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pirestani
19-04-2002, 01:08 PM
Good time
What is a general expression (rule) to estimate
weight to be charge into a typical aircool
systems versus ; con. & eva. conditions ,
nominal capacity , inside volume and type
of refrigerant?

Thanks s.pirs.:confused:

terrygoodrich
02-06-2002, 02:58 PM
Your question is not detailed enough to get an accurate answer. System capacity varies widely with different coil designs, size and length of liquid and suction lines, etc. Most cap tube or fixed orifice systems require a critical charge of a specific amount to give the proper superheat. That amount is either determined by the manufacturer or by trial and error while operating the system and taking temp and pressure measurements as you charge it. Start by evacuating and charging liquid into the high side. Then when the suction pressure rises and levels off, start the compressor. Slowly add refrigerant while checking the superheat. The box must be down to normal temp and the condenser under normal ambient condition before making final adjustments to charge. A system with an expansion valve should have enough refrigerant to clear the liquid sight glass with a little reserve under normal conditions. Be sure to allow for flooded condenser head pressure control if applicable. Knowing approximately how much refrigerant a system might take comes with experience and can't really be put in writing.