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Mike Hopkins
21-11-2001, 02:11 AM
Anyone out there run across any new machine running R407c?
Any retros and experience with the stuff? Supposed to be close
to R-22 properties, haven't checked yet to see what it's about.
Seems to be an upcoming choice here in the states for R-22 chiller
type applications.

Mike Hopkins

Brian_UK
21-11-2001, 11:07 PM
My firm has installed quite a few DX split A/C units running 407c without too many problems.

Quality of brazing and flare joint are of prime importance to reduce leakage. I know that is good for any job but these new gases with their smaller molecules really seek out the holes.

I've found some condensing units tripping out on high pressure during our feeble UK summer but that was down to slightly dirty condenser coils. I also think that the manufacturer was rather mean with his sizing of the coils/fans but could have been a 'one-off'.

BritCit_Juve
09-12-2001, 12:15 AM
R407C tends to run with a slightly higher head pressure than R22, typically (30PSI higher) although the suction stays about the same.
As its a refrigerant mix the local conditions need to be taken into account when using R407c, due to the change in the characteristics of the system as the higher boiling point refrigerants in the mix reach their lowest point and the lower boiling point refrigerants come to the fore. In lower ambients ie UK, Canada ect head pressure control is a definate requirement reduce the likelyhood of the evaporator freezing.
As regards to retrofitting R22 systems with R407C then that is ok as long as the compressor/ system is charged with polyolester oil and any seals ie in the TEV's ect, are compatible. If the system contains mineral then use CARE 50 otherwise you need to remove all the oil - with a maximum of 5% mineral by volume.
The cardinal rule here is DONT MIX Mineral Oil and R407C
An R22 system converted to R407C will have a performance drop of about 4%

I hope this ain't too long winded lol

Mike Hopkins
09-12-2001, 06:51 AM
Not long winded at all by my standards. Appreciate the input.
What is this CARE stuff I have seen you fellas talking about, I am not familiar with it. Oil I assume maybe POE but what viscosity, grade, manufacturer, etc.

Mike Hopkins

BritCit_Juve
11-12-2001, 09:00 PM
The oil is POE, from memory SW32 or there abouts, whose depends on the manufacturer. ICI Emkarat is one supplier.
As to care thats a range of refrigerants based on hydro carbon mixes and produced in the UK by calor. It tends to be as efficient as its HCFC equivalent while requiring a lower charge volume, Care 50's charge being around 40% of R22's.

frank
11-12-2001, 09:37 PM
Hi Mike

We've been using R407c kit for quite some time now and in fact is is getting hard to get R22 kit.

NEVER installed R22 kit converted to 407 as this really is a no no. How can you get all of the mineral oil out of a system? and be sure that the 407 doesn't mix with it?. Also, as 407 is a blend the equipment should be purposely made to suit to prevent glide.

When installing 407 kit there is not a lot of difference apart from ensuring clean tools and making extra sure the the system is not left open to absorb moisture as just a small amount can be fatal to the compressor. Efficiencies are about 5% less than 22 with air con systems and efficiencies really drop off with evaporating temperatures below freezing so it is not really suitable for cold work.

We went on a training course with Mitsi recently and the tutour was saying that before they had purpose made kit they were retrofitting r22 systems to 407. This was achieved by drilling a hole in the base of the compressor to drain the oil before plug welding the hole and charging with 407 - can you believe this??

Mike Hopkins
12-12-2001, 03:55 AM
Frank,
I was thinking along the lines of machines out there already
factory charged with poe oil running R22 and converting to R407C
down the road. Sorry for confusion there. The CARE refrigerant mentioned sounds like some of the refrigerants we have over here that can run with mineral oil. They aren't cheap though, one we have used rather regular for R12 drop in (so to speak) with out pulling mineral oil is around 9-10 US dollars a pound. I have also seen the filter drier manufacturers coming out with enhanced moisture capacity cores specific for HFC and poe oils. I think if I went to the trouble of welding on a hermetic (assuming) it would be to weld an access valve on the base so one could change the oil too at a later date. Those poe oils aren't cheap either, probably still paying for R&D on them or maybe higher refinement cost, quality.

Mike Hopkins

BritCit_Juve
14-12-2001, 06:29 PM
There is no problem converting equipment or R22 to R407c as long as the system is charged with POE.
If you want to change a system with mineral oil then you have to get it below 5% mineral before you add the R407c. At the same time its better to replace the compressor.
There are blends out there which are a direct replacement no matter which oil is used but they are expensive.