How to charge correctly?

[david2008]

Calculate by hand? or looking at the glass when charging? Thanks.


Cheers,
David

[chemi-cool]

After you are satisfied with the vacuum, charge liquid into the receiver, about 3\4 of the system charge, fill the low side with gas and start the unit, add gas slowly while the system is balancing and when you are close to the set point, the sight glass should clear and all left to do [ if necessary], is to set the superheat.

[GXMPLX]

chemi-cool is right but assumes you know the system charge.

I suppose you don't know this.

In a one evaporator system you could charge looking at the sight glass IF IT IS PLACED CORRECTLY just before the inlet of the expansion valve. Moreover I would prefer the liquid line to come vertically down to the TXV. Some don’t like to leave a sight glass there permanently but I’ve had no problems with leaks insulating it (yes I know you have to tear the insulation to use it the next time). In any other situation I wouldn’t use it (to charge).
Even if you calculate by hand you have to use another method to check your charge and that would be measuring subcooling. If the condenser or receiver outlet has enough subcooling to feed your expansion device correctly, you reached the necessary charge BUT this should be done at maximum load and RE CHECKED at minimum load. And believe you me, even estimating when this happens is difficult because ambient conditions are also involved.
So you are left with re-checking, therefore listen to chemi-cool, buy equipment that states the system charge and follow manufacturer’s recommendation.

[david2008]

Thank you chemi-cool and GXMPLX.

David

[Arc]

When chargining an air con system with know reciever or manufacterers info what is the best option for charging?