Trane chiller problem

[uke]

Hey guys ,
Looked today on Trane "baby" chiller - 10 tons aircooled , 2 circuits 5 tons each .Problem running both circuits all the time- cann"t bring chilled water temperature below 52 F. Both circuits running pretty much same 225 head,72 back. Sightglasses nice and clear. Suprerheat is 18 F, subcooling 22 F . Two TXV's.NBo temperature drop across filter driers, sightglass is clear. System is over 15 years old, always run no problem , in the beggining of the season usually needs some air bleeding on CHW lines.Tried to bleed today ,didn't see no air .Pressures on CHW lines are same as always. No load added, same as always.
Apreciate Your thoughts and advice.

[psychometric]

sounds like evap might be scaling up, poor transfer maybe. Have tubes been checked?

[el kabong]

When was the last time the evap barrel was rodded out? Also check any stainers in the water side. Maybe the pressures are constant, but the flow is slower. I'd ask about the evap tubes first. They may be fouled. Is this a glycol or water loop?

[maxster]

what was your amps running/tagged,and how was the air going into the condenser....what temp.

[scott123]

You need to check delta T and delta P. Once you've done that, then compare these values to the design data on the unit. This will tell you if you're running at normal capicity.

[absrbrtek]

Why with 72#s suction and 18F SH, why would you think the HTEX is fouled?
Originally posted by psychometric
sounds like evap might be scaling up, poor transfer maybe. Have tubes been checked?

[ej45]

That size of unit most likly has a plate and frame evap

[Edited by ej45 on 07-11-2006 at 09:26 PM]

[jimbob73]

Tubes or plates being fouled or a low flow isn't your problem because your suction pressure and superheat you indicated would be much lower. I know you said nothing has ever changed, But sounds like too much flow thru evap or extra load caused by something like outdoor air dampers open on a AHU if that is what it supplies chilled water to. Need to check Delta T, Delta P like scott mentioned.

[Edited by jimbob73 on 07-11-2006 at 10:21 PM]

[uke]

Thanks for replies. I was thinking about brushing tubes , I have scheduled that already. I took off insulation from around head of the barrell. It looks like nobody opened that barrel. and I cann't get in touch with guys who serviced it before.
Just wanted to see if i'm missing something. Let You guys know how it worked out.

[scott123]

Brushing tubes? I may be wrong but I think you have a non flodded evaporator, and brushing tubes isn't an option. Condenser yes. (if water cooled)

[chiller mekanik]

Can you provide a model number?
Would this little jewel happen to have a bypass of anykind?(waterside)
Here are a few things to think about.
Everything on a chiller is relative.
Actually, the same can be said for any type of cooling or heating equipment.
52* leaving water means nothing to me, neither does 45* leaving water.
The temperature difference & the pressure difference (delta T & delta P) are what we need to be concerned with.
Most likely the design delta T for your machine is around 10*.
A delta T greater than that would indicate low water flow.
A delta T less than that would indicate too much flow.
However, an accurate delta P compared to the design delta P would tell us very quickily what we need to know about the water flow.
Sounds like you are describing a DX chiller.
Thats why we need that model number.

[shelby]

it doesn"t sound like you have a problem with the chiller a suction of 72 indicates a moderate load , sounds like the building has added additional load

[stanbyyourword]

i agree refrigeration fine ,look inside check air handlers and boiler/ heating valves in zones regards stan

[Edited by stanbyyourword on 07-12-2006 at 05:04 PM]

[uke]

You right scott123, there is no tubes to be brushed.

As far as added load ,I didn't see any new fancoils or any changes at all.

This chiller they use only when building is empty for the exeption of few offices , so they do not have to run main absorber . They have switchover valves.

As far as air in the system I had to bleed it only once on a start up before season.

model # cgacc107ccn1122

[Healey Nut]

Good luck brushing the tubes on a dx evap let me know when yuor done !!!!!??????

[grendil]

Check your fluid. Is it glchol? Or water? If water make sure Concentration has not gone up through the years from winterizing ect. If glycol make sure % is correct. Does chiller have Got gas?

[absrbrtek]

My bet is on a switch over valve problem causing a water flow issue thru the evap barrel.
Originally posted by uke
You right scott123, there is no tubes to be brushed.

As far as added load ,I didn't see any new fancoils or any changes at all.

This chiller they use only when building is empty for the exeption of few offices , so they do not have to run main absorber . They have switchover valves.

As far as air in the system I had to bleed it only once on a start up before season.

model # cgacc107ccn1122