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  1. #1
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    Mitsubishi problem



    Hey, iv been working on a mitsubishi heavy duty inverter condensor with 4 indoor units. The problem i have is that each remote was flashing E36 which indicates high discharge pressure. I reset the fault then put my guages on the condensor and started her up, expecting her to trip out straight away but it never happened. The suction pressure on cooling was 6.5 bar and On the high side the condensor fans went off at 15 bar and the compressor carried on running flat out for 15 mins and very very slowly crept up to 27 bar which was when the condensor fans started again. The compressor sounded horrible really really loud. My question is could the compressor be faulty as it seemed that the compressor was working flat out but the high pressure hardly went up. The compressor sounded like it was going to fail when it was ramping up and down and a few times i heard a loud hiss like a pressure release valve coming from the compressor but mitsubishi say the compressors dont have a release valve built in. I think im going to recover all of the refrigerant 21kg to be sure that the correct charge is in because i was told that someone from another company was working on it a few weeks ago "topping it up" with refigerant. Do you think thats the reight idea?



  2. #2
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    Re: Mitsubishi problem

    Hi
    It would be a good idea to try and do a recovery and then charge again
    If the compressor was faulty ( inafficiant) then you will not get high press build up.....also you can check the superheat and subcooling to try and see if it overcharge(at least a general idea)
    Also chack amps drew

    I assume the refrigerant is 410?

    Good luck mate
    ALONEI

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    Re: Mitsubishi problem

    hi no the refigerant is r407c,i checked the amps to the compressor and i was getting 100 amps on each one?

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    Re: Mitsubishi problem

    Hi
    what is the nominal amps?

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    Re: Mitsubishi problem

    100 amps ? at which point where you checking the current,

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    Re: Mitsubishi problem

    100 amps is far too high, this is the sort of current the screw compressors on some of our chillers run at, there must be an incorrect reading somewhere. Use a jaw type clampmeter and check between the inverter board and compressor. High amp draw is caused by high discharge pressure as the compressor is having to consume more power to work against the pressure. This sort of reading should have tripped the main fuse, failing that it would trigger a fault code related to the high current. Can't remember what it is, but on the Mitsubishi Electric I think it's 4310 or something ??
    The suction pressure is high, 6.5 bar in cooling. I would take out the charge and weigh in the correct amount again in liquid phase.
    James
    a problem shared is a problem halved

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    Re: Mitsubishi problem

    Hi
    And don't forget this is 407c if there was a major leak there could be problems if you "topping it up".
    in a major leak the remaining refrigerant needs to be change
    Cheers

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    Re: Mitsubishi problem

    as the other guys said somethings wrong,i would check the current before the inverter because some of them are DC,some are AC and some a mixture as they play with the signwave witch will give a wrong reading on your meter,we proved this just last week on the CITB electrical qualification,even the tutor was a bit screwed,also becarefull of the inverter pack as some hold a deadley charge !!

  9. #9
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    Re: Mitsubishi problem

    Hi Guys!

    I recently installed 5 units of MHI's KX4 inverter type AC system and i got the shock of my life. The units are 24Hp, with 380V, 3 phase power supply. The units were suppose to operate between 60 to 120 Hz.

    These units are dual inverter type units and it is the upgraded version of the KX2 that had one constant speed compressor.

    Mitsubishi Heavy Inc engineers advised me that the required circuit breaker is 200A and that would 1000A on my 5 units! Correct me if I'm wrong but a usual 24hp unit would usually require a 75A circuit breaker from a 3phase 380V supply.

    I'm wondering if anyone have an idea with the dual inverter system. Pardon for the intrusion, this is my first post.

    Thanks,

    Rynor

  10. #10
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    Re: Mitsubishi problem

    sorry to come into this one abit late but ive a great inverter pcb checker from dakin given to me that i use on all makes of ac,will find the part nymber out if anyone wants it(about 40)
    Paul


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    Re: Mitsubishi problem

    Ignore any current readings downstream of the inverter, your clamp on will expect to see normal frequency, take your current readings at the incoming cable after the isolator.

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    Re: Mitsubishi problem

    Fluke do a DMM designed for inverter drive testing, it has a high pass filter button that lets the meter ignore the high frequency noise put out by the invereter, and only reads the true output frequency/amps/volts to the compressor. Model is 87v.

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    Re: Mitsubishi problem

    Quote Originally Posted by laf100 View Post
    Fluke do a DMM designed for inverter drive testing, it has a high pass filter button that lets the meter ignore the high frequency noise put out by the invereter, and only reads the true output frequency/amps/volts to the compressor. Model is 87v.
    Be careful where you stick your meter I would not recommend checking the output of an inverter with a standard meter and would be very reluctant in fitting any meter, even a special to an inverter.

    Maybe meters of this type nowadays can deal with the drive outputs, but remember that drives give out square wave, which is neither DC or AC, that is the problem.

    I have seen voltages over 700 volt off drives. Clamping the amps is a better way to go, but only gives an indication as the voltage will vary so the amps may be higher than expected.

    In short don't do it or be very very careful

    Kind Regards Andy
    If you can't fix it leave it that no one else will:rolleyes:

  14. #14
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    Re: Mitsubishi problem

    Quote Originally Posted by superswill View Post
    sorry to come into this one abit late but ive a great inverter pcb checker from dakin given to me that i use on all makes of ac,will find the part nymber out if anyone wants it(about 40)
    Yes please.
    Brian - Newton Abbot, Devon, UK
    Retired March 2015

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    Re: Mitsubishi problem

    Hi
    Remember a high pressure fault can occur in heating and cooling,although the noisey compressor does not sound too good.Flick it on to heating you might have a blocked filter/evap.

  16. #16
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    Re: Mitsubishi problem

    Quote Originally Posted by Brian_UK View Post
    Yes please.
    brian that part number is 1225477 and they call it a power transisto checker,bar the flask its the best bit of kit going in my eyes
    Paul


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