Charging a chiller
Weigh, do not guess
The nameplate gives the charge for the machine as built. On a field-piped system the commissioning record gives the actual figure, including whatever was added for the line run. That number is the target, and the way to hit it is a scale.
Superheat and subcooling confirm that the charge is behaving correctly once it is in. They are the check, not the method. Charging to a gauge reading on a machine with a fouled condenser or a restricted metering device produces a confidently wrong answer.
Find the leak first
Refrigerant is not consumed. A chiller that needs gas has lost gas, and putting more in without finding out where it went means doing the same job again, at the same cost, plus the emissions. On a system with a significant charge, a repeated top-up is also a reportable quantity of fugitive emissions for any organisation that tracks Scope 1.
The leak detection guide covers the methods and what each one is good for. A standing pressure test with dry nitrogen remains the most decisive on a system that can be isolated.
Liquid charging and glide
R-407C is zeotropic and has a temperature glide of several degrees. Its components boil off at different temperatures, so drawing vapour from the cylinder changes both what leaves and what remains. Charge from the liquid valve, metering into the low side so liquid does not reach the compressor directly.
The same discipline applies to R-410A and R-448A. R-134a is a single component and does not shift composition, but liquid charging is still the faster and more controllable method.
After a large loss on a zeotropic system, the correct procedure is to recover what remains, evacuate, and weigh in a full fresh charge. Topping up preserves the leak and the wrong mixture.
Evacuation before charging
Any system opened to atmosphere holds air and moisture, and moisture with POE oil is a slow way to destroy a compressor. Pull a deep vacuum, break it with dry nitrogen, pull again, and hold the vacuum to confirm it is not rising. The evacuation guide sets out the targets and why POE makes this less forgiving than mineral oil did.
What we supply
Chiller gases in the sizes on each product page, from Stallion and Refron (GFL). For a full recharge the quantity is usually worth confirming against stock before a shutdown is scheduled, and we would rather have that conversation a week early than on the morning of the job.
Quick answers
How much refrigerant does a chiller take?
It depends on the machine and the pipe run. The nameplate gives the base charge and the commissioning record gives the actual figure for a field-piped system.
Can I charge a chiller by pressure alone?
No. Weigh the charge against the nameplate or commissioning figure. Superheat and subcooling confirm the charge is behaving, but they are the check rather than the method.
Should I top up a chiller that is low on gas?
Find the leak first. Refrigerant is not consumed, so a low system has leaked. After a large loss on a zeotropic blend, recover, evacuate and weigh in a fresh charge.
Why does R-407C have to be charged as a liquid?
It is zeotropic. Its three components boil at different temperatures, so vapour charging changes both the mixture entering the system and the mixture left in the cylinder.
- ASHRAE Standard 34 · refrigerant designation, blends and glide · ashrae.org.
- AHRI Standard 700 · specifications for refrigerants · ahrinet.org.
- US EPA · refrigerant leak repair and good servicing practice · epa.gov.
This guide is general information compiled from the cited sources — not legal, safety or engineering advice. Read our full disclaimer.
Related: Which refrigerant your chiller runs on · Evacuation and moisture · Leak detection · Glide explained