GE Motor Design Defect

[lilliput1]

My Ruud forced air gas fired heater/central air unit fan motor seized after 4 years & 10 months. The motor is a GE 1/2 hp (4) speed motor model S018S with sealed bearings. I used to have a Lennox unit that run for 30 years. I run the fan continuous summer and winter. Suddenly it started screeching. At first I thought that the fan wheel was rubbing the scroll but it turned out it was the bearing seizing after it got hot. I bought a replacement from the Ruud dealer but the replacement is a Protech motor. I noticed that the GE motor did not have fan type blades on the rotor to cool the back bearing. The rotor at the front end had blades on the rotor but they did not look like good air movers. They were stuby and the sided taper down towards the end of the blades. The replacement Protech motor had efficient looking fan blades at each end. Without the fan to cool the GE motor, I imagine it building up heat first gradually until it dried up the lubricant in the sealed bearings (no evidence of lubricant leaks at each end but turning the rotor makes you feel the dry bearings). Then with bearings dried up, the build up of heat occur faster until the bearings seized. Don't you agree with me that this is a GE design defect? What is the maximum temperature that a sealed bearing can tolerate before the lubricant degrades?

 

[MikeHalloran]

By modern standards, the GE motor is a successful design, because it worked through the warranty period. Some young PhD probably got to keep his CFD driver job for another year by saving the cost of an internal fan.

Welcome to the 21st century. ;-)





Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA

 

[pennpoint]

lilliput1
You say, you run the motor continuously winter and summer. What does that mean in total operating hours?
For me, four years of continuous service is not bad for those types of motors. I'm guessing a 42 frame +/-.
Dont toss out the GE motor, because when the Protech motor fails you can then compair construction and design of both.
Let us know in four years, more or less how they faired.

Best Regards

pennpoint

 

[jraef]

IMHO it is premature to assume anything about GE's design simply by observing things from the outside. The motor may have a high temperature insulation system that requires less air movement than the Protech, which may in fact make the Protech the "cheaper" of the two. The sealed bearing may have been a design answer to overcome contamination issues that someone found to be a cause of more failures than overheating. it could have just been a defective bearing, things happen.

It could also be that you are using the unit in a manner for which it was never designed. I am not saying it is your fault, just that whomever picked that GE motor may have had an overall system design spec that had a lower operational cycle time than what you were used to with your old Lennox system, which may have been designed as a ventillation system as well as a heating/cooling system. That could be Ruud's issue; it may have been a H/AC only unit, not HVAC. I don't work for GE and as a matter of fact I am not even a big fan (no pun intended) of their stuff, but jumping to conclusions is not really usefull. I would take it up with Ruud by first asking them what they consider to be "normal" use of that system.

"Venditori de oleum-vipera non vigere excordis populi"

 

[mc5w]

I have a few instances where I needed a bigger motor. One time I changed out the motor and controller for a 1/2 HP 3-phase fan. This worked for a while but on very hot days the overload relays would niusance trip. Turned out that the new motor was turning the blade a bit faster than the old motor. If I had known this would happen, I would have put in a 3/4 HP motor and sized the overload relays for 5/8 HP.

 

[lilliput1]

Being a HVAC guy I would think cooling fans would be important to good motor design. If a part is generating heat and the construction does not allow heat to dissipate, then heat will build up to the point that heat can dissapate to the air, albeit at a higher temperature. The sealed bearings would not present a good heat transfer path because the bearing seals are not conductive to heat. I am dissapointed GE did not incorporate it in their motor design. I wonder if newer ones have this feature added.

I run the fan continuos because I thought avoiding start/stop will lessen the strain on the motor and its capacitor. Four years and 10 months of continuous operation is about 42,340 hours. If industrial design, motor life would be 200,000 to 250,000 hours.

 

[aolalde]

Motor are manufactured to comply with local and/or international standards. For USA the standard is NEMA MG1. After the motor manufacturer test and approves a design, the adequate selection of the motor is responsibility of the system designer. Actually a large percentage of failures on electric motors are due to improper selection to match the application.

 

[MachineryWatch]

The system designers are ultimately responsible for selecting the best motor fit for the application. While there may be deficiencies in the motor selected for your application, I doubt most home HVAC system designers anticipate 24/7 operation of the fan motors.

Industrial guys don't always get it right either. I work with a plastics plant that would love to get a year of life out of their motors that run belt driven process fans. The system designer installed motors that were obviously not intended for a belt drive application. The drive end bearings are ball bearings rather than cylindrical roller bearings. After several years of living with it while they try to get the vendor to "make it right" they are finally on the road to replacement with the correct motors, at their own expense.

Skip

http://www.machinerywatch.com

 

[Marke]

Hello lilliput1

For many small fans used in industry, 40 - 50k hours is about average. Some of the small DC fans are rated at 70k hours.
This may well be what the manufacturer expects the life to be.

Best regards,

Mark Empson

http://www.lmphotonics.com

 

[lilliput1]

Thanks all for your response. I wish GE and other manufacturers will strive to make their products better, longer lasting, instead of cheaper, not as good as they used to be.

 

[smallmotorguy]

The GE motor was probably a 5KCP39 48 frame as that is what most blower motors are. Sleeve bearings need to be oiled at least once a year for seasonal duty and at least twice a year for continuous duty. Some spec 20W non-detergent and others use detergent. Bearing life dramatically decreases if their temp exceeds about 70°C, even with the modern lubricants like permawick/anderol.

New design motors vary from old design in the following ways: Less lamination stack, Less magnet wire, less mass,
iron sintered bearings vs bronze bearings, smaller bearings,
better lubricants, better efficiencies (designed for specific applications) It is very difficult to obtain a motor that is designed to last past 20,000 hrs.