If you’re DC motor garage door opener seems weak, either your door is too heavy or the springs are past half their life. Be prepared to shell out some dough.
If you’ve been in the market for a garage door opener in the past 5 years or so, you may have noticed the switch from AC motors to DC motors. Manufacturers like Chamberlain (Liftmaster/Craftsman) market the DC motor openers as “Ultra-Quiet” versus just “Quiet” of the old.
The 2018 California SB 969 mandates that new garage door openers are available with battery backup – that necessitates the motors to work on DC power off of a battery. The rest of the country gets to enjoy the benefits and pitfalls of this new device at their own leisure.
Yes, DC motors are quiet, especially if they are paired with a belt drive instead of the traditional chain drive mechanism. No clanking, no buzzing, no thunk at the start and end of the cycle. The AC/DC inverter (transformer) quietly supplies constant steady power to the drive system.
But because it doesn’t draw its power directly from the house’s AC circuit, it will not answer to demand. That means, if the the springs on the door gets old and weak, you’ll notice the door slow down. If you’re an installer, you’ll also find out the hard way that the motor will not be able to assist you when lifting the door under a broken spring.
This is not because the motor itself is weak. It is because the motor is not allowed to draw more current from the house because there’s a DC inverter playing gatekeeper. It is in theory a safety mechanism that prevents problematic doors from being lifted and then falling on a person. The controller board should register an error and cease to function until the problem is remedied.
Unfortunately there is an unintended effect. In case of a broken spring, the door will move a smidge under extreme load and damage the motor control unit – not the physical motor, but a small gearbox and circuit board attached to the motor.
In an effort to make safer more quieter garage door openers, manufacturers have complicated the design of these units and made it more difficult to diagnose and fix. Fortunately, we have the internet, so we can sit at a desk and search instead of tinkering with the greasy innards of the garage door motor.
The easiest solution for manufacturers would probably be to increase the motor current to 24V and put two 12V batteries in there…