Original message
| Rusty
 |  "Mircobubbles in a Chiller System"
, posted Sun 14 Nov 22:08  
Have come across a spratic problem with a new R-134A Trane screw chiller, where the chiller locks out on low pressure. Manufacture is suggesting that the water system has "microbubbles" which is acting as an insulator along the laterial face of the evap barrel.
This is the first time I have heard of "mircobubbles" effecting a chiller before. Have double checked the existing air separator performance and thpipe strainers and haven't found anything out of the ordinary.
Design engineering firm is finding it difficult to prove this is the cause of the chiller lockout.
Has anyone else come across this situation? If so, what did you do to resolve it?
Once you think you've got it idiot proof someone finds a better idiot!
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Replies:
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| chiller guy
| "Re(1):Mircobubbles in a Chiller System" , posted Sun 12 Dec 11:40
Rusty;
Still curious as to whether this is an air cooled or water cooled machine. Please advise as I want to check into this a bit deeper.
All refrigerants are safe - All refrigerant are dangerous. The difference is YOU !!!
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| just a mechanic
| "Re(1):Mircobubbles in a Chiller System" , posted Sat 4 Dec 09:22
hi...im not saying this...microbubble...thing isn't a possiblity or even true, but it is the first time i have ever heard of it in my 26 years. i would look at the more obvious things such as refrigerant pressures, water flows, pressures drops and temperatures. can you give more information on it? temps in and out, pressures on both refrigerant and water, approach's...also is it tripping out at a specific time of day or night or just randomly?
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| chiller guy
| "Re(1):Mircobubbles in a Chiller System" , posted Thu 25 Nov 08:15
Cam;
I agree with what you are saying. I have worked on a couple of water chillers over the years (primarly Trane)and have never heard this of this problem (in any brand chiller). However, I am still teachable.
I was hoping to see a reply from Rusty so we could kick this thing around and perhaps all learn something.There are several things that could create a low pressure shutdown depending on the style of chiller and its use and that is why I asked all the questions.
All refrigerants are safe - All refrigerant are dangerous. The difference is YOU !!!
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| | Rusty
| "Re(2):Mircobubbles in a Chiller System" , posted Thu 9 Dec 09:16
quote:
Cam;I agree with what you are saying. I have worked on a couple of water chillers over the years (primarly Trane)and have never heard this of this problem (in any brand chiller). However, I am sti
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Hi Cam
Even with my 30 odd years in the trade, this is the first time I've even heard of it. Yet Trane is fixatied on the microbubble issue saying that it is a common problem on the trane screw chiller.
I have even gone as far as contacting Taco and Armstrong and inquiring about "Microbubble rated" air separators. And yes, there are such air separators made! Surprised the hell out of me for sure. Seems that these air separators use a finer screen and have a different design arrangement inside the can.
Taco, by the way was the first company to market a micro bubble unit, and they offer courses on their air separators for the trade guys, which I have quickly signed up for one here in Toronto.
Hopefully, I'll be able to understand the reasoning for installing this type of separator and just what the real benefits are!
Once you think you've got it idiot proof someone finds a better idiot!
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| | cam
| "Re(3):Mircobubbles in a Chiller System" , posted Sat 11 Dec 17:03
Rusty
All the other guys trying to help out with this weird problem have some good points.
Maybe if you can give us some operating conditions and readings we can get to the bottom of this together.
Can you also identify the chiller for us.(Air cooled or water cooled?)
cam
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| cam
| "Re(1):Mircobubbles in a Chiller System" , posted Thu 25 Nov 07:55
I've never heard of this explanation as a reason for low pressure trips on a chiller.
I'd be more inclined to check refrigerant level, tube cleanliness, correct water flow across evap, superheat etc.
If there's air in the chilled water system you're more likely to have proof of flow problems ( flow switch or differential pressure switch) than low refrig. pressure.
cam
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| Chiller Guy
| "Re(1):Mircobubbles in a Chiller System" , posted Mon 15 Nov 19:46
What is the model number (RTAC or RTHC ?) Did you perform start up or did Trane. Is this a variable flow system. When is it tripping off (day , night, light loads) Has anyone put gauges on the unit and taken a log. Is there a start up log you can lay your hands on? Are you running glycol in the system? What temp water are you making? Who is actually telling you about the "microbubbles" (field tech, service mngr, factory engineer)? Also, has there been any oil added to the unit?
All refrigerants are safe - All refrigerant are dangerous. The difference is YOU !!!
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| | Gary Lloyd
| "Microbubbles" , posted Tue 7 Dec 13:54
What are the following?
Condenser air in temp
Condenser air out temp
Saturated condensing temp (from P/T chart)
Liquid line temp near condenser
Liquid line temp near metering device
Evaporator water in temp
Evaporator water out temp
Saturated suction temp (from P/T chart)
Suction line temp near evaporator
Suction line temp near compressor
________________________
Gary R. Lloyd CMS
HVACR Troubleshooting Books/Software
https://www.merchantamerica.com/tmethod/
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| | geterdone
| "Re(1):Microbubbles" , posted Thu 16 Dec 21:43
In my experience if you were having air bubbles in the cooling water causing the system not to dissipate heat it would cause a high pressure trip out not a low. How is your head pressure?
If your system can't get it done it's time for Get Er' Done HVAC.
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| | cam
| "Re(2):Microbubbles" , posted Fri 17 Dec 06:43
geterdone
Rusty's low pressure trips are a result of these "microbubbles" on the evaporator side (chilled water not cooling water). This isn't a high side problem. But, we're still waiting for more info from Rusty on type of chiller ( air or water cooled) and some operating conditions.
Until we get this info, I'm inclined to agree with chiller guy about the little tap dance theory. They've waltzed me around the floor a few times before on other issues.
cam
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| | Bieb
| "Re(3):Microbubbles" , posted Tue 21 Dec 08:49
I doubt if your main problem is microbubbles. I installed a RTAC185 earlier this year for process cooling. Propelyne glycol maintaining 14 deg. Trane designed GPM was 650gpm for this type of glycol. There are TONS!of microbubbles in the system. With no low pressure shutdowns.....yet. I would look at something else. Possibly flow rates these 134a machines like lots of flow.
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| | Gary Lloyd
| "Re(4):Microbubbles" , posted Tue 21 Dec 16:32
Given the list of temperatures in my post above, we can tell you everything you need to know about the system. Without them, all we can do is take a wild guess.
________________________
Gary R. Lloyd CMS
HVACR Troubleshooting Books/Software
Written by a veteran Service Technician
https://www.merchantamerica.com/tmethod/
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