Question: Please clarify cord configurations on central vacuum power units for all brands. What is the vert position of the cord on larger units? What is the difference between the motors in 110 and 220 units? What is the difference between 110, 120 and 220, 240? Is one better? What happens if 240 motors are plugged into 110 and the other way around?

Answer:

Nema 5-30 Socket / Plug (Hot is the Straight)	Nema 6-20 Socket / Plug
All brands that are 110 volt and pull more than 15 amps require a 30 amp outlet with 10 gauge wire and a Nema 5-30 plug. (If under 15 amps, a regular every day 3-prong plug is used on a standard 20 amp 110 volt circuit. For example SilentMaster S2 110 volt.) For example, this is for MD's SilentMaster S5 - 110 volt model. A 5ft cord extends from the bottom right side of the unit with this configuration.	All brands that are 240 volt require a 20 amp outlet with 12 gauge wire and a Nema 6-20 plug. For example, this is for MD's SilentMaster S2 and S5 240 volt models. A 5ft cord extends from the bottom right side of the unit with this configuration.

Are the motors the same in the 220 and 110 versions of central vacuums? No, the motors are wound differently, the transformer is different, the minibreakers are different, and the cord and wiring are different. Please therefore, be sure to specify with your installer exactly which power unit you desire.

What is the difference between 110/120 and 220/240 volts and is one better?

Sometimes 120 volts is referred to as 110 volts or 115 volts and 240 volts as 220 volts or 230 volts.

As a central vacuum manufacturer we use the 120 and 240 volt motors, not the 110 or 220 volt ones. The 120 and 240 motors will not be adversely affected if used with lower voltages. The 120 volt motor will be fine on a 110 volts. And a 240 volt motor will be fine on 220 or 230 volts. But not the other way around. A 220 volt motor would be "damaged" if used for long periods of time on a 240 volt circuit. And the same for a 110 volt motor running on 120 volts. The motors we use will also run fine any variation of 50-60Hz.

MD Manufacturing is one of the few manufacturers to offer all their central vacuum units in both 120 volt and 240 volts.

Is one better? For the most part, our motor manufacturer has very similar performance statistics between the voltages. Our 120 volt Silent Master S5, for instance has 139 waterlift and 191 CFM with a peak of 905 Air Watts. The 240 volt version has 136.4 waterlift and 190 CFM with a peak of 866 Air Watts. These stats are extremely close. But there is quite a difference in our Silent Master S2. The 120 volt has 85 waterlift and 183 CFM with a peak of 514 Air Watts. It’s 240 volt counterpart has 95 Waterlift and 208 CFM with a peak of 722 Air Watts. That is actually a significant difference. So for the price, the 240 volt S2 is worth the extra power but the S5 is not.

Operating Cost. The cost to operate a 240 volt vacuum unit 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 (not large ones) at the same time. Worst case scenario, the 120 volt version might cost 12 cents per hour additional to operate.

Duration of Life. We personally feel that the 120 volt versions of the vacuum motor will last longer. They contain a higher amount of copper and thus the heat has a greater ability to dissipate. The 120 volt motors are also much easier to find replacements for as they are a common motors in the industry. The 240 volt version motors are not used very often and vacuum shops around the country do not normally stock it. They would first stock the 120 volt motors.

For some homes, they may be close on the maximum amperage for their panel and thus the 240 volt version offers the best benefits. We sell far more 120 volt units because they simply plug into any 20 amp electrical outlets and have plenty of vacuuming power.

What happens when 240 is accidently plugged into 110 and 110 into 240? If you plug a 120 volt unit into a 240 volt circuit and immediately turn the motor(s) on they will run with a tremendous amount of suction. The motors will be spinning almost 40,000 RPM ! If you run it very long the motors may disintigrate. But before that happens, the transformer will likely burn out. This will immediately shut the motor(s) off.

Normally all you need to do is replace the transformer and the system will be as good as new.

If you left the jobsite without testing the vacuum and later found that the new system did not work, then it is likely the electrician powered it up with 240 volts. Just sitting in the off position the unit will burn out the transformer in 3-5 minutes or less.

If you plug a 240 volt unit into 120 volts, it will not run correctly. Good news is the transformer or motor(s) will not be hurt. You will only be running it on half speed. In fact, this is the way you should "break-in" new motor brushes when they are changed out down the road. (Run the unit in at half speed.) Also note that the transformer will not activate the relay unless it has 240 volts.