Should I leave my compressor on continously or have it on auto ON/OFF?

[downforce]

I have a 30HP Compressor 480V 3PH. It is starts up and runs for 8 minutes and stops. It would start up every 10-15 minutes throughout the day. Would it be more economical for me to just leave the compressor on all day? If it even matters, it is a rotary vane air compressor. Any inputs or advice is greatly appreciated. TIA

 

[MikeHalloran]

If you just left in ON continuously, you'd be venting air through the system relief valve, which is an expensive way to regulate the supply pressure.

If you're concerned about cost of operation, find and fix all the leaks.



Mike Halloran
Pembroke Pines, FL, USA

 

[Compositepro]

Electric motors are only capable of a limited number of starts per hour. Large compressor motors will usually run continuously while a valve in the air inlet will modulate the airflow to match need. If the compressor runs unloaded for more than 15-30 minutes then the motor will turn-off. Closing the inlet to a compressor removes most of the load on the motor.

 

[waross]

If your compressor is running on that duty cycle, it should have an unloader. I can't tell from here if one may be retrofitted. An unloader lets the compressor spin without working. the motor and compressor spin all the time and when the pressure drops the unloader loads up the compressor. When the cutoff pressure is reached, the unloader unloads and lets the motor spin free until the cutin pressure is reached and the cycle repeats.
If you can add another storage tank you can extend the run time and the reserve and lessen the number of starts in a day.
BEWARE, when looking for a pressure tank, many of the used tanks you come across may be in poor repair. Even if they look good they may have a lot of internal corrosion.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[edison123]

Go for a bigger tank so that you get a larger reserve with lesser starts.

Muthu

http://www.edison.co.in

 

[Skogsgurra]

Check pressure switch for too small hysterisis. If pressure moves between say, 100 PSI and 101 PSI or similar, you need to either repair or change the switch.

Fixing leaks is also important and, considering the 8 minutes run every 10 - 15 minutes, seems to be the thing to do first.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[electricpete]

Lots of good solutions above: unloading is an ideal way to keep motor running without wasting much energy. Or if motor on/off control is kept, the number of starts can be reduced through bigger surge volume or larger hysteresis in control switch if larger pressure variation is tolerable.

To explore another option - how many starts can the motor be expected to tolerate, see the first link here: (we need to know the speed of the motor... estimate of inertia of load would help also).
faq237-1285

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[electricpete]

and if compressor is belt driven... need sheave diameter ratio to compute effective inertia.

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