RTHC Oil Loss Problem

[jogas]

First time post to this forum, so hello all!

At one of our sites we have a 400 ton RTHC, water cooled that has had a history of running oil loss problems. We have checked oil sensor, charge, master oil solenoid, oil filter(s), etc.,. I don't have it with me but every item in the IOM manual for running oil has been checked. The chiller will run for a week, a month, 2 months and then go down.
This last Sunday we had another shut down on oil. When I arrived, I checked the oil sump level, 7". Trane says 2-6" is good. I set up my VOM on the optical oil sensor and started the machine. It started up fine, with a .24VDC optical oil signal. It ran about 10 minutes. I then heard a click and a slight clunk from the pueblo loop (oil filter area), the optical oil signal immediately went to 19.89VDC(never saw that happen), and the machine shut down in 5 seconds on running oil loss. When I looked thru the optical oil sensor site glass, the line appeared empty.
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Per Trane Service Bulletin:
0-2VDC = wet reading (all oil optically sensed)
2-20VDC = foam optically sensed
>10VDC = after delay, will shut down chiller on running oil loss
*these values are from memory, correct me if needed
_____________________________

I thought it was the master oil solenoid dropping out. I got another pair of eyes on the job. we set up min/max VOM's across the pressure switch and starter contacts that could drop out the k400 contactor that would close the master oil solenoid, drain the pueblo loop, and dump the machine. We ran the machine and the problem never reoccurred. The chiller has been running since.
Has anyone had oil problems like this on an RHTC?
Is there any do's and don'ts any one can pass along on this type of machine?
Yes, I am planning on going to an RTHC class this winter. But we gotta get thru this problem first.

Readings:
CHW Setpoint = 42*
Tower Water Setpoint = 78* Low Speed, 82* Hi Speed
Discharge Superheat = 18-26*

Cond Approach = 2* - I know, a little low. But we recently found another chiller connected to the loop that has a evap to chw refrigerant leak. The chw had a lot of foam in it(glycol protected) and I don't think the evap on the RTHC was loaded as good as it is now. Previously, at setpoint, we ran 22-28% loaded and now that we've isoloted the other chiller and bled the system, we are running 38-44% loaded at setpoint. Anyway, my next visit I'll add some 134a.

Evap Approach = 6* - Another variable as the other chiller is tee'd into the RTHC chiler's supply with a B&G Flow Setter in between each to cause a pressure drop to feed the other chiller. Real down and dirty and another brilliant engineering cost cutter. Bottom line, I'll have to check flow thru the RTHC to verify where it's at right now.

Suction = 33#
Discharge = 103#

Any help on this issue would be greatly appreciated. Our backs are to the wall as the other chiller down for evap repairs right now is our backup to this chiller. Without it, a good part of the campus is without chilled water.
TIA for all replies,
Jogas

[absrbrtek]

Cant help you out but its a very good post, full of information. Wait till you read some of the crap these other posters post and expect to get help on.

[brian9695]

I think you are on the right path with your diagnosis. You stated you heard a noise that might be consistent with a contactor or solenoid if I understood you correctly shortly after the noise your safety tripped on what seems to be a true loss of oil from the optical.. Try using circuit monitors across your possable trip points that would take out your oil flow.. ( The kind that you can leave on site and not miss if they grow legs ). Good luck and post back when you find it.

[jogas]

The RTHC has not dropped out again since my last post.
I was at the job working on the other chiller and added 120# to the RTHC in an effort to raise my condenser approach. The condenser approach stayed at 0*, and the evap approach dropped from 6* to 3*. Sub-cooling ended up at 5*.

[flemsteele]

Originally posted by absrbrtek
Cant help you out but its a very good post, full of information. Wait till you read some of the crap these other posters post and expect to get help on.

Abs,

You are killing me!!

[bill-hvac]

like the specifics of your post, I wish they were mostly that good. I have had intermittent problems like this maney times. I use a tattletail, either bought or I make up my own using a fuse holder and a 200ma amp fuse matching the voltage of the circut your on. fuses rt radio shack or any electronic supply houses.

[chiller joe]

think about your approaches 2 on cond 6 cooler you sound like you could be low on charge I had from fact low on charge and as your load changes oil return could be a problem also raise water to 44or 45

[jogas]

joe,
I'm thinking (hoping) it's not low on gas. 1.5 years ago, the charge was removed, pressure tested, pulled down to 500 microns and re-charged (850#) to dataplate amount.
I will do a leak check to make sure.
I've found the cartridge style reliefs leaking on several of the Trane screws by removing the relief discharge piping and putting a baloon over the relief outlet. Run the head up or leave the baloon on for a while and Wa La...Leak found!

Originally posted by chiller joe
think about your approaches 2 on cond 6 cooler you sound like you could be low on charge I had from fact low on charge and as your load changes oil return could be a problem also raise water to 44or 45

[r404a]

Jogas,
I am having identical issues with two identical machines side by side. Seems to be when fully loaded. Was this the same in your case? Did you have the issue again?


r404a

[wisecracker]

Check your flow (pressure drop) thru the evaporator. Had a RTHD tripping on Low Oil Flow recently because of that.

[r404a]

Wisecrack,
I had the controls tech at this job adjust his DPs to cut the machines out before they got to minimum flow. I am still leaning that way, but the issues always seem to come up at 100 percent load. Thanks for the reply.

r404a