GE motor running very hot

[bigwilly104]

I have a small ge moter in a packedge heat pump that is running 190 F. This is the third moter in this unit. Its a 230 volt single phase condensor fan moter. checked and double checked every conection. Amp draw is 3.7 and the name plate rates the RLA at 4.8. This seems way to hot. Also GE has a company that is making some of there small motors like this. Has any one seen any corolation between that and motor quality going down. I was having a problem with a head presure controll and a over heating fan motor and the guy from ICM told me GE is crap and to buy AO Smith. Not in those words of course. All my whole salers cary GE though. Input?

 

[KiwiMace]

Where are you measuring the temperature and what is the insulation class of the motor? Has the lubricant been topped up?

 

[bigwilly104]

This is a sealed bearing motor and I am mesuring the sidde of the motor case in the middle with a wire thermister taped to the side. This is not very acurate because the fan is blowing over the thermister if I shut down the unit the temp runs over 200 deg because the fan stops and of course the moter holds the heat. and class B insulation

 

[imok2]

Anybody changed the fan blade? In direct-drive applications the motor is typically designed to use the fan’s airflow for its cooling. Too little airflow and the motor will run hot. Too much airflow and the motor will strain and also run hot. In a belt-drive application the motor may not directly be in the airflow of the fan; however, improper selection of the fan blade can easily cause motor overload.
The number of blades will impact airflow and
It is important to match a fan blade to a motor’s horsepower and speed. Do not replace a 1,100-rpm motor with a 1,725-rpm motor using the same fan blade, as the increased speed can cause the motor to overload.

 

[bigwilly104]

Thanks for the help. I did think about the fan blade and what had been done with it previousely. The unit is two stage with two compressors and twop condensor fan motors. both motors and fan blades are the same. its a york and they gave me a discription of the motor. so I know I have the right motor. but it is a generic GE not OEM. If I keep having problems I am going to order OEM motor and blade. I really want to know how hot is to hot for amotor like this. The worst part is it never fails when I am there. I see it running hot but I never see it trip.

 

[MikeHalloran]

Air conditioners are designed for extreme climates, like, say Ohio. Here in SoFla they run 24/7/365 and they're best treated as consumables.

That said, the symptoms reported suggest the system may be slightly overcharged, or the condenser has become clogged with grass clippings, or has lost some fin area to corrosion, or ... is crap.

[ My current system is out of commission because the borderline magical government recommended high efficiency variable speed evaporator fan motor died and nobody sells a replacement for less than twenty percent over the price of an entire air handler, but that's a different rant. ]

Over the years I've screwed around with condenser fan motors on patched- together systems, which I squeezed a few more years out of by using a somewhat stronger than stock condenser fan motor, with a low- pitch four- blade fan, and a motor- sized fan mounted on the same shaft. Your A/C parts wholesaler has those small fans with big hubs hung on the wall right behind the counter; he sells a lot of them.



Mike Halloran
Pembroke Pines, FL, USA

 

[DrRTU]

190 is hot for that motor. Do you have the correct run / start capacitor? You listed the RLA at 4.8 - that is locked rotor amps. You need to be looking at full load amps (FLA). If you are into the service factor, I believe you have a fan blade / motor mismatch issue.

 

[zekeman]

Why don't you call GE and ask what the design temperature of the motor is ;and from your measurements of power and temperature of the air leaving the condenser and a description of the airflow across the motor get them to estimate the motor temp for this application . From your measurements, assuming a PF of .85, I get a power draw of
.85*220*3.7=691 watts
If its efficiency is 60 % (typical) then you have to dissipate
.40*691*3.41 BTUH=943 BTUH thru the surface of the motor. GE should show you what that airflow will yield for a thermal coefficient coupled with the delta T (motor to air temp you measure)to estimate the motor temperature.
Note that the temperature rise across the condenser should not be greater than 20 degrees, since that might signal poor airflow and consequently a poorer thermal coefficient.

 

[bigwilly104]

Thank you for the replies I think there is a misunderstanding about the nameplate abreveations. LRA Stands for locked roter amps and RLA stands for rated load amps unless I was taught wrong. I will check that. As far as checking with GE that has been the most frusterating part of this. GE lets a company called Regal-beloit use there name so I called GE and they can't help they gave me Regal-Beloits number but I have been leaving mesages and had no response. Thanks again for the responses.

 

[KiwiMace]

My former company made a monitoring system that alarmed at 176degF on motor casings, as was my recommendation. Not that this is the definitive answer... I've been looking for an online motor handbook since my first post and can't find it anywhere, which I used to justify that number at the time.

But I think try a class F motor next time she goes, increasing the winding design temp from 130 to 155degC (266 to 311degF), on a 40degC (104degF) ambient basis. The extra 25degC might go a long way - the rule of thumb was 10degC reduction will double the insulation life.

Surface temps can normally be 80-100degC (176 to 212degF) according to a quick web search that turned up sites I can only confidently reference as 'folk lore':

http://www.iprocessmart.com/leeson/leeson_motor_temperature_article.htm