Tag: accumulator

The suction line accumulator is designed to keep liquid refrigerant from entering the compressor while still allowing for oil return.

The trouble is that if the oil return port/screen clogs, the accumulator can fill with oil and actually cause the compressor to fail. In addition to that, it can hold contaminated oil in a burnout.

As standard compressor replacement practice, you may want to consider removing the accumulator and dumping / properly disposing of excess oil to both remove contamination and check for excessive oil buildup as well as acid testing the oil.

In the case of a bad burnout, it may be best to replace the accumulator completely in addition to the other burnout protocol measures.

Here is a great video on accumulators from AC Service Tech

— Bryan

In air conditioning service we don’t always see systems with accumulators, if fact they are pretty uncommon unless you work on a lot of heat pumps.

We are Carrier dealers in Florida so we work on heat pumps with accumulators all the time. The majority of Carrier systems use a fixed orifice piston for the heat mode metering device and the accumulator is necessary to prevent compressor flooding.

As a quick review, the job of the accumulator is to prevent any saturated liquid-vapor mix from entering the compressor directly. The refrigerant travels down the suction (vapor) line and drops into the accumulator where the liquid refrigerant and oil drop to the bottom. The compressor suction then draws from the top of the accumulator to prevent liquid flooding into the compressor.

There is a small port with a screen at the very bottom of the return u-bend that allows oil and a small amount of liquid refrigerant to return to the compressor but any liquid will boil off before it makes it to the compressor.

An accumulator is very good at doing its job of protecting the compressor from liquid flooding during certain load conditions but it can lead to issues with charging if you don’t pay attention.

When adding charge to the suction (vapor) valve on a split heat pump with an accumulator, the liquid refrigerant will and to collect in the suction accumulator.

The only way the liquid charged into the accumulator can boil out and enter the compressor is through heat from the ambient outdoor air. This means that as you add liquid refrigerant to a system with an accumulator it takes more time for your readings to change than in a system with no accumulator.

If you aren’t careful you can easily overcharge an accumulator system due to the delayed response time waiting for the refrigerant to boil out.

Here are some best practices when charging an accumulator system-

  • When possible meter in as vapor, this will limit the chilling effect to the accumulator that will result in it holding liquid
  • You can charge carefully into the common suction port if it feeds in after the accumulator. Just be CAREFUL not to flood the compressor
  • Weigh the refrigerant as you add allow to stabilize every so often.
  • Make sure to allow the system to run a good long while after you are done charging to ensure you don’t overcharge

— Bryan

Suction Accumulators

A suction accumulator is used to prevent liquid refrigerant Flood-Back to the compressor. A compressor is designed to move vapor refrigerant NOT liquid and the accumulator can really help us win that battle.

Accumulators are commonly used on Heat Pumps, Transportation Refrigeration Systems. Low -Temp supermarket systems and any place that liquid refrigerant flooding back to the compressor is likely.

The accumulator is installed in the suction line close to the compressor.

It usually is a vertical container with top connections. An internal U-tube reaching down near the bottom is installed on the accumulator outlet connection so that the inlet tube is near the top of the container. This allows the accumulator to be almost full before a Flood-back can occur if the accumulator is sized correctly.

A small hole is drilled in the U -tube near its lowest point. This hole allows controlled meter of any liquid refrigerant or oil back to the compressor with a siphoning action. That hole is generally covered in a screen to keep the hole from plugging and preventing oil return. Accumulators need to be kept clean and free of debris or that screen at the bottom of the U-bend can potentially block as well which is why the accumulator should be emptied and flushed when a system has a significant burnout or another type of contamination event.

To work best it is sometimes advisable to have a heat source on the vessel to assist in evaporating the liquid refrigerant. This may be an electric heat tape or pad. Some accumulators have connections so that a liquid line loop can be piped into the bottom of the accumulator. This improves the performance of the system by subcooling the liquid refrigerant and protects the compressor against liquid slugging by providing additional superheat to the suction gas.

— Louie Molenda




In this episode Bryan talks about diagnosis and replacement of air conditioning compressors. Including:

  • Proper compressor diagnosis
  • Using a megaohmmeter
  • Fool proof testing to confirm a shorted compressor
  • Diagnosis of thermal overload
  • Compressor open winding diagnosis
  • Locked compressor diagnosis
  • Compressor not pumping diagnosis
  • Acid testing
  • Proper filter drier and accumulator protocol
  • Correct charging and testing procedures

And Much More…

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