A 1 1/4 HP belt-driven garage door opener should be more than capable of handling a garage door with a net weight of 48 lbs for the long term, even if the door is slightly unbalanced. Garage door openers are designed with safety margins to accommodate variations in door weights and resistances.
In your case, the garage door opener has a significant amount of power compared to the weight of the door. The 1 1/4 HP (horsepower) rating indicates a robust motor, which should easily handle the lifting and lowering of a 48 lbs door, even if it's slightly unbalanced.
However, it's essential to consider a few factors to ensure smooth and safe operation:
Springs: As you mentioned, the springs off-load most of the weight of the garage door, making it easier for the opener to lift. Make sure the springs are in good condition and properly adjusted to counterbalance the door's weight effectively. If the springs are worn out or improperly adjusted, it could put more strain on the opener and affect its long-term performance.
Opener's Rated Capacity: Check the manufacturer's specifications for the garage door opener to ensure that it is rated to handle the weight of your specific garage door. While a 1 1/4 HP opener should be sufficient for a 48 lbs door, it's always best to confirm with the manufacturer's guidelines.
Balance and Maintenance: Regularly check the balance of your garage door and perform any necessary maintenance to keep it running smoothly. An unbalanced door can cause additional strain on the opener and potentially lead to premature wear.
Safety Features: Ensure the garage door opener has proper safety features, such as infrared sensors or photo eyes, that can detect objects or obstructions in the door's path and automatically reverse the door if necessary.
If you have any doubts about the garage door opener's ability to handle your specific door, it's a good idea to consult with a professional garage door installer or technician. They can assess your door's condition, the opener's compatibility, and make any necessary adjustments or recommendations to ensure safe and efficient operation in the long term.