Outdoor condenser fan stops after heating up

[nick_wayne]

Hi All the knowledgable people,

The fan on my outdoor condenser unit turns off after 10-20 mins of running. The compressor keeps running and the A/C only gives room temp air. I promptly shutoff the unit to keep it from burning. The fan does not turn on when you start the system again when it is still hot. However it fan starts working again after you let it cool for an hour or so.

I got a new motor put in 2 years ago and that did not fix it. I don't think the run capacitor is bad either as it runs for 20 mins and then turns off.

Any tips will be helpful.

 

Regards,

N.

[dkpd1581]

When you replaced the motor did you get a generic or the one from the manufacturer.  If you got a generic, it may not have matched up the specifications just right for the condition and it could be over/under loaded which can cause it to stop spinning due to the heating from the internal overload.

Did you replace the blade when you replaced the motor.  If yes, generic blades are sometimes heavier than the original, the pitch may be off. 

Another thing to look at is is how the blade is fit into the housing.  If its set too high or to low on the shaft, it will not move the air across the unit as it is supposed to.  This distupted airflow will give you similar symptoms.

Give us a bit more info and write back.

[nick_wayne]

The earlier symptoms were that the motor stopped just as it does now and gave a humming sound. It was difficult to turn it as if current was flowing through it but somehow not enough to make it spin.

So I got the motor replaced via home insurance company. I have lost the contact info for the meachanic and cancelled the insurance since then as it did not fix the problem. The mechanic did not replace the fan wings. He replaced the motor only. The wings sit about mid way on the shaft and move a lot of air. You feel a strong upward draft of hot air if you stand close to condenser when motor is running.

Here are more details on the model of the condenser and motor.

Motor: Marathon Electrics, Part No: S88-157, Model: AWH 484 A11T 569B P, HZ-60 HP:1/4 RPM:1075 (All these are from sticker on the motor)

Condenser: BPP Division (Division of Carrier Corp) Model: 5676042RCU, Product: 567CB0042000ACAA (all these and below are from sticker on the condenser unit)

Compressor: RLA 226, LRA 111, Volts 230 Hz 60

Fan: FLA 16, Volts 230 Hz 60

 

[nick_wayne]

Here is the direct link to motor:

http://www.marathonelectric.com/MMPS/details.jsp?item=48A11TB569

I could not find anything on condenser unit on internet.

[dkpd1581]

It sounds as if somehow the motor became over heated and the bearings are seizing up.  You should feel warm air...but really hot air may be your condensor coil being dirty and then raising the temperature of the air going over the motor and windings.  If so its possible that this higher than normal ambient air over the motor is contributing to the problem.

Again, the position of the blade in the housing  may not be correct and is not moving enough air - causing the condesor coil to get hotter than usual (the really hot air you are experiencing).  Again the ambient air over the motor could be too high and causing bearing damage.

I would still verify the applied voltage and capacitor value.  Verify that the value on the capacitor body is the same value as is necessary for the motor.  The motor name plate will tell the required capacitor value in microfarads.  I have seen motors changed out only and not the capacitor.  The new motor needed a different value capacitor or if it is the same, the original one was out of 10% tolerance.  I assume that the FLA is 1.6 and not 16 amps.

[dkpd1581]

Another thing to think about is perhaps your fan blade is out of balance and is putting an uneven load on the motor.  Also make sure that the motor purchased is designed to operate in the position is is installed.  Some motor orientations are designed for horizontal while others are vertical.  Having a motor designed for one configuration and installed in another may contribute to premature failure.

[nick_wayne]

ok, so the repairman came today. It was rather cold day with swift cold breeze blowing.  We let the A/C run for sometime. The Fan and the Comp were running fine. He noticed a bit of freezing in the cold coil after 10 min. He said the system could be low on Freon so he put in a little bit. Everything was running fine. He started to get ancy saying there is nothing much he can do. And then it happened. The Fan just stopped. We felt the motor and it was too hot. Seemed like an internal switch had shutdown the motor to keep it from burning. We took the motor out, cooled it by wrapping moist cloth around it. He checked the capacitor and said it was fine, but he changed it just for good measure and we started the system again. I noticed that the fan was running slow this time. He stopped the system and put in the old cap back and fired up again. The Fan was running the usual fast speed now. He checked the voltage acorss the motor. It was 244 Volts. The same across capacitor.  After a while I felt the motor. It was getting hot again. But he could not figure out why.  He left recommending that I change the whole system.

But I am not ready to spend $3000 yet. The reason being I live right next to SF Bay and the weather is windy and cool whole year except for just couple of days. So problem is motor is getting hot and stopping. And the solution is keep it cooled. Here is what I think 

1. The motor is rated for 230 volts, but it is getting more than that. 244 Volts. Is that making it hot? Can I bring it to 220V by putting a resistor in series to drop 25V?

2. Can I make some kind of cooling fins, from metallic screen etc. and install them around the motor to keep it cooled?

3. Can I use  a moist cloth to keep it cooled as it seems to be sealed motor?

Let me know please.

Nick

[dkpd1581]

The motor can operated +/- 10% of the listed name plate value.  244 volts is within the listed range.  Remember that this is the applied voltage on a non-peak demand day which will bring the applied voltage down and still be within the name value.

Most likely the replacement motor in service now is not of the same specs as the original OEM.  The best avenue is to make a call to the Supply House with the model/serial and get the details of the OEM's stock motor.  Sometimes Tecs will replace one bad OEM with a generic on the truck or get a generic motor which does not have the same specs as the original.  This translates into an over or under loaded motor and will give you similar problems that you are seeing now. 

Make sure to get the rotation, RPM, frame size, enclosure type, insulation class, motor duty type.  Best thing to do is go with the OEM, yes it costs more; however, it is the motor exactly designed for the system.  The OEM motor is much

 cheaper than a new unit.

Motors have their own methods for keeping the windings cool so there is nothing practical for you to do to add to the cooling effect other than to make sure that the fan blade is on the correct way, has the correct diameter/pitch/number of blades, is rotating in the correct direction, and keeping the condensor coil clean and unobstructed around the sides and top.

I am assuming that you are the original tennant/owner,  that the unit was installed new, and that you know the complete history of it.  If not, we are all assuming that the motor and blade in service at the time you took possession (and at the time of first failure) was in fact the correct ones to begin with.  This may in fact may not be the case.  Again, a call to the OEM supplier will clear up all questions and let us know if whats in the unit and failing now is correct for the job.

Let us know.

[dreeme1]

  I agree with [user=16896]dkpd1581[/user] and git ya a motor. I wouldn't be suprised if the one you have there isn't quite up to specs with what is supposed to go in there. Good Luck!

  Bob

[RegUS_PatOff]

...and a new capacitor, the one you have may be bad or not the right one for the old motor nor for the new motor.

 

[applianceman18007260692]

A quarter horse motor is pretty lame Get a new Lau blade and hub and go with a one third horse motor and problem solved.

[nick_wayne]

I agree with you all. I was just going to get 1/3 HP motor but just wanted to share with you my latest tests.

Ok, Here are some more tests I did. I ran the motor without the fan and it still got really hot but DID NOT stop. It ran for more than an hour untill I switched it off. It was so hot that it could not be touched with hands more than one second. Than next day I ran it with fan and it stopped after 25 mins. The old motor that I replaced used to get hot and cease up. This one gets hot and stops due to thermal protection. Now I am thinking could there be something wrong with my electric circuit also? I mean could the problem be that too much current is flowing through the motor making it hot? I remeber when the repairman checked the volatge across motor connections it showed 244V. What is the best way to measure current flowing through the motor?

I have a standard Digital Multimeter and it has markings for ACV, DCV and DCA but not ACA.

Nick

 

 

[dkpd1581]

The fan without blade will get very hot because it is and Air Over Motor referring to the fact that it must have air over the body and windings to cool it.  So that it got hot is very well expected. 

The fact that it didnt survive with the blade on it leads to the fact that the motor is the wrong one for the application.  Again, it is overloaded.  Chances are very high that you have the wrong motor for the application.  This could be the wrong RPM, the wrong HP, etc. 

The applied voltage is correct according to you.  Check the name plate of the motor and verify what capacitor value it requires.  Look at the one in the control panel and verify that its the same value.  If you have a capacitor tester, test it and prove that its within 10% of name value.  Alot of techs will say "Oh yeah...its good" because they dont have the capcitance checking feature on their meter.  Look at the wiring diagram and with the power off, follow every wire of the motor -by hand- and make certain for yourself that it is wired correctly.

The best way to measure current through a motor without breaking the circuit is to use a clamp on Amp Probe.  Rising amp readings is a sign that the motor is overheating, bearings are seizing, and/or the load is to much for the applied motor.

The real measure of your problem lies in the answers you recieved from the Manufacturer when you called.  The original specifications for the OEM motor will most likely point to something different from what is listed on the name plate of the motor you have in service.

Call the dealer for the brand you have (have model and serial number in hand), tell them you are some Tech out on scene - use some other company name or make one up, let them know that you are following behind some other company that changed the motor, that you dont believe it to be the original type and it has again failed, and have them read out the details for the correct motor.  Write it all down, tell them thank you, and compare what you have to what is required.

[RegUS_PatOff]

someone wrote:

...and a new capacitor, the one you have may be bad or not the right one for the old motor nor for the new motor.

 

[ourstocks2002]

One thing to add, the slightly higher voltage (244 vs 230)would cause the amps to run lower, not higher. Inductive devices (motors) behave opposite to resistive devices (incandenscent lights, heaters).

As the other folks mentioned, it sounds like the motor is overloaded. it likely stops because of internal overloads (thermal protection). You don't need to necessarily go back with the OEM motor but you do need to match the voltage, RPM, HP, and frame size. My guess is that the motor got switched with the wrong one.

On final thing. The RLA, LRA and FLA values that you listed are off. FYI, LRA is typically around 5 times RLA. You listed an RLA of 226A which would be for a large unit, somewhere around 75 Hp. The info you listed for the fan is 1/4Hp, 16 FLA, RPM 1075. The FLA of a 1/4Hp motor 230/1/60 is typically 2.9A. The RPM is typically 1750 for this application. Confirm with info from the unit (NOT the motor that is currently installed).

Good luck and post more info as it is available.

[jb8103]

[user=26139]nick_wayne[/user] wrote:

Ok, Here are some more tests I did. I ran the motor without the fan and it still got really hot but DID NOT stop. It ran for more than an hour untill I switched it off. It was so hot that it could not be touched with hands more than one second. Than next day I ran it with fan and it stopped after 25 mins.

How could this happen? If the motor is thermally protected, it should stop when it overheats whether the fan is mounted or not, right?

[applianceman18007260692]

Depends on the condition and the size of the blade. It might have ran for an hour without a load but with an oversized blade it could easily bog down and die. Maybe there is a mismatch to begin with. Like I said, new blade new motor problem fixed.

[Shootist]

You need to contact Bryant and find out what the RPM was on the original motor. I'm betting you originally had an 825 rpm motor and the home warranty flunkie installed a 1075. If you try to spin a heavy blade with a deep pitch at 1075rpm you're going to fry your motor every time.

BTW, if you run your motor without a blade on it you're going to cook it. That motor depends on the air flowing past it to cool it.