Recovering refrigerant from a commercial refrigeration unit is a routine but safety-critical job for HVAC-R technicians. Before a recovery machine is even connected, one of the first questions that comes up is how many access valves are needed. The short answer is that you need at least two access valves — one on the high-pressure (liquid) side and one on the low-pressure (suction) side of the system. This article explains why two access points are required, how they work together, and how to use them correctly for a fast and compliant recovery.
The short answer: two access valves
A commercial refrigeration unit is a sealed circuit divided into two distinct pressure zones. Refrigerant exists in both zones, and a single access point simply cannot reach all of it. To recover the full charge you need:
- One access valve on the high side — typically on the liquid line or at the receiver outlet (the king valve). This is where liquid refrigerant is recovered, which is much faster because liquid is far denser than vapor.
- One access valve on the low side — typically on the suction line or compressor suction service valve. This is where the remaining vapor refrigerant is pulled out after the liquid is gone.
If you only access one side, refrigerant trapped on the other side stays in the system. That means incomplete recovery, wasted refrigerant, and — in many countries — a direct violation of environmental regulations.
Understanding the two sides of the system
To see why two access points are necessary, it helps to look at how a commercial refrigeration circuit is laid out. The high side runs from the compressor discharge, through the condenser and the liquid receiver, up to the expansion valve. The low side runs from the expansion valve, through the evaporator, and back to the compressor suction.
On a typical commercial unit you will find service valves at several locations:
- Compressor suction service valve (low side)
- Compressor discharge service valve (high side)
- Liquid line (king) service valve at the receiver outlet (high side)
- Schrader access ports on the suction and liquid lines
For a standard recovery job, connecting to one high-side access point and one low-side access point is sufficient. In practice, most technicians use the liquid line service valve (or king valve) as the high-side point and the suction service valve as the low-side point.
Step-by-step recovery using two access points
- Identify the refrigerant from the unit nameplate and confirm that your recovery machine and recovery cylinder are compatible with it.
- Connect the recovery hoses to the high-side and low-side access valves, using a manifold gauge set to monitor pressures.
- Purge air from the hoses so that non-condensables do not enter the recovery cylinder.
- Recover liquid from the high side first — this removes the bulk of the charge quickly and efficiently.
- Switch to vapor recovery, pulling from both sides until the system reaches the required vacuum (0 psig for most high-pressure systems).
- Close the valves, weigh the cylinder, and label it with the refrigerant type and the amount recovered.
When more than two access points are needed
Some larger commercial systems have multiple circuits, multiple evaporators, or a liquid receiver that holds a large charge. In these cases, a technician may need additional access points to reach refrigerant trapped in isolated sections. The rule of thumb stays the same: every section of the system that can hold refrigerant needs an access point on both its high and low side. Two access valves are the minimum for a standard single-circuit unit, not a universal maximum.
Choosing the right recovery equipment
The number of access valves matters, but so does the quality of the recovery machine. A capable refrigerant recycling machine with a dual input design, multi-stage filtration, oil separation and air separation handles both liquid and vapor recovery efficiently, which shortens the time the unit is out of service. San Lan Technologies Co., Ltd manufactures refrigerant recovery machines such as the SD-680 and the RRM-650, both designed for commercial refrigeration service, along with complete refrigerator recycling equipment for end-of-life appliances.
Environmental and safety considerations
Recovering refrigerant is not optional — venting refrigerant into the atmosphere is illegal in most jurisdictions. Proper recovery protects the ozone layer, reduces greenhouse gas emissions, and keeps technicians safe from frostbite, asphyxiation, and toxic decomposition products. Always use certified equipment, wear appropriate personal protective equipment, and never overfill a recovery cylinder beyond 80% of its water capacity.
Conclusion
In short, recovering refrigerant from a commercial refrigeration unit requires at least two access valves: one on the high side and one on the low side. This setup lets you pull liquid from the high side first, then vapor from both sides, ensuring complete and compliant recovery. With the right access points and a reliable recovery machine, the job is quick, safe, and environmentally responsible.
