chiller model?? follow the OEM guidelines because the top up method of refrigerant varies as per the type of electronic or thermostatic expansion valve, flooded or dry expansion shell and tube heat exchanger...etc. check the sub cooling and suction super heat if it is built with TXV. check the refrigerant level and percentage of EXV if it is built with flooded shell and tube and electronic expansion valve.
Typically you need a sight-glass or you're doomed. If you don't have one open the system and put one in.
Alternatively you need to completely drain the system so you can start from scratch recharging it. If you go this way, reclaim it all. Replace the system dryer-filter and recharge.
I want to predict how much i must expect to charge it. using calculation method.
that's prior to charging itself and monitor subcooling and superheat to adjust charge.
i dont want to drain it and recharge it.
A lot will depend on the refrigerant used, if you have a blended gas you may have to drain and recharge by weight or volume to get the glide correct.
B.E.
You are judged not by what you know, but by what you can do.
There is no really a way to quantify how much refrigerant to add unless the system is completely flat. You can add refrigerant and check Subcooling, use sight glass etc.
Check the logbook and see if any leak developed in the chiller before and check how much refrigerant they have added to the system, this might give you an idea.
