MERV vs. Motors

ECM expert Chris Mohalley joins the podcast to talk about the balance between selecting air filtration and motor performance, also known as “MERV vs. Motors.”

As the industry realizes that filtration is more important, we're starting to see an interest in filters with MERV ratings of 13 or higher. However, there are some design challenges associated with static pressure drops across filters, motor responses to static pressure, and airflow. If the airflow isn't set properly, that could affect the refrigerant charge and temperature rise.

PSC motors' performance directly follows the load; as static pressure increases, the airflow rate produced by the motor decreases. They may also make loud noises when the static pressure is high but satisfactory airflow. However, they are robust and don't typically fail quickly due to high static pressure.

Electrically commutated motors (ECMs) are operated by electronic controls and come in constant torque or constant airflow varieties. The former has a performance curve (like a PSC motor) but doesn't appear to suffer from longevity issues when the static pressure is high; the latter can adjust airflow based on static pressure, but it is likely to have issues maintaining airflow during high static pressure conditions. Regardless, there is still an operational envelope; going outside of that envelope will likely result in a capacity and/or efficiency hit if there is high static pressure.

Chris and Bryan also discuss:

COVID-19 pandemic and the evolution of filtration
Face velocity across filters
Amps in constant torque vs constant airflow motors
Swings in airflow/performance
Educating the customer about “upgrading” filters
Using performance manuals

Learn more about Regal Rexnord's training at https://regal.mmu.com.

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In this short podcast episode, Bryan talks about the CPS Molecular Transformator and what it does.

The Molecular Transformator is a version of a tube-in-shell heat exchanger, which is a method of exchanging heat from one fluid medium to another fluid medium. Tubes containing a fluid pass through a shell containing water or glycol, and there is a heat exchange between that secondary fluid and the fluid being circulated in the tubes. In a Molecular Transformator, the fluid being circulated is recovered refrigerant, and the secondary fluid is water (in a bucket), which absorbs heat from the refrigerant and cools it down to make sure that the refrigerant enters the recovery tank as a liquid.

Refrigerant recovery machines have condensers inside of them, but they are quite small and don’t hold a lot of refrigerant by design; many recovery machines use microchannel coils. A lot of the time, the refrigerant leaving a recovery machine is a liquid-vapor mix and too high-temperature; a lot of people run a hose over the tank or put it in a bucket of ice. The “Molecular Transformator” tries to settle the vapor molecules down into a liquid; it transforms the vapor molecules using the same mechanism as a tube-in-shell heat exchanger.

The main issue is that there will be leftover refrigerant in the Molecular Transformator after recovery. However, you can mitigate this problem with ball valves and proper purging. Do so responsibly to avoid venting refrigerant.

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