Quote Originally Posted by AmmoniaMike View Post
Ok, so how is this as a step for optimization. I have a new plant that was commissioned in February of this year. We have a spiral freezer that has only been in full service for two months. The freezer has four coils which are set up to defrost (hot gas) one at a time 1 or 2 times per shift each depending on length of shift. Problem: when coil B goes into defrost temp in freezer climbs 6-7C when the other coils defrost there is only 1-2C rise in temp. 6-7C temp increase means the product is not fully frozen so the metal detectors have a fit and reject product like crazy. The coils are run using a 600 hp screw with an economizer, set points are suction 12" Hg and discharge of 120 to 140 psi depending on outdoor weather conditions. To give us time we dropped the suction to 18" Hg so we run the freezer colder so the temp increase won't give us too much trouble. Of course that is not great for efficiency and you have more moisture loss from the product. Now why is that coil troublesome? We look at liquid supply, hot gas supply, backpressure valve etc. all for coil B and can find no problem. The issue? Some sod left the liquid supply line for coil A closed (A and B are top coils, C and D are bottom coils) so when B was in defrost no top coil was doing anything. Also the refrigeration mechanic who set this thing up left two of the suction stop valves 1/2 closed. The final result? The compressor which had been running at about 80% capacity on average is now running at about 65% capacity on average and the dwell time in the freezer is down to 70 minutes from 80. Now there was some question on this thread about end users. I guess as the chief operating engineer of this plant I would be considered an end user so how can I optimize my plant?
Regarding to mentioned coil. If you have a problem with cooling, first thing you check frost formation on evap. coils and evap. fans rotation. Most likely this coil had much less frost than other coils.
Regarding to optimization. We need more information about your plant. Compressors, condensers(how many, models). Suction pressures. Temperatures in refrigerated rooms. Time(hrs) between defrosting. How do you control head pressure(PLC, pressurestats)? What kind of product do you freeze?...