Originally Posted by Jolly Roger bus 223
over charged can/will show the same symptoms as undercharged and could eventually kill the compressor.
roger - the minisplits have an accumulator for this purpose.. in the manuals for every single one of them that I have an installed (including fujitsu) the books manetion that the pre-charge is for "up to" a certain lineset length..
the accumulator is designed to hold extra liquid, because that liquid is in an insulated bottle you dont have issues with boil-off causing high evaporator pressure.. with the expansion device in the outdoor unit you have quite a bit of difference in capacity need for heat vs cool , the accumulator handles that discrepency in charge...
to the Original Poster
I dont recommend precharged linesets.. esp if you try and buy them with a unit that has already been precharged in its condensor for a full charge.. only use them as part of a package where they are designed for the unit they are sold..
many minisplits come precharged for 25 feet of lineset maximum.. shortening it to 10 feet isnt going to cause an issue.. it will run just fine. ive installed more than one with 10 feet of line ..
if you go longer then you will likely have just-fine cooling but the heating cycle will lose efficiency and capacity unless you weigh-in the extra charge per the formula given in the install manual..
anyone installing a unit do be sure to Vac it down or have it done.. and leakl tested.. the flare fittings are notorious for leaking... so when I have the luxury like putting in one of my own units.. I vac it down and punch it with 200 PSI of nitrogen and let it sit overnight..
since the king / service valves are closed, the refrigerant is safely sotred away in the condensor but you fill up the rest of the system including all 4 flare connections...
if you have a good flaring tool and know what you are doing, you can shorten a lineset and make new flares..
I also like the flare seals sold everywhere.. they are a plastic-coated Copper sealing washer.. I havent had a set leak with the sealing washers yet.. I decided to try them to see if it would help the DIYers get good seals on the (often) crappy flares from china..
I didnt have any luck with the flare seal Liquid (I purposely cut a somewhat shady flare for testing in my HVAC lab at home).. but the physical seals work good so far..
getting a system Vacuumed down is important. I know some will tell you they are cowboys and just winged it.. and the unit will run.. for awhile and probably even blow cold air but it likely wont last super long and not be as efficient..
theres a reason ive gotten 14 years from 2 of my 3 Cheap chinese chigo units when most were tossing them for failure after 5 (one of mine got whacked by lightning)... the 2 units still in service havent had an ounce of freon added since 2010 (after I learned how to flare right)..
so if you put them in right you can get great service out of them.. granted mine are stationary and not getting bounced around in a bus all the time..