Whoops, I didn't know that. SorryQuote:
Originally Posted by Dallas Duster
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Whoops, I didn't know that. SorryQuote:
Originally Posted by Dallas Duster
Make sure you check the subcooling using a gauge connected to the liquid line, not using the high pressure transducer, which is on the oil separator and is hot gas pressure. There is a substantial pressure drop across the condenser due to the U tube circuits, as much as 50 PSI.
You really need your laptop to work on these chillers. There are some readings and settings you can't see on the DynaView display. You can only read EXV position on the laptop which is needed to diagnose the chiller.
These chillers absolutely can't be overcharged with oil, even 1/2 gallon, or they are going to wreak havoc on you. It sounds like you may have an oil logged evap. If your running 100% EXV with low liquid level and 0 deg discharge superheat, that’s probably your problem. Oil temp is the same as hot gas temp so you can use the display to determine discharge superheat. Of course, verify calibration of all temp sensors and pressure transducers first. The small line going from the bottom of the evap to the bottom of the compressor is the oil return line otherwise known as the "oil scavenger line". Make sure the strainer (or drier on later model chillers) isn't clogged up. It very well could be since you had a compressor failure and any trash will make its way to the bottom of the evap and to the strainer in the scavenger line. To check oil level, run FULLY UNLOADED for 20 min, let sit for 20 min, and check oil level in the separator. The highest level you probably will see is around 8" and the rest will blow through the separator and make its way to the evaporator. You may need to bring the level to around 2-4" and go through the process again. If it’s back up to 8", you will have to keep repeating the process until the level stays low, and then carefully adjust oil level to bring it back up to proper level.
Your drier shells may be causing issues but I’m not sure as I’ve never seen that done before. I would think it could possibly be causing a restriction and affecting EXV position. I would get rid of the driers, put the factory shell with new felt filter back in, and follow manufactures cleanup procedure which is installing a cleanup kit on the chiller or having a company come out and flush the refrigeration circuit. If it was a severe burnout, the flush is probably your best bet but it's not cheap.
After all excess oil is removed, driers removed from liquid line, and assuring oil scavenger line strainer (and line) is clear and free, you should have 50 - 70% EXV position at full load on that circuit. Discharge superheat should be around 17* and approach should be under 6*. Sight glass should be clear and subcooling will probably be around 10 to 20. These readings are at design chilled water temp.
Also, as Healey said, you need to check your chilled water pressure drop across the barrel USING 1 GUAGE.
This morning I removed one gallon oil. Isolated low side and pulled strainer on oil return line that had plenty of trash in it but wasn't plugged. Ran for an hour it loaded fine and unloaded as it should based on setpoint. Rechecked the level at five inches above inside bottom of separator. Approach was around 8* subcooling 22* exv at 67% and sightglass was clear the entire time. The approach on the other circuit was still lower at 5*. Also discharge superheat was at 20*. The trash in the strainer was fine strands of copper about the thickness of a hair and also small "bearings" about the size of a ball point pen.
Sightglass is only for seeing exv position. Has nothing to do with charge.
The sight glass is one of the many things you check to determine low charge.
You are correct 123. I went back and looked it up in IOM. Guess I was thinking of clearing sight glass alone as charging procedure. I know some have done this and its not correct.
I myself do not use the sightglass as a charging tool.Quote:
Originally Posted by socotech
the sight glass is PART of an invaluable tool...what that means is that you only can use it to see vapor. 45F subcooling and sight glass of bubbles and you have non-condensibles. 45F of subcooling and no sight glass...now you are thinking over charge....see the difference? I use the sight glass for charging...up to a full sight glass, after that, it is all about subcooling only.
Good info.Quote:
Originally Posted by jayguy