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  1. #40
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,104
    My response was tempered.

    You are asking the same question on 2 forums, and posting the answers I guess from each to the other. I know barbar has been looking at the responses here, he checked them at 6:28 AM today.

    You have been advised against it on this site. And say the other site has given you technical info/data. No they haven't, it only sounds good to you.

    You didn't answer what brand he installs and works on. And, too many cooks do spoil the soup.

    I wish you good luck.
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  2. #41
    Join Date
    Nov 2011
    Posts
    22
    Thanks beenthere,
    My response was that of frustation and should have been "more tempered".
    It is frustrating and confusing to say the least when experts give opposing views.
    I am knowledgeable in Electrical/Electronic engineering but sadly lacking in the field of refrigeration and thermodynamics (which is also frustrating).
    But, I will percevere untill I get to the bottom of this.
    The guy you mention who was back and forthing with you through me was having to do so as he was not allowed to post on my thread in your forum.
    It would be great if you two were somehow able to argue directly.

    Regards

    pilko

  3. #42
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,104
    I don't argue. But I debate strongly sometimes.

    The requirements to become a Pro member, and to become vetted to post reponses in AOP discussions are for equipment owners benefit. Some don't think its worth their time.
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  4. #43
    Join Date
    Nov 2011
    Posts
    22
    Update:-
    I have been defrosting with the indoor fan shut down for the past 5 weeks . (approx. 120 defrost cycles). It works fine and I have had no problems.

    pilko.

  5. #44
    Join Date
    Jul 2009
    Location
    South Carolina
    Posts
    3,222
    Quote Originally Posted by pilko View Post
    Update:-
    I have been defrosting with the indoor fan shut down for the past 5 weeks . (approx. 120 defrost cycles). It works fine and I have had no problems.

    pilko.
    I've been reading through this thread & though I haven't read it all it is a lot more interesting than I thought it would be. Any HP manufacturer or tech support would say as a fact that the indoor blower should always run during defrost & I would agree. You have evidently done significant research & found some conflicting data to support the alternate view which most anyone who works on HP's would disagree with. You have to remember HP's are designed for a variety of climates & yours may be such that a defrost is not needed very much so you mat be able to get away with stopping the blower while someone in another climate may not. There is no question that stopping the blower motor during defrost will lower the added cooling btu's entering the structure & also lower power consumption during that time but it also will make the defrost less efficient if it is really needed. Also compressor flooding should be a serious concern.
    Gary
    -----------
    http://www.oceanhvac.com
    An engineer designs what he would never work on.
    A technician works on what he would never design.

  6. #45
    Join Date
    Nov 2011
    Posts
    22
    Thanks Gary, for being a little more open on your thoughts.
    It would seem that only North American heat pump systems continue to run the indoor fan on defrost, much of the rest of the world, turn off all the fans during defrost. These system are designed to run as low as -15C ambient. This is limited to refrigeration compression ratio limits, and not defrosting limitations.
    Your concern on flood back is valid, in this case total charge and size of the suction accumulator was taken into consideration. Liquid flood back would not occur. How ever vapour at saturation may enter the compressor, but this is not really an issue, as the refrigerant passes over the comp motor, picking up sufficient superheat to ensure that oil dilution will not occur for the short defrost period.
    Technically there is no reason why all systems in your neck of the wood s can not be converted, but there are practical limitations, such refrigerant distribution (primarily the out door coil), defrost sensor position and general control scenario. How do we determine defrost efficiency, defrost should be slower without a fan running (less energy picked up from the evap), so it would be fair to say efficiency is less, but if we include the energy to recover after defrost, then defrosting without a fan is more efficient.

    Regards

    pilko

  7. #46
    Join Date
    Jun 2003
    Location
    Hell Hole Swamp
    Posts
    4,180
    When I was young (and poor) I installed a used system in the house I was renting, there was insufficient electrical service for auxiliary heat, as expected the defrost cycles caused a problem, I configured a relay to turn off the indoor fan during the defrost cycle to see what would happen, at first it seemed to be ok, longer than normal cycles but the cold air and severe temperature drop were gone, but most of these defrost cycles were the "unnecessary" ones inherent with a time/temp defrost system.

    Then came a cold and damp weather system, it wasnt long and I had an iceberg sitting behind my house, attempting to defrost itself every 30 minutes and terminating on the time limit, while I was inside freezing my rear off.

    Id like to see how you fare after some harsh weather conditions, such as mid 30's and rain.

  8. #47
    Join Date
    Nov 2011
    Posts
    22
    @ Swampfox,
    Here in Nova Scotia we have had all the bad frosting conditions in the past 5 weeks, from freezing rain to wet snow to -14*C. Defrosting has not been a problem.
    My friend who lives 30 KM closer to the coast is also having no problems since he started with this mode 5 weeks ago.

    pilko

  9. #48
    Join Date
    Apr 2011
    Location
    SE Washington
    Posts
    536
    Carrier has never designed an American market heat pump system that shuts down indoor fan during defrost. Not engineered that way...
    Total Energy Management, inc

  10. #49
    Join Date
    Nov 2011
    Posts
    22
    @ woody19,

    "I wonder how long it will take you to recover what you have spent in designing, making, installing, and testing your unit".

    It is not my intension to recover my costs -- I am retired. Electronics is my hobby.


    "Sometimes over-engineering is ridiculous and I believe you have accomplished at least that"

    My Heat Pump like many others is under engineered, I'm just putting it right.


    "Bash me all you want but imho all you are doing is trying to glorify your ego"

    You do not know anything about me or what motivates me.
    As far as ego, I think you need a mirror rather than a magnifying glass as you appear to be the one with the inflated ego.
    As a professional member of this forum I would have thought that you would have learned the power of constructive criticism rather than destructive insults.

    pilko

  11. #50
    Join Date
    Nov 2011
    Posts
    22
    @ Woody19,
    I came to this forum with a simple question which is the title of this thread:-

    "Should indoor fan shut down when Heat Pump on defrost?"
    The reason I came to this forum was for a second opinion after being told on another forum that it would be OK to stop the fan during defrost.

    On the other forum I was asked questions in order that an informed decision could be made.

    On this forum I was given an outright no.

    I went with the decision of the other forum and it works fine.

    Bottom line --- I got usefull information from the other forum and useless information from this forum.

    Since you have been in business 40 years with a well defined and solidified ego, why didn't you interject with usefull information.

    pilko

  12. #51
    Join Date
    Jul 2009
    Location
    South Carolina
    Posts
    3,222
    Quote Originally Posted by pilko View Post
    Thanks Gary, for being a little more open on your thoughts.
    It would seem that only North American heat pump systems continue to run the indoor fan on defrost, much of the rest of the world, turn off all the fans during defrost. These system are designed to run as low as -15C ambient. This is limited to refrigeration compression ratio limits, and not defrosting limitations.
    Your concern on flood back is valid, in this case total charge and size of the suction accumulator was taken into consideration. Liquid flood back would not occur. How ever vapour at saturation may enter the compressor, but this is not really an issue, as the refrigerant passes over the comp motor, picking up sufficient superheat to ensure that oil dilution will not occur for the short defrost period.
    Technically there is no reason why all systems in your neck of the wood s can not be converted, but there are practical limitations, such refrigerant distribution (primarily the out door coil), defrost sensor position and general control scenario. How do we determine defrost efficiency, defrost should be slower without a fan running (less energy picked up from the evap), so it would be fair to say efficiency is less, but if we include the energy to recover after defrost, then defrosting without a fan is more efficient.

    Regards

    pilko
    If it's true that only in North America they run the indoor fan during defrost that's news to me. The principles of refrigeration shouldn't change that much with longitude & latitude so either we're missing something on this end of the globe or you've been misinformed yourself. I'm not one of the schooled guys or instructors on this forum that knows enough of the science to argue the point so I'll leave it to them. I'm just a guy who knows how to keep HP's running like they're designed to. The blower not running during defrost is an interesting concept if it really works. I just don't see how enough heat is generated to defrost the coil if it gets a good amount of frost between cycles. Again it goes back to climate & not just temp. On some cool damp days a unit might begin to frost up after 5 minutes of run time so by the time the cycle runs its course the coil is frosted over completely. I just can't see a blower-less defrost being able to handle that. I would think you would need an air sensor to check for a pressure differential across the outdoor coil. It also seems that you're going to have to defrost more often with this setup which may defeat the initial purpose. I always set my defrosts to 90 minutes & never have any problems with the cycle being too long to defrost properly. Since you're monitoring the defrost & it works it's hard to argue with success & if any freezing problems come up in the future there's no real harm done. The only real concern is whether or not any damage is done to the compressor. I don't think there is any way to know for sure. When you mention about the size of the accumulator to prevent flooding I highly doubt it unless the unit was originally designed for blower-less defrost.
    Even manufacturers & engineers make mistakes when it comes to changing a design to make things better so its still a roll of the dice.
    Gary
    -----------
    http://www.oceanhvac.com
    An engineer designs what he would never work on.
    A technician works on what he would never design.

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