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  1. #14
    Join Date
    Oct 2011
    Posts
    40
    When you hear the first click, are the defrost heaters energized at that point or are they energized on the second click? It sounds like the defrost timer is working correctly and you have a defrost termination swich location problem or faulty sensor, is the "X" wire hooked up in the timer? if so, try unhooking for a day or so and see if defrost completes, if so, than sensor problem.

  2. #15
    Join Date
    Mar 2005
    Location
    N.J.
    Posts
    149
    The system is time initated temp. terminated. The timer should advance thru unassisted.The 60 min. setting you speak of is a fail safe setting and should not be looked at as a primary defrost time.The uneven frost pattern you mention could be caused by many different things.You must do alot more trouble shooting on this system for a proper diagnoses!!

  3. #16
    Join Date
    Oct 2011
    Location
    Chicagoland Area
    Posts
    4,622
    What brand evaporator coil is it? Heaters on the bottom only or heaters on the bottom and back? In most cases the defrost should only last 20-25min then terminate via the defrost termination switch(X) terminal on the clock. The fact that you have a door that is not being closed with warm WIC air blowing into the WIF will also be an issue. Also check pipe chases and the box seams for air infiltration. You say the heaters only stay on a couple minutes? What's causing them to deenergize? A heater limit? The DFTS(sometimes they short internaly)? Are these switches located on the utubes or attached to a bracket? I have always set timers in WIF in restaurants to defrost every 6hrs and set the backup for 45min.
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  4. #17
    Join Date
    Nov 2011
    Posts
    9
    The heaters energize after the second click, after the pump down. The unit is time initiated and temp terminated. That fact may resolve one of my concerns that the heaters do not stay on long enough. Once that coil reachs 50F the defrost termination switch will denergize the heaters and energize the solenoid. There are two heaters one loops through the coil and the other is a drain pan heater. Its a Heatcraft evap. The timer is set for 60 min every 6 hours. There are deffinetly more problems with this unit, I just wanted to understand how the timer works. If its set for 60 mins and the heaters heat up that coil to 50F within 20 mins will it cycle the heaters on and off or is the defrost over once the defrost termination switch closes?

  5. #18
    Join Date
    Oct 2011
    Location
    Chicagoland Area
    Posts
    4,622
    Defrost termination switch/fan delay switch energizes the X terminal on the time clock which is connected to a soleniod that switches the NO to NC and the NC to NO and the freeze cycle begins again.
    Edit: The heater safety and termination/fandelay are affixed to the side support located on the outlet side of the coil approx 1/2 way up from the bottom. This would explain why you continue to see ice on the top half of the coil if one or both the switches are bad. The drain pan heater may not be working causing the bottom half of the coil to stay frozen. Both heaters should draw the same #of amps. With the info given, I'd be wiiling to bet the warm air infiltrtion is the main issue which iswhy the front (outlet) of coil is freezing.
    Last edited by 2sac; 11-30-2011 at 07:27 PM.
    Officially, Down for the count

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  6. #19
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,670
    Maven445,

    You need to look at the system as a whole rather than focusing on JUST the timer.

    The frost pattern you are describing is somewhat unusual and not likely caused by a timer problem.

    Check your charge and superheat.

  7. #20
    Join Date
    Oct 2011
    Location
    Chicagoland Area
    Posts
    4,622
    Quote Originally Posted by jpsmith1cm View Post
    Maven445,

    You need to look at the system as a whole rather than focusing on JUST the timer.

    The frost pattern you are describing is somewhat unusual and not likely caused by a timer problem.

    Check your charge and superheat.
    Based on what the OP described
    The front freezes up really bad with soft ice on top and solid ice on the bottom. The back freezes up just on top.
    I also agree it's probably not a defrost issue.
    Do you really think it's a SH or Charge issue? I understand your thought process to a point but the fact that the entire front of the coil freezing up makes ke think it's due to high humidity levels or air infiltration. It's been my experience that a charge or metering device issue would freeze the bottom or inlet portion of the coil, but shouldn't have an effect on the entire face of the coil. No? Could be a combination of issues.

    OP, Have you checked fan rotation? Aftermarket Heatcraft fan blades have the hub on the opposite side as the OEM fans.(when installed the hub is on the motor side of the blade rather than the fan guard side of the blade) It's possibe someone could have replaced a fan blade and installed it backwards, reducing airflow across the coil.
    Officially, Down for the count

    YOU HAVE TO GET OFF YOUR ASS TO GET ON YOUR FEET

    I know enough to know, I don't know enough
    Liberalism-Ideas so good they mandate them

  8. #21
    Join Date
    Feb 2004
    Location
    British Columbia, Canada
    Posts
    521
    Old thread but the following info still applies...

    Defrost coil completely with hot water/ice cutting gun.
    Shut the door. Problem solved. Have seen this same situation all too often. Put buzzer on freezer door switch if staff can't be trusted to shut it completely.

    IF door HAS been confirmed shut and problem still exists, Airflow checks, Heater checks, DTFD checks(proper #'s for that evap-have seen someone replace with what they had-not good enough), Adjust duration to LESS than 60 minutes, all as explained above.

  9. #22
    Join Date
    Apr 2012
    Location
    Northern Virginia
    Posts
    30
    You need to make sure that the defrost termination thermostat is opening and closing at the correct temperatures. After that the only other issue would be the defrost clock and or a wiring issue. Nobody's perfect man. We've all done it before. Just double check your wiring diagram.

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