Charging formula

[zimbo]

sorry to talk shop over the festive period, but i am looking for a formula for accurately charging up an ac system, if anyone knows of any links where i could find this it would be much appreciated. merry christmas.

Zimbo

[Abe]

Charging is strictly by weight

You also refer to your gauge pressure to ensure the evaporating temp is right

[Lazarus]

Have never believed refrigerant charging to be an exact science.... In over 20 years have never met a system to be at its optimum with the calculated charge.... or even two identical systems to behave the same.... but thats a different story! Refrigerant charging should be done while taking many different things into account, some of which are pressures, state of coils and pipes, liquid line flashing.... the list is probably far longer than i could produce with my limited knowledge. A reasonable engineer will take all these things into account while achieving the best balance.

[Abe]

On your outdoor unit there is a "nameplate" which will give you info on the Model, Serial number, etc

It will tell you also what refrigerant and the quantity.


System is usually precharged for a 7 metre pipe run. Check with the manufacturer .

You add so many grammes per extra length of pipe run, or remove refrigerant accordingly.

Refer to the manual which comes with the system.

[chiller563]

If your dealing with a specific manufacturers unit and the charging info is not with it, contact the company for either the specific weight of charge or the psychometric charging table for the unit. If neither of these is available I have used a mthod for years that works well for me. Obviously we are refering to a fixed metering device and not a TEV. Charge the system, SLOWLY, to obtain a 10 degree F subcooling and a 10 to 15 degree F superheat with the unit at temp. It is important that the box be at its design temp. because the subcooling and superheat change dramatically from the point of start up till you meet design conditions. As long as all other variables are normal and the coils / compressor etc. is still factory spec. you should be ok with this method.

Chill

[Peter_1]

There isn't such a thing as a simple phormula for charging an airco
If it should be that simple, then there should be not such a shortage of techs, just learn some phormulas out of your head and your a qualified tech.