Arkansas HVACR NewsMagazine May 2024

HVACR NewsMagazine May 2024

Tech News

available at the return before adding paths from rooms and areas with additional grilles.

Modulating Dampers

Opinions have differed over the years on zoning and controls for air flow. In recent history zoning single speed condensers has become increasingly scrutinized. Not because it has always been wrong, but because multi speed or inverter driven equipment is available and no one wanted to step on the zoning market ’ s toes. Delivering variable amounts of air across an evaporator supplied by a single speed compressor has always been risky at best, and downright destructive when air flow was cut more than 20%. Lennox engineers was aware of the fact, so they pushed the true two speed compressor on the market back in the 1980’s. In the meantime, the industry tried many ways to offer zoning. This included dump zones and barometric bypass systems. We saw freeze stats and other auxiliary controls to get around the laws of physics. Many engineers, including John Proctor, of Proctor Engineering Group have an unfavorable view on zoning. Particularly zoning with barometric bypasses. In today’s market, we have multispeed and variable speed compressors that make zoning much easier and without risk of damage to the mechanical systems when administered correctly.

Using this option makes it easier for contractors to identify and customers to understand. This method sets sensible expectations where filter life is concerned. Keep in mind these grille sizes keep static pressure down only when deeply pleated filters like April Aire or similar pleated filters are present. Every filter grille or service point on a system means there are opportunities for air leakage. Additional filters means additional costs for replacement. Washable filters are generally poor filters and points for biological growth to occur over and over. 300 fpm is the face velocity criteria established by a number of authorities to keep noise low and deep pleated filters happy on the static pressure side. This face velocity is important when making blowers perform efficiently. As a final point on understanding adequate air flow, remote returns, undercut doors, and wall transfers never add supply to the system if sizing to the blower compartment is restricted. Make sure the cardboard cutout equivalent is