Results 1 to 7 of 7
  1. #1
    Join Date
    Oct 2005
    Posts
    40
    I was wondering if someone could explain to me how a defrost cycle works. From what I have been told the unit has a sensor and when the sensor detects that the coils have reached a certain temperature it initiates a timer to start the defrost and this timer can be set at intervals of around 30,60, 90 minutes. What I am wondering is does this timer only initiate the defrost if the compressor has run continueously for this time or does it also does it also calculate time in between runs. Lets say the timer is set at 60 minutes and the unit only runs 15 minutes at a time. Would it initiate a defrost after the unit has run about 4 or 5 cycles at 15 minute intervals?

  2. #2
    The timer only ticks when the unit is running.

  3. #3
    Join Date
    Oct 2005
    Posts
    40
    When the unit turns off does the timer reset?

  4. #4
    Nope.

  5. #5
    Join Date
    Oct 2005
    Posts
    40
    Thanks that answered my question. I noticed our unit going into defrost mode even when it was frosted over and noticed sometimes the unit is only on for a few minutes when the defrost cycle kicks in. It makes sense if its doing this if the timer doesnt reset when the unit is off and is calculating the run time from the previous cycle.

  6. #6
    Join Date
    Apr 2005
    Location
    Kingston Ontario Canada
    Posts
    1,211
    Originally posted by mgfarmer
    Thanks that answered my question. I noticed our unit going into defrost mode even when it was frosted over and noticed sometimes the unit is only on for a few minutes when the defrost cycle kicks in. It makes sense if its doing this if the timer doesnt reset when the unit is off and is calculating the run time from the previous cycle.
    Yes, I have noticed that my heat pump does the same. That is the problem with timed defrost, rather then demand defrost. If the heat pump is close to a pre-set timed defrost and the stat becomes satisfied and shuts the heat pump off, the next time the stat calls for heat (even though the frost may have naturally disapeared)it will still go into a timed defrost even though it is not warranted. I have seen this happen numerous times in my case. This is why I wouldn't buy a heat pump again unless it has demand defrost, rather then times defrost. Too many un-warranted defrosts with timed defrosts.

    Thorton
    ________________________
    We cannot change yesterday. We can only make the most of today, and look with hope toward tomorrow.

  7. #7
    Join Date
    Oct 2005
    Posts
    40
    Thanks for the reply. I have never really paid attention to it until last night. I wasnt sleeping well and since the unit is outside our bedroom window I could hear when it was going into defrost.

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