Counterweight System

A counterweight system is a door balancing method that replaces springs with physical mass. Heavy steel or cast-iron weights hang on cables that run over pulleys and connect to the door. As the door rises, the weights descend, pulling against the door's weight through the pulley system. As the door closes, the weights rise again, storing energy for the next opening cycle.

This is the same principle used in old-fashioned double-hung windows and in freight elevators. The counterweight does not store energy by deforming a spring. It stores potential energy by lifting mass against gravity.

Why counterweights instead of springs:

Springs are the right choice for most residential and commercial sectional doors because they are compact and efficient. Counterweights become practical when a door is too heavy for available spring hardware, when extreme cycle life is needed with minimal maintenance, or when the application makes spring replacement difficult or dangerous.

Industrial freight doors, foundry doors, and some high-clearance parking garage doors use counterweight systems. The weights are sized to match roughly 90-95 percent of the door weight, leaving just enough imbalance for the door to stay closed by gravity and for a motor or chain hoist to close it completely.

For example, a solid steel blast-containment door weighing 2,000 pounds cannot use conventional torsion springs. A counterweight system with 1,850 pounds of hanging steel makes the door manageable by a small motor.

The counterbalance system on a standard sectional garage door uses torsion springs instead of weights. Springs are smaller, lighter, and easier to service. Counterweights are the rare alternative for applications that springs cannot handle.