C408.2.2 Air Distribution System Testing, Adjusting and Balancing
Construction documents shall require that a written balance report be provided to the owner or the designated representative of the building owner for HVAC systems serving zones with a total conditioned area exceeding 5000 square feet (465 m2). Air distribution systems shall be tested, adjusted and balanced by a licensed engineer or a company or individual holding a current certification from a recognized testing and balancing agency organization in accordance with generally accepted engineering standards.
- Buildings with cooling or heating system capacities of 15 tons or less per system may be tested and balanced by a mechanical contractor licensed to design and install such system(s).
- Buildings with cooling or heating system capacities of 65,000 Btu/h or less per system are exempt from the requirements of this section.
Air system balancing shall be accomplished in a manner to first minimize throttling losses; then for fans with fan system power greater than 1 hp, fan speeds shall be adjusted to meet design flow conditions. Balancing procedures shall be in accordance with the National Environmental Balancing Bureau (NEBB) Procedural Standards, the Associated Air Balance Council (AABC) National Standards, or equivalent procedures.
Exception: Damper throttling may be used for air system balancing with fan motors of 1 hp or less, or if throttling results in no greater than 1/3 hp fan horsepower draw above that required if the fan speed were adjusted.
- Building envelope pressurization should be either neutral or positive to prevent infiltration of excess latent load.
- Commercial kitchen hood exhaust cfm should be sized to prevent depressurization. Discharge dampers are prohibited on constant volume fans and variable volume fans with motors 10 hp (7.5 kW) and larger.
Individual hydronic heating and cooling coils shall be equipped with means for balancing and measuring flow. Hydronic systems shall be proportionately balanced in a manner to first minimize throttling losses, then the pump impeller shall be trimmed or pump speed shall be adjusted to meet design flow conditions. Each hydronic system shall have either the capability to measure pressure across the pump, or test ports at each side of each pump.