how to calculate weight of refrigerant

[steven86]

i hav a coolroom system . so how to calculate the system need how many weight of refrigerant ?

[wkd]

You need to know what state the refrigerant is in at individual parts of the system IE gas or liquid,then calculate the volumes of each component based on the density of the refrigerant.For example suction line volume & gas density at expected suction temperature or pressure from the refrigerant tables should give you KG/M cubed.Do this for all components and you have an estimate of charge.Be careful with mixed fractions of refrigerant.Once you have an estimate you can charge the unit and adjust as needed for the system application.Don't be surprised if its different though.
Hope this helps.

[steven86]

if i want learn this , where can i find the information is about this ?

[The MG Pony]

if i want learn this , where can i find the information is about this ?

From all that I have learn't dont bother trying to gues it, just charge the system via super heat and sub cooling then jot down what it took, this seems to be the best most effective methode.

But non the less I may be wrong, but thats what I have picked up so far from the guys on this board and from the local techs here that I've worked with.

[carlfoster]

From all that I have learn't dont bother trying to gues it, just charge the system via super heat and sub cooling then jot down what it took, this seems to be the best most effective methode.

But non the less I may be wrong, but thats what I have picked up so far from the guys on this board and from the local techs here that I've worked with.

I would agree with MG above.

Never charge a system based solely on estimated refrigerant weight. Always base it on the superheat, subcool, dry bulb and wet bulb temperatures and the temperatures of the various pipes.

If you weigh the amount of refrigerant you put in, you will then know how much you have charged.

[davej]

we were always told to keep an eye on a clamp meter checking compressor run current when charging a system as well

[aoehero]

Can you use the weight of the cylinder to do your initial OZ input?

[ErickDavey]

I am in total agreement with Davej. Ive been taught by my 'old school' boss & if you have no design information to go on or you are retrofitting then charge as per running amps of the compressor, assuming the compressor is new. Obviously bomb charge the system with a base charge usually just before gauge/system pressure equalises then switch on & monitor running amps.

Then you can verify with superheat measurements and air on air off both heat exchangers comparing against room temp. I would always do this over charging a system to full sight glass as this often masks fault conditions at the expansion valve . Then document all findings & label unit with commissioning sheet.

[Brian_UK]

Can you use the weight of the cylinder to do your initial OZ input?

If you want to but it is a very strange question

[aoehero]

most all liturature will say something like 260 oz +/- something. Why give a measureable figure if noone uses it?

[Brian_UK]

most all liturature will say something like 260 oz +/- something. Why give a measureable figure if noone uses it?

And how does this relate to your question about the cylinder tare weight inclusion?

260oz for what? A total charge or a top-up, what does this refer to?

[squil]

The only way to know exactly the required refrigerant charge is with a void fraction model applied to the evaporator and to the condenser...
It can of course be evaluated by making rough hypotheses...