Need help with a Hill Pheonix rack leak
I'm new to the forum and really liking it so far but really need help or rather advice to help me find a leak on this rack. The rack i'm working on is a parallel refrigeration rack using R-404a gas and is being used for low temp cases. This rack has 12 circuits and handles coffin freezers, W.I.F's, and multi deck closed freezers. For the past month I have being trying to locate a leak on this rack. We are losing 100 lbs of refrigerant every 2 weeks. Now with that being said you would think the leak should be easy to find but unfortunately I can't seem to find it. I spoke with several tech support agents @ Hill-Pheonix and have no luck. So we are clear this rack has 4 compressors, 12 solenoid valve's, 12 EEPr's,12 suction and liquid ball valves, 28 evaporators and txv's. I do have & circuits that do run underground in 3 seperate chases. I have checked all evaporator coils, all TXV's, all solenoid valves, all schrader cores( I have found 6 cores leaking badly on liquid line and replaced cores with new), found discharge service valves gasket leaking on 2 compressors and replaced both, rack has a tube and shell heat reclaim coil and I have isolated it from high side of system and nitro test @ 300 psi and it held for 24 hrs with no pressure loss. I have closed suction ball valves and fed liquid into suction lines for each circuit 1 by 1 and allowed pressure to reach 135 psi and set to deforst and searched each circuit 1 by 1 with no success. The only thing I haven't done is isolate each circuit, pump down and recover residual to vacuum pump to 300 microns to see if circuit holds vacuum but I was hoping maybe there are some other ideas you all can share with me to see if I can locate and eliminate this leak. I have searched for this leak with a standard leak detector, ultra sonic leak detector, nitrogen, and soap bubbles. SOMEONE PLEASE HELP ME LOL..
Any advice will be more than appreciated. Thank you very much.
Time to isolate the branch liquid/suctions and pump them up with some nitro for some standing pressure tests.
Originally Posted by Phase Loss
I have done that and each circuit held 200 psi for 1 hr.
Time to get a good leak detector.
You mean to tell me that you aren't getting ANY indication of a leak as you work around it?
Shut down the HVAC equipment. Shut down the exhaust fans. Shut down the WHOLE rack.
Go have a coffee.
Now, fire up your sniffer (I use an H-10) in a KNOWN CLEAN atmosphere. I start 50-100 yards from the front door. VERIFY that the detector works against a KNOWN good reference (another reason that I like the H-10)
Work slowly and methodically. Make mental notes of ANY noise that the detector makes that is out of the ordinary.
Cover the entire rack. Every system, every door, every foot of case. Don't forget heat recovery coils and the condenser. Check piping chases or pits, too.
As you're walking the store, you're also listening for a leak, watching for oil in the drain pans and smelling for the oil (yeah, I know, you aren't supposed to be able to smell leaks, but I've found them that way.)
Are the lines run overhead or in trenches in floor ,if there is access point see if detector picks up refrigerant ,what kind of detector , .Do not enter where lines are in floor if there is access unless you have training in confined space. can you isolate cases .,also check where lines penetrate roof ,anyplace where chafing can happen ,In mechanical rooms my leak detector would start beeping ,started using the leak detector used with propane ,not sure if that would work with 404. Let us know how you make out.
Idk if that would work but have checked all chases and roof penetrations. Checked all over head lines as well. This is exactly why i'm smh
Im using an H-10 as well and nothing found. also I can't shut down hvac and exhaust due to the fact this a walmart and they wont let kill 36 rtu units and the 3 dehumids. it sucks. I have verified the rack is solid and cases are solid. its almost as if the refrigerant is disappearing into thin air.
Originally Posted by jpsmith1cm
I've never had any luck with the "isolate and pressurize" method of finding leaks.
I'm always afraid to run the pressure too high with inert gas and load the rack up with non condensibles because a GD ball valve leaked past. Can't test using a micron gauge for the same reason. Was the leak due to valve leakage or an actual leak to atmospheric?
Let's put this in perspective. You're losing 50# a week or a little less than 10# of gas per day. That is one H**L of a big leak. Start popping ceiling tiles and looking for oil with a powerful flashlight.
What detector are you using?
It IS disappearing into thin air.
Originally Posted by rackguy813
What sensitiivty do you have the H-10 set to and have you properly adjusted the sensor heat?
I realize the scope of your leak search, is larger then 80 lbs. circuit R-404A I have worked on. Sniffers aren’t real effective R-404A; I used R-22 Trace charge topped off to max. Coil pressure with nitrogen .
This is the point that I've been driving at.
Originally Posted by 2nu2no
Particularly with the H-10, R404 leaks are harder to find. Use the highest sensitivity and follow every indication of a leak you get.
Now, supposedly the Infrared sensor technology has a more consistent response to HFC/CFC/HCFC refrigerants. I'm still not convinced.
I am not a rack guy but what about the condensing side of the house any leaks on the condensers ?? It sounds like you have covered everything inside the store except put down new tile floors
Last edited by james264; 09-27-2011 at 09:14 PM.