Electrical Wiring in the Home/Problem: Century Motors get HOT

Advertisement


Question
Hi Will-Tom has been asked to replace 5 motors in Airtherm Cabinet Unit Heaters- Model: 121-1L-F Serial# August 1996 ST.

Because of its age there have been replacements to original double shaft motors which we think were Magnetek SER:34G 11648P MOD: DE2F064N 43100111,125V,60HZ,1.6 A, 350 RPM,0.13HP,1PH

The motors that replaced these were Genteq 5KCP29FK,.13HP,1.2 A,1350 RPM,120V which Grainger said was no longer available but the comparable motor was a Century Grainger # 4UU22 -see link for specs
http://www.grainger.com/product/CENTURY-Room-Air-Cond-Mtr-4UU22?searchQuery=4uu2

We have tried to use them. Two get super HOT within minutes-can't be used. One doesn't get too hot but on runs on one speed only although wired for three. One runs way way too warm but runs as expected. (It won't last long like that-)

Tom thinks the motors are crap-just junk that has not been tested under a load following manufacturing. We have crossed off every possibility on the troubleshooting list-he is meticulous and very thorough. We just wonder if you have a little known tip, suggestion or experience with Century PSC variable speed motors that may shed some light. Tom is beyond frustration. He has never had this type of trouble with any other motor! Thanks Will for sharing your wisdom!

best regards,
jill

Answer
Dear Jill,   I am trying to make sure whom I am replying too,  I am assuming it is TOM of TOM MCGANN LLC ?

First I appreciate the very complete history of the issues,  that is often not provided or partial at best,  so you did very well in getting the info I need to get started,

But there are many questions in the one document.    

ALSO some of the info is not firm,  so I need to ask some follow up questions,  I am going to  use a word processor,  as there are many parameters to be discussed,   

My private email is wbwill@sbcglobal.net,  work email is repair@mearservice.com   feel free to use either of those email addresses,       I will cc this to myself and finish this reply



Hi Will-Tom has been asked to replace 5 motors in Airtherm Cabinet Unit Heaters- Model: 121-1L-F Serial# August 1996 ST.

Because of its age there have been replacements to original double shaft motors which we think were Magnetek SER:34G 11648P MOD: DE2F064N 43100111,125V,60HZ,1.6 A, 350 RPM,0.13HP,1PH

The motors that replaced these were Genteq 5KCP29FK,.13HP,1.2 A,1350 RPM,120V which Grainger said was no longer available but the comparable motor was a Century Grainger # 4UU22 -see link for specs
http://www.grainger.com/product/CENTURY-Room-Air-Cond-Mtr-4UU22?searchQuery=4uu2

We have tried to use them. Two get super HOT within minutes-can't be used. One doesn't get too hot but on runs on one speed only although wired for three. One runs way way too warm but runs as expected. (It won't last long like that-)

Tom thinks the motors are crap-just junk that has not been tested under a load following manufacturing. We have crossed off every possibility on the troubleshooting list-he is meticulous and very thorough. We just wonder if you have a little known tip, suggestion or experience with Century PSC variable speed motors that may shed some light. Tom is beyond frustration. He has never had this type of trouble with any other motor! Thanks Will for sharing your wisdom!

OK NO RICH FORMATS ALLOWED SO I WILL START OVER HERE

There is a question waiting for you in the category of "Electrical Wiring in the Home".

Subject: Problem: Century Motors get HOT

Question:
Hi Will-Tom has been asked to replace 5 motors in Airtherm Cabinet Unit Heaters- Model: 121-1L-F Serial# August 1996 ST.

Because of its age there have been replacements to original double shaft motors which we WE THINK???  Please explain,  there is doubt to the OEM motor? think were Magnetek SER:34G 11648P MOD: DE2F064N 43100111,125V,60HZ,1.6 A, TYPO ?   should read 1350 correct?   350 RPM,0.13HP,1PH
If this was the original motor  it was rated at 125 VAC @ 1.6 amps.    Second motor was 120 VAC 1.2 amps,   same BASE RPM
I am OK with the junk theory,   and if this had been the first swap out, I would probably stop there and say that is the issue.  There are tons of junk out there, not just motors,  but motors yes,      and down in these lower HP ratings, the QC is less and less,      

BUT this is not the first rodeo for these heating units,    so that in itself puts a bit of doubt on the junk aspect,   not saying that is what you are dealing with, but it would odd,   that replacement motor three,   at least,    is having issues  no different than the previous motors,  
  I say different,  maybe the other motors failed mechanically,  No way of knowing?,    but these are 1996 units,   two motor sets prior,  10 years per motor, is reasonable,  but most motors  if installed correctly,  if the right motor for the application is selected,  some minor maintenance,  can last decades as you know,       

So we will keep junk as a possible explaination,  but I have a feeling even if they are junk,  this heat issue is not totally junk related,      

Have you swapped the moderately hot with the severely hot units?
Proved the problem followed the motor?

Do you know what the voltage at the units is?  Do you know what the running current is on either speed, or all three speeds, [again I did not see three speeds only two but I have more research to do] ???
I also see the pdf of the units stating 1150/850   but we have a 1350 base speed motor.
They are not trying to control base speed on a PSC motor with voltage are they?  I did not do the math on this,  but they demand starting at 78% of data plate rating,    I guess,   or is it 78% of 115 volts AC nominal?
It says rated voltage,   yet one motor was 125 VAC,  the other 120,    the ampere rating from 1.2 on one,   1.6 on the other,  oddly I believe the higher rated voltage was the higher current.   Should be the other way around,   unless it is efficiency,  design or something else, but all things being equal,  a  220/440 volt motor using 10 amps at whatever HP rating,   is going to be rated at 5 on 440,  not the other way.
Basically, was it the voltage or the eff of the motors,  with one at 1.6 amps to produce x HP and the other 1.2  amps to produce the same HP.

These temperatures of hot, warm, so on,   one motor on just one speed,   not using the three speeds,    or two of the possible three,  what is the temperature ? I see there are intergal temp switches,  I assume of the "Klixon" variety?  Bi metal,  auto reset?  Klixon is of course a brand name,  but is used pretty much universally as any auto reset, internal thermal protective device.
Is the thermal line level,  and auto reset, or are there leads to tie to the contactor? Or alarm or whatever?

So are/have the thermals been tripping off?    ON ANY OF THE MOTORS?   Is there a history of the thermals tripping?
You are obviously experienced in these applications,  and you understand a hot motor is not necessarily a bad motor,  most all motors cool through the case,   TEFC blows the heat from the shell,   ODP is simple transfer to ambient.
Have you considered burying some sort of thermistor in the windings to measure the winding temps?
Have you used a thermal gun/camera on each motor to compare the skin temps?
How are the mechanical conditions of the devices?   The units,  and I hope I have the right unit pdf,     It about has to be,     direct drive,   how are the bores of the blower wheels?
Flats with set screws?  Are the blower bores loose over this many years?
How about the wear on the blower fins themselves?    Wear is not exactly always equal,  and "dull" or distorted blades from unit to unit, could create a huge false load.
I really need voltage measured at the unit,  at the motor better,  amperages,  and exact temperatures,    I would prefer some sort of buried thermal,  that would provide an internal winding temp,  or for testing you could use a FLUKE or other brand with a J type probe,    if there is a physical method to get the probe down into or onto the windings,  versus a permanent type device buried inside,    it would be good enough for comparison,  and some empirical data.
That and a thermal gun,  thermometer  whatever,   to compare the skin temps in degrees,   I understand you can feel the temps,  but at this point we need to know if the device,  mechanics of,  ambient,  air draw,  RESTRICTIONS,  are acting on the motors  or are the motors simply   JUNK?
I am not saying they are not junk,  but even at junk,   this is replacement of the motors for the third time at least,   and not sure of the existing or OEM, or original motor  as you THINK the first or existing motor was as you specified.

Plus the differences in temperatures,   and by the way,  two were hot,  1 unit on one speed only,   one semi-warm  not likely to last,     total four       but there are five units,   what is unit 5 doing?

MY EXPERIENCE   
I have tons of experience with PSC motors in all kinds of applications, and some very unique,    especially many critical applications for the National Weather Service,      

The upper air system for the National Weather Service is operated was operated by a rotational dipole antenna,    for DECADES  they fussed with a PSC  fractional HP SYNCHRONOUS motor,     yes SYNCHRONOUS, constant duty,  vertically mounted,  with tach spud,  in an enclosed "cone" or "pylon"     If you were to look at the large antennas out in the country as opposed to a radio type telescope,   the design where a 20 foot dish has a large center piece,  in a cone shape,  with a ball shaped end.

That cone was the rotational radio antenna center,   it tracks the launched weather ballons,  all across the country,  two flights a day normally in fair weather, more in severe or suspected severe weather.

The payload of the balloons carry all types of weather instruments in real time,  from temp to wind speed, direction, rise rate,  humidity so on,   a very crucial part of the forecasting of any weather and actually all weather.     
Believe it or not a FEW would run at a sync speed of 1800  RPM   a few,  out of hundreds,    the sync was accomplished as rare as it was,   by the use of a massive bank of capacitors,  a "special ROTOR",   and a wish and prayer,     the majority failed,   
WE corrected the problem  back in 2004-2008 , reverse engineered all antenna units, cure was to cure the hoards of mechanical problems,    convert the odd frames of the motors, that fit in the application,  by converting the motors to three phase,  modifying the rotors outselves, and driving with a VFD,    as the devices were 115 AC with a power cord,  an actual 115 volt plug,   the GOVT does not like any change,  so the modifications were done in a manner that allowed for the orginal cord to be used,  so all internal changes were not visual,  by using a 115 single phase to 230 volt THREE PHASE drive,  once I developed the winding, then developed a change to the rotor resistance rings,    it took some trial an error but we got it,    and it plugged right back into their 115 outlet.
I have made PSC motors run for testing wind speed testing units,  where the wind bottles were ran at 2 sync speeds,   they wanted a third speed added to nothing more than a rotary switch,     600, 900, 1800 RPM   had to hold a min torque tolerance,  but was allowed a plus or minus 1RPM,      as opposed to the upper air units that were plus or minus 0 RPM, due to a feedback tachometer that synced their receiving electrontics with the sending units,     with the drive it was no problem,   mounting and adjusting the drive was a long term trial but we got it,   

To the problem at hand:     

I see we are on at least batch three of motors for this application,      at this point I have not read the specs on the Century, the driven load, as best I understand it is a floor mount unit, with direct drive CAGED BLOWERS,  dual speed,  with 25% possible outside ambient draw, controlled by a servo type damper, it is about 121 inches wide,  and so far I see the two speeds with 850/1150 RPM choices,       I also read form the pdf I found:  

MOTORS
All motors shall have integral thermal protection and start at 78 per cent of rated voltage. All motors shall be of p.s.c. design
and be capable of operating in high static conditions. All motors shall be factory run-tested and assembled in unit prior to
shipping.
ELECTRICAL
All primary internal wiring shall be done at the factory and every unit shall be factory tested for reliability.
Are the specs usage or tolerances?  As to static,  what is HIGH? Kind of like hot, warm, cold,  so on,    hot is what?  Measured where?  78% of rated voltage is ton,  why is that spec in there?   Any idea?  Is it for variants in utility voltages,  or just what is that all about?   


  but will      however I have questions on those I will highlight,  but for now,  it says 2 hot within minutes,  not useable, one semi-hot but is run on one speed although wired    [wired=capable?] of three speeds,   one runs too warm,  but runs as expected,        
The motors that replaced these were Genteq 5KCP29FK,.13HP,1.2 A,1350 RPM,120V which Grainger said was no longer available but the comparable motor was a Century Grainger # 4UU22 -see link for specs
http://www.grainger.com/product/CENTURY-Room-Air-Cond-Mtr-4UU22?searchQuery=4uu2
I see a couple potential problems with the replacement motor link above. Firs thing that jumps out, these are OAO frame motors.  OPEN    AIR OVER.   I have not dug into or may not be able to tell,  but by the photos in the pdf on the devices,   I see no way these motors could cool air over.
Air over means the motor is the path of the machine it is driving air path. This particular type motor is double shafted,  but also it states AC use.  When used with double shafts for AC units, one shaft has the blower wheel for the exhaust to the room of cooled air,  and the other shaft holds the axial fan for the condenser, the motor is in the air stream of the axial fan, and provides a method of drawing the heat off the motor.
In this application with dual blowers  unless I am missing something,  there is no way the motor is any air stream, and with an OAO configuration, there MUST be cooling air drawn over the motor body.
That could explain the heat very easily.
Next I see the base speed is 1650   I have not had time to compare HP ratings to speeds,  I know four speeds can be use in three speed applications chosen correctly,   but if the 1650 versus 1350 is now using a lesser HP to get to the lower speeds,  then it would or could enter overload range fairly easily.
This motor looks completely wrong for the application. I will need to look at the specs of the older motors more completely  but an AO motor seems completely wrong in this application.
You would need a NEMA DRIP PROOF  double shaft motor,  not an AO motor with no way to get the motor frame into an air stream.

This may be the entire problem.  Nothing against Graingers,  they have a barn full of motors, but I would never depend on their technical expertise on any electric motor,  they go by part numbers.

I would look closely at this.
And this is not intended to insult,  but the motor is also rated for a single direction,   has the rotation been checked?  It is a simple thing but one of the most commonly overlooked parameters of motors and generators,   ROTATION>  Worth a look,       


We have tried to use them. Two get super HOT within minutes-can't be used. According to the specs on the unit,  the motors need to start at 78% of rated, an also contain intergal thermal devices,   if like most, they are in line thermals,  do the motors trip off with the internal thermal?   One doesn't get too hot but on runs on one speed only although wired for three. One runs way way too warm but runs as expected. (It won't last long like that-)  That is four of five.  Explain way too warm versus hot,  but runs as expected,   ??   The hot motors although hot do not run as expected?  Please explain.  And the fifth motor?

Tom thinks the motors are crap-just junk  Possible but even junk tends to act the same  that has not been tested under a load following manufacturing.  Correct,  even 20 HP motors are not all load tested,   some manufactures do, some don't,   each have their own risk tolerance, and most are spot load tested,  due to cost,   and I doubt these little fractionals are tested but one in hundred or more. We have crossed off every possibility on the troubleshooting list-he is meticulous and very thorough. We just wonder if you have a little known tip, suggestion or experience with Century PSC variable speed motors that may shed some light. Tom is beyond frustration. He has never had this type of trouble with any other motor! Have any idea  what the failure mode of the existing motors is?  Or the previous or OEM/Original  which is not identified in certain as I understand it   You obviously know that restrictions on blowers is critical.  When under test,  are the restrictions for each unit,  adjusted to the same amount both incoming and outgoing?
If I am reading the correct pdf on these units,  then there are intake openings,  servo controlled dampers,  plus testing with or without covers, baffles etc,   could create a false negative. Blowers are not fans.  Blowers are blowers,  and will attempt to suck the air out of the entire world, unless some type of adequate restrictions are in the design and in use,   have you used an amprobe and tweaked the restrictions to see to what degree if any the restrictions have on the running current?  ALL SPEEDS.
   The heat could be a lot of things,  first I have to know something besides HOT,    I am not doubting they are hot,   but how hot,  how fast, and what temp?   B design motors have 200 C insulation in them,   and I am still not understanding why the tolerance for 78% of rated voltage is about.
So there is a pretty good list of things to try,   needed info,  I need to be corrected on the info I am assumming at this point.
Are these two or three speed units?
What three speeds?
What is the rated current, versus the measured current?
What voltage is being applied to the motors?  [Even a 440  motor,  at some point,  say some run fine on 502 volts,   and some do,  even more efficiently,   but a long story,   anyway,  at some point  even though the 440 volt motor runs fine at 502 VAC    there will be a voltage   where one more volt,  will bring the amperage level to the knee of the curve,    at that point,  say  509 now 510  the amperage goes off the charts,    in every motor, and all are different,  there is that exacting point of voltage and load that is as efficient as it can be,  but at some point,   both over and under voltage,   the breakover point will be reached.
Restrictions    are all units setup with the same incoming and outgoing restrictions?
What are the skin temps in degrees?
Any amperage changes that follow changes in restrictions?
Condition of the blower wheels,  including bore wear,  blade wear, TIR,  general condition,  are the wheels replaced, reused,  available?   How are the blades held to the dual shafts?  Sweat fit,  flats with set screws,  so on?
Can you get a temp probe down in the windings?
New capacitors?   MFD RATING?   
Let me look up the specs on this replacement motor, and I will report on it.
I am assuming these tests are being performed in the units?
Have you bench tested [with restrictions]  each motor?   VOLTAGE APPLIED AND NO LOAD CURRENT OR LOADED CURRENT  loaded would be adjusted by restriction to the nameplate.
Is there a service factor on the motor?  
Noise?
Alignment options of any kind?  Shims?
If you can provide me with some more detail,  I know I can resolve this issue.  I have been through these kinds of things a thousand times if not more.
I o know there is junk out there, and it might just be the situation,  but with three replacements on these devices, and the newer motors,  seem to be all over the board in performance and heat,  normally even junk tends to fail in the same kind of mode.
We shall see.
Remember worse to worse,  we have a complete motor shop,  can perform warranty repairs for about any manufacturer and these could easily be mailed to us,  where we could perform :
Insulation resistance  megger test  
Surge test
Cap test
Variable voltage testing
Inductance testing of the rotor.
Disassembly and visual testing.
Visual and exacting measurements of the bearings, housings journals.
T.I .R.
Dynamic balance if required.
Full load current monitoring.
Skin temperature monitoring,  internal winding temperatures.
Independent stator testing.
Air gap.
Written Report
But I imagine we can figure this out with a little more detail as outlined.  You can go back through allexperts, or you can use my personal email,   or shop email.
Help me with what I have wrong and then with whatever missing data I need,  and we can go from there.




Thanks Will for sharing your wisdom!
You are most welcome.
best regards,
jill

Please go to http://www.allexperts.com/expertx.cgi?m=11&expID=79197&qID=5001849 to answer the question.

Thanks for generously volunteering your time to help others.

Please do not respond to this message. If you have any questions, send to experts-help@about.com.  
About Electrical Wiring in the Home
This site answers questions related to home electrical wiring, home wiring, general electrical help,and other electrical questions related to aleternating current (AC). You can find help on the National Electical Code, home electrical issues, wiring electrical outlets, installing lighting, electrical grounding, and general electrical help for do-it-yourself projects not require an electrician. If you do not see your home electrical wiring question answered in this area then please ask your electrical wiring question here

Electrical Wiring in the Home

All Answers


Answers by Expert:


Ask Experts

Volunteer


Will Babbitt

Expertise

Electrical issues of all types, wiring, control, appliances, components, specialty in Electric MOTOR or APPARATUS trouble shooting, electric motors, electrical problems, single phase, three phase, DC, capacitors, elevator MG-Sets, modifications, reverse engineering, VFD Drives, single to three phase convertors. Repair of most any electrical/mechanical/electronic apparatus, OEM, AC, DC, Industrial Applications, Three phase, single phase failure mode, determining the root cause of the equipment failure BEFORE failure repeats, Antique appliances, electric motors, fans, ceiling fans, base mount fans, poor equipment performance, Modifications, habitual failures, vibration, redesign, obsolete issues, collectible items restored, rewinding. Owner of EMR Repair Inc www.emrrepair.com More information on electric motors, under Engineering/Motors Ask about any electrical or mechanical problems in the home, office, or even at your work. B2B or business to business CONSULTING I can do but it would be a much more complex issue, that would require a significant amount of time. repair@mearservice.com from there we can discuss and begin work on about anything. Industrial electric motors, controls, troubleshooting, vibration, alignment, any type of industrial or commercial electric/electrcical equipment For the home owner, renter, apartment if you have odd things going on, describe to me, photos are normally very helpful, appliances, heating and air conditioning issues, light switches, installation, DIY PROJECTS FOR THOSE NOT EDUCATED IN ELECTRICAL, we can do some things, but for safety and sanity reasons, I may refer you to a local electrician, and help you find one, help you with pricing and even speak directly with anyone you hire if you have issues,

Experience

Over thirty years with a major repair and sales company, VP of Operations, and former owner of my own specialty repair shops, MEAR Services local to Kansas City Missouri EMR Repair Inc., located in Kansas City Missouri, 2014 sold both businesses to JCI Industries, Lee's Summit Missouri wbabbitt@jciind.com Evaluation and repair of electrical/mechanical apparatus. Electrical and mechanical repairs, trouble shooting including, vibration and balance issues. About.com provides this service, and the huge costs to provide help on about any subject. They provide the servers, the people to vet the experts, costs that would be the same as operating a good sized business, They should be appreciated for what they do, the huge costs and the great help they provide for free, Electric motor questions, can be answered here but there is a dedicated category that has other experts to help and add to a solution. Other common questions, are noises in the walls, breakers tripping, devices not starting or shutting down for no apparent reason, smoke alarms buzzing, thermostat change outs, or sizing wire or needing information for a new project, but anything can be resolved, anything, with enough effort and patience, DIY, with electrical is possible, but in most cases the use of a simple ohm meter or volt meter is needed, they can be purchased at any hardware store for a few bucks. If you have smoke, or smell smoke, don't be writing me, call 911 the Fire Department has no problem looking for smoke smells, better then spraying water on a blazing fire. DO NOT GET CAUGHT INVESTIGATING AND TRAPPED IN A BASEMENT LOOKING FOR A BLOWER FAILING< As to the tip jar, it is up to you, it is appreciated, every expert spends out of pocket that I know, we spend on IP time, computer wear, printing documents, books, and of course our time, but if we prevent a $400 service call, we did well,

Organizations
Former IBEW, EASA, IEEE, UL, ..............

Publications
SEE ELECTRIC MOTOR CATEGORY

Education/Credentials
10 plus years, various Technical Schools, followed by Industrial College Credit and non Credit Courses, electronics courses, experience in most any electrical apparatus, electric motors and generators, AC OR DC, fractional to above 5000HP, other electrical apparatus, slip rings, sleeve [plain] bearings, lubrication, identification-no data plate, control components, service and sales. I have continued night schools for decades, the list is extensive. I have been in the business of repairing most anything with wires or mechanical parts for decades, I have some helpful hints and directions you won't have to dig up. Or hopefully not have to pay a huge service call invoice to find.

Awards and Honors
Yes

Past/Present Clients
Federal Government, National Weather Service, NOAA, Commercial Power Plants, Major Vehicle Manufacturers, Printers, Other industrial and Commercial Businesses

©2016 About.com. All rights reserved.