central ice plant

[koolncali]

This question is for anyone who is familiar with centrifugal chillers. We are getting an chiller ice plant at the school where I work. The company that's doing the design/build wants to install two 500 ton trane HCFC 123 chillers so we can get LEED pts. I would prefer HFC 134A chillers because 123 is soon being phased out and inventory will be low. I have heard from another centrifugal service tech that trane's have rotor bar problems. what about the reliability of trane chillers as opposed to york,carrier, or mcquay? any thoughts anyone?

[drivewizard]

Why would you want R-134a, If, no, when you develop a leak the refrig is gone, never to be used again.
You need to talk to customers that have R-134a systems and ask them how many pounds of refrig they have put in their chillers due to shaft seals leaking, Brass WOG valves leaking at the threads because of cracks, etc. etc.
Then go ask a customer that uses R-123 regardless of wether it is Trane or York. Ask them how much refrig they have lost and had to replace. York used to make a good chiller in the YT (R-123).

IF R-123 is not manufactured any more it will be a non issue. Just look at all the R-11 out there, people said it would not be available any more too. There will always be enuff R-123 available due to reclaiming and de-commissioning older chillers. So in the event that you have a large fire in your chiller room and blow rupture disc AND lose ALL the refrig there will still be supplies available! Or if a 8-9 point earthquake hits your area and you crack a pipe and lose all refrig, you will still be able to get some. Aside from those two things happening you should be good to go for the life of the chiller.

Ask the other manuf about a refrig warranty. See if they will give you a ten year warranty. Trane will.

Think about service also, try replacing an angle valve or other small fitting on the fly on a R-134a chiller!!! Especially if its below the liquid level or on an oil line, Good luck, it aint gonna happen.

Rotor bar problems? That is a new one, never seen a Rotor bar problem in the last ten years. Competitors used to say since our chillers are hermetic and not open drive that when the motor has a burn out it contaminates the whole system. Unlike the open drive brand.
Well, I haven't seen a bad motor burn since we quit using dashpots.
The new electronics prevent that sales pitch from holding any water, so I guess now it's the rotor bars. To funny.

[emcoasthvacr]

I never seen chillers leak like 134a -- I hate the crap.

[koolncali]

thanks drivewizard for the reply. I assume you would also recommend an r-123 machine for chilling a glycol solution to 23 degrees to run through TES tanks. do know what the best control valves are for a chiller plant?

[acjourneyman]

There will be far more problems getting 134A in the future than 123, reason being is it will all be floating around in the atmosphere causing global warming.I have not seen a rotor bar problem on a Trane chiller in 15 years, I have added less than 100 pounds of 123 gas to a chiller in the last 10 years.There is a close to 0 percent loss of refrigerant a year on 123 chillers but huge losses associated with 134A chillers.I have personally added over 10000 pounds of 134A to chillers in the last 7 years , after leaks were fixed of course.The only problem is, if you aren't leak checking monthly you won't know until you start losing capacity.Take the points and do yourself a favor and get the best machine on the market without having to worry about refrigerant ever again.

[jayguy]

This question is for anyone who is familiar with centrifugal chillers. We are getting an chiller ice plant at the school where I work. The company that's doing the design/build wants to install two 500 ton trane HCFC 123 chillers so we can get LEED pts. I would prefer HFC 134A chillers because 123 is soon being phased out and inventory will be low. I have heard from another centrifugal service tech that trane's have rotor bar problems. what about the reliability of trane chillers as opposed to york,carrier, or mcquay? any thoughts anyone?

all of your thoughts and concerns are valid. you will have to decide for yourself what it is that you want most. i think that R123 will decrease your LEED points on the surface but because R123 is so much more effecient than R134a, you gain all of it back and more (i may be wrong on that point...i think that i read it somewhere). regardless, all refrigerant is only harmful (to the environment or people) if it leaks out. but what happens if the refrigerant stays in? R134a is less effecient mathmatically (therotically) than R123. so every hour that a 134a chiller runs, it is using more energy than a 123 chiller and the harm to the environment happens at the energy plant instead of the chiller plant. like drive said, while it is true that R123 is being phased out, the supply is quite good. very few trane chillers that i have worked on have ever leaked out...most leak air in. if the refrigerant does not get out, you do not have to replace it.

i have seen rotor bar issues on one chiller...a bazillion starts and stops on that one, so it was not real surprising...but across the board? no rotor bar issues. as far as reliability goes, that is a marketing game. all manufacturers say that they are more reliable than everyone else. if the chillers are installed properly and maintained properly (big if on that one!), you should not have too much trouble. some chillers are more prone to certain issues than others, nobody's perfect. these chillers were built, shipped, installed, maintained and operated by man...man makes mistakes and errors.

the one thing that i would caution you about...schools are notorious for being cheap (relatively speaking...just because you are spending 2 million dollars or whatever, still could be cheap). they are not given much money to do things correctly and the plant will suffer forever. if you have the ability, really stay on everyones a$$ about getting it done correctly.

good luck.

[drivewizard]

thanks drivewizard for the reply. I assume you would also recommend an r-123 machine for chilling a glycol solution to 23 degrees to run through TES tanks. do know what the best control valves are for a chiller plant?

Sorry, can't help you there. Not much ice makin up here in the NW. Yet.
Utility rates still to low to make it worth while.
Can't really make any recommendations on valves either, to many out there and to many applications.
Just remember, cheap and low initial cost is not always better. Usually never better. Look at long term costs and service.
Talk to other owners and ask them lots of questions. Don't blindly believe the salesman, no matter who they work for. Trust but verify.

[koolncali]

thanks drivewizard for the advice.

jayguy- you guys are giving me sound advice about r-123 vs r-134a. an energy project management company called ameresco is doing the design/build on our central ice plant. they pitched the whole idea to top management at my job. they will install the plant then we pay them back there projected energy savings making off-peak ice. yes schools are cheap always going for the lowest bidder and i've got to stay on top of these ameresco guys i see their game already and the rules keep changing as go. they are proposing 2 500 ton trane r-123 (cvhe) centrifugals and 45 tes tanks with the capacity to expand.


acjourney- thanks for the advice about leaks on a high pressure machine. i know negative pressure machines have their little problems with sucking in air with its moisture but hopefully trane has a better purge than carrier who used to have really crappy purges. and your right r-123 is the global warming friendly refrigerant as opposed to r-134a which is the ozone friendly one but i realize that r-123 has very low odp.

[r404a]

A Trane R123 centrifugal would be the choice I would be happiest with. Low pressure will always be my preference and the abscense of a shaft seal makes it that more attractive. I work on on 134a screw ice builders and low pressure centrifugals for the same application and say it is wise to heed what was said earlier about "on the fly" repairs. When you have KW penalties to think about, an "on the fly" repair is a life saver.
I wonder if this guy is talking about VFD bearing failures when he speaks about rotor bar failure? I know there are bulletins on broken rotor bars, but we are going back a ways thereand I have never seen it. That don't mean squat, I just haven't seen it.

r404a

[r404a]

thanks drivewizard for the advice.

jayguy- you guys are giving me sound advice about r-123 vs r-134a. an energy project management company called ameresco is doing the design/build on our central ice plant. they pitched the whole idea to top management at my job. they will install the plant then we pay them back there projected energy savings making off-peak ice. yes schools are cheap always going for the lowest bidder and i've got to stay on top of these ameresco guys i see their game already and the rules keep changing as go. they are proposing 2 500 ton trane r-123 (cvhe) centrifugals and 45 tes tanks with the capacity to expand.


acjourney- thanks for the advice about leaks on a high pressure machine. i know negative pressure machines have their little problems with sucking in air with its moisture but hopefully trane has a better purge than carrier who used to have really crappy purges. and your right r-123 is the global warming friendly refrigerant as opposed to r-134a which is the ozone friendly one but i realize that r-123 has very low odp.




The "D: purge is a marvelous machine. Still, the best was the "C" purge, in my opinion but the theory is basically the same, except for regenration and new control scheme.

[koolncali]

thanks r-404a you guys doing the repairs have the best opinion and knowledge about low pressure vs high pressure machines. i was only thinking in terms of ease of leak testing with a machine always under pressure but i won't be working on these machines anyway only monitoring them. i will assume the "d" machine you mentioned is for the trane purge. no vane shaft seal is a blessing knowing all the problems carrier had with these seals.

[DCSCO]

The Trane 123 chiller is quite. Have only seen bound vanes at 22,000 hours. With ice system worry about design and control first. How will you measure inventory, if that dosen't work spot on, you may have alot of hot afternoons. Also ice systems can have a high pressure drop compaired to chiller. If you are operating in a chiller and icemelt mode, you need more than a three way butterfly valve set up to control ice melt rate. If you get a inexperienced poor design you can use any contractor with equal results.

[koolncali]

DCSCO- they are going to install two 500 tranne hcfc 123 chillers (chve). The primary pumps will pump a glycol solution through the TES tanks from 11pm to 8am and then run the secondary pumps 8am to 11pm circulating water through a heat exchanger while the chillers sit idle. the capacity of the ice tanks will be 6300 ton-hours. i believe there is an ice inventory sensor that can be monitored by the ems if that going to help me. what's the high pressure drop you speak of.

[DCSCO]

Kool,
The high pressure drop mentioned was for the TES. Specifically, for serpentine coil in water bath type. The delta P through the chiller may be 7’ of water, the TES can be more than 3 times that. However, because you will operate in ice build mode or ice melt mode, you won’t have the balance problem I did with operating the TES in parallel with the chiller plant.

The other problem I had was with the ice inventory measurement. Our system used the increase in water level as ice is made to calculate inventory. We started with a pressure sensor on a water column. Eventually ended up with a sensor composed of a ceramic rod that changed captaincy with the depth the rod was submerged. Anyway the short story is that inaccurate ice inventory readings can cause less than 100% ice build. Also, without a temperature test of the TES supply, the system can mistakenly read inventory remaining when you actually have none, thus warming the TES. Multiple sensors add backup.

If you use water level to measure ice inventory and if the system looses water from evaporation or draws humidity from the air, you will get an error in the inventory calculation. To calibrate to zero you have to melt all the ice. I usually kept a 5% bias because if the TES warmed up to 65° it would take about 90 minutes to get temps back down to 32°. Our design called for ice build until 8am. But the building needed cooling to start at 5am to cool down to comfort zone temps. I was lucky to build 90% inventory overnight.

If you use air pumps for even ice melting, that can add to the ice inventory calculation by increasing the water level.

We tried ice build temps as low as 20° degrees. Our Heat Transfer Fluid was good down to 16°. If you lower the freeze point of the HTF you also change the pumping energy and heat transfer rate. Lastly, use a 20 year Heat Transfer Fluid, from Dow if possible (they give free annual analysis). Make sure you don’t get automotive glycol.

[koolncali]

DCSCO-

Thanks for that detailed info, it looks like there's lots of potential problems with TES. Right now the project manager is in the design stage so there is still opportunity to make changes regarding equipment brand and design. I've worked on centrifugals years ago but I'm not familiar with the in's and out's of an ice plant. I'm really concerned about the design of this ice plant as it will eventually provide all the cooling for a jr college. The designers seem set on HCFC 123 Trane centrifugals with Calmac thermal energy storage tanks, Paco primary and secondary pumps, and Belimo control valves. I'm concerned about correct hydronics during ice build and ice melt modes and as you've had problems with-proper inventory of ice. We have a Siemens EMS system but the project manager is pushing to use Lonworks to interface with our Siemens and control the central plant. I'm not familiar enough with Lonworks and I'm thinking this will just add more complexity.