split inverter unsure of proper charge spec.. how to charge?

[cadillackid]

so I go out on site and find there is trouble in 2 of the customer's mini splits... one is an amcoraire and one is a Grunaire similar to the 3 i have at home....

the amcor was easy.. thank god since the company is gone.. was electrical supply problem...

the grunaire brought me to my knees... its low on charge... I find a leak in a flare at the outdoor unit.. recover it, and i recovered over a pound less than the label on the machine...

customer ordered the unit as a kit with included 25 foot lineset... similar to my units...

so I read the label on the machine, pull out the PDF from grunaire and realize there is a discrepency...

the grunaire book says anything over 16.5 feet requires additional charge per the included formula...

this unit not critical so I leave site and start researching...

so now im at a loss....

the wholesaler contacts grunaire and they say that the units are built specially by chigo with a 25 foot lineset charge in the outdoor unit..

Chigo the manufacturer from china gives me no real answers but says "try charging by the Book"....

the book from grunaire says charge 0.7 oz additional R-410A for each foot of pipe over 16 feet...

the grunaire people claim the units are charged for 25 feet of line....

these are R-410A inverter units..

so whats my best route to go here? 410A is sensitive.. its near impossible to charge an inverter with gauges... is it better to be under or overcharged...
it would seem to me if the unit were undercharged it would tend to work Ok on cooling but not as well on heating... and if overcharged it would tend to work better on heating but lack on cooling...

mainly because of the amount of liquid line in use wit hthe expansion device in the outdoor unit....

what do you guys think??

do any of you have chigo built units that are advertised and sold for 5 meters(16.5 ft) of Line versus 7.5(25 ft)? that you can read the label of charge and then I can compare to the labels on my and my cusatomer's machines?
-Christopher

[ballvalve]

what size are the pipes

[cadillackid]

the pipes are 3/8" and 5/8" on the 1.5 ton unit...

I ended up weighing in the charge spec'd on the label and running the system... of course it ran in cooling just fine... in heating on max the discharge line was a bit warmer than the pressure indicate.. so i weighed in the extra amount of refrigerant per the formula in the manual.. it indicate .7 oz per foot of lineset.. and I have 9 more feet or 6.3 oz.. I weighed in 7 oz....(to account for the little im going to lose unscrewing the gauges...)....

really amazing how a small amount of charge can affect a unit...

the unit was about half down on charge when I started... i weighed out 2.6 pounds... and in cooling mode it still raun fine... typical mini split - runs fine in cool on way low charge...

in heat mode it was easy to tell long before leak testing it was low... (discharge temp of 171 degrees, liquid temp of 118, and air temp 108) and of course low pressure... and compressor was running maxxed flat out all the time

after the label charge was pushed in.. discharge temp would rise to 140, liquid temp 125.. air temp 118 and compressor would reduce a bit but still run awful high for the warm day it was... pressure still didnt quite match PT chart

pushed in the extra 7 ounces... discharge temp 132, liquid temp 122 and air temp 120-124.. compressor was running much less than capacity.. and pressures and temperatures dead on...

so i guess it means the "Grunaire" people need to quit "advertising" their systems are ready to go!...

so i went home, reclaimed, and weighed in charge on my 3 units at home....adding proper charge per book....

I really hate advertising sometimes....!
-Christopher

[sedgy]

cadillackid. how much gas do you loose every time you pull off your gagues? dont you use quick relese conections?

[cadillackid]

for the mini split I have to use the 1/2 x 20 adapter that is screw on and cannot use my quick release connectors.. ..
-Christopher