charging r407c by weight

[bezsenne]

Hi everybody,
I am learning how to charge units now. Today I was charging heat pump with R407c. The service valve was on LP. The amount of refrigerant due to rating label is 900g. I used rothenberger roklima 4f, which charge the unit with bottle pressure. The bottle pressure was 8bar. In this conditions I charge only 280g.
Please teach me what should I do now. Is it possible that the amount of refrigerant on rating label is wrong? I am wondering if i should run compressor to charge the full amount?
Hope for tolerance reply since I am newbie in this area.

[paul_h]

Did you evacuate the system first?
Were you charging liquid from the cylinder?
Is it really cold where you are? Might have to warm the cylinder up first.

Edit: If there's a liquid line valve or condenser schraeder valve, better to charge into there rather than the LP valve, but I doubt there is for a system that takes only 900g.

R407c isn't big in australia, for all those wondering why I work on R22 systems all the time. R407c was only used by a couple of Daikins and a few euro brands like delonghi. Every other brand stayed with R22 until R410a come out a few years later, and of course there's hundreds of chinese units here (some mainstream western brands, but made in some chinese factory), that kept using R22 until about 2 years ago).

[bezsenne]

Refrigerant was evacuated, one element was substitutet without change in heat pump construction. Then vacume was made, before charging.
The temperature in a room in which the charging was made was around 20 Celsius degree.
Renew:
Is it possible that the amount of refrigerant on rating label is wrong? I am wondering if i should run compressor to charge the full amount?

[paul_h]

Is it a reverse cycle a/c or some other application?
I've never had a problem getting 900g of liquid refrigerant into a split system heat pump.
600-900g is a small system and never had a problem at 20C.
edit: and as I asked before, did you charge refrigerant in the liquid state? You must do if using R407C, R410a, R404a etc anyway.

You could do it for any fixed charged system too, I always do it with R22 systems for example.

[Brian_UK]

Rating label will be correct, you charging method is not.

[bezsenne]

Well, refrigerant in the bottle is in liquid state.
In the mean time i repare 3 units, when the charging stops, before whole amount was charged into unit i turn on unit. Then compressor work decrease the suction pressure and make it possible to charge with the amount from rating label.
Is it correct method of charging?

[Brian_UK]

If it works then it is OK.

[botrous]

Hi Bezsenne , Hi Btian and paul

Bezsenne ,
1) R407 is a mixture , you should charge liquid , if the cylinder is not equipped with a deep tube , you should turn it up side down to get the liquid.
2) The system should be evacuated from the refrigerant it was inside and a vacuum must be applied, those decreasing the pressure in the unit to -1 Bar, so if the cylinder pressure is 8 bars , the deltaP would be 9 bars a you would charge.
3) if the pressure in the system became equal to the pressure in the cylinder then no refrigerant will pass from the cylinder to the unit , you must creat a deltaP , either by heating the cylinder (not with direct fire , i've seen that happening for who might wonder), or by turning on the unit.
4) keep charging until you reach the desired ammount.

Best regards