1999 Trane chiller with 100 ton screw compressors. Wye Delta motor starter. Impressive that this thing still runs.
I have a water-cooled, 90-ton Trane chiller with 2 screw compressors from the late 1990s that I have been maintaining for many years. Near as I can tell, it has been run every summer for about 30 years, long before it came into my possession, but over the past 2 years, it has developed noticeable leaks in some of the condenser tubes of one compressor (Trane doesn't make any condenser replacement parts any more), and my go-to contractor can't figure out a way to rebuild it in his shop.
Over the years, I have replaced many of the Trane's contactors with refurbished and new old stock I bought on eBay (because nobody makes them anymore, and even the secondhand surplus is drying up), and last year replaced one compressor's leaky expansion valve with a janky non-OEM because Trane doesn't make the valves any more either. I've replaced the starter and rebuilt the condenser and chilled water pumps more times than I care to remember.
The various leaks over the years have reduced me to the last few pounds of my stockpiled R-22 reserve (I bought a couple tanks before the phase-out and bartered and bought some recovered R-22 over the past few years). After this summer, I won't have any more left.
I'm thinking it might be time to give up and acquire a new chiller after this summer, even though the screw-compressors are still running like champs.
I heard you can run an eddy-current test to identify the leaky tubes and use stoppers to plug up a certain number of leaky tubes up until a certain point without severely impacting the efficiency of the system, but I have a gut feeling that more of the tubes are going to start leaking soon, and besides, the non-OEM expansion valve requires daily resetting and adjustment since it cannot automatically communicate with Trane's OEM controller. I don't know if I can endure many more years of manually resetting and adjusting the expansion valve every morning, every day, for the rest of the chiller's life.
For replacement, I was thinking to go with an air-cooled chiller setup this time, to increase redundancy. One of the most aggravating issues with water-cooled is all the potential failure points in the many components on the cooling tower side. The condenser pump seal and shaft and bearings, the pump motor and their coupling, the starters and overload relays and breakers for condenser and cooling tower fan motors, the cooling tower gearbox, the water treatment for an open-loop cooling tower. It just goes on and on. If any one of the water-side components fails, the whole system is completely down and it will often take me days to get everything back up and running, despite the ever growing stockpile of motors, starters, couplings, pump seals, etc that I try to keep on hand.
There is so little redundancy in the water-cooled system.
I know air-cooled will use more electricity, but I'm ok with it as long as I can get more redundancy in exchange. I'm thinking a 100-ton chiller, or maybe 2x 50-ton chillers. Although I've gotten mixed responses from other HVAC guys I talk to, about whether it's actually more redundant or not to have 2 chillers instead of 1 with more compressors.
I figure I also want maximum redundancy since everything seems to be scroll-compressors these days, and even if they still make screw-compressor chillers, I probably couldn't afford it. I don't have any prior experience with scroll-compressors, but I doubt they last as long and I'm thinking it'd be better to be in a situation where I can still run with 1 compressor down whlie waiting for replacement to come in.
My other unreliable backup option is to keep trawling my local HVAC surplus dealers' inventory for the perfect surplus new or barely-used replacement chiller, whether that's air-cooled or water-cooled. They don't have anything good right now, but I heard other guys having great experiences with surplus new chillers when they are lucky enough to find something that is a perfect fit for their setup. I've been looking for almost a year now, and still haven't found anything that's just right (ie, anything compatible that hasn't already got 20+ years of running time on its compressors)
I also had a good firsthand experience with surplus, but that was on the cooling tower side - I got a giant all-stainless steel tower for cheap during the pandemic lockdown, which I can resell for good value back to a surplus dealer anytime, or even get the purchase price back in the scrap metal value. Even the most minor components of the tower are stainless steel, like the bracing cables, bolts, hot water deck's cover plates, etc.
I also talked to some of the faculty at a local technical college who are big shills for mini-split, but I'm thinking that would be a lot of units to match the original 90-ton capacity, and they would want to tear up 2 good roofs and 2 concrete floor slabs, plus the better part of 60 000+ sq ft of ceiling mechanical space to gut the old ducting and air handlers and install the piping and new ducting/cassettes.
What you guys think? I could use some second opinions, as I never went to school for HVAC and have zero new-install experience, and my friends and go-to contractors who did go to school are very unimaginative and tend to overlook basic stuff unless I'm there to check their work.
