Exhaust Fan Motor "Burning Up."

Has anybody checked for air flow restriction? This will cause the motor to overheat and fail. Also just adding a bigger motor in such case will not fix it, but only exacerbate the issue. A duct system is designed for a specific flow and a restriction of any sort will increase the resistance to the motor rotation, and subsequent heating. Two considerations, was the motor when replaced at some point sized to the design specs. of the ventilation system, and is there some other restriction happening, fan bearings failing, over tensioning of the belt drive etc.
 
Fred B said:
Has anybody checked for air flow restriction? This will cause the motor to overheat and fail. Also just adding a bigger motor in such case will not fix it, but only exacerbate the issue. A duct system is designed for a specific flow and a restriction of any sort will increase the resistance to the motor rotation, and subsequent heating. Two considerations, was the motor when replaced at some point sized to the design specs. of the ventilation system, and is there some other restriction happening, fan bearings failing, over tensioning of the belt drive etc.
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Generally, restricting the airflow lowers the fan HP.
And in this case, the flow from the fan is not used for cooling the motor.
 
I worked in a glass factory and along the float lines temperatures were were over 300 degrees . We had blowers on the outsides and duct work being the air over the motors and these were big ,big motors.
 
ptonsparky said:
I don't remember if this an axial flow or centrifugal. Details keep trickling in that change everything.

Similar to calling Dr. and saying 'my foot hurts, what's wrong?' ...click
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They are axial fans. The latest one is a downdraft. The others are updraft. Doesn't change what the real problem is. Where they are is hotter than they are rated for.
 
retirede said:
He now states that the motor is roof-mounted and not in the flow of air being exhausted from the building. I wonder why it’s XP?
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Because it is a natural gas compressor building. The fan is to ventilate any released gas in addition to heat from the internal combustion engines driving the compressor. The better designed compressor building will shutdown if there is not enough fans running.
 
In case you or the customer gets tired of replacing explosion proof motors, or searching for, higher temperature non existent 1Φ ones, they may consider a fan replacement that is suited for the purpose.

These are commonly used for paint booth's, paint curing ovens and paint mix room exhausts. The motor is totally isolated from the airway and located outdoors on the roof mounted models. The belt drive is also isolated in it's own enclosure, sealed off from the airway. They can be had with a base that sits on a roof curb, and have a blow open cap on the top of the stack. The discharge stack can be added to extend the discharge height, above the roof if required

The motor and belt drive sheave can be enclosed in it's own rain proof enclosure with a service door. The motor can then be a standard NEMA model with whatever insulation class rating you desire, but standard TEFC ones last for many years when located outdoors on the roof in it's rain proof doghouse. And as far as temperature is concerned they are rated up to 200 F in the airway. Can be had from several manufacturers. A couple examples.

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NYB Tubeaxial Fans are designed for moderate-pressure ventilation & industrial-process use where axial flow is desirable & space is at a premium. Contact us today!
www.nyb.com www.nyb.com

 
MTW said:
In case you or the customer gets tired of replacing explosion proof motors, or searching for, higher temperature non existent 1Φ ones, they may consider a fan replacement that is suited for the purpose.

These are commonly used for paint booth's, paint curing ovens and paint mix room exhausts. The motor is totally isolated from the airway and located outdoors on the roof mounted models. The belt drive is also isolated in it's own enclosure, sealed off from the airway. They can be had with a base that sits on a roof curb, and have a blow open cap on the top of the stack. The discharge stack can be added to extend the discharge height, above the roof if required

The motor and belt drive sheave can be enclosed in it's own rain proof enclosure with a service door. The motor can then be a standard NEMA model with whatever insulation class rating you desire, but standard TEFC ones last for many years when located outdoors on the roof in it's rain proof doghouse. And as far as temperature is concerned they are rated up to 200 F in the airway. Can be had from several manufacturers. A couple examples.

View attachment 2578243

View attachment 2578244

|

NYB Tubeaxial Fans are designed for moderate-pressure ventilation & industrial-process use where axial flow is desirable & space is at a premium. Contact us today!
www.nyb.com www.nyb.com

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OP described a fan similar to that as what he has, but with a 40C motor driving it. Thinking he wants explosion proof as they must be considering the area near the fan outlet to be a classified location as it could be exhausting natural gas at times?
 
Hey! I could have them bring in 3-ph service and install a VFD driven fan, with class F insulation, to keep the existing single-phase, with class B insulation, exhaust fan cool! (Sarcasm)
 
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