RTAA condenser fans

[602tech]

RTAA200. vintage 1998. i havent found any SB on condenser fan motors failing, but a few chillers have no baffles to separate airflow between fan sections. in lower ambient conditions the fans cycle off and spin backwards. I think this is why the fail often. i have seen a fan spin backwards so fast, when the contactor pulled in it ran backwards. anyone know of any SB on this. I am thinking of installing vfd control on the fans, any thoughts?

[fearlessfurnace]

ease into it. we got a bunch of bad speed controls that caused a lot more trouble than they solved ( like 10 years ago but it left a real bad taste)

[jayguy]

trane does not use baffles...i wish they did...but they don't.

the fans that are off rotate (windmill) backwards when some fans are on.

dirty condensers prevent the airflow from going through the condenser and this causes the 'off fans' to windmill faster...you now how the rest goes.

clean your condenser.

so here is the $1 question...customer says that trane should have known that condensers get dirty and should have engineered a better solution.

trane says that customer should have known that the condensers would get dirty and that they would need to clean them.

in the end, you get to drag a hose around.

i know of a chiller that is only a few years old and has 10 of 14 condenser fan motors that need to be replaced...you can barely tell that the unit has condenser fins because of the dirt.

i know of another chiller that gets cleaned several times a year...complete shutdown...everybody goes in on a saturday to clean all of them...all fan motor are original and the chiller is 13 years old.

pretty easy to see the difference.

[602tech]

The coils get cleaned once a year. This is a data center and the chillers are 24-7. I think i will take your advice and clean the coils. Thanks

[fearlessfurnace]

jayguy you realy scooped me on that one

[Phisher]

Have you checked for correct voltages to the motors?

[johnnykling]

nothing hurts when the motors spin backwards, even if fast, if when the contactor pulls in and the motor stays spinning in that direction either the caps are bad( if it has caps) or the motor is weak and it doesnt have enough ass to overcome the spinning, if you can the customer a vfd, do it , its so worth it. theyll save so much money. how many motors does your rtaa have cause all the ones i have under contract have at least 10, its a hard sell to sell someone 10 1/2hp drives. are they single or three phase, if there single sell them p86 controls

[jayguy]

nothing hurts when the motors spin backwards, even if fast, if when the contactor pulls in and the motor stays spinning in that direction either the caps are bad( if it has caps) or the motor is weak and it doesnt have enough ass to overcome the spinning, if you can the customer a vfd, do it , its so worth it. theyll save so much money. how many motors does your rtaa have cause all the ones i have under contract have at least 10, its a hard sell to sell someone 10 1/2hp drives. are they single or three phase, if there single sell them p86 controls

rtaa's have 3 phase fan motors...no capacitors to fail. tranes voyager and precedent rtu's have 1 phase condenser fan motors. if the motor spins backwards on these...you have the same problem...dirty condenser...assuming that there isn't another problem that is.

as for getting hurt. the motors can spin in their brackets which stretch the wiring to the point of breaking. the condenser fans also can crack at the rivets on the older units. on the newer units, the motors that are bolted in with motor ears...the bearings take all of the extra brunt...somethings gotta absorb all of the extra energy no matter the design.

[chnrgr]

I have considered putting some kind of shutters over the fan grills to stop them spinning and pull the air through the coils as intended. My coils are clean and they still spin backwards. Has anyone tried this approach?

I also realize that since Trane was nice enough to put multiple fans on a single contactor, when a motor burns out the otherone will single phase until it overheats enough to blow the other fuses. I started buying an extra motor every time one burns out expecting to lose another one shortly.

[Healey Nut]

trane does not use baffles...i wish they did...but they don't.

the fans that are off rotate (windmill) backwards when some fans are on.

dirty condensers prevent the airflow from going through the condenser and this causes the 'off fans' to windmill faster...you now how the rest goes.

clean your condenser.

so here is the $1 question...customer says that trane should have known that condensers get dirty and should have engineered a better solution.

trane says that customer should have known that the condensers would get dirty and that they would need to clean them.


Ditto what Jay says ..... Got a customer with 4 99 vintage RTAA200 14 fans per unit = 54 fans total its 2011 and Ive only replaced 5 motors since new .
Gotta keep the coils clean .

in the end, you get to drag a hose around.

i know of a chiller that is only a few years old and has 10 of 14 condenser fan motors that need to be replaced...you can barely tell that the unit has condenser fins because of the dirt.

i know of another chiller that gets cleaned several times a year...complete shutdown...everybody goes in on a saturday to clean all of them...all fan motor are original and the chiller is 13 years old.

pretty easy to see the difference.

Ditto what Jay says , got a customer with 4 1999 vintage RTAA200 , 14 fans each = 54 motors . Only replaced 5 motors since new .
Gotta keep the coils clean

[spinning wheel]

You can also VFD two fans together with a larger drive. This an economical solution as well. It all comes back to how cheap they make units now. It makes no sense to me, $500 worth of sheetmetal or thousands on new fans. I hate where my industry is heading. It is a race to the bottom.

[Healey Nut]

Dont know why my post got messed up but I do know I cant add up 14x4=56 not 54

[jayguy]

all of this talk about fixes to the issue...how about cleaning the coils? keeps the fan motors online, keeps the fan blades intact and keeps the energy bills down.


crazy ideas, i know, but it seems to work well.