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  1. #1
    Join Date
    Oct 2007
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    New Zealand
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    45
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    Critical charge DX system



    Hey. As per our Aussie neighbors us kiwis have signed up to an Emissions Trading Scheme and our refrigerants will soon cost a whole heap more. I have a DX R404a glycol chiller using remote air cooled condensers and a substantial receiver that needs to be relocated. I have proposed to my customer that to reduce the refrigerant charge we remove the air cooled condensers and install PHE's to minimize future refrigerant costs should a leak develop. I have considered this further and I have pondered a critical charge system without the receiver.
    I have commissioned many critical charge NH3 systems with high side float in exactly the same application so why not with R404a? I guess the serviceability will be reduced as there will be nowhere to pump down to should a component fail but I think I could get the charge down below a single jug (10.9kg) doing this. The thought was to update the current TE12 TEVs to Carel E3V to make it more stable and as it is in a pretty stable process (no wild swings) I could see this as a reasonable option. The current remote condenser was not installed by me and the liquid drain is hideously small, creating liquid hang up in the condenser. This system currently holds far too much refrigerant and Id guess we could decent the bulk of it and have surplus should it be needed.
    Any thoughts, or does anyone have a setup operating as described in the real world that runs well?



  2. #2
    Join Date
    Nov 2008
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    australia
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    Re: Critical charge DX system

    hey kiwi, all our super market a/c have massive dx plant. depending on budget. you could have a muller 3c cooler with a plate heat ex for condenser and drop your refrigerant charge by a massive amount. the 3c cooler will stop water treatment costs associated with a cooling tower. r404a is worth a fortune now. with a plate heat ex you could also put in a small receiver. the carel e3v would also help with efficiency. I guess the rate per KwH is also going up.

  3. #3
    Join Date
    May 2007
    Location
    Auckland
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    67
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    Re: Critical charge DX system

    Hi Kiwi.
    interesting proposition, I would start by fitting MOP TXV s for a start to stabilize/gauge actual liquid storage requirements between max load and min loads. PHE's don't rapid cyclic temp changes. I would still be installing a smallish receiver vessel for pump down reasons after you change condenser to PHE. The system volume charge will reduce conciderably.

  4. #4
    Join Date
    Oct 2007
    Location
    New Zealand
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    45
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    11

    Re: Critical charge DX system

    Quote Originally Posted by Magoo View Post
    Hi Kiwi.
    interesting proposition, I would start by fitting MOP TXV s for a start to stabilize/gauge actual liquid storage requirements between max load and min loads. PHE's don't rapid cyclic temp changes. I would still be installing a smallish receiver vessel for pump down reasons after you change condenser to PHE. The system volume charge will reduce conciderably.
    Yes, the Carel EEV has a MOP function which I also considered as a good reason to use them. The existing TEVs are OK but still no where as stable or accurate as the EEVs. I have seen a slave type receiver on another system that is not in service in normal operation but can be used as storage for service work.

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