charging a system

[paulwild]

hi guys
talking to old school fridge engineer the other day and he was talking about how he used to charge systems till one of the lines frosted up then release refrigerant till it chased back ???
can anyone expand on this old teqnique
cheers

[The Viking]

Hmm,

Dosn't sound like good engineering practise.

But I have seen it done.

It will only work on capillary (or fixed orifice) units and has never been considered good engineering practice.

[paulwild]

did this used to be a common practice???(thaks for the quick reply)

[pendlesteve]

Yes, it was common practice. Years ago electronic scales did not exist and charging columns (stills) were very expensive so the easiest method was to overcharge & let a bit out.
Today of course that would be illegal.

[paulwild]

very much so

[panas]

Hello!
It's my first post for this forum. I am new in this field. I am from Israel. I can the only add that this method of charging is one of the populare in Israel nowdays too. Why? It's simple and enough effective. Don't need to study much. If one need to start he would beging by this way. But I am going to learn and practice the modern charging methods now by help of this forum.

[paulwild]

thanks jollycold a very detailed and informative reply into past techniques ( or maybe not so past in some cases????)

[s/market guru]

this was used on capillary systems if you were unsure of refrigerant charge,over chargeing system on capillary would cause the suction to frost back to compressor ,then letting enough refrigerant out would cause the frost line to drop of suction.this was when you new you had the charge right, of course this practice is highly illegal today especially in australia.due to refrigerant licensing laws.

[nike123]

Good method, when charging, is that you put some good (precise) thermometer on suction line and CAREFULLY monitor temp. As you adding refrigerant, temperature of suction line, in some point, will start to rapidly fall (in comparison to temperature change before). This is point where you are in 5% of correct charge. Now carefully add refrigerant by monitoring superheat and sub cooling to required values.
I draw some chart to illustrate this.

http://www.mediafire.com/imageview.php?quickkey=alibmjlbykg&thumb=4

[paulwild]

thanks for all tour replies