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  1. #1
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    Aug 2016
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    Daikin precharged unit, vacuum low side only?



    Hi there.

    I have a new multi-split heat/cool unit to install (4MXS80). The job is over on a wee island and my boss has left me alone to complete the work while he's away. Thing is, I've not done a domestic unit with precharge before so I need some pointers.

    1. The Daikin guide says to connect manifold low side to gas service port and close off high side to vacuum line sets. I normally connect both sides before vacuuming. This sounds strange to me. Is it right?
    2. No subcool or superheat tables in guide. Weird. Says 20g/m over 30m...so I need to add refrigerant...
    3. The R410A bottle doesn't mention whether it has a siphon or not. It has to go in liquid so should I assume no siphon and invert the bottle on my scales?

    Anything else I need to know about these precharged installations?

    New market, new boss and just qualified...bad combo on a unit I am also totally unfamiliar with. Any help greatly appreciated.



  2. #2
    Join Date
    Apr 2008
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    Southampton, England
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    Re: Daikin precharged unit, vacuum low side only?

    I found the manual and have to agree, it makes it sound very confusing.

    Outdoor is precharged so connect both manifold lines and vac as normal. When vac is complete, shut off manifold, add the extra charge to one or both pipes and open hexagon screw on service valve and gas will be released into the system. Otherwise add extra charge to suction when in cooling, works either way.

    If only one valve on bottle then probably this is vapour but have seen one valve bottles with a label saying liquid so you'll have to check around bottle for labels or confirm with the wholesaler. Otherwise can you let a sniff out and monitor the sight glass on the gauge to see if liquid or vapour?
    Red valve should be liquid, blue vapour.

    When removing gauge I normally pump it down, save refrigerant shooting out the high side. Don't need to go through the official pump down procedure. Just run in cooling, shut liquid, wait for gauge to reach 20psi odd, whip line off then slowly open liquid valve again. If you are quick enough then you can get the suction off the same time. Try not to let it go in vacuum as you might suck some air in when removing the hose.

    When commissioning run each indoor unit on its own to ensure no pipe and wiring is crossed. If you've got it wrong one indoor will run but another will get a cold coil. On the Daikin there is a wiring error check but this would take a bit longer. Does the same thing, runs an indoor and checks if the right coil gets cold.
    Guess you know but just in case, can only have them all heating or cooling, no simultaneous heat and cool.

    Cheers,
    Andy.
    Health and safety first..........unless I'm in a hurry.

  3. #3
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    Re: Daikin precharged unit, vacuum low side only?

    Thank you for this reply Andy, it's a big help.

    I've spoken with the supplier and he seems to think the Sinochem R410A bottle does have a siphon. There are no markings on the bottle indicating liquid or gas, no mention of a siphon and only one tap which is green...just in case I needed one more reminder that Hong Kong is in China.

    The other thing that I've realised is that because the unit is precharged and I'm using both service ports to vacuum the linesets I am without a service port to connect the digital pressure gauge to. Since connecting the digital gauge to the pump is a no-no, I've ordered a tee connector for the service port (Mastercool part 99333) which should come in handy--I use a Mastercool digital manifold set here.

    Thanks again Andy.

  4. #4
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    Re: Daikin precharged unit, vacuum low side only?

    No worries. If the boss is paying get some quick release connectors as well. :-)
    Health and safety first..........unless I'm in a hurry.

  5. #5
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    Aug 2016
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    Re: Daikin precharged unit, vacuum low side only?

    OK. So I came back to this job yesterday. I evacuated the linesets down below 100 microns and left it there for an hour. I cracked the gas a wee bit and checked once again for any leaks and all looked good. I removed my manifold, reinstalled shrader valves, opened both valves fully, reinstalled caps etc.

    When I fired up the system though, refrigerant only flows to zone B. Turning indoor units on one by one still just zone B producing cool air. Forced cool mode same thing--only pipes to zone B cool down.

    The unit was in storage at the customer's place for a couple of years but it was new out of the box so I'm not sure how three out of four metering devices could be faulty.

    Ever come come across something like this on a multi-split inverter?

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