues like you are describing.

  6. #6
    Join Date
    Jun 2009
    Location
    NYC
    Posts
    423
    Both fan motors should be the same rpm, hp and rotation.

  7. #7
    Join Date
    Jan 2010
    Location
    Toronto,Ontario Canada
    Posts
    355
    so getting a new motor will fix the problem? but. how come the old motors were doing that. one was on its way out? i will get back to you on this one. hopefully Monday
    Get er Done!

    Do what has to be done
    when it has to be done
    as well as it has to be done
    And doing it all the time.

  8. #8
    Join Date
    Oct 2004
    Location
    Central WA
    Posts
    1,497
    Let's back up a little bit to the original problem. Was it actually skipping defrost (switch in then switch out at the same time) or was the clock stopped? Did you try pulling the "x" wire, then rolling it into a defrost before you changed the clock?

    Skipping defrost coupled with strange fan behavior sounds more like a defrost terminator/fan delay switch problem to me. The epoxy seal on those breaks down over time and they fill with water.

  9. #9
    Join Date
    Jan 2010
    Location
    Toronto,Ontario Canada
    Posts
    355
    ok when i got there the coil was frozen so i was advised to turn on the defrost i tried. first few times it skipped past it. my boss quickly said ok replace that so i did. i finally got it into defrost after like 3 tries. thats why i replaced the defrost clock.

    *note* i just came out of school like 6 months ago passing my intermediate so i got jumped into refrigeration stuff i know the basics by reading it but actually seeing it in the field is a whole different can of worms. i dont often work on freezers but when i do i tend to be ok. but this will take time. i know enough to be left alone. and i was told doing everything by the book will make ur job a lot longer then it actually can be. my boss told me i should have been out of there in 3 hrs. still a lot to learn.
    Get er Done!

    Do what has to be done
    when it has to be done
    as well as it has to be done
    And doing it all the time.

  10. #10
    Join Date
    Oct 2009
    Location
    Raleigh, NC
    Posts
    794
    If it "skipped past" defrost when you manually attempted defrost, then you most likely have a bad defrost termination/fan delay. The old clock was probably OK.

  11. #11
    Join Date
    Jan 2010
    Location
    Toronto,Ontario Canada
    Posts
    355
    Booo dont tell me that. that sucks
    Get er Done!

    Do what has to be done
    when it has to be done
    as well as it has to be done
    And doing it all the time.

  12. #12
    Join Date
    Oct 2009
    Location
    Raleigh, NC
    Posts
    794
    When that happens, I immediately disconnect X wire and try again. If it is the termination/delay that is bad, defrost will proceed as normal after X is disconnected.

  13. #13
    Join Date
    Oct 2004
    Location
    Central WA
    Posts
    1,497
    With experience your boss would be right, and you could have been in and out of there sooner. Over time you will tend to see the same failures over and over.

    But -- that's boring, and troubleshooting can be fun if you have really good knowledge of how the thing works. Check out page 40, the 2nd diagram of the attached manual.

    HEATCRAFT.pdf
    The "DTFD" allows the fans to run in normal operation. When the unit switches to defrost and heats up, the 'DTFD' will switch contacts, opening up the fan circuit (that is already dead from the clock being in defrost mode) and closing the circuit to "X"

    "X" powers a coil that throws the defrost clock back into normal run mode early. "X" is powered on the other side off of the "3" terminal which drops out as soon as the timer switches, so that coil is only ever energized for a split second. It will actually burn up if it ever sticks on.

    Refrigeration starts, and once the coil cools down, the "DTFD" switches back again closes the fan circuit.

    If that DTFD is shorted it can pass power to X all of the time and cause defrost to skip. Because your fans run through it as well you can see some strange voltage related behavior there, too. You can also get a nasty shock off of the case of that evaporator.

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