5 Common Mistakes You can make while you Install an Oil Separator!


Dry All as a leading manufacturer of Full Range of HVAC&R Line Products is constantly innovating, developing and designing products to meet the requirements of the industry.

Since its inception, Dry All stakeholders with their most efficient design and R&D team has always emphasized on producing the latest technology products to meet the challenges of the constantly evolving technology in the HVAC&R industry.

Dry All “5 Common Mistakes” series is designed to help the installer / technician to avoid most common mistakes that one can make during product installation.

The first series is on Oil Separator. Here are five common mistakes you can make while Installing an Oil Separator.  

1)   No Pre-charging of Oil in the Oil separator

Mistake – Float ball type Oil Separators come with instruction on the quantity of oil to be charged before installation. It is observed that technician miss out this instruction because of negligence and sometimes because of a lack of understanding on why this is required. This pre-charge is required to bring the oil separator mechanism to activation level. Oil Separator manufacturer cannot give you the same pre-charged because the oil has to be exactly the same grade as the compressor oil.

Consequences– If the Oil separator is not pre-charged with oil quantity as prescribed by the manufacturer, then the oil coming out of the compressors gets accumulated in the oil separator up to the activation amount of the float ball mechanism; this may result in the failure of compressor due to starvation of Oil

Solution-All Oil separators with float ball mechanism have to be pre-charged with the amount of Oil prescribed by the manufacturer. A little more oil than the amount required for the activation of the float, ball mechanism helps the oil coming out of the compressor to return back quickly to the compressor.

2)   Opening of the NPT port

Mistake – Oil Separators are provided with NPT port, closed with a dead nut. The NPT port is provided for installation of pressure relive device as may be required by the system design. Common mistake observed is that the technician opens and uses this port for charging of oil.

Consequences – In the manufacturing process the NPT port is closed with the help of a dead nut using a special quality sealant. It is strongly recommended that the dead nut from the port has to be opened only and only for installation of pressure relief device. If the dead nut is opened for charging of oil, the opening process destroys the sealant used. In addition, after the oil charge when the dead nut is installed back, the previous tightening torque may not be achieved. This creates a leak at the NPT port immediately or over a period of time.

Solution- The NPT port should be opened for only attachment of the PRV or any other pressure relief device and not for oil charging or any other purpose. In case the port is used for installation of any other device, the technician has to make sure that there is no leakage from this point.

3)   Closing of the Oil Return line

Mistake – Smaller size of oil return line or blockage of oil return line.

Consequences-Due to the small size or blockage of the oil return line the oil is unable to travel back to the suction line and to the compressor. This creates a tremendous hydraulic pressure on the ball of the float ball mechanism and eventually the ball gets pinched resulting in the failure of the Oil Separator

Solution – Install adequate oil return line size according to the system design to insure travel back of the oil to the compressor. Use of an oil strainer on the line is strongly recommended to filter the oil and prevent such blockage. 

4)   Oil Charging Procedure

Mistake – Not pre-charging of the oil into the Oil Separator before start of installation.

Consequences– The most common mistake noticed is pre-charging of oil through the outlet of the oil separator after the inlet tube has been brazed. If oil is charged after one joint is brazed it gets tough to pour the oil through another port due to the air pressure. Also, the oil cannot be charged through the NPT port as explained above.

Solution – Remove the Oil separator from packing. Remove inlet and outlet rubber plugs. The Dry All Oil Separators are pre-charged with positive nitrogen. Allow the same to escape completely. Pre charge from inlet keeping the outlet port open. Now braze the oil separator to the system. Make sure to use wet rag so that the brazing heat is not transferred to the Oil Separator joints or body.   

5)   Charging of wrong grade of Oil

Mistake – Not charging the right grade of oil or the oil of the grade and type different from the Compressors.

Consequences– The compressor needs the lubrications as it contains moving parts. The lubricating oil for the compressor is designed with respect to the different parameters such as refrigerant, temperature, viscosity etc. Due to the mismatch of the grade or type of the oil in the oil separator and compressors the lubrication gets affected and in over a period of time compressor fails

Solution –Check the data sheet of the compressor manufacturer and identify the oil and its grade. Pre charge the Oil Separator with same grade of oil as the data sheet    

If you have any suggestion or recommendation or you would like to add to the above, please do write back to us. Your practical experience and sharing of your knowledge will help the HVAC&R trade fraternity. We look forward to hear from you.

Stay tuned for more such “5 common Mistakes” writeup on other HVAC&R Line Products.

Technical Inputs for this write up is by Shreyas Kulkarni, R&D Engineer, Dry All

Reach Us At

Dry All Oil Separators are available direct to our OEM customers and through our Wholesalers, Dealers across India & worldwide

For more details please visit our website http://www.dryall.net  

You can also contact us on info@dryall.net


The content in this presentation has been prepared by Dry All and is general information about HVAC&R line products. This information is given in the summary form and does not purport to be complete. The information provided is for education purpose only. Before acting on any information, you should consult or take the advice of Dry All Engineers. 

Author: Dry All

Manufacturer of "Full Range of HVAC&R Line Products"

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