R407A

Lubrication

POE lubricants must be used with R407A since it is not miscible with mineral or alkyl benzene lubricants. As with many HFC blends, retrofitting will require a change to a polyolester lubricant (POE) to ensure reliable oil return and circulation throughout the system. When retrofitting, a lubricant flushing procedure is necessary to reduce the original oil content below 5% of the new POE charge. For refrigeration systems using an oil separator, multiple oil flushes may not be required. New R407A equipment will be charged with the OEM recommended lubricant, ready to use with this gas.

Charging

Due to the zeotropic nature of R407A, it should be charged into the system as a liquid to prevent fractionation (changes in refrigerant composition due to vapour charging). In situations where vapour is normally charged into a system, a valve should be installed in the charging line to flash the liquid to vapour while charging.

Retrofitting

R407A can be used to retrofit existing R22 and R404A systems in positive displacement, direct expansion refrigeration and air conditioning equipment. Retrofit procedures are straightforward and similar to those of other HCFC and HFC system retrofits. Pipework and expansion valves can be equivalent to those of R22 and are within the range of R404A systems operation. R407A should not be used in centrifugal chillers or equipment that uses a flooded evaporator due to its high temperature glide.

Material compatibility

Whenever retrofitting air conditioning or refrigeration systems, compatibility of system materials must always be taken into consideration. Items such as elastomers, hoses, and filter-driers respond differently to different refrigerants and oils. For these reasons, before performing any refrigerant retrofit, Harp International recommends contacting the OEM for specific recommendations.

R404A to R407A retrofit procedure

Whilst R407A is a good match for R404A, check OEM recommendations to ensure the existing system design is suitable, including system capacities, relief valve sizing and equipment seal material compatibility. Like R404A, R407A is a HFC refrigerant and a POE lubricant will be required. Whilst it is likely that the same lubricant may be suitable for use with both, R404A and R407A, check with the compressor manufacturer.

System preparation

• Record the system performance to obtain a baseline prior to retrofit, e.g. suction and discharge pressures, discharge temperature, temperatures in and out of the condenser and evaporator and the energy consumption if possible.
• Check the system service history for any on-going issues and to highlight any regular maintenance activities that may need to be undertaken.
• Remove the R404A from the system and record the system charge weight.
• Check and repair any existing leaks on the system.
• Check condition of compressor lubricant.
• Replace all seals on joints that have been opened and on the liquid receiver.
• Replace receiver float seal.
• Repair or replace old solenoid valves and ball valves to minimise leaks.
• Replace system filter drier.
• Evacuate the system to at least 1 mbar and perform a system strength pressure test with oxygen-free nitrogen in accordance with EN 378.
• If system fails the strength test repair any faults or replace any defective components and re-test.
• Perform a triple evacuation procedure, each time ensuring a vacuum of 1 mbar is pulled and held. Repair any leaks.
• Reset pressure controls for R407A.
• Charge the system with R407A. Typically the charge will be around 95% that of the original R404A charge weight.

Note: If charging into the suction line on a running system the liquid from the cylinder must be vapourised before entering the system.

System start-up

• Start the system and check for any leaks.
• Set the expansion valve settings. For calculating the sub-cooling use the R407A bubble point as the saturation temperature. For calculating the superheat use the R407A dew point as the saturation temperature.
• Monitor refrigerant and oil levels and adjust amounts as required.
• Record performance data and compare to that obtained for baseline performance.
• Label the system in accordance with the F-Gas Regulation and indicate all required information in the system log book.

R22 to R407A retrofit procedure

Before converting an R22 system to R407A, check OEM recommendations to ensure the existing system design is suitable, system capacities, relief valve sizing and equipment seal material compatibility. R407A is a HFC refrigerant and a POE lubricant will be required. Older R22 systems may contain a mineral or alkyl benzene based lubricant that is not compatible with HFCs like R407A. Check with the compressor manufacturer for any recommendations they may have.

System preparation

• Record the system performance to obtain a baseline prior to retrofit, e.g. suction and discharge pressures, discharge temperature, temperatures in and out of the condenser and evaporator and the energy consumption if possible.
• Check and repair any existing leaks on the system.
• If not a POE, remove the oil from the compressor sump, oil separators, oil float and suction line accumulators. Record amount removed.
• Replace all seals on joints that have been opened and on the liquid receiver.
• Replace drier.
• Add the recommended viscosity grade POE.
• Evacuate system and check for leaks.
• Re-charge with old refrigerant.
• Re-start system and check for leaks. Check oil levels.
• Run system for at least 24 hours.
• Check mineral oil concentration in the POE using a refractometer. Ensure residual mineral oil content is not more than 5%. Repeat oil change if necessary.
• Remove R22 from system.
• Install a HFC compatible filter drier.
• Replace receiver float seal.
• Repair or replace old solenoid valves and ball valves to minimise leaks.
• Evacuate the system to at least 1 mbar and perform a system strength pressure test with oxygen free Nitrogen in accordance with EN 378.
• If system fails the strength test, repair any faults or replace any defective components and re-test.
• Perform a triple evacuation procedure, each time ensuring a vacuum of 1 mbar is pulled and held. Repair any leaks.
• Reset pressure controls for R407A.
• Liquid charge the system with R407A. Typically the charge will be around 95% that of the original R22 charge weight.

Note: If charging into the suction line on a running system the liquid from the cylinder must be vapourised before entering the system.