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Thread: R290 top up

  1. #1
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    R290 top up



    Hi guys new to this site,
    Looking for advice on r290 , I've never worked on this before in my many years I've been in the trade, but came across a fosters fridge the other day that was sat at 28 degrees, everything was working (evap/cond fans, comp etc) pressures where -11inhg low side and 50psi high side , after researching what the running pressures should be I've come to the conclusion it's low on gas, I've arranged to pressure test and recharge but the drier is in the most horrendous place as is almost impossible to replace and braze with out burning the side panel which cannot be removed,
    Would anyone just Risk not changing the drier ? And please correct me if any of my assumptions on the pressures are wrong
    Thanks
    Last edited by Leee87; 27-08-2017 at 06:21 PM.



  2. #2
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    Re: R290 top up

    Depending on the fridge model it can be possible to remove the condensing section to make repairs.
    Brian, retired in Devon.

  3. #3
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    Re: R290 top up

    Unfortunetly this is not one of those models the condensor and comp are sat on the top and the drier is sandwiched between the condensor and the side pan of the unit

  4. #4
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    Re: R290 top up

    Maybe advisable to get a basic 1/2 HC course under your belt to ensure your up on the safety side of these refrigerants. A1 rated evacuation pump and recovery machines required.
    R290, as with other HC known to readily mix with oil which moves through the system freely. On integral type systems such as a Foster unit, blocked drivers are not un common I believe.
    I would cut out the drier and blow through the system with OFN as part of the repair process to eliminate a blocked drier.
    As with HFC Foster units some times the 1/4 pipe, drier , capillary assembly can be manipulated into a more easily accessible position to cut out the drier, and a new item soldered in.
    For safety purge through entire system with OFN to remove all traces of R290 prior to undertaking any hot work.

  5. #5
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    Re: R290 top up

    Condensors block with dirt then block capillarys prone to this fault we have had same issues with access either reposition drier or use lock rings we tend to use lock rings more on the flammable gas as I like my eyebrows !

  6. #6
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    Re: R290 top up

    Thanks for your helpful reply Yes I think I'm going to arrange a HC course for future reference, but for the time being I will wheel the fridge outside and let the gas go into the atmosphere then chop out the drier and try re position it, Inwill have to make do with my standard vacuum pump this time (hoping that is safe to use)

  7. #7
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    Re: R290 top up

    .

    There is a lot of hype and fear regarding HC's.
    Treated with respect it is no more risk to you than
    the older R22 refrigerants.

    I would highly recommend doing the HC course minimum
    one day but recommended if you want to buy the stuff.

    Venting in the carpark is an option but I would recomend
    purging with Oxygen Free Nitrogen (OFN) while you attempt
    to braze in the new dryer.

    Actually you need to purge OFN and vac the thing 3 times before
    attempting to remove the dryer (if you unbraze it).

    You do not have to buy a new vac pump, what you do need though
    is an extension lead and only ever switch it on the wall 3 mtr away.

    Use a dryer with a schrader charging stub pre-fixed into it, that way
    you can measure the high and low side.

    Rob

    .
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