Receiver/driers (also sometimes called “filter/driers” or “receiver/dehydrators”) look like small metal cans with an inlet and outlet. They are only used in A/C systems that use expansion valves.
Receiver/driers are located in the high-pressure section of the system, usually in the plumbing between the condenser outlet and the expansion valve inlet, although some may be connected directly to the condenser.
Receiver/driers serve three very important functions:
- They act as a temporary storage containers for oil and refrigerant when neither are needed for system operation (such as during periods of low cooling demand). This is the “receiver” function of the receiver/drier.
- Most receiver/driers contain a filter that can trap debris that may be inside the A/C system.
- Receiver/driers contain a material called desiccant. The desiccant is used to absorb moisture (water) that may have gotten inside the A/C system during manufacture, assembly or service. Moisture can get into the A/C components from humidity in the air. This is the “drier” function of the receiver/drier.
Damage can occur if there’s excessive moisture inside an A/C system. It can cause corrosion, as well as possibly degrade the performance of the compressor’s lubricating oil.
The receiver/drier should be replaced any time the system is opened for service, and most compressor warranties require it. The desiccant is only capable of absorbing a certain amount of moisture, and when the inside of the system and/or the receiver/drier are exposed to the atmosphere, the desiccant can become very quickly saturated from humidity in the air. If this occurs, the desiccant is no longer effective, and will not provide future protection. Additionally, the filter inside the receiver/drier could be restricted by debris that may have been inside the system. This could diminish refrigerant and oil flow.
An accumulator is comparable in purpose to a receiver/drier. It serves similar, but slightly different functions. An accumulator is also a metal cylinder, but differs from a receiver/drier in these three ways:
- An accumulator is considerably larger than a receiver/drier, usually around twice the volume.
- The accumulator is connected to the evaporator outlet, in the low-pressure section of the system.
- The accumulator’s primary function is to store liquid refrigerant that is exiting the evaporator, to prevent it from reaching the compressor. If liquid refrigerant were to enter the compressor, it could cause damage, as the compressor is not designed to pump liquid, only vapor.
Accumulators are only used on systems that contain orifice tubes. It is a characteristic of orifice tube systems to have large amounts of liquid refrigerant leaving the evaporator. In other words, unlike in expansion valve systems, where all or most of the refrigerant turned into a vapor while passing through the evaporator, in orifice tube systems, the refrigerant leaves the evaporator still as a liquid. The accumulator is the component in which the refrigerant gets the opportunity to warm up and change from a liquid to a vapor before being drawn back into the compressor
Like receiver/driers, accumulators also serve as a temporary storage containers for oil when the oil is not needed by the system.
Lastly, accumulators also contain the system desiccant and a small filter, so compared to receiver/driers, the same “rules of replacement” apply.
Things that can go wrong with receiver/driers and accumulators
Receiver/driers and accumulators rarely fail themselves, but as mentioned previously, need to be replaced whenever the system is opened for any other type of service. When a failure does occur with a receiver/drier or accumulator, it is usually due either to clogging from debris inside the A/C system (like from a failing or failed compressor), or that the bag containing the desiccant has broken open, allowing desiccant material to circulate throughout the system with refrigerant and lubricant. Sometimes, the desiccant material will disintegrate into small sand-like particles. This can cause possible clogging in other system components.
When having your mobile A/C system professionally serviced, insist on proper repair procedures and quality replacement parts. Insist on recovery and recycling so that refrigerant can be reused and not released into the atmosphere.
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