View Full Version : Cutin & Cutout Pressure for Copeland compressor
05-25-2004, 12:33 PM
I run a small grocery store which has an indoor walk-in cooler built by HEATCRAFT. The complete refrigeration unit is located on the top of the cooler room. As the weather is getting hotter and humid (storms almost every day) and the store does not has A/C. Lately, I discover the evaportor coil get frozen up (since the store has no A/C) frequently, and the cooling is not quite as efficient as in later summer. It was able to go down to 34F with no problem. Lately, it seems that the compressor is continuouly running, but the cooler temperature stays at 38-40F (even when the coil is not covered by ice) and I suspect that the liquid refrigerant (R12) is circulating the condensor coil but not going down to the evaporator coil inside the cooler room. I remember 2 years ago my refrigeration technican told me due to the hot (in the summer) and cold (in the winter)temperautres, the cutin and cutout pressure settings on the Penn diff. pressure need to be adjusted.
Anyone has any info regarding to the pressure setting versus the surrounding temperature? The compressor is made Copeland and the refrigerant is R12. Thanks.
05-25-2004, 05:10 PM
hello friend; you need exhaust fan,(clean cond.)(check the evap is clean) (all fan checked) OK everything ok first be sure the evap.is clean,them put the manometer, in low side wait and see the presion go down,(its no easy)but do the function the you want. take your time.mayby in one or 2 hours.the low presion go to 15 or 20 (ex. go to 15psig put the control,pressure in 16. them put the unit off, and wait again,(take the time when you put unit off) lock the pressure go up take 15 to 25 min. to get mayby 48 or 58psig ex,58psig take 25min put the control in 57.( setting the control with the freon tank. (THE KEY IS IN THE WIAT TIME)
05-25-2004, 05:19 PM
Is the low side of the dual presure control controlling box temp. or a liquid line solenoid?
What is the ambient temp around the cooler?
Do you have good seals on the door?
It sounds as thought you are getting excessive humidity into the box, which is where the frosting up is coming from. The pressure control does not need to be adjusted from season to season, don't know where he got that from.
Is the unit sized properly?
Is it designed for outdoor application?
If not, the condensing unit may not be able to reject the heat absorbed from the cooler as the outdoor temp rises.
Does the unit ever shut off? If not, eventually you'll have a nice block of ice on the coil.
05-25-2004, 05:57 PM
HELLO FRIEND; WHEN YOU BUYING A NEW PRESSURE-CONTROL-SWICH YOU PUT THE NEW CONTROL, AND NOT SETTING, I TREAT TO TELL HIM THE MODE, I DONT NOW IS THAT UNIT HAS RESISTENCE IN THE EVAP.HE SAID THE COMP.RAN ALL THE TIME.THEY HAD A PROBLEM WITH THE PRESSURE-CONTOL-SWISCH
05-25-2004, 07:16 PM
A walk-in cooler whose temperature is solely controlled by the low pressure switch will never perform well or consistently. It's the cheapest form of control there is and although it is a preferred method in some applications, walk-ins aren't one of them.......and since this beast is an R12 unit, it's likely growing a bit long in the tooth so it doesn't owe you a nickel. ;)
It's time to call a qualified refrigeration service company to go through the system, evaluate it and at least install a thermostat and pumpdown solenoid valve. Since you like to try to run the box at 34 Deg F, you had better spring for a good defost timeclock as well.
05-25-2004, 07:48 PM
I just hated it whenever I ran into such an installation with no room to vent the heat and you have to stand there scratching your head and cursing the guy who put it there.
I agree with Iceman, call some reputable refrigeration
contractor in and let them yank that condenser off that hot attic or you will end up changing alot of compressor later.
I think you know HVAC/Refrigeration very well, just having a hard time understanding what your saying.
Es un poco duro entender su inglés.
Usted puede ser que desee considerar un Web site de la traducción, él puede ser que ayude todos nosotros.
Entendía lo que usted decía, y usted tiene buena información.
Goce de su amigo del día.
05-25-2004, 09:02 PM
UCP excuse my english but i try to understand everybody i now i need more practic thank
05-25-2004, 09:07 PM
Hey that translator is fancy
That Translator works ok, its not real accurate, I think some things get lost in the translation. I hope I didnt insult anybody.
Thier lucky in Puerto Rico to have good techs like him.
06-21-2004, 09:40 AM
Thanks for the input and suggestions to my earlier post. The cause of icing (first starts with one or two coils) on the evaporator is due to not enough refrigerant running through the unit. I was fooled by the the "green dot" shown the sight glass which it only indicates the refrigerant is dry and not necessary the level of refrigerant. A service call was made and the refrigeration technican found a small leak and pointed out that he counld see any refrigerant running behind the sight glass. After recharging (actually drainning and replacing the old R12 with new 409) by a refrigeration technican, the unit runs cools and no more ice formed on the evaporator. I hope someone can use this piece of information. Thanks for those who replied to my earlier post.
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