Help with enviromental control room
With my new job I am running in to some different types of systems I am not overly familiar with and could use some help understanding what is normal operation for some of them.
I am currently working on a fair share of environmental rooms that use hot gas bypass and digital controllers to keep the room within a few 10ths of a degree for experiments requiring precise temperature stability.
These use central chilled water for condenser cooling and run 24/7 just switching a liquid and hot gas solenoid back and forth.
Usually they are R-22 or R-12 and sometimes R-416
There are a couple of components that I am having a hard time adjusting and understanding.
One of them is a CPR or crankcase pressure regulator and is supposed to be set by compressor amp draw.
What is its purpose?
Also another component is the water regulator. I understand what this does opening and closing it allows more water or slower water movement around condenser coil and effects the high pre4ssure but I am not sure what a good pressure is.
I have been instructed that by taking the inlet water temp (Ours is usually around 45) that the outlet temp difference should be around a 20 F rise or 65 F.
They also have TXV valves and site glasses for charging.
I recently replaced the CPR in one unit and my superheat was very high over 30 but the room was 90 degrees.
When I came back in the morning it was frozen all the way back to the compressor. I recovered some refrigerant which caused bubbles to appear in the site glass but the frost went away.
Later that day I returned only to find the evap now starting to freeze.
It is a cold room set at 4 C and is keeping it steady at that but I need to understand more about this system and do something about the evap now freezing.
Any help would be greatly appreciated.
start by finding as much info on the equipment you can...Than see if you can find the sequence of operation. Than break down each system to each component and read the operational manuals on those. I have worked in a Drug manufacturing company and there is a lot to know and learn. Do you have a DDC system as well?
Thanks, good advice.
Originally Posted by dlove
We have a lot of material on our systems so I can use it as a reference.
We have Norlake, Biocold, Enviro Systems, Cascading ultra lows and many more.
We do have DDC but have control guys for that as well as several Central Chilled water and steam plants.
Lots to learn for a guy who is only about ten years away from calling it quits but I must say it is interesting and has proven to me once again that in this industry and career one could never run out of things to learn.
CPR is really a pressure limiting control switch it protects the compressor from excessive suction pressure during the startup. I have a similar system I sometimes work on in a clean room where the system is not designed to cool as low as they are trying to go... usually has the same problems as you are describing. anyhow hope that helps and cant wait to hear more about the equipment I love this stuff any day without something to learn is a wasted day.
Water cooled condenser out 65f ? No wonder that you have erratic ref. flow. That would give you only app. 130 R22 and 76 R12 head pressure!
Originally Posted by mcjo tech
Without an op manual, 95f outlet water temp is a starting point. Too hi flow erodes the coil & wastes water.
Originally Posted by IRBH