Welcome to the PROBLEM PAGE.

We find many people request assistance in the practical aspects of the industry. In response we will investigate the problem and endeavour to present the best possible solution.Thank you for all your questions sent in. Send your problems (and sometimes your creative solutions) to acra@netactive.co.za with problem page in the subject line. You may include pictures.

I have noticed a trend towards R 410A replacing R22 in split type and similar air conditioning units. I also have heard many rumors regarding the use of R 410A. What are we dealing with and what is the problem with R22? Do we need new vacuum pumps, manifold gauge sets for example? Could you please shed some light on the subject? Regards Albert Simms.

Hi Albert, I am aware that some suppliers have R410A units entering the market. The reason for the change is the R22 is a HCFC. The phase out of CFC based refrigerants began in 1995 and the manufacturers are following national and international protocols and trends in the phase out of R22.

R410A is an azeotropic blend comprised of 50% R32 and 50% R125. You will experience the problem of temperature glide with R410A which necessitates liquid phase charging. The glide is small (Less than 0.17K).

R410A is Non toxic and Non flammable butuse in a well ventilated area. Leakage in an airtight room creates risk for oxygen starvation accidents.In the case of R410A coming in contact with fire a poisonous gas is given off. R410A saturated vapour pressure is approximately 60% higher than that of R22.

The composition of the refrigerant and the increased pressures necessitate R410A dedicated tools and procedures.

Looking at the following diagram illustrates an example of typical air-conditioning parameters.

As you will need to make several changes lets start with the most obvious. You will need a dedicated R410A manifold gauge set. The charge lines and gauges themselves are made for the higher pressures generated by R410A. In addition the charging lines have a nylon coating for HFC resistance. It is important to note that to prevent possible accidental use of inappropriate manifold gauge sets on R410A systems the service port size and charging line fittings have been changed from 1/4” to 5/16”.

The second consideration when using R410A is that the copper tubing requirement has changed to deal with the increased pressures. The use of R410A necessitates the use of seamless copper tubing. In addition the wall thickness has been increased.

The table below illustrates the R410A seamless copper tubing requirement.

Experiencing problems of a technical nature, drop us a line at acra@netactive.co.za with problem page in the subject line.

Problem PageBy Grant Laidlaw

3070 kPa

930 kPa

R410A

Diameter of tubing Minimum wall thickness (R410A)¼” (6.4mm) 0.80 mm3/8” (9.5mm) 0.80 mm½” (12.7mm) 0.80 mm5/8” (15.9mm) 1.00 mm

The third change lies in the flare nut sizes. The width of the flare nuts to be used with R410A has been increased as follows:

Diameter of tubing

Flare nut width for R22

Flare nut width for R410A

¼” (6.4mm) 17 mm 17 mm3/8” (9.5mm) 22 mm 22 mm½” (12.7mm) 24 mm 26 mm

5/8” (15.9mm) 27 mm 29 mm

Whilst I am on the subject of flares, flare nuts when used particularly with R410A require the use of a torque wrench when tightening. The manufacturer of the unit will give the torque values in the installation manual. The following instructions are supplied with the torque wrench.

This torque wrench has various sized interchangeable open spanner type heads and the torque setting is determined at Figure 1 and adjusted at Figure 2.

The fourth point is in the area of evacuation. On discussing the matter with various suppliers I found that the method most desirable is the triple evacuation method. The steps are as follows:

Step 1: Evacuate the system to 2000 microns.Step 2: Break the vacuum with nitrogen to 100 kPa. Step 3: Release pressure and draw vacuum to 1000 microns.Step 4: Break the vacuum with nitrogen to 100 kPa. Step 5: Release pressure and draw vacuum to 500 microns.Conduct leak rise test.

Note: Always use a regulator on a nitrogen cylinderYour vacuum pump should have a non return valve installed on the inlet.Of course this implies that your vacuum pump should be able to draw the required vacuum. Test your pump as follows.

Step 1: Visually inspect vacuum pump mechanically and electrically.

Step 2: Visually check the oil in the sight glass for level and colour.Should the oil be whitish (Moisture) or black(Carbon deposits) replace.Step 3: Connect vacuum gauge, open necessary inlet valves and turn on vacuum gauge and pump.The vacuum pump should draw a vacuum of 500 microns or less.Note:If after 2 minutes the pumpis unable to draw 500microns, replace oil. Shouldthe pump still be unable todraw 500 microns, overhaulor replace.

The suppliers of the R410Aunits are recommending a risingleak test, using nitrogen, proceed as follows:

The fifth point to remember is that R410A is a azeotropic blend and the refrigerant must be charged from the cylinder in liquid phase. These units tend to require critical charging by mass.

Looking at lubrication we find that mineral oil and HFC refrigerants are not soluble, therefore R410A requires the use of ester oil. This oil is hydroscopic. (Moisture is readily absorbed.)Oil returning performance drops.Lubricating performance drops as chlorine has a lubricating feature.

This explains one of the reasons why evacuation and dehydration have received so much attention.

Note:You should purge with nitrogen when brazing copper tubing; this prevents oxidization of the internal surfaces and contamination of the system.

Albert, I hope that this answers your questions and addresses your concerns

REFERENCES: Thanks to: Daikin SA

Thanks to all for writing in with interesting questions. Looking forward to hearing from you – Grant Laidlaw

ElectronicVacuumgauge