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R. skiffington
21-01-2013, 09:31 AM
Hi guys.

So a fairly simple question.

We still have plenty of R22 plants here in New Zealand and more and more often we have to retrofit. R407c, in my opinion, is a high temp refrigerant, suited to air conditioning applications. R404a is suited to medium/Low temp applications.

The question is, at what point do we choose R407c over R404a, in regards with evaporating temperature etc.

My way of thinking says if you're evaporating over 0 degrees C then go with 407c, anything below go with 404a.

I'm interested to hear opinions either way.

frank
21-01-2013, 10:22 AM
Here's (http://www.osti.gov/bridge/servlets/purl/491413-AD0ufq/webviewable/491413.pdf) a research report on the fractionation of R407C

and here's (http://www.refrigeration-engineer.com/forums/showthread.php?1275-R-407-C-fractionation) a blast from the past

chillerman2006
21-01-2013, 08:17 PM
fractionation is only an issue if the system will be left dormant for long periods and the system is open during shut down

strategically placed NRV's and or solenoid valves can prevent migration of the different refrigerants to particular parts of the system

the glide with R407c must be observed on compareter which is 7k at some points

and commisioning/service engineers need to clearly differentiate between dew/bubble points

saying that many a/c comfort cooling chillers run fine on R407c

I would use R407c for above 5*c requirements

and R404a for below 10*c

although both can do high/low temp they would be in a better pressure range with these temps

R's chillerman

p8er76
21-01-2013, 11:42 PM
Hi, r407c is a good gas for use in AC, you can also use it for low pressure installation. But is runs on POE-oil and if you want to retrofit the system you need to flush the oil 3x for 24 hours. r-404a is also a good gas but runs also on POE oil same trouble and takes a long time for retrofit, and r-404a haves a very high global warming point. you will see in a couple of years that will be also banned out. and i think your costumers won't be happy to here that they have to retrofit there systems again. one of the best gasses is r-417a runs on mineral/poe oil,so no flushing. low global warming point. but reconment if you use this gas change the o-rings in your solenoid valves. bad experiance with old systems >12 years. hope you have information enough....
Best regards Peter.

p8er76
21-01-2013, 11:49 PM
sorry i forgot r417a runs -30C degrees 0.3Bar and 0C degrees 3.1Bar. i know 0.3 bar is very low but it runs good. needs good fine tuning.i do this now for the last 5 years never had trouble. and if you have semi hermetic compr. or scroll put some acid away in the oil (you have mineral/poe) it cleans the oil.adjust the LP switch on 0.1Bar.. hope this is helpfull... best regards peter..

R. skiffington
22-01-2013, 06:28 AM
Thanks for the input guys.

I realise we'll need to carry out a few oil changes but that's n drama.
We are using R417 a bit but I see it as a temporary fix rather than a permanent solution, I'm aware of the problems it causes with the o-rings, the R22 swells the o-rings but they contract with the R417a causing the leaks.
The system I'm thinking about is an air conditioning system on a Superyacht, 4 x Copland scrolls, water cooled condensers, easy oil changes.
My main concern is efficiency.