C408.2.2 Systems Adjusting and Balancing
Each supply air outlet and zone terminal device shall be equipped with means for air balancing in accordance with the requirements of Chapter 6 of the International Mechanical Code. Discharge dampers used for air-system balancing are prohibited on constant-volume fans and variable volume fans with motors 10 hp (18.6 kW) and larger. Air systems shall be balanced in a manner to first minimize throttling losses then, for fans with system power of greater than 1 hp (0.746 kW), fan speed shall be adjusted to meet design flow conditions.
Exception: Fans with fan motors of 1 hp (0.74 kW) or less are not required to be provided with a means for air balancing.
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.
Exception: The following equipment is not required to be equipped with a means for balancing or measuring flow
- Pumps with pump motors of 5 hp (3.7 kW) or less.
- Where throttling results in not greater than 5 percent of the nameplate horsepower draw above that required if the impeller were trimmed.