R22 to R407c

[sacoolman]

I carry out maintenance on 97 air conditoning heat pumps.I want to convert them to R407c as the compressors pack up.Is there a filter drier I can fit to clean the system or do I have to flush out all the tubing.
I am an ex-South African living in Algarve Portugal.
Can anyone give me some advice please.

[Thermatech]

R22 split systems used mineral oil.
R407c need synthetic oil.

When you retro fit R407c you need to also replace all the oil with new synthetic oil.
This is difficult because the oil is all around the system not just in the compressor & there is no oil drain port on most split system compressors.
For instance some split system heat pumps have suction accumulator & there will be large volume of oil always in the bottom of the accumulator.

The percentage of old mineral oil left in the system generally needs to be lower than 5%.

One method to replace the old mineral oil with the new synthetic oil is
1/ drain the mineral oil out of the new replacement compressor.
2/ Drill a hole & braze a 1/4 schreader valve into the bottom of the compressor.
3/ Refill with new synthetic oil the same volume as mineral oil drained out & then install the compressor as normal.
4/ Let the system run for a day or 2 & then using the 1/4 schreader stub in the compressor base drain the oil which is now a mixture of mineral & synthetic.
Replace with new synthetic oil.
5/ Use a refractrometer to measure the oil refractive index & calculate the percentage oil mixture.
6/ If the mixture of old mineral oil is still higher than 5% then allow the system to run for a few more days & then repeat the oil drain & replace procedure again untill you get the mixture down to below 5%.


If you dont get the oil mixture down to <5% the oil mixture will make sludge
which will cause blockage & will be very difficult to clean out the system after you get sludge.

[sacoolman]

Thanks very much for the advice.Will have to discuss the problem with my client.
Once again thank you.

[kev99]

it may be worth considering a drop in replacement for r22, but check if there any warranty issues with the manafaturer. its a route i have only thought about so far as most clients seem to prefer new plant.

[Shibhrac]

What i know so far from manufacturers of A/C systems, that it is not ideal to retro fit small systems as the cost of modifying small systems may exceed the capital cost of new equipments .

[chemi-cool]

http://www.arkema.com/sites/group/en/products/detailed_sheets/fluorochemicals/forane/refrigerants/forane_427a.page
http://refrigerants.dupont.com/Suva/en_US/pdf/trng_roberts.pdf