•35% annual leak rate of commercial and industrial refrigeration
•15% annual leak rate comfort cooling chillers and all other equipment
R407c Considerations
R407c equipment for leak detection are the same as R410a. However, the technician CANNOT use the exist- ing refrigerant in the system after leaks have occurred. There can be a significant change in the refrigerant com- position during multiple leaks and recharges. Unit should be recharged using the manufacturer's recommended charge. However the service technician must remember that when adding R407c to the system, it must come out of the charging cylinder as a liquid to avoid fractionation and for optimum system performance
Refrigerant Recovery
Use an R410a approved recovery device. Due to the increased pressure of R410a, recovery equipment has been redesigned to handle these higher pressures. Recov- ery equipment rated for R410a must be used. Recovery cylinders must have a service pressure rating of 400 psig (DOT 4BA 400 and DOT 4BW 400 are acceptable). DO
NOT USE STANDARD DOT RECOVERY OR STOR- AGE CYLINDERS WITH A 300 PSIG RATING WITH R410A! As stated earlier, a specific gauge set for use with R410a is required. These will allow pressure measure- ments to 800 psig on the high side and 250 psig on the low side. Hoses should have a service rating of 800 psig.
Figure 2. Triple Vacuum Procedure
R410a Application and Service Guide
Evacuation
Heat Controller recommends two evacuation methods, the deep vacuum method and the “Triple Vac” method.
The Deep Vacuum Method
The deep vacuum method requires a vacuum pump ca- pable of at least a 500 micron vacuum and a micron gauge capable of measuring this vacuum. The deep vacuum method is the most positive way of assuring a system is free of air and moisture and is the recommended method.
Triple Vacuum Method
The triple evacuation method should only be used when the vacuum pump is not capable of pulling a 500 micron vacuum. See Figure 2.
Figure 3. Vacuum and Time
The following is the Triple Evacuation procedure:
1.The unit should be evacuated to at least 29.72 in. Hg.
2.Break the vacuum with dry nitrogen and wait 1 hour.
3.Evacuate until at least 29.72 in. Hg. is reached and then continue for 15 minutes.
4.Break the vacuum with dry nitrogen and wait 1 hour.
5.Evacuate until at least 29.72 in. Hg. is reached and then continue for 20 minutes.
6.Isolate and Turn Vacuum Pump Off and wait. Vacuum measurement should stay low and not rise above 29.5 in. Hg. A rise above 29.5 in. Hg indicates a leak or moisture in system.
Refrigerant Charging
An undercharged TXV unit can be identified by:
•Low evaporating pressure
•High superheat
•Low subcooling
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