Motor is heating up??

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jahilliard

Senior Member
Recently we installed a 15Hp 208-230V 3 phase Baldor Electrical motor with a Berkeley Pump inside a vault for an architectural fountain/pool. This is an underground vault with plenty of air space and vented so the ambient temp is not unusually hot. There is also another pump (Marathon) in the same vault same size serving the same purpose. The issue is that the baldor motor is getting so hot you literally can noot touch it it will severely burn you its so hot. Both pumps are operating at allowable ratings for Voltage and Amperage. Incoming Voltage is no lower than 205V between any two lines. Any ideas why the Baldor motor is SO much hotter than the Marathon?
 

jahilliard

Senior Member
I was "told" the amperage was "within range". I am asking the person actually on site the exact amperage observed for each motor.
 

GoldDigger

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Location
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Retired PV System Designer
I was "told" the amperage was "within range". I am asking the person actually on site the exact amperage observed for each motor.

It does not explain why one motor is hot and the other is at most warm, but a 120C motor is designed to run at higher than the boiling temperature of water, and would definitely burn your skin.
One motor might be oversized or be cooled more effectively by mechanical connection to the pump and piping with water flowing through them.
 

Jraef

Moderator, OTD
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Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
If the current is really below the FLA, there is no immediate cause for concern. But look at the current balance as well. Even a slight current imbalance translates to more motor heating than normal given the same loading. In other words the heating of the motor is WORSE than it should be, but the current is still within spec. If the current between all 3 phases is within a few percent, I wouldn't be too concerned, but if it's 5% or more different, I would be looking for a cause.
 
Its not unusual for electric motors to run too hot to touch,
But is it really too hot ?
What you think is too hot
might be different to what the manufacturer thinks
Have you taken a reliable temp reading ?
Then contact the manufacturer ask what would be normal.
 

JFletcher

Senior Member
Location
Williamsburg, VA
Is the pump also hot, or just the motor? If the pump is hot, look for a severe flow obstruction or shut valve. Basically, the pump will be putting all its mechanical energy into a fixed volume of water, causing overheating.

Misalignment between motor and pump will cause increased temperature, as will improper or insufficient bearing lubrication.

I assume motor rotation is correct? Also check for air cooling obstructions.

In my experience, motors of this type/size and application would not be uncomfortable to the touch; maybe 140*F max.
 

Besoeker

Senior Member
Location
UK
Recently we installed a 15Hp 208-230V 3 phase Baldor Electrical motor with a Berkeley Pump inside a vault for an architectural fountain/pool. This is an underground vault with plenty of air space and vented so the ambient temp is not unusually hot. There is also another pump (Marathon) in the same vault same size serving the same purpose. The issue is that the baldor motor is getting so hot you literally can noot touch it it will severely burn you its so hot. Both pumps are operating at allowable ratings for Voltage and Amperage. Incoming Voltage is no lower than 205V between any two lines. Any ideas why the Baldor motor is SO much hotter than the Marathon?

It could be that they have different insulation classes. Class F was usually specified for motors (and transformers) that we supplied. Maximum hot spot temperature is 155C. About 50C is all you can endure to touch. The external frame of the motor could reach that or more. I've experienced that a number of times. It doesn't necessarily mean that the motor is overheating.
 

Besoeker

Senior Member
Location
UK
Is the pump also hot, or just the motor? If the pump is hot, look for a severe flow obstruction or shut valve. Basically, the pump will be putting all its mechanical energy into a fixed volume of water, causing overheating.

Misalignment between motor and pump will cause increased temperature, as will improper or insufficient bearing lubrication.

I assume motor rotation is correct? Also check for air cooling obstructions.

In my experience, motors of this type/size and application would not be uncomfortable to the touch; maybe 140*F max.
That's 60C. And would be uncomfortable to the touch.
 

Sahib

Senior Member
Location
India
Closing the outlet shut off valve to a centrifugal pump will not usually cause the current taken by the motor to rise but to fall to about 30%.

The problem is with the pump, not with the motor (current is within limit) and not with the power supply as the other pump is working okay.
 

jahilliard

Senior Member
to clarify, the Motors are the same size. If the motor and pump were not aligned properly wouldn't there be a noticable vibration to say the least? Also, if there was an obstruction, that would reduce flow, wouldn't that also reduce motor load?
 

Besoeker

Senior Member
Location
UK
to clarify, the Motors are the same size. If the motor and pump were not aligned properly wouldn't there be a noticable vibration to say the least? Also, if there was an obstruction, that would reduce flow, wouldn't that also reduce motor load?
I agree with both points.
 

Sahib

Senior Member
Location
India
if there was an obstruction, that would reduce flow, wouldn't that also reduce motor load?
It would increase the total head on the pump while there is a reduction in water output. The power input of the motor is proportional to the product of head and water output. So it depends.
 
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