Gas charging

[tvrao161]

Please if somebody can advise me on the following problem.

We are trying to recharge Gas R134a into a refrigerant dryer after replacing the faulty filterdrier & expansion valve. but the gas is not going into the system fully from the cylinder. we have started the unit & try to fill but tripping on LP. now the ambient is also little low.
what & how to do in this case?

regards
tvrao161

[RONB]

You say you are charging a refrigerant dryer? Is this an air dryer or are you charging through the filter dryer. I may be getting the wrong end of the stick but if you are trying to charge through the high side you will not be able to fully charge without pumping down and adding the refrigerant after the shut off valve which you have shut on the liquid line. If you are charging from the low side and your bottle pressure is equalising to suction pressure you may have to slightly warm up your gas bottle to increase the pressure in it so the gas will move into the system. You can buy electric bottle warmers or if you are very careful you may put the bottle in some warm water to raise the pressure. If it is a blended refrigerant I would only draw off liquid if you are going to do it this way. But be very careful and keep an eye on your bottle pressure. You also say that your system is tripping on lp,this is probably because as you say you can not get the gas in in the first place,but are you sure you have opened all the service valves etc you closed when you replaced the parts. If the system is on a pump down control is the liquid solenoid energised. I may be stating the obvious but there has to be a simple reason for the gas not going into the system.

[Rob White]

.

In all honesty if you can't charge the system, you ought to consider
whether you are qualified to do the job.................

But giving you the benefit of the doubt,

You need to start with all the refrigerant removed and the thing
in a deep vacuum. You then weigh in the refrigerant in liquid form
into the liquid side of the system while it is off.

If you can't weigh in the full amount then you need to run it and
bleed the liquid into the suction side until the correct amount has
been added.

If you are trying to charge the thing with vapour it will not move
enough refrigerant before the pressure equalises and it will be undercharged.

If you are trying to add the refrigerant to the liquid side of the machine while
it is running, you will never do that because of the pressure difference.

Rob

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