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How to run a small vacuum off an uninterrupable power supply unit

How to run a small vacuum off an uninterrupable power supply unit

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  #1  
Old 05-15-14, 11:20 AM
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How to run a small vacuum off an uninterrupable power supply unit

Hey gang,
I am not an electrician (obviously! ), but I'm trying to understand why I can't plug a small canister vac into my computer's UPS. The UPS is a standalone unit, made by APC and has the following output specs: 120v , 60Hz , 330w (550va) , 4.6A

The vacuum's specs are: 120v , 60Hz , 4.0A

Since the operating amperage of the vacuum is less than the power supply puts out, I'd have thought it would work. But when I plug it in and turn it on, the vac starts, and then cuts right out after about 1 second. The UPS emits a warning tone that I assume signals an overload. If I turn it off and then on again, it resets and all is well. Except the vacuum still won't run.

I'm sure a vacuum -even a small one- pulls more juice than a computer; but if anyone has some info on what I would need to get in order to run it, I'd be grateful.
Does it all come down to watts? Do I need to determine the watts of the vacuum's motor and get a UPS with a higher wattage output?

Thanks!
Leo
 
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  #2  
Old 05-15-14, 11:33 AM
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Welcome to the forums. Standby, the pros should be along shortly.

If I were to guess, I would guess that the starting amperage is 2 - 3 times the running amps, and that is the problem.
 
  #3  
Old 05-15-14, 11:42 AM
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Do I need to determine the watts of the vacuum's motor and get a UPS with a higher wattage output?
If you look on the back, most computer UPS's say for computer use only.

You're going to need to use a standard 12v battery type invertor of probably 750 watts minimum.
 
  #4  
Old 05-15-14, 12:14 PM
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Isn't 4 amps at 120 volts 480 watts? That alone is more than the UPS's peak output of 330 watts without even considering the surge required to start the vacuums motor.
 
  #5  
Old 05-15-14, 12:19 PM
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Why not a 12 volt shop vac and a deep discharge 12 volt battery. More efficient and you don't need an inverter. Example: Robot Check
 
  #6  
Old 05-15-14, 05:23 PM
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I don't understand why you want to use the vacuum with the UPS since you obviously have 120 volts AC available in the same location to power the UPS but...

The problem is that the UPS is just too small. It DRAWS 4.6 amperes (552 watts) but only outputs 2.75 amperes or 330 watts, the 550 VA is meaningless in this example.
 
  #7  
Old 05-16-14, 11:53 AM
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Thanks for all the info, guys.
I have a really good portable cannister, and I need to use it where there is no AC receptacle. Was hoping not to need yet another mediocre 12v vac, hence trying to use the UPS. I see now that it is underpowered for the job.
Thanks PJ for the 12v inverter suggestion; I'll look into it and see how it goes.
 
  #8  
Old 05-16-14, 03:55 PM
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How about a bigger UPS? Or even a cheap 2-stroke generator from Harbor Freight would work, and they can be had for under $100 if you can find a coupon.
 
  #9  
Old 05-16-14, 05:47 PM
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Not all UPS's or inverters can produce a true sine wave. A motor needs that true sine wave.
 
  #10  
Old 05-17-14, 02:33 AM
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Most smaller inverters or UPS systems are modified sine wave, a stepped square wave. Most vacuum cleaners use series-wound or "universal" motors and will work fine on a modified sine wave. They MAY run a bit hot, though.
 
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