With the greater distance the air has to travel, central vacuum systems have the biggest disadvantage to overcome to be a good cleaning vacuum. The distance through a 2″ PVC pipe and however many 90 degree elbows is one thing but mostly the 1 1/4″ diameter 30ft hose that is not smooth on the inside nor straight in a line (usually curled up on the floor) is where the greatest airflow is lost. One study measured through a curled up hose versus a hose straight in a line and found that you could lose up to 25% of the airflow. Most central vacuum companies claim in their brochures that they have 2 to 3 times more power than a portable vacuum cleaner. Those claims are hollow words with no substance.
Don’t get me wrong here. You can get one of the most effective cleaning vacuums with a central vacuum system. I have a central vacuum in my own home. In other words, central vacuum systems are not created equal.
The best central vacuums have almost the same CFM (cubic feet per minute of airflow) as suction (normally measured in inches of waterlift). Many central vacuums have high suction but have very low CFM or high CFM and low suction. Airflow is important particularly in carpet cleaning wholesale pipes. You want to move the greatest amount of air through the carpet fibers. For vacuuming hardfloors, suction or lifting the dirt up off the floor is most important. Most homes today have a combination of surfaces and having a motor unit with both powerful suction and high airflow is a necessity. Don’t be fooled by the term Airwatts (a mathematical formula that even includes the amount of electricity used) or a square footage figure that is supposed to tell you the minimum amount of power needed to clean. Have you ever bought any vacuum for the minimum amount of power to clean? I rather doubt it.
Another important feature to look for is the filter system of the motor unit. The best type is a bagged system. With a bagged system, the motor of the central vacuum is on the bottom of the canister. The air is moved through the large surface area of a bag (some are as large as 12 gallon in size). The best thing is that only clean air goes through the motor and motor fans and it does not require venting outside. The motor runs so much cooler when it does not have to vent the air thus extending motor life. Those that are bagless have the motor in the top of the canister claiming that the dirt drops down in the bucket so you do not have to buy bags. However the dirt that you suck up off your floors and furniture is basically weightless and will follow the air through the motor which is up to the top of the unit and then needs to be vented out. This dirt, hair and dust builds up over time on the fans of the motor causing wear on bearings and causes extra heat to the carbon brushes.
Also it is amazing to me that so many of the sales of central vacuum systems come from businesses that are in new construction so a lot of systems are put in by heating and cooling people, closet organizers, music and sound people and others that know nothing about vacuum cleaners and how a vacuum works. Seek out a vacuum professional usually in an independent vacuum store in your area. They can explain why their system works and cleans better and will be there to help if service is ever necessary.