motor overheating question

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steveng

Senior Member
Location
Texas
3hp 460 3ph chill water end suction type pump,
the motor is a 3hp Baldor, the temp of the housing is over 200 ambient
the sf 1.15 the insulation temp is 40c, the motor rla is 8.1 and the actual load is 7.3 7.4 7.4, this motor has been is service for several yrs, but the temp is a concern,
any suggestions, comments on this issue?
 
mdshunk

mdshunk

Senior Member
Location
Right here.
What has the case temp been, historically? Pumps are good for a bit of a trickle out of the seal making the front bearing stiff but not showing up as a leak on the floor. Has anyone changed the (glycol?) chemistry around the time that would coincide with a change in pump motor temp?
 
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steveng

Senior Member
Location
Texas
jimday said:
Was a VFD added recently????
Click to expand...

I would suspect blocked or broken cooling fan blades in the motor. Secondly I would suspect bearings without lubrication.
__________________

there is no vfd, this is a booster pump, 60 hz, for a chill water loop of a multi bldg complex, i have to agree with quog, i think he is close to the problem, i cleaned out the vent openings near the front of this motor. i greased the motor brngs,


what is the max temp a motor with 40c insulation can handle?

my infrared thermo, read 200F, on the housing
 
mxslick

mxslick

Senior Member
Location
SE Idaho
steveng said:
I would suspect blocked or broken cooling fan blades in the motor. Secondly I would suspect bearings without lubrication.
__________________

there is no vfd, this is a booster pump, 60 hz, for a chill water loop of a multi bldg complex, i have to agree with quog, i think he is close to the problem, i cleaned out the vent openings near the front of this motor. i greased the motor brngs,


what is the max temp a motor with 40c insulation can handle?

my infrared thermo, read 200F, on the housing
Click to expand...


I don't think 200 deg. F is excessive...depending on ambient temp. around the motor. I don't remember the conversion from farenheit to centigrade but 200 deg. F doesn't sound much over 30 deg C anyways.



Remember: The 40c rating on the motor is the maximum allowable RISE above the ambient temp.
 
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petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
mxslick said:
I don't think 200 deg. F is excessive...depending on ambient temp. around the motor. I don't remember the conversion from farenheit to centigrade but 200 deg. F doesn't sound much over 30 deg C anyways.



Remember: The 40c rating on the motor is the maximum allowable RISE above the ambient temp.
Click to expand...
200 Deg F = 93 Deg C
30 deg C = 86 Deg F

Generally if you can touch the motor, its not really that hot.
 
C

coulter

Senior Member
steveng said:
3hp 460 3ph ... the motor is a 3hp Baldor,... the sf 1.15 the insulation temp is 40c, the motor rla is 8.1 and the actual load is 7.3 7.4 7.4, ...
Click to expand...

Steve -
It is hooked up to 230V isn't it?

carl
 
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winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
It is very unlikely that the motor has in insulation temperature rating of 40C, and similarly unlikely that it is rated for a 40C rise.

Instead, that 40C number is the _ambient_ condition that the motor is rated for.

It is entirely normal these days to build motors where the winding temperature will exceed 160C at full load. Not necessarily the 'best' design in terms of motor life or efficiency, but it does make for cheaper motors (primarily less copper). Of course, this is the temperature at the hottest part of the motor, not the housing.

I too would be uncomfortable with the outside of the housing at 200F (93C), but this may be entirely appropriate for the motor in question.

-Jon
 
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steveng

Senior Member
Location
Texas
winnie said:
It is very unlikely that the motor has in insulation temperature rating of 40C, and similarly unlikely that it is rated for a 40C rise.

Instead, that 40C number is the _ambient_ condition that the motor is rated for.

It is entirely normal these days to build motors where the winding temperature will exceed 160C at full load. Not necessarily the 'best' design in terms of motor life or efficiency, but it does make for cheaper motors (primarily less copper). Of course, this is the temperature at the hottest part of the motor, not the housing.

I too would be uncomfortable with the outside of the housing at 200F (93C), but this may be entirely appropriate for the motor in question.

-Jon
Click to expand...

i checked it again today, i noticed the insulation was a f rating, does anyone know what a f rated insulation max temp is?, i have priced an new tefc motor just in case this one goes, this pump/motor serves 3 ahu's in large student cetner. most other motors i checked were around 150 - 160 f, but none were 200f, so far no problems, i put a fan on it till i get a new motor.

thanks for your suggestions and comments.
 
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winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
Class F means a maximum permitted temperature of 155C at the 'hot spot' of the motor. This 'hot spot' is of course, somewhere buried inside the motor. My gut tells me to be very concerned about a motor with Class F insulation and an outer temperature of 200F (93C).

-Jon
 
C

coulter

Senior Member
steveng said:
... the motor rla is 8.1 and the actual load is 7.3 7.4 7.4, ...
Click to expand...
Steve -
What's an "rla" - an "fla" with slip up of the fingers?:wink: The reason I'm asking is 8.1A is high for a 5hp on 460V. Even at 7.4A I would expect a 5hp to be hot, that's about 95% loaded.

carl
 
S

steveng

Senior Member
Location
Texas
winnie said:
Class F means a maximum permitted temperature of 155C at the 'hot spot' of the motor. This 'hot spot' is of course, somewhere buried inside the motor. My gut tells me to be very concerned about a motor with Class F insulation and an outer temperature of 200F (93C).

-Jon
Click to expand...

thanks jon, did u say 155c ?

what is the conversion of 155c in farenheit?
 
chaterpilar

chaterpilar

Senior Member
Location
Saudi Arabia
Hello Steve,

Try checking the no load amps also.

93 Deg C is definitely high,... i know you must have checked it but can you check the name plate again..

Is the motor connected in star or delta ?

if it is a 460 V/ 660V (D/Y) winding then connecting it in star at 460 volts will cause problems.

We had a similar issue with a glycol pump, a 230/380 volts D/Y winding was connected in delta at 380 volts by a contractor.

Cheers.
 
S

steveng

Senior Member
Location
Texas
chaterpilar said:
Hello Steve,

Try checking the no load amps also.

93 Deg C is definitely high,... i know you must have checked it but can you check the name plate again..

Is the motor connected in star or delta ?

if it is a 460 V/ 660V (D/Y) winding then connecting it in star at 460 volts will cause problems.

We had a similar issue with a glycol pump, a 230/380 volts D/Y winding was connected in delta at 380 volts by a contractor.

Cheers.
Click to expand...

thnaks chat, how do you check no load amps on a chill water pump in service?
i will get a closer look at the wiring and nameplate.


how long u in the desert?
i appreciate your comments
 
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weressl

weressl

Esteemed Member
Location
Texas by the Gulf, geat crab, great shrimp
winnie said:
Class F means a maximum permitted temperature of 155C at the 'hot spot' of the motor. This 'hot spot' is of course, somewhere buried inside the motor. My gut tells me to be very concerned about a motor with Class F insulation and an outer temperature of 200F (93C).

-Jon
Click to expand...
155C is the rise over maximum ambient, so the actual temperature could be 195C. If you have a 20C ambient you are still OK with a higher rise of 175C as long as the actual temperature does not rise above 190C.

As the conservation efforts gain more focus, new 'high efficiency' motors will run much hotter than older designs. Advancement in insulating materials and core materials allow higher thermal designs. Actually in some places safety people started questioning the need for personnel protection of hot surfaces in relationship to motors.
 
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