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Mr.Nacogdoches
06-09-2016, 09:11 AM
Hi,

We have a customer who have a new provision plant running on R407C. It has several freezer rooms on the same compressor and a fairly long pipe routing (40 meters), so the superheat is fairly high. I have measured discharge temperatures on the compressor top to 125C (approx 260F). How much higher is it inside the compressor?

What would be a good refrigerant substitute? R407F - will it have lower discharge temp? Same capacity?

What about R448A or R449A? How are discharge temp and capacity compared to R407C? Can the same expansion valves be used?

Any other alternatives, without having to change liquid and suction line?

chemi-cool
06-09-2016, 02:22 PM
407f or 507.

40 meters is very bad design.

Mr.Nacogdoches
08-09-2016, 08:09 AM
Hi,
Thanks for the reply.

507 is not an option. It will be banned soon in Europe. Need better GWP values for this new system.

cduque
08-09-2016, 11:48 AM
I do not have direct experience but according to the informations of the manufacturers, R448A or R449A may have a lower discharge temperature comparing with R407C or R407F. I think the diference is not much.
Maybe a controled liquid injection system could solve the high discharge temperature problem...
In the HFC world when the GWP reduces normaly the discharge temperature increases...

Sandro Baptista
09-09-2016, 03:46 PM
Hi,
Thanks for the reply.

507 is not an option. It will be banned soon in Europe. Need better GWP values for this new system.

You are right. I would use the HFO R449A (it is not a HFC). This refrigerant doesn't have so high discharge temperature as the (R22) and R407F. With (R22) and R407F you need extra cooling to the compressor. But with R449A it's almost as the R404A/R507 which only at part loads and lower suction pressures combined with high discharge pressures you need a extra cooling with refrigerant (CIC system), or water or fan forced air at the compressor heads.

Sandro Baptista
09-09-2016, 04:01 PM
407f or 507.

40 meters is very bad design.


40 meters it's "what is it". Some plants have the machine room next to the services others not. Sometimes there is cold stores at 60...100 meters of pipe running between the cold stores and the machine room.

Of course we have to count with suction pressure loss increasing or not the nominal diameter.

In the current thread if you the superheat is very high at the compressor suction inlet so open a little more the expansion valve...so the aircooler will give a little more capacity and the compressor will say "thank you" lower discharge temperature and increased capacity.

chemi-cool
09-09-2016, 08:44 PM
When there a too long lines, a cap tube between liquid line and suction line near the compressor, SV controlled can do wonders to extend compressor life.