Sometimes 120 Volts is referred to as 110 Volts or 115 Volts. These differences often represent the range of voltage supplied by the power source to the appliance, which can drop a little from the peak values (at the source, called nominal voltage) depending on the type and length of the wires used 1. Likewise, 240 Volts can be referred to as 220 Volts or 230 Volts. Check with a qualified professional, such as a central vacuum dealer or electrician, if you are unsure of the exact voltage supplied by an electrical outlet.
Are 120 or 240 volt vacuum units better?
For the most part, our motor manufacturer has very similar performance statistics between the voltages. Our 120 volt Silent Master S900, for instance, has 139 water lift and 191 CFM with a peak of 905 air watts. The 240 volt version has 136.4 water lift and 190 CFM with a peak of 866 Air Watts. These stats are very close. But there is quite a difference in our Silent Master S500. The 120 volt has 85 water lift and 183 CFM with a peak of 514 air watts. Its 240 volt counterpart has 95 water lift and 208 CFM with a peak of 722 air watts. That is a significant difference. For some homes, maximum amperage for their panel may be close, so the 240 volt version offers the best benefits.
Differences in operating costs
The cost to operate a 240 volt vacuum can possibly be less than its 120 volt counterpart, because both phases of the power are being used simultaneously. But even the 120 volt version may not be wasting much power if the opposing circuit is being used by lights or other appliances at the same time. In the worst case scenario, the 120 volt version might cost a few additional cents per hour to operate.
How the duration of life compares
We believe the 120 volt versions of the vacuum motor will last longer. They contain a higher amount of copper, which naturally has excellent thermally conductive properties 2, and thus the heat has a greater ability to dissipate. The 120 volt motors are also much easier to replace, because they are common motors in the industry. The 240 volt version motors are not used very often, so vacuum shops around the country will normally stock the 120 volt motors, but not any 240 volt options.
Questions and Answers
Can my appliance be used with slightly more or less voltage?
As a central vacuum manufacturer we use the 120 and 240 volt motors. The 120 and 240 motors will not be adversely affected if used with lower voltages. The 120 volt motor will be fine on 110 volts. Likewise, a 240 volt motor will be fine on 220 or 230 volts.
However, it does not work the other way around. A 220 volt motor would be damaged if used for long periods of time on a 240 volt circuit, and so would a 110 volt motor running on 120 volts.
The motors we use will also run well in any variation of 50-60Hz.
Are the motors the same in the 240 and 120 volt versions of vacuums?
There are significant differences: the motors are wound differently, and the transformer, mini-breakers, cords and wiring are all different.
What happens if you plug a 120 volt unit into 240 volt circuit?
If you plug a 120 volt unit into a 240 volt circuit and turn the vacuum on, it will spin at nearly twice its normal RPM. If not immediately turned off the motor may disintegrate. But before that happens, the transformer will likely burn out. Normally, all you need to do in this situation is replace the transformer and the system will continue to perform.
What happens if you plug a 240 volt unit into 120 volt circuit?
If you plug a 240 volt unit into a 120 volt circuit, it will not run correctly. The good news is that neither the transformer nor motor(s) will be hurt. You will only be running the system at half speed. In fact, running the unit at half speed is a way you can "break-in" new motor brushes when they are changed out down the road. Also note that the transformer will not activate the relay unless it has 240 volts.
Cord Configurations and differences
USA Plug and Cord Differences
Heavy Duty 30 amp 110-120 volt
Nema 5-30 Socket / Plug (Straight = Hot, L-shape = Neutral, Round = Ground)
Appliances with 110 volts that pull more than 15 amps require a 30 amp outlet with 10 gauge wire and a Nema 5-30 plug. If the 110-120 volt appliance is under 15 amps, a regular 3-prong cord is used.
Regular 20 amp 220-240 volt
Nema 6-20 Socket / Plug
(Hot is both the vertical and straight)
Appliances with 240 volts require a 20 amp outlet with 12 gauge wire and a Nema 6-20 plug.