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 . :grin2::grin2:

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.

[drivewizard]

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.

but it's so much more fun to modify and tweak stuff. Coil cleaning is just BORING!! and you get all wet!

[ob1kelley]

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.

[jayguy]

but it's so much more fun to modify and tweak stuff. Coil cleaning is just BORING!! and you get all wet!

no, your NEWBIE gets wet while you drink coffee and talk up the secretary!

[chnrgr]

no, your NEWBIE gets wet while you drink coffee and talk up the secretary!

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.

[ryan1088]

Wouldn't a vfd go out on over current if the fan is spinning backwards while it was commanded off?

[mustafaali]

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

[chnrgr]

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

[mustafaali]

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

thanx for your replay chnrgr now i have compressor defictev on the same chiller just i want know its esy to open the compressor on the site or it required to remove it from chiller and the motor stator it can be removed easly or not

[chnrgr]

thanx for your replay chnrgr now i have compressor defictev on the same chiller just i want know its esy to open the compressor on the site or it required to remove it from chiller and the motor stator it can be removed easly or not

I have been told you can do it onsite but you have to know what you are doing. Most of the guys I know recommend pulling it.

[Old Soul]

I have pulled the stator out of a 100 ton compressor before. DO NOT wish to do that again ever! In a shop with proper tools and on a work bench maybe but never again in the field.

[Mongo and me]

THE OLD FANs ON A TRANE RTAC !!!
Well for the fact of clean coils; what presents a restriction to air flow ??? A "CLEAN" coil, or an open airway between fans ???? So take your "CLEAN" coil line back to TRANE !!! How does one expect the air to come through the coils if right next to the running fan is an open area for free air flow, a baffle plate and or a cover back draft damper system would increase the air flow through the coils as needed per fan running. MAYBE< JUST MAYBE if they designed it right we wouldn't need 28 fans per chiller x 6 units here = 168 fans with a 60% fail rate so far in 4 years.

VFD !!! Yep, if your load is so low, a greater number of us are at a place that has a load that will never get low enough to have just one VFD running, and at the $$$$$$ TRANE ask for those things, I just jump out and say run you little buggers............constant 75 - 80% load 7/24.

NOW let’s talk short cycle air flow >>>>> that’s were the air coming out the top comes right around back into the side of these beast, EVEN with the required 12 feet between units we see an entering temp of 115 / 125 on a 97 deg. day, no fancy calibrated test instruments’ needed. Just walk down between them, my $1,274,852 micro chip implants on my finger tips and forehead will confirm it !!!!

So let the comments continue, may your rain suit stay dry and keep the wind at your back, that "BLUE" stuff will tell on ya !!!:gah:

Another brilliant idea, let’s have them crawl up under inside the thing to clean these coils, BRILIANT< just BRILIANT !!!:censored:

[ncboston]

I've used the anti windmill device on this page
http://catalogs.johnstonesupply.com/3128_johnstone_202/full.asp?page=195
on smaller carrier units that had the same problem.
Used to take care of an rtaa240 that had the same problems mentioned in this thread. Never thought to try the brake.

[Mongo and me]

Interesting, what material is the rod made out of ??
How much time now since installed, did it do the job ??
I could make some money on these ..............!!

[ncboston]

This device solved the problem we had at the time on a carrier rtu. That was about 5 or 6 years now.
I don't remember the specifics about the brake, but they performed as advertised.
Might be worth looking into with regards to the rtaa problem. Of course, putting one of these on doesn't fix the underlying issues, but you might save some money on fuses and motors.

[Mongo and me]

will look into it a bit more, just for the record, you did not mount this on a TRANE TRAC ??

[ncboston]

no.

[Mongo and me]

No problem, I'll swing by Johnstone and take a look at one.............
Could be the begining of a whole new adventure !!!

[ncboston]

Good luck. Let us know if it helps in your particular application.

[Mongo and me]

K