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  1. #1
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    R407 C wall mount LG 7 Kw



    Need an insight into this one. Last year installed an LG Wall Mount, 7Kw Cooling only R407C

    In my opinion it was never as cold as I thought it should be, I put it down to the gas. never mind.........got a call today, unit is struggling

    I hooked up gauges, back pressure is settled on around 2.7 Bar..........then condenser fans cut, I hear a whooshing sound as if a solonoid has opened..........back pressure zooms up to +8 Bar..........condenser fans cut back in and back pressure starts going back to 2.75 Bar again

    After a while compressor and fans stop...............after a while restart again

    Any ideas anyone??



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    Re: R407 C wall mount LG 7 Kw

    I am assuming this is an A/C unit?

    This sounds like a defrost cycle.

    Have you taken a full list of temp measurements?

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    Re: R407 C wall mount LG 7 Kw

    Hi Abe,

    I agree with Gary. If it goes into defrosting cycle when its hot out, check the charge. Another problem that I would check, is the evaporator coil temp sensor. You should check its resistance to see if it is function OK. That sensor is responsible of defrost in cooling mode.

    Another thing that comes to mind. Does the compressor works all the time?
    You say its cooling only so there might not be a 4 way valve in the condensing unit.

    Chemi

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    Re: R407 C wall mount LG 7 Kw

    Given the low back pressure/low SST (about 21F), I would say the sensor is just doing it's job.

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    Re: R407 C wall mount LG 7 Kw

    Yes Gary, but if its cooling only unit then I doubt if there a 4 way valve to preform the defrost.

    Faulty compressor comes to mind, the sound Abe describes is a scroll stopping and starting.

    Chemi

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    Re: R407 C wall mount LG 7 Kw

    A full list of temp measurements would clearly tell the story.

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    Re: R407 C wall mount LG 7 Kw

    OK, I will wait to see what Abe got to say now.

    Chemi

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    Re: R407 C wall mount LG 7 Kw

    Why would an A/C unit on R407C evaporating at 5C go into defrost in cooling mode??

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    Re: R407 C wall mount LG 7 Kw

    I will take full temp readings and report back tomorrow. Yes it is AC , Cooling only.
    Some time back one of my engineers opened the system, I suspect he lost gas in process
    Im thinking..........do I remove all R407 and recharge again??
    I know unit has fan condenser control........hence condenser fan keeps cutiing in and out
    But why did the compressor cut out???

    For a 8KW unit, I would have expected better performance then Im getting

    Its hot like hell, wife wants me to go to supermarket........Ive been working till midnight all last three to four days.........

    But, Im not complaining........

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    Re: R407 C wall mount LG 7 Kw

    Hi Frank,

    I dont know how the LG is built and on our side there is no such thing as "cooling only" but......... when the evaporator coil freezes, a gefrost cycly comes in, controled by the evaporator coil temp sensor.

    It can last for only a few minutes and then back to cooling.

    Because Abe said its a "cooling only" unit, I figured that there is no 4 way valve and it can not go into defrost cycle.

    Frome that point my thouts went to a foulty compressor.

    Chemi

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    Re: R407 C wall mount LG 7 Kw

    Quote Originally Posted by frank
    Why would an A/C unit on R407C evaporating at 5C go into defrost in cooling mode??
    21F = -6C, not 5C. But now that I think about it, perhaps it shouldn't. We need to see the rest of the numbers.
    Last edited by Gary; 10-06-2004 at 08:54 PM.

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    Re: R407 C wall mount LG 7 Kw

    PHP Code:
    I know unit has fan condenser control........hence condenser fan keeps cutiing in and out 
    Have you put the gauges on the high side so you can see the points where the fans cycle off? What about amp draw? What time elapses between the comp off and then back on again?

    So many questions Ayb

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    Re: R407 C wall mount LG 7 Kw

    Surely the boffins in Slough should know the answer to this ..........
    ________
    Jeep XJ history
    Last edited by Argus; 07-02-2011 at 09:06 AM.

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    Re: R407 C wall mount LG 7 Kw

    I don,t know the unit you mention. But I have have worked with 407c I find it a trouble some gas (400 range Zeotropes Blends which remain in the correct proportions only as a liquid)
    Its R134a R32 R125.Your pressures will be all over the place until it settlesI,ve had problems with cellar cooling where it will just not make temp then half the coil ices up then de-ices then the compressor cut out as it red hot.Its no good just topping up the system as the blend proportion will be all wrong.If it was a pre gharged unit then maybe it had a leak from manufacturer and thats why you were never happy with the temp.I would recommend leak checking and recharging but remember R407c can leak from smaller holes than ofn can.Hope this info helps

    Regards

    Bernard

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    Re: R407 C wall mount LG 7 Kw

    Fan speed reduces to maintain head pressure, if system is short of gas the compressor could also be cutting out on it's thermal overload.

    Jasper

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    Re: R407 C wall mount LG 7 Kw

    Taking full readings Saturday morning............Will report soon

  17. #17
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    Re: R407 C wall mount LG 7 Kw

    just seen this one..;-)


    it's to do with the fan speed controller adjustment.

    we had this on an lg unit not too long ago. basically the fan will slow to stop. hp rises then compressor internal relief valve opens and THEN the fan speeds up.!!

    check the set points on the two pots on the controller c/b or that the sensor is in the correct place...

    for proof wire out and see the unit operate correctly

    2.7 bar is about right but up to 3.3 would be okay (providing it's not icing back....)

    cheers

    richard

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    Re: R407 C wall mount LG 7 Kw

    [COLOR=DarkGreen][QUOTE=rbartlett]just seen this one..;-)

    check the set points on the two pots on the controller c/b or that the sensor is in the correct placeRichard

    Im going there 2 moro..........check set points on controller c/b ??

    is that in outdoor or indoor unit???

    for proof wire out and see the unit operate correctly
    Please elaborate

    sensor, that will be on outdoor..........where exactly should it be tied to.

    Thx

  19. #19
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    Re: R407 C wall mount LG 7 Kw

    the circuit board is on the out door unit.
    there are two dials to be set -i think the LG paper is in the car -
    call me after 9.00 am tomorrow (sat)

    i can talk you through it..


    cheers

    richard
    07786960486

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    Re: R407 C wall mount LG 7 Kw

    Overfilled (?) and then high pressure bypass via the internal safety bypass and then final cut-out on the internal discharge sensor?
    Just a guess.
    What are discharge pressures an temperatures Aiyub

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    Re: R407 C wall mount LG 7 Kw

    Thx Rich

    I appreciate your help

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    Re: R407 C wall mount LG 7 Kw

    Ok here goes..........got a bit more info.

    Unit is an LG Cooling only 7.9Kw CS-C306MLBO
    This is the operating scenario

    Back Pressure: 39 PSI
    Head Pressure, hard to tell, only can read pressure from the valve position which is after the expansion device.........no schraeders before the expansion device.
    Anyway HP at that point around 75 Psi
    both condenser fan and compressor ( scroll) running
    then..........Condenser fan cuts off
    Back Pressure starts rising slowly...........then a " whooshing" sound, which I originally thought was some solonoid opening up.........No, its actually coming from the top of compressor head........
    Back Pressure rises to 110 PSI

    At that point condenser fans kick back in............followed by a clicking sound, ( clicks once ) this comes from a power relay on the outdoor circuit board..........Back pressure quickly comes back down to 39 Psi

    This cycle repeats two or three times.............Then both condenser fan and compressor stop running.

    After around three minutes start up again.

    Other data. Compressor running amps fluctaute betwwen 11 and 8 am

    Outdoor Unit
    Air On: 27 C
    Air Off 33 C

    Indoor Unit
    Air On 24.4 C
    Air Off 8.5 C

    Outdoor Unit, Could see no pressure devices , or sensors
    I suspect the condenser fan is being controlled via sensor in indoor unit.

    Condenser Fan cutting in and out, making compressor hot......I think compressor is tripping out.........

    Either a faulty circuit board or a faulty indoor unit sensor

    Sometime back I asked Thermo Cryo for a troubleshooting , or technical manual.........They said.......we dont have such a thing

    I personally feel that technical manuals are a vital necessity, LG, Do u hear?????

    I bought this unit from Hawco.......

    All I know, I need to get this thing sorted before real damage occurs......

    Is it possible to download a manual for this particular model??

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    Re: R407 C wall mount LG 7 Kw

    Hmmmmm... Very strange. Any pressure after the metering device is low side pressure. Interestingly, 75psi corresponds to the evap air off temp. And the other low side pressure is 39psi. This suggests an EPR, designed to regulate the evap air off temp.

    Also the evap airflow seems slow, but this could be deliberate, in an effort to maximize dehumidification. Another possibility could be a restriction somewhere between the two pressure reading points, acting like an EPR.

    It would certainly help to have a piping and wiring diagram.
    Last edited by Gary; 12-06-2004 at 09:23 PM.

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    Re: R407 C wall mount LG 7 Kw

    What do you make of the two pressures after the metering device, Marc? Is there an EPR? Or restriction?

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    Re: R407 C wall mount LG 7 Kw

    Just out of interest

    I also have a problem with a LG 6.9Kw Casette heat pump running on R22. The problem seems to be the exact oposite to Abes problem (Air off is 1.5c, air on is 28c) the indoor coils are icing up, but what I have noticed with the condenser fan is that it will run on its slow speed for a little while, and then slow down / stop, meanwhile the compressor can be heard to become more vocal (Labouring), suddenly the fan motor fires up in its highest speed for a few mins and then return to its slowest speed, suction pressure is 55psi throuhout this. Refrigerant charge is accurate, as these units can be sensitive to the correct charge. I am of the belief that the fan control ( in the outside unit) is not as it should be, though it may also have further issues, I shall be taking a closer look at this unit next week.
    Karl

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    Re: R407 C wall mount LG 7 Kw

    Without latent load, that 5C air off would eventually get you to about 30%RH. This seems like excessive dT, but perhaps the latent load is so high that you need that much dehumidification. I wouldn't want to see the air off temp any lower than that. Dehumidification sacrifices cooling power and efficiency. I would be tempted to speed up the evap fan a little for more cooling and less dehumidification.

    Air off temp of 1.5C seems extremely low to me, indicating insufficient airflow through the evap coil.

    Abe's air off temp (8.5C) seems about right. I think Richard nailed it. Condenser fan speed control problem.
    Last edited by Gary; 13-06-2004 at 02:58 PM.

  27. #27
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    Re: R407 C wall mount LG 7 Kw

    Air off temp of 1.5C seems extremely low to me, indicating insufficient airflow through the evap coil.

    this isn't unusual for a UK installed japanese type split...

    you must remember that these japanese systems run at much lower evap pressures -3 bar approx so on 22 that's well below freezing. this accounts for the high TD. not poor airflow

    note one condenser size fits all round the world-so ours tend to be oversized for the climate...

    with 'proper' fan control (99% don't have FSC fitted as std) the suction comes up to near 'normal' and therefore the TD drops back.

    ask an australian what suction he normally sees from a japanese splt in summer as opposed to us working on the same kit

    i guess they don't ice up that often because we tend to oversize in the UK (or at least we did in the good old days...) and therefore it has a longer off period and they are seasonal use mainly..

    plus there is usually a sensor on the indoor coil to prevent freeze ups anyway.....

    cheers

    richard

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    Re: R407 C wall mount LG 7 Kw

    the only fitting application for an lg wall mount is in a guard shack, hence the term "central Air conditioning", regards

  29. #29
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    Re: R407 C wall mount LG 7 Kw

    the only fitting application for an lg wall mount is in a guard shack, hence the term "central Air conditioning",


    sorry stan this doesn't mean a thing to most of us here..;-)

    cheers

    richard

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    Re: R407 C wall mount LG 7 Kw

    Richard,

    Yes, I think it is Condenser Fan Problem..........the Indoor Unit sensor is probably faulty or not reading right

    I want to connect Condenser Fan permanently in " on " position. whilst compressor operates.

    This unit is only switched on during summer on hot days.

    Im not sure u have wiring diagram ........please advise best way to bypass the condenser fan controller

    Thx

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    Re: R407 C wall mount LG 7 Kw

    Ahhhhh

    Some guys have all the luck !!!!

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    Re: R407 C wall mount LG 7 Kw

    Hi Mark

    Its not a question of luck, you make your own luck in this world!! Its knowing which " key" to use for the right lock.

    Sean is a very good Marketing Man, I know that. So its really great that you guys are doing some sterling and innovative work out there. ( That well hole job )

    You know Reagan has just left us, well if theres anything he taught us is this, The cup is always half full.....

    Getting the right type of work with the right company/ business

    Anyone can put in an air con in Mr Bengalis Tandoori.......and look at his stained teeth and grin as he asks u for a discount..

    Its the right clientelle......I think you guys have cracked it.......

    Well Done

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    Re: R407 C wall mount LG 7 Kw

    Ok, this is an update on the troublesome LG Air Con.

    I rang LG Distribution boffin with symtoms...........Guess what ??? He said wire the condenser fan direct !!!! He even sent me a wiring diagram..........Well, well........

    That fan kicking in and out must have played hell with both back and high pressures......and the scroll compressor

    Anyway, I put in a "fresh" charge of refrigerant......bypassed condenser fan...........and this is what I get.

    Outdoor Unit

    Air on 29C
    Air Off 37C

    Back Pressure ..........Steady on 60 Psi

    Indoor Unit Air On 24 C
    Air Off 7.6C

    Customer says............Wow its cold in here!!!

    The outdoor unit, tripped, cut off once, completely
    But after that stayed on..........and ran

    So we will see what happens, The LG guy says indoor unit air off must be no lower then 12C

    Im getting 7.6C. Is he right?????
    He said any lower then 12C and the coil will ice up.
    Well on some of my units it gets to 5C and lower...

    What Ive learnt.......from this

    I dont think LG and R407C make good company. The way they have designed their systems dont seem to work in harmony, thats my view.

    Hey Mark, fancy letting me have some of your Daikins at your preferential new prices????

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    Re: R407 C wall mount LG 7 Kw

    Evaporator airflow/dT is a trade-off between more humidity removal/longer run time/lower efficiency (lower airflow), OR more cooling/shorter run time/higher efficiency (higher airflow).

    As a rough rule of thumb, in a humid area, the air off temp should be 20-25F/11-14C below the temp at the thermostat, when the room is near cut-out temp.

    For example, if the thermostat is set for 75F/24C, and the room temp is 75F/24C, then the air off temp should be 50-55F/10-13C.

    Heavy latent load may require a lower air off temp, but this brings us closer to freezing the coil.

    In dry areas, the air off temp can be set higher (higher airflow), but too much may overload the compressor and/or condenser.

    There is no "right" air off temp. Everything is balances and trade-offs, and every situation is unique. The system can and should be tuned to the particular needs of the customer.

    Marc's system provides a good example of this. Because the system is undersized, the air off temp (5C) handles the latent load, but not the sensible load. I would increase the airflow a little to optimize the trade-off in the direction of a little more sensible heat removal, and a little less latent heat removal.

    I would also go to full condenser airflow. This system needs all the help it can get.
    Last edited by Gary; 15-06-2004 at 04:55 AM.

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    Re: R407 C wall mount LG 7 Kw

    Indoor Unit Air On 24 C
    Air Off 7.6C
    As you get down to set point Ayb the air off temp will reduce and so cause frosting on the coil. The figures you give don't add up. You are only getting 8K across the outdoor unit where I would expect somewhere around 15K but you have around 16K on the indoor unit? somethings not right.

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    Re: R407 C wall mount LG 7 Kw

    Quote Originally Posted by frank
    As you get down to set point Ayb the air off temp will reduce and so cause frosting on the coil. The figures you give don't add up. You are only getting 8K across the outdoor unit where I would expect somewhere around 15K but you have around 16K on the indoor unit? somethings not right.
    At 24C air on, it should be pretty close to setpoint.

    The low condenser dT indicates more than enough airflow, which should be expected with the fan control bypassed.

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    Re: R407 C wall mount LG 7 Kw

    [QUOTE=Marc O'Brien]So now we'll never know what the problem is. My money's on "short charge", just the for the hell of it

    I think short charge was a definate factor

    I thought we couldn't read back pressure?


    Could not read head pressure

    On LG, low loads or low charge can cause condenser fan hunting when fan speed is controlled via sensed evaporator temperature. We don't know what fan speed control Abe's systems has, well, I don't.

    The condenser fan was controlled via sensed evaporator temperature


    My immediate instincts when first faced with this erratic ac was........Sensor fault, or faulty pcb, giving false readings , hence condenser fan cutting in and out, I was all out to change settings on outdoor unit pcb board...........LG guy even said, change settings , the effect i was hoping for was to allow the condenser fan to run longer

    But this particular model does not have pc board on with settings which can be changed.

    I posted the initial back pressure which was...........39Psi
    No member pointed out that 39 Psi was probably too low and system could do with more gas and a higher back pressure..........more like 50 + Psi

    Getting Condenser Fan to run was priority, and loaded with new charge, well..........something got cured..........

    But, I understand what u say, I should not have had to link condenser fan direct.......System should run as designed....

    Funny.........The Lg guy did not even know that the condenser fan was controlled by evaporator sensor...

    I checked on progress of unit today.............Customer says it is so cold, he has switched it off!!

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    Re: R407 C wall mount LG 7 Kw

    No leak...........I pointed out my engineer opened system last year . Reason, during installation, being a cooling unit only, he thought only suction pipe required insulating.

    So, he pumped down , disconnected pipes . I think in the process he " probably" lost some charge.

    But the unit worked..........okayish.........after that, as I pointed out I was never entirely happy with the performance, I blamed it on R407C.........I posted a thread even about the lack lustre new gas R407C........I called it Dastardly.!!

    The problem may have been compounded by the unit sitting idly all winter, and some further loss of gas.........through ill made flare.........maybe........but not significant, I dont think.

    This summer.........efficiency was worse then last year........hence my probing and investigation...... Last year, CF was cutting in and out...........I did notice that.........The cassette models just run continuosly...........only the wall mounts.

    But, I will carry out a through leak test.........just in case

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    Re: R407 C wall mount LG 7 Kw

    No member pointed out that 39 Psi was probably too low
    Actually, I think I mentioned low SST early on, and then asked for a full list of temps.

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    Re: R407 C wall mount LG 7 Kw

    Its not just the quantity its also the blend as the glide between the gases is vast.I,m surprised the compressor has not given up.

    bernard

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    Re: R407 C wall mount LG 7 Kw

    This thread just wont give up!!
    Compressor is running sweet as a nut.........thanks to my swift intervention.......
    And frankly..........apt and useful advice from fellow members.

    My argument has been.........Yes..........R407C does glide..........but the consequences of a shortage of refrigerant.........or exessive glide conditions will cause thewhole system to malfunction........and yes.......for the compressor to fail.

    Hooking fan controller to evaporator sensor is not the best design configuration.......

    LG............have " screwed" up here. I am not convinced that there was a severe shortage of refrigerant........it probably needed a touch more.........yes agreed.......but on this system the gas charge has to be spot on.........

    I could, if I wanted, reconnect te fan condenser through its controller, and see what happens.........

    But I wouldnt want to......I know......the compressor has suffered enough.......

    Would any other ac system........Mitsu, Toshiba.....Daikin.....have suffered the same fate under these circumstances??? ie: are the condenser fans controlled by evaporator placed sensors???

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    Re: R407 C wall mount LG 7 Kw

    Hi Ayb

    I've been to a Daikin R407C heatpump unit that I fitted, during winter, and was amazed to see 2" (or 50mm) (another thread entirely :-) ) of ice build up on the outdoor coil (evaporator).
    The outdoor fans were not running and at first I jumped to the conclusion that the unit had a problem.

    Only after speakng to Daikin and understanding the operational characteristics of the software did I realise that there was no problem . The indoor room was up to temperature and the defrost logic determined that it was not time to go into defrost.

    I've seen many a weird thing happen with 407 kit and still struggle to understand the logic of the software controls. Have you ever fitted a small 407 wall split, only to switch on and have to wait about 15 minutes for the suction pressures to come up to normal?

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    Re: R407 C wall mount LG 7 Kw

    Frank,

    I refuse to have anything to do with R407
    Every 407 I have put in has had probs.................

    410 A seem to be working fine though.........

    Why have the manufacturers " abandoned" R407C ??????
    We should get compensation from them

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    Re: R407 C wall mount LG 7 Kw

    Hi Ayb

    We installed a new R407C split cassette system for one of our bigger customers about 2 years ago in Buxton. No problem with the install - worked as sweet as a nut

    Problem came when vandals broke into the back yard one night and kicked 7 bells of sh*t out of the condensing unit and pipework

    When we got there the next day we broke into the pipework and put in a nitrogen holding charge to protect the indoor unit and then tried to order up a replacement condensing unit only to be told that we could not have one as Daikin had stopped making them in readiness for the change over to R410a. We had to go back to the customer and tell him that we had to condem the whole system and install a new complete system at his cost - how embarrasing was that!

    We've got the cassette in stock now for spares and we had to scrap the condensing unit.

  45. #45
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    Re: R407 C wall mount LG 7 Kw

    I have learnt something.............150 grams can make or break...... But in the excellence of things, one has to aspire to get things right.

    So, in retrospect, perhaps, If I had paid more attention to the charge of this unit, the probs may have never occured.

    But I know know how important attention to detail is.

  46. #46
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    Re: R407 C wall mount LG 7 Kw

    I recently fitted a LG wall mounted unit (R407c) and spent ages trying to find the leak that I had left on the pipework. Pressure would drop and vacuum wouldnt hold no leak found, It was driving me nuts.
    One of the valves holding the refrigerant in condensing unit had a slight leak and under that little extra pressure was allowing refrigerant/ nitrogen to pass HO HUM...

    I shall now make a point of rcovering the refrigerant and recharging with fresh, a little overkill perhaps, but I do like things to be right

    Am still to return to my little cassette, so no news there yet
    Last edited by Karl Hofmann; 18-06-2004 at 08:44 AM.
    Karl

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    Re: R407 C wall mount LG 7 Kw

    I spoke to a project manager of a AC maintenance company. They have had same " fractionalisation" probs with R407C

    So I am not only one, only the manufacturers have kept it a " low key" affair..............No one has pointed out the major probs with R407C

    No one has yet been able to tell me............" Why have the manufacturers abandoned R407C in favour of 410??"

    In LG's case..............they way they designed a evap sensor to control cond fan.............is " flawed" ie: it does not make for a forgiving system.

    And they wanted plumbers and electricians to installl them??????

    Ha haaaaaaaaaaaaaa

    I will not now fit another LG.............ever!!!! You can stick all your carrots, bonus points.........incentives

    I will fit maybe Fujitsu........

  48. #48
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    Re: R407 C wall mount LG 7 Kw

    in my previous company there was a major issue with 407 which very very nearly ended up in court.

    (the units in question came from the west country reigon..)

    i think 407 will be left to wither on the vine as 410 takes hold and becomes the accepted 22 replacement as all the scare stories have pretty much died out..

    these issues are all related to the speed which cfc's were driven out.

    cheers

    richard

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    Re: R407 C wall mount LG 7 Kw

    Rich

    You warned me about LG a year ago...............Now, I agree with you
    They are the dogs dinner........Lack real class
    Just shows, you can spend all the money on marketing
    strut your chest.........end of the day, real quality will always prevail

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    Re: R407 C wall mount LG 7 Kw

    Hi Abe.

    Just remember to keep this information away from your customers.

    Chemi

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