HVAC Installations

Permit Requirements
When installing or replacing heating, air conditioning or air handling equipment or appliances, regardless of cost, a permit is required.

Examples of projects that would require a permit include:

• New or replacement furnace
• New or replacement air conditioner
• New or replacement air handling or treatment device (i.e. energy recovery ventilator, humidifier or de-humidifier equipment)
• Outdoor heating devices

Balancing Dampers
There has been some ongoing discussion regarding the requirements of balancing dampers in HVAC supply systems. Wisconsin Uniform Dwelling Code (UDC) Section 23.09(1) states “Volume duct dampers shall be provided to permit balancing of the system.” The Code Commentary goes on to state “Register dampers do not satisfy the requirement for volume duct dampers due to their looseness. If duct volume dampers will be concealed behind finish materials, access panels shall be provided to allow future adjustment. Alternatively, dampers may be placed behind registers, which could be removed for future access to the dampers.”

System Testing & Balancing
All HVAC systems are required to be balanced in accordance with the Wisconsin Uniform Dwelling Code (UDC) Section 23.18(2). City policy requires an affidavit of testing and balancing form to be completed by the installing HVAC contractor and submitted to the City prior to a final inspection.

Make-Up Air
All HVAC systems are required to provide a maximum of 40% of the total air that would be exhausted with all exhaust ventilation in the dwelling acting simultaneously in accordance with the Wisconsin Uniform Dwelling Code (UDC) Section 23.02(3)(a)(4). The following chart taken from the UDC Code Commentary can be used to determine the proper size ducting for make up air.

Commentary 23.07 - Duct Velocities
Per the below example, the minimum duct velocity is 500 feet per minute and maximum allowable is 800 feet per minute.

Example
Determine size of make-up air duct required for these exhaust systems.

• Range hood = 180 cubic feet per minute (CFM) (intermittent) x 40% = 72 CFM
• Bath exhaust 1 = 50 CFM (intermittent) x 40% = 20 CFM
• Bath exhaust 2 = 75 CFM (intermittent) x 40% = 30 CFM
• TOTAL 305 CFM (intermittent) x 40% = 122 CFM

Based on the Formula of Quantity = Velocity x Area (Q=VA). Therefore:

• A = Q / V, or A = 122 / 800, or A =.1525 square feet x 144 = 21.96 square inches (required)
• Try 4 inch round duct = 3.14 x radius squared = 3.14 x 2 x 2 = 12.56 square inches (too small)
• Try 6 inch round duct = 3.14 x radius squared = 3.14 x 3 x 3 = 28.26 square inches (acceptable, since > 21.96)

Not doing the calculation described above to appropriately size the air intake may result in an oversize intake and cause the problems noted above. Note: System should be tested per 23.18 to make sure the design amounts of air are actually provided when the system operates.