Replyease 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)
Regular Guest
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?
Professional Member
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)
Professional Member
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.
"Right" is not the same as "Wise".
Don't step on my favorite part of the Constitution just to point out your favorite part.
Just because you can measure it, doesn't mean it is important. Just because you can't measure it, doesn't mean it isn't important.
Regular Guest
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
Professional Member
jayguy you realy scooped me on that one
Professional Member
Have you checked for correct voltages to the motors?
Regular Guest
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
Professional Member
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.Originally Posted by johnnykling
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.
"Right" is not the same as "Wise".
Don't step on my favorite part of the Constitution just to point out your favorite part.
Just because you can measure it, doesn't mean it is important. Just because you can't measure it, doesn't mean it isn't important.
Regular Guest
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.
Professional Member
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
The toy chest is officially full ... I got a new toy..... 2007 Aston Martin V8 Vantageand yes it still gives me goosebumps
You bend em" I"ll mend em" !!!!!!!
I"m not a service tech, I’m retired ….I used to be a thermodynamic transfer analyst & strategic system sustainability specialist
In the new big shop , greasin', oilin' . tweakin' n shinin' !!
Professional Member
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.
Professional Member
Dont know why my post got messed up but I do know I cant add up 14x4=56 not 54
The toy chest is officially full ... I got a new toy..... 2007 Aston Martin V8 Vantage
You bend em" I"ll mend em" !!!!!!!
I"m not a service tech, I’m retired ….I used to be a thermodynamic transfer analyst & strategic system sustainability specialist
In the new big shop , greasin', oilin' . tweakin' n shinin' !!
Professional Member
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.
"Right" is not the same as "Wise".
Don't step on my favorite part of the Constitution just to point out your favorite part.
Just because you can measure it, doesn't mean it is important. Just because you can't measure it, doesn't mean it isn't important.
Professional Member*
but it's so much more fun to modify and tweak stuff. Coil cleaning is just BORING!! and you get all wet!
“If your work speaks for itself, don't interrupt.” ~Henry J. Kaiser
"Highly efficient equipment and LEED Bldgs are very expensive to maintain in order to keep that efficiency!" ~ Me
New Guest
We have placed breakers on the individual fans to keep one that goes bad from blowing fuses and stopping / single phasing other fans.
Fins in need of combing would also increase the drag through the coils and thus windmilling.
We have some RTAAs where previous contractors sprayed water on the coils for extended periods and they have a heavy build up of minerals on them that makes this problem worse. Early RTAAs had issues with the fans staging up too slowly and needed some software upgrades. Between that and slide valve problems that often present as head pressure / oil flow problems, their solution was to spray the coils with water.
Professional Member
no, your NEWBIE gets wet while you drink coffee and talk up the secretary!
"Right" is not the same as "Wise".
Don't step on my favorite part of the Constitution just to point out your favorite part.
Just because you can measure it, doesn't mean it is important. Just because you can't measure it, doesn't mean it isn't important.
Regular Guest
Make sure you give him the purple stuff. It bites real good when you get the overspray.
There are still issues as these machines get older that a coil cleaning just doesn't cure. I have clean coils and it is cool these days out there when I get failures. These compressors don't unload. It cranks up quick and cycles off not a good thing for a 100 ton pump.
Time to pull the compressors apart and do some serious surgery. Oh yea the bosses are gonna cry when they get this bill.
Professional Member*
Wouldn't a vfd go out on over current if the fan is spinning backwards while it was commanded off?
Regular Guest
i have also same problem in the trane chiller model rtaa condenser fan runing backword durling winter time only then i have to stop all chiller and start then it will be o.k
Regular Guest
It looks like its running backwards but its actually spinning from the neighboring fan. make sure the coils are clean. I want to find some shutters to mount on the fans
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