Keeping your HVAC and refrigeration equipment in good running condition requires consistent care. Last month, we reviewed the types of preventative maintenance programs available for your units, and the filters commonly used during PM services. This month, let's talk about belts.

Not all HVAC/R units use belts, but for those larger systems over 5 tons, a well-tuned belt can make all the difference. Belts get old. They crack, loose tension, and can even break during operation. And if belts aren't properly maintained, if they're too loose or too tight, your efficiency starts to drop.  Belts should be checked regularly, and changed out as needed before productivity is lost or breakage occurs.

Know Your Belts.

Most belt driven HVAC systems today utilize V-belts. These tapered belts connect the motor pulley to the blower wheel pulley, powering the blower and pushing air into the duct-work. V-belts come in three styles: fractional horsepower (FHP), classical or narrow. V-belts come in a wide range of sizes for most larger air conditioning systems.

There are also cogged, or synchronous, belts. Used less frequently than V-belts, cogged belts have the potential for better long-term efficiency. Synchronous belts are thinner than a V-belt, reducing friction and eliminating slip by using a toothed grip design. And compared with a V-belt, which runs anywhere between 98% to 83% efficiency depending on maintenance care, cogged belts run at a consistent 98%.

However, cogged belts need to operate in units with enough reinforcement. They are “sensitive to fluctuations in the sheave center-to-center distance that inadequate brackets causes.” They vibrate more than V-belts, and tend to make more noise. Not every HVAC unit has the structural strength to convert to synchronous belts. But you can have your equipment evaluated for the swap over, especially if you want to tap into the potential savings on electrical costs.

Standard V-type Belt.
Cogged, Synchronous, Belt.

Efficiency and Energy Savings.

When you consider that air conditioning, cooling and ventilation make up over 30% of the average commercial building’s electrical usage, unit efficiency becomes crucial. Maintenance plays a major role in determining your fan belts’ efficiency.

A belt that isn’t tensioned properly during a PM can either slip or over-stress the pulley systems. Slippage, caused by loosely tensioned belts, causes wear on both the pulleys and belt. This can wear both parts out prematurely. And an overly tightened belt stresses the drive motor bearings and has a higher chance of breaking during use.

Your units also need the correct size fan belts to operate efficiently. HVAC fan belts are sized by the distance between each pulley and the circumference of the pulleys themselves. Your maintenance technician should have that information recorded after their first visit.

In a critical situation, such as a broken belt on a very hot day, a technician can use an emergency belt in place of a matching size belt. An emergency belt is pricier than standard rubber but can interlock to fit most common sizes. With approval from the customer, technicians can also leave a backup belt in the HVAC units to use in a worst-case scenario.

Worn Drive Pulley.
Broken HVAC Belt.
Emergency Belt for AC Systems.

Direct Drive and the Future of Belts.

Not all HVAC units have belt driven systems. Units under 7.5 tons, and especially under 5 tons, use direct drive fans that are more efficient and require less maintenance. These fans are hooked straight up to the fan shaft, reducing the number of moving parts and chances of random part failure. Without pulleys or belts, a direct drive also makes less noise and vibrates less.

The downside to a direct drive motor is power and speed control. Systems with larger motors can utilize additional belt drives, or even additional motors, to increase capacity. This allows for more complex speed adjustments. Some manufacturers are working on developing larger capacity direct drive motors to work in higher heat assemblies. But for now, bigger HVAC/R units still rely on their belts. And while it may seem frugal to skip regular scheduled belt changes, a new belt could protect your business from unexpected, and likely unpleasant, belt failures in the summer. Take care of your air conditioners, and they'll take care of you.