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In this article, we discuss the accumulator tank, its function, why its used, and its location in the system. The photo below shows the inside of an accumulator tank (left) and an accumulator tank mounted on the side of a rotary compressor (right).
Uses of an Accumulator Tank
An accumulator tank is factory installed on the following:
Heat pumps as a storage tank because during heating mode there may not be as much refrigerant needed as when in cooling mode.
Some outdoor condensers that have the potential to lose superheat before the refrigerant enters into the vapor compressor. If there is low superheat or no superheat, the accumulator is the safeguard to protect the compressor from liquid refrigerant entering.
Rotary compressors because these are very susceptible to damage from liquid refrigerant.
Locations of an Accumulator Tank
The accumulator tank is located on the vapor line right before the inlet to the compressor (see photo below of an accumulator on the left and a scroll compressor on the right).
On a rotary compressor, the accumulator is actually mounted to the side of the compressor.
The Design and Function of the Accumulator Tank
When the refrigerant enters the accumulator, it should already be in the vapor state. However, if the refrigerant is not entirely in the vapor state (i.e. still saturated), the liquid refrigerant falls to the bottom of the accumulator tank while the vapor refrigerant remains at the top of the tank. The vapor at the top of the tank exits the accumulator and enters the vapor compressor. The accumulator tank essentially is a storage vessel for the liquid refrigerant. The accumulator tank protects the compressor by not allowing any liquid refrigerant to enter the vapor compressor.
The tube that is connected to the exit of the accumulator is u-shaped and the large opening inside the tube is at the top within the tank. This top inlet is the largest opening in the tube
1. The largest opening is at the top of the u-shaped tube near the top inside the tank (see photo below). The vapor refrigerant enters the tube through this vapor inlet, which is the main vapor inlet to the compressor.
2. Another hole is at the bottom of the tank where the tube bends. In front of the hole is a screen (see photo below) used to protect the hole from clogging up with any loose debris.
This small hole located in the bend of the tube is used as a metering device (see photo below).
A small amount of the liquid refrigerant in the bottom of the tank flashes into vapor as it enters through the metering device. However, the purpose of this hole is to allow any refrigerant oil that accumulates in the bottom of the tank to cycle back into the circulation again. Oil flows with the refrigerant through the system continually to lubricate components, especially the compressor.
3. The third hole is up high, where the vapor refrigerant is within the tank (see photo below).
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The photo below shows an accumulator that is mounted on the side of a rotary compressor (see photo below). This particular rotary compressor came out of a window air conditioner.
This type of accumulator allows a window air conditioner to run at a very low temperature. When there isn't enough heat available for the air conditioning system to change the saturated refrigerant into a superheated vapor before it enters the compressor, this accumulator safeguards the compressor.
The photo below shows the shell of the accumulator cut open and the tube inside the accumulator tank is seen (see photo below).
A strainer screen with very fine mesh sits on top of the tube inside the accumulator (see photo below. Any saturated refrigerant that enters the accumulator has a chance to vaporize as it goes through the strainer screen before entering the tube. This screen also protects the compressor from any debris.
The bottom side of the screen has four larger holes (see photo below-bottom view of the screen). When the screen sits on top of the tube, half of each hole is over the tube opening while the other half of the each hole is outside the tube. This design allows any vapor refrigerant surrounding the tube to be sucked through the holes into the tube
Tech Tips and Maintenance!
The accumulator and the drier filter are two steel components that are usually located outside the building. Both are made with a thin steel shell that is painted. Because of this, they are susceptible to rusting. (NOTE: Whenever possible, install the filter drier inside the building.)
The accumulator tank tends to rust on the top and/or the bottom (see photo below).
The filter drier typically starts to rust right where the tubing has been brazed (see photo below). This is because the paint is either melted or burnt.
When doing preventative maintenance on a system, note if these components are rusted. Add a protective coating to these components to protect them from eventually leaking refrigerant. A spray paint with rust primer, plasti-dip, or wheel-well paint can be used.
Looking for a video on How the HVAC Suction Line Accumulator Tank Works? Check out our
"How the HVAC Suction Line Accumulator Tank Works" video below!
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Published: 7/20/2022
Author: Craig Migliaccio
About the Author: Craig is the owner of AC Service Tech LLC and the Author of the book “Refrigerant Charging and Service Procedures for Air Conditioning”. Craig is a licensed Teacher of HVACR, Sheet Metal, and Building Maintenance in the State of New Jersey of the USA. He is also an HVACR Contracting Business owner of 17 years and holds an NJ HVACR Master License. Craig creates educational HVACR articles and videos which are posted at https://www.acservicetech.com & https://www.youtube.com/acservicetechchannel
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