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  1. #14
    Join Date
    Apr 2004
    Location
    Niantic, Illinois
    Posts
    545
    Originally posted by BaldLoonie
    30 degree drop? You ain't movin' much air! Do the customer a favor, go back on a warm day. Wrapping the coil simulates a warmer day but most charging charts ask outdoor temp. What is "outdoor temp" on a 55 degree day with plastic around the coil? If charging a piston system properly, you need indoor wet bulb. In cool weather, so low it is off the chart.
    It's easy enough to figure out and close enough to get you by. It varies from seer to seer. Let's look at a 10 seer. The condensing temp on the inside scale of the liquid guage is approximately = to the discharge air temp of the condenser. We know a 10 seer matched unit has a 20 degree delta t across the condenser coil. Wrap the condenser coil and maybe even block the condenser fan to drive the liquid pressure up until you reach 95 on the inside scale. Take your 95 and subtract your condenser delta t and now you know you can charge the unit like it is a 75 degree day. Take your wet bulb and everything else as usual. Just make sure your liquid pressure is holding steady. You must have the home up to 74 degrees inside and a little humidity from the humidifier doesn't hurt. If there is no indoor load there are no tricks in the world to help with that.

  2. #15
    right on berad ... and if you are going to paint anything paint the drier so it wont rust ... we install a sight glass on every single unit ... yea i know but it is fun to watch the bubbles

  3. #16
    Join Date
    Jan 2003
    Location
    Kansas City
    Posts
    1,484
    Another way to approximate simulated outdoor temp when wrapping a coil is to record condensing temp of unwrapped coil---record stable condensing temp with wrapped coil--take the difference of these two temps and add it to the actual outdoor temp and use the sum as your adjusted outdoor ambient.

  4. #17
    Join Date
    Sep 2001
    Location
    Vancouver Canada
    Posts
    996
    How new is this system, are you sure it has a leak or was it never properly charged after install? Ducane is notorious for undercharging their units. The charge in the comp. is only good for 15' lineset and matched coil. Need to add .6 oz for every foot over 15'.

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