Blower motor overheating.
- Thread starter powerplay
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You haven't told us anything about what type of motor it is nor anything about the type of pump its drivin and how. It would be nice to know the voltage, 1ph or 3ph, the HP etc. Providing such information would be helpful in getting an answer that is relavent to you application.
The motor is used to pump air through a 2" hose to aereate a water supply. The motor is single phase 230volts, 6.5 amps with a 250volt standard plug. The rotation was correct, no single phasing, but owner plugged in for 7 minutes connected to a long air hose with nothng attached to it. For moving air I would have thought no need for overloads, but for maimum protection an motor controller would have helped. Since factory 240volt plugs are not to be cut off, do we install an 240volt receptacle with motor controller for an Regenerative Blower motor? Was too long a hose the cause of overheating?..or lack of some backpressure?
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
No back pressure means more volume of air will be easily moved. More volume of air moved means more load on the motor. Your motor was not unloaded but infact had even more load on it when not connected to create some restriction on the blower output.
Proper overload protection on the motor should shut it down if it is drawing too much current, does not matter that the motor is in the airstream. Yes the motor in the air stream helps keep it cooled but if motor is overloaded to begin with that only helps to a certain extent, but is still possible to overheat windings if enough load is present.
broadgage
Senior Member
- Location
- London, England
Some types of centrifugal air blower or water pump require a minimum air or water resistance connected to the outlet of the blower or pump.
If connected to an open ended outlet they draw more current, possibly enough more to overload the motor.
This is counter intuitive, one might expect an obstructed outlet to increase the current drawn, but this is not the case, and may be confirmed by experiment if desired.
If the air blower in question is intended for aerating water, this implies that it is intended to generate appreciable pressure, probably to force the air through small holes in a submerged pipe.
If the blower is run connected to an open ended hose or pipe, then the air resistance may be insufficient and the motor overloaded.
I would suggest a BRIEF trial with an open ended pipe and noting the current drawn.
Then connect up as intended and again note the current.
You will probably find that with the open ended air discharge that the motor current is excessive.
A motor overload trip seems desireable, either the tradditional thermal relay or a more modern device giving similar protection.
If connected to an open ended outlet they draw more current, possibly enough more to overload the motor.
This is counter intuitive, one might expect an obstructed outlet to increase the current drawn, but this is not the case, and may be confirmed by experiment if desired.
If the air blower in question is intended for aerating water, this implies that it is intended to generate appreciable pressure, probably to force the air through small holes in a submerged pipe.
If the blower is run connected to an open ended hose or pipe, then the air resistance may be insufficient and the motor overloaded.
I would suggest a BRIEF trial with an open ended pipe and noting the current drawn.
Then connect up as intended and again note the current.
You will probably find that with the open ended air discharge that the motor current is excessive.
A motor overload trip seems desireable, either the tradditional thermal relay or a more modern device giving similar protection.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
Bingo. 'Nuf said about that, he is dead on.
Purists however might point out that this situation would not be the case if it were a positive displacement blower, but the fact that the situation happened is proof to me that it is centrifugal.
But as to the comment "For moving air, I would have thought no need for overloads". Read the NEC, article 430, repeat as necessary until you fully accept it in it's entirely. There is NEVER a case when the circuit does not need overload protection. The connected load is immaterial, in fact even if you run a motor that is not connected to anything else, it must have overload protection. When you occasionally see small 1 phase motors that require no EXTERNAL overload relay, that is only because the motor has it built-in. But the only time you can do that is if the motor SPECIFICALLY says something akin to "Thermally protected" on the nameplate ( sometimes the wording is slightly different).
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