Chiller, air condenser,fan blades

[porttss]

I have a question regarding blade position in shroud, of an air condenser, using 14 fans. On a % basis, should most the blade,be in the shroud ,say, 70%,or only say 30% for max air movement? Some one told me most of the blade should be below for more air movement,but with many fans working to pull the air through I thought maybe Pressure differential, might be more into play then, volume. Does anyone have any thoughts on this?

[porttss]

I notice Trane for this unit, puts the blade hub even with the shaft, which puts the blade mostly (70% to 80%) in the shroud,( I was thinking this might have been done for easier removal of blade,s) I feel we need more air movement,I have allready replaced half flow with full flow blade,s, but was now contemplating, moving the blade,s more into condenser, for greater volume,once again any thoughts?

[klove]

Why do you feel that you need to change the unit design by changing the blades or the blade position? What's the original design, and how is the machine operating at present? Blade position is something that is set by the manufacturer according to fan speed, design, orifice design, etc.

[Octopus]

Klove is correct and I don't think trane did it to make it easier to remove the blade. If you are having issues such as high head you should take into consideration many parameters such as superheat, sub cooling, chiller approach, ect. If you just want to change the design just bec you feel like it don't! Like klove said they do things for a reason.

[porttss]

Well as far as the half flow blades are concerned, the discharged air,was reentering the condenser, If you where standing next to the chiller you could feel it. The half flow fans made it possible to cool at 0 F and the full flow from 15 F, We do not cool under 50 F. On cool days this discharge air returning was not an issue but on very hot days our head would go to high and cause shut down on various things related to high head. AS far as the blade position in the shroud I will just go with what most of the blades where set at , as I try it deeper in and it did not seem to make that much of a difference. As far as questioning how anything works or was done on this machine ,At a latter date I will make a full list of all the things I have found wrong ,bad motor,s broken wiring to fans,leaks ,compressors running out of control because of loading issue,s , fans not staging fast enough etc..... ect.... As far as having a highly trained tech come out , this has been done 2 time every year since I have been here (8 years), things seem to run fine until it got hot out. LOL I may be no expert at this but I am getting things done. We where still running over 107 F on the roof which since I have been here was unheard of.

[jpsmith1cm]

Given the problem you are describing, is the coil clean?

Mess with motors and blades all day long, if the coil isn't clean it won't make a difference.

[zw17]

The Trane chillers must have the half pitch blades. The RTAA uses fan staging depending on the saturated condenser and saturated evap temps. The lead fans could need be half pitch.

Is your UCM set up for either 0 or 15 degree ambient fan configuration? If you are using 0 it will lead with half pitch. 15 leads with full pitch.

Also check your refrigerant temp sensors. Make sure they are in range. They fail often.

[porttss]

Bring your finest china, they are spotless.

[porttss]

The fan staging works great except its about 20 minute to late.I plan on doing the e-prom install before next years heating season, though the comments I have heard on here where not to promising. Anyway besides the staging, the real problems occured when fans where allready at 100% and the discharge air was reentering the condenser. The half flows are off and replaced with full flow so I do not think this will be to much of a problem any more.

[porttss]

And yes I set the parameters in the factory menu to D to reflect the fact that half flows where replaced.

[klove]

Seems to me, then, that the whole issue could have been avoided by getting rid of the recirced air to the condensers. What is causing this issue, and can it in any way be corrected?

[porttss]

Thanks all for the input problem is solved. TIM

[Tranetek]

Sounds to me like you are addressing the wrong issue. You should be looking at what is causing the air to recirculate. What reason is there that the air is not moving away from the unit. You can change the motors but you will still have an air circulation problem. Problem doesn't sound like it is with the machine but more with the installation.