Mini Split Recharge R410a by pressure?

[LChaminés]

Hi, I'm from Portugal and we started working with mini-splits recently and things are going smoothly but it appeared a difficult situation of sorts..

The case is, we were called to see an mini-plit system witha possible leak (Panasonic) that someone else installed, as we got there we found the leak (bad flare making a corner almost inside the wall..).
So, after we fixed the leak we had to top up teh R410a (it made no cooling air and the client said it had ice on one of the pipes before, I'm guessing it was the hi-pressure side).

So instead of reclaiming all gas, making vacuum and top up with weight (the good way), we didn't do that since we haven't yet buyed a reclaiming gas machine (name is wrong I know), so, we trapped the gas inside the exterior unit, vacuum it and after that we added gas by pressure, The technical assistance said that the normal operating pressures are under 6.5Bar and 11.4Bar on the service valve, so we toped it to 8.5Bar, since it was making cool air again we left it like that.

Finally.. So my question is, does anyone knows of a chart/table that indicates recomended pressures for mini-splits r410a so we could use this method to top up without weight, or is this so wrong that no one should try this and therefore there's no pressure table for adding gas ina mini-split.

[Brian_UK]

You should always charge by weight as you have suggested.

This is be specially true if the split is an inverter driven system.

[The Viking]

The only way to ensure you got the right charge in the system is by weight. By reclaiming the charge and weighing the correct charge in.
Further more, R410a is a blend of two refrigerants and if you had a significant leak then it is likely that the mixture of the remaining gas is no longer R410a, therefore if you had a leak the best practise is to recharge with virgin refrigerant.

But, ignoring best practice, to verify that the charge is in the right ballpark the only option is to look at the subcooling whist the system is at full load/speed. But to do this you also need previous running data or an identical (fully operational) system to compare with.

[nike123]

By subcooling if it is electronic expansion valve, and by superheat table if it is capillary tube used as expansion device.
Also, charge should be adjusted for operating mode in which unit need more refrigerant (usually heating mode).
Since in heating mode, on split system, there is no low pressure connection, superheat cannot be checked by measuring pressure, without adding service valve.

To OP! Buy reclaiming device, because that is only way for avoiding repeated calls.

[LChaminés]

Thanks for all the answers, I thought i dropped the ball on that one and so I did, we usually don't go on assistance calls and that's why we never bought the recover gas pump, but i guess before the next assistance (we only had that one..) we´re gonna have to invest some more money..
Thanks again for all the help, have a nice day.

[assailant]

...we toped it to 8.5Bar, since it was making cool air again we left it like that.

the previous replies are all entirely correct. but at that pressure i reckon your unit will be spot on and you wont have any troubles

[nike123]

And you saying that without knowing any temperature at that place!

Not mentioning that at that pressure unit can be heavily overcharged as much as correctly charged.

[assailant]

it aint perfect, it aint right... but itll be fine.

the charge should always be weighed in with new 410a, but now its done i wouldnt expect anyone is instructing the OP to revisit site, recover that system and weigh in new refrigerant. 850kpa is about right for splits in normal conditions.
..but next time, weigh it in.

[r.bartlett]

it aint perfect, it aint right... but itll be fine.

the charge should always be weighed in with new 410a, but now its done i wouldnt expect anyone is instructing the OP to revisit site, recover that system and weigh in new refrigerant. 850kpa is about right for splits in normal conditions.
..but next time, weigh it in.

which begs the question, what exactly is normal?

[CraigF]

is this a wind up?

[LChaminés]

Don't know what you are asking sorry?