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  1. #1
    Join Date
    Aug 2011
    Location
    Kingston, Ontario
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    207

    A/C sometimes runs for very short time

    We have a Mitsubishi Zuba heat pump. Approx 3ton. Consists of Mitsu outdoor unit married to ADP air handler and controlled by Honeywell VisionPro tstat.

    The system works well for both heating and cooling. However, I have noticed that at times, the outdoor unit will start up and only run for a very short time - maybe 15sec, then shut down again.

    Would that be normal?

  2. #2
    Join Date
    Dec 2002
    Location
    Houston,Tx.
    Posts
    15,849
    Could be low on charge and shutting down on low pressure, I would call for service soon.
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  3. #3
    Join Date
    Aug 2011
    Location
    Kingston, Ontario
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    207
    Ok thanks. I will try and get someone to come and look at it.

    It was just installed new last Fall, so should not have leaked. Installation still under warranty.

    ADDED: Just a thought - could this be just the outdoor fan (not the compressor) starting and shutting down because of high temperature? My car has an aux fan that does something like that!

  4. #4
    Join Date
    Jan 2011
    Location
    Metro Atlanta
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    777
    Quote Originally Posted by Mr Bill View Post
    Could be low on charge and shutting down on low pressure, I would call for service soon.
    Quote Originally Posted by Freeagent View Post
    Ok thanks. I will try and get someone to come and look at it.

    It was just installed new last Fall, so should not have leaked. Installation still under warranty.

    ADDED: Just a thought - could this be just the outdoor fan (not the compressor) starting and shutting down because of high temperature? My car has an aux fan that does something like that!
    Lets just say it is the fan, you still need a pro to tell you the issue with it and fix it right?

    Do what Mr Bill said, and I would call before major damage occurs.

    A leak can happen anytime.
    The opinions expressed by me are not that of my employer.


    insulation modern marvels
    http://www.youtube.com/watch?v=g37riSkyZzM

  5. #5
    Join Date
    Aug 2011
    Location
    Kingston, Ontario
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    207
    Quote Originally Posted by NY2GA01 View Post
    Lets just say it is the fan, you still need a pro to tell you the issue with it and fix it right?

    Do what Mr Bill said, and I would call before major damage occurs.

    A leak can happen anytime.
    Well I did say in my first sentence that that was what I was doing. In fact the Mitsu distributor's engineer will be here tomorrow.

    My secondary question about the fan was just because I don't want to bring the installer here to look at something that may be quite normal. And because installation and workmanship is under warranty, it will be on the installers dime. Don't want to waste their time unnecessarily.

    I thought that I might get some insight here on that issue, but I guess best thing is to talk to the guys tomorrow who know something about how the system works.

  6. #6
    Join Date
    Jan 2011
    Location
    Metro Atlanta
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    777
    Quote Originally Posted by Freeagent View Post
    Well I did say in my first sentence that that was what I was doing. In fact the Mitsu distributor's engineer will be here tomorrow.

    My secondary question about the fan was just because I don't want to bring the installer here to look at something that may be quite normal. And because installation and workmanship is under warranty, it will be on the installers dime. Don't want to waste their time unnecessarily.

    I thought that I might get some insight here on that issue, but I guess best thing is to talk to the guys tomorrow who know something about how the system works.
    I was not giving you a hard time, just telling you how to get the problem repaired properly.

    Here is the big problem, this is the internet, we are not standing at your unit to be able to see what the unit is doing, so it's hard to tell you what's wrong accuratly.
    The opinions expressed by me are not that of my employer.


    insulation modern marvels
    http://www.youtube.com/watch?v=g37riSkyZzM

  7. #7
    Join Date
    Aug 2011
    Location
    Kingston, Ontario
    Posts
    207
    Quote Originally Posted by NY2GA01 View Post
    I was not giving you a hard time, just telling you how to get the problem repaired properly.

    Here is the big problem, this is the internet, we are not standing at your unit to be able to see what the unit is doing, so it's hard to tell you what's wrong accuratly.
    From discussions with rep today , it seems fan behaviour is likely normal, but will confirm with tech guy on Monday. System is cooling very well even in recent very hot weather. Before heating season, we will definitely have the system checked out.

    Re this being the internet, you are right that you can't diagnose at a distance. Haven't been here for a while, but reason to have such a forum must be more than just telling anyone posting a question to call in a tech. Owners like me, are looking for a little insight into problems before deciding on best course of action (which may very well be to call in tech)

    I think I am good on this thread now.

  8. #8
    Join Date
    Aug 2011
    Location
    Kingston, Ontario
    Posts
    207
    I discussed this with Mitsu rep and he said it could be unit running and opening valve for short while so as to return oil to compressor after a period or running at low load.

    But today I happened to be there again and it seems this was just a red herring! The outdoor appears to start up and run for 10-15sec. But, in fact it is not shutting down. It just runs at high rate briefly before, I guess, the controls take over and it cuts back to a low rate. It is so quiet after cutting back that it seemed it had shut down. Have to look inside to see it was actually running (indoor unit running too).

    So sorry for the misleading question. It seems all is good!

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