discharge Pressure

[st1300]

I have just replaced my compresser in my choice vende 224 with a enbraco ffi12hbx that cross referenced my old aspera with 134a, new compressor new dryer it is putting out 235 psi of discharge pressure that I think is to high I have charged it to 12 PSI suction it runs great cools fine and cycles normal, my cavalier puts out 180 psi discharge with the same compressor, Can any one give me some feedback on what there discharge pressure is running on some different machines or if I have a problem.

[johnieG]

Without knowing where your test points are in the system, offhand I'd say you have a possible restriction in the capillary tube, the suction side is bit low for a soda machine/medium temperature application, normally it would run between 18-30 psi on the lowside & 130-180 on the high, depending on ambiant temperature & evaporator temperature, was the machine originally equipped with a R12 compressor? or was it a R134a unit? the reasoning I'm thinking is have you watched the low-side pressure upon startup & does it start in the normal range & then goes low?  ( maybe a bit of ice formation restricting the capillary tube) or a non-functioning condensor-fan? 

[globalcompressors]

I don't think there's a mystery here...the FFI12 BX is a 1/3+ hp compressor and is too large for the system you installed it in. Most, if not all, older soda machines,  are running 1/4, 1/5, and some 1/6 hp systems. The only time I've seen a 1/3 compressor used, is in a large chest type machine, like a Westinghouse wd22 or something similar.

Get the correct sized compressor and you'll be set...1/4hp.

Eric

[st1300]

I think I have figured out my problem, I was watching the discharge pressure after the condenser and before the dryer and noticed it was functioning from 235 psi to 244 psi and that the capillary tube would vibrate or surge as if it had gas going thru it some times so I figured it had none condensable in it,  Remembering back to when I added the charge after pulling vacuum for 2 hrs I added the 134a without purging out my 4 feet of hose, 2 feet
From can to gauges and 2 feet from gauges to suction line, So I am going to start over, I hooked up the vacuum pump and evacuated the charge after pulling for 1 hr I primed or purged out my hoses by
Hooking up a loose fitting to the check valve in the end of the hose and turned the refrigerant can upside down until liquid came out and then removed the loose fitting trapping refrigerant inside the hoses and then hooked it up to the suction line and then added just the gas let it set and then started it up let it run until I had the right amount of charge
I have now got 165 psi on the discharge 70 F outside temp and 18 psi at suction 44 F inside it looks more right now, It is cooling down quickly I am satisfied it just had air in the system hopefully the dryer is still good and the capillary tube is not surging.

[johnieG]

Ahh, good news then, live & learn!