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Thread: R407c

  1. #1
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    R407c



    I have a mitz city multi system that was under performing. I decanted the gas (30kg) - and found that it was about 1kg short of the initial charge. I carried out a leak test and found a small leak on a flare nut.

    I know that R407c is a composite of 3 gases and in theory you don't know what gases you have lost. But given that r407c is currently 36 kg - I'm temped to put the original charge + 1kg of new gas back in.

    Would I just be wasting my time doing this - and should I opt for a new virgin charge or is it worth a try?



  2. #2
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    Re: R407c

    .

    I was always told if above 10Kg then advise customer and let
    them decide, if below you would be better off replacing.
    Just make sure the customer is aware of the situation.

    The only trouble is, has it had other leaks before this one,
    who knows what the blend is?

    Some people work to a 5% - 10% rule, if the loss is less than
    the percentage you use then add away if not replace with new.

    Rob

    .
    Last edited by Rob White; 14-02-2018 at 06:54 PM.
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  3. #3
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    Re: R407c

    I'm no Mitsi guru but 1kg short out of a 30kg charge wouldn't have thought you'd have noticed the under performing.
    If your leak was on a liquid line then you shouldn't have changed the composition. Back in my college days I remember the teacher saying the same also goes for a gas line too. The only place that will change the blend is a leak where the glide is. Needs someone brainer than me to confirm that but perhaps something to mull over.
    Smaller glide I know but have seen plenty of Tesco packs topped up with 404 (back when it was cheaper!) and never had any grief.
    Cheers,
    Andy.

    Another edit:
    Came across this, see page 9.
    https://www.google.co.uk/url?sa=t&rc...fXVxlaxfrmhv0L
    Last edited by Tayters; 13-02-2018 at 10:56 PM. Reason: Added stuff because every little helps.

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    Re: R407c

    Thanks. Decided I will drop in a KG and see what happens. That was interesting reading, re the effect of loss on composition. For years - id always been advised that any loss rendered the gas useless.But with gas prices spiraling out of control - it is useful to know, that there maybe some margin for loss without significant loss of performance of the gas.

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    Re: R407c

    .

    407C is a funny gas, they stopped using it in vrv's because of
    the glide. 407C has about 7K glide and in some vrv's the
    refrigerant fractures (fractionisation) and the refrigerant stops
    working properly.

    Another funny thing it does is it changes to 410A

    R407C is made from R32, R125 & R134a and R410A is
    made from R32 and R125 so because the 134a leaks
    out first 407 turns into 410A.



    taz

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    Re: R407c

    Quote Originally Posted by Rob White View Post
    .

    407C is a funny gas, they stopped using it in vrv's because of
    the glide. 407C has about 7K glide and in some vrv's the
    refrigerant fractures (fractionisation) and the refrigerant stops
    working properly.

    Another funny thing it does is it changes to 410A

    R407C is made from R32, R125 & R134a and R410A is
    made from R32 and R125 so because the 134a leaks
    out first 407 turns into 410A.



    taz

    .
    Hi taz,
    Another interesting answer which confuses me somewhat!
    So if a system leaks and the remaining charge becomes R410A.
    What happens to the operating pressures?
    Does not R410A work at much higher pressures
    Grizzly
    Despite the High Cost of Living it still remains Popular!

  7. #7
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    Re: R407c

    .

    Exactly, one of the side effects of 407 breaking down
    is that the pressures go wappy.

    Normally when refrigerant pressures change the high side
    and low side change together, both up and down but when
    407 breaks down the pressures go wappy. The discharge
    goes very high but the suction goes quite low and it can
    cause confusion if you have never seen it before. The trouble
    is because leaks are different the pressures change differently
    and not all faults show the same symptoms.

    Rob

    .
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    Re: R407c

    It would be interesting to hear how that happens theoretically.
    From what I read here in link, pressure could go down, if anything, hopefully someone can explain to us.

    https://www.wikihow.com/Calculate-Partial-Pressure

  9. #9
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    Re: R407c

    .

    As a blend if 407 was condensing at say 35degs c the pressure would be about 13 barg.
    410 @ 35 degs c is about 20 barg

    Glide has an effect with bubble and dew point differences but I have had so many conversations with engineers who have experienced high head pressure with 407 when it loses part of it's charge.

    Rob

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  10. #10
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    Re: R407c

    Quote Originally Posted by RANGER1 View Post
    It would be interesting to hear how that happens theoretically.
    From what I read here in link, pressure could go down, if anything, hopefully someone can explain to us.

    https://www.wikihow.com/Calculate-Partial-Pressure
    Partial pressure of the gas when the gas is ideal but refrigerants are not ideal and I'm not too sure what happens when gasses condense into a liquid. Because the combined pressure of 407 is lower than 410 at any given temperature, the component that is different is the 134 and that makes a big difference.

    R125 & R32 evaporate at similar temps at 0 barg (-50deg c) R134a is practically half that at about -26 Deg c so as the 134 leaves the system the 407 slowly turns to 410.

    Rob

    .
    Last edited by Rob White; 14-02-2018 at 10:37 PM.
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  11. #11
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    Re: R407c

    .

    Plus the molecular size of the 134 is smaller than that of other refrigerants.
    134a leaks out of holes that don't exist so the 134a part of the refrigerant nearly always leaks out first when you have a weepy leak.
    R134a will get where water won't

    Rob

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  12. #12
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    Re: R407c

    Bring r22 back asap oh and r32 while we are at it,we now have more equipment that's got to be scrapped because new refrigerants are not compatible the world's gone barking mad

  13. #13
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    Re: R407c

    Whoops spellchecker should have read r12! !

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