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Member Post posted an update
March 12, 2025 (edited)
30hxc126ry-161ka
2507Q07571
Gonna through this out here for ideas…
Have a carier 30HXC that has been the one unit on this entire site that has always been a hassle for me since I started here. Something always happens with it… oil pumps, oil check valves, dirty condensers (general site oroblem), Exv failure, cond water vakve failure it goes on…
So for awhile now i have known that it has been running a high approach temp and a low inlet vs outlet temp drop and I’ve been getting to that and finally have but I’m kinda out of ideas.
System:
-Chilled glycol 40%
-134a
-Diverting valve for cond water
-Diverting valve for ahu coil
-AC duty 55 degree setpoint
-No buffer tank
-water cooled
Recent work to correct approach:
-Brushed both cond and evap
-Acid flushed evap (pretty clean now but still a bit of green patina throughout evap pipes)
Findings with stage B only running:
-36/125 psi (confirmed with my guages)
-41 saturated suction temp
-100saturated cond temp
-88 degree measured liquid line temp (12 degrees subcooling)
-74 psi discharge oil pressure
-58.5 entering water temp (confirmed with external probe)
-56.3 Leaving water temp (confirmed with external probe)
-15.3 degree approach
-clear sight glass in liquid line that had been added to OEM along with removable core drier
-1 degree temp drop accross inlet/outlet of external drier
-flashing through EXV sight glass that is 20” away from clear liquid line sight glass
-10 psi evap outlet pressure
-20 psi evap inlet pressure
-10 psi evap pressure differential
-77 degree space and space setpoint (electrical room)
I will add that the unit does keep the space at tenp and there are no customer complaints running like this, i just dont believe its running correct.
Thoughts?
18 Comments-
your approach does seem very high, could be more debris like you said, an exv issue, or maybe the compressor is staying loaded when it shouldn’t be. can you throw some photos in the comment, and answer the following questions?
1. what is ac duty set point? your leaving chilled water set point, or something else?
2. whats your discharge superheat? (your instruments)
3. does this one have an economizer or a liquid level sensor (some do, some dont)?
4. whats your expansion valve position?
5. is the compressor calling for full load, or partial load?-
@the-chiller-guys
1-chiller control point 55
2-20 degree discharge SH same as controller reads
3-no economizer or liquid level
4-23%
5-full load running only stage b for testing (cap 46%/ Dem L 100%)
Posted some videos of the controller operating in the thread
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Why is your glycol so thick? 40% seems quite high and will definitely impact your approach temperatures and performance.
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@jayguy the site for whatever reason likes to run everything 50/50 here idk if this was actually designed as such or just what someone arbitrarily decided 30 yrs ago. I’ve thinned a lot of systems that have no need for such strengths to hit a normal 33%. Other units here do see -40 temps which makes sense for that strength but this one does not see those extremes.
I have had the thought that the higher strength is part of my problem and could try thinning it out some over the next 2 days when I have a moment.1-
@trevor-dudeck It could cause a little issues with the glycol being so concentrated, but 15 degrees is pretty on a flooded evap. I have ran machines with 40% that weren’t that high of an approach.
Another thing to look at could be the divider plate gasket if the th es are clean.
I had one on a WMC that messed me up.1
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I have had this unit running for a bit with a full bypass of the evap diverting valve due to being in a shutdown with low load from the MCC room. This is after running for a good 15 min to bring the loop down from being off all day to around 55 leaving water
1:01
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This image is my own probes to go with 55 degree leaving water video space temp 25.5C
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This is the unit running another 10 or so minutes later with leaving water now down to 50 ish degrees
0:46
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This is my probes again at 50 degree lwt
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Condenser and evap diverting valves though I don’t see it being relevant
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Video from inside evap tube after running brushes followed by a run of descaler. It’s hard to tell but the internal tubes still mostly have a green patina to them still.
0:56
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@trevor-dudeck that bore scope was on the evaporator?
Have you checked your oil level? Is it possible that you have a bunch of oil in the evap?
What’s your liquid sub cooling? I didn’t see an accurate Subcooling reading.1-
@the-chiller-guys oil 1/2 way up the upper sightglass I actually looked today. 12 degrees subcooling measured by my tools yesterday.
Yes the scope was the evap.I really like the blown divider gasket theory at this point bc it would make a lot of sense, much more likely then a glycol strength being the issue. It’s also the simple issue I Nev er thought of the possibility of bypassing fluid around the evap.
I am ordering a gasket tomorow first thing and failed or not it’ll get replaced when it arrives.
If it’s the gasket the chiller guys will be 1000% worth the membership fee right there lol1
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@trevor-dudeck it’s just an idea, the best is to drain the vessel down, and use the borescope, next time check it when you punch evap tubes.
I would still be concerned about the oil in the system as well.
Is it possible that oil issues happened in the past, and someone pumped a lot in?
Also, you said that 40% was the measured glycol right? Not just what they say is in?-
@the-chiller-guys
1-40% was measured glycol strength yes.
2-I spoke with the local carrier wholesaler in town about a divider plate gasket Friday morning. On the parts breakdown which I was also looking at on the screen as well, there was only the round 3/8” outer end plate gasket. He messaged some people and nobody could seem to find a divider plate gasket, does anyone know if for sure there is a second gasket in there? If so a part number would be awesome.
3-As for potential oil logged in the evap from previous work… how would you for sure confirm if that is the case? Also how would you get it out? Naturally you could reviver all the refrigerant than force nitro through the system with schrader removed on the evap inlet with a hose to a bucket and see what comes out. If oil was present and you ended up pulling it out through the recovery process it would end up in the recovery tank. Then when you put the refrigerant back in how would you ensure your not sucking it right back into the evap while draining the recovery tank… pump liquid into the condenser via the discharge line and a recovery machine? Aside from that what can you do??
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One more kick at the can here…
Ok, did a bunch of things to this unit still 10 degree approach.
-thinned glycol to 35% from 40%.
-triple brushed evap tubes.
-ran acid through evap tubes after brushing.
-separately but adds to things, replaced relief valves and did an oil and oil filter change because it failed analysis.
-forced nitro out through evap access port to blow out any potential oil but none came out.
-recharged system by vapour only from the top of recovery tanks to prevent possible recovered oil from entering system. This was because oil was suspected to be logged in evap causing poor heat transfer.
-18 degrees sub cooling (82 degree liquid refer temp)
-zero temp drop accross filter dryer.
-24 degrees discharge superheat.
-100 degree sat liquid.
-125/30 psi operating pressure full load.
-20-25% exv.
-fully loaded.
-49 entering water temp.
-46 leaving water temp.
-flashing exv sight glass.
-pressure probes and temp probes verified by my tools to be reading accurately.
All I am thinking I am left with is that the evap water connection side end bell is bypassing internally allowing supply directly into return. I spoke with the local carrier supplier who spoke with the big boys at carrier about there being a failed divider plate gasket. As far as anyone can tell me there is only the outer o-ring gasket on the end plate. I have been told that whatever they have for a divider on the piping end plate is likely just a metal to metal seal.
I am now out of time with this shut down so this unit will need to be put back into service as is. Also to even remove the end plate is quite the ordeal due to piping, nothing simple like isolate and spin off some unions.
Can anyone see something I may be missing aside from popping off the end plate?
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