606.4 Heating, Ventilating and Air-Conditioning (HVAC) Piping Insulation

Piping with a nominal diameter greater than ¹/₄ inch (6.4 mm), including associated valves, fittings and piping system components, in heating, ventilating and air-conditioning (HVAC) systems shall be thermally insulated in accordance with Table 606.4. For insulation outside of the conductivity ranges specified in Table 606.4, the minimum thickness of the insulation shall be determined in accordance with Equation 6-4.

T = r [(1 + t/r)K/k - 1]

(Equation 6-4)

T	=	minimum insulation thickness (inches).
r	=	actual outside radius of pipe (inches).
t	=	insulation thickness specified in Table 606.4 for applicable fluid temperature and pipe size.
K	=	Conductivity of alternate material at mean rating temperature indicated for the applicable fluid temperature (Btu × in/h × ft2 × °F).
k	=	the upper value of the conductivity range specified in Table 606.4 for the applicable fluid temperature.

1. Factory-installed piping within HVAC equipment tested and rated in accordance with Section 606.2.
2. Piping conveying fluids having a design operating temperature range between 60°F (15.6°C) and 105°F (40.6°C).
3. Piping conveying fluids not heated or cooled such as roof and condensate drains, cold water supply, and natural gas piping.
4. Where heat gain or heat loss will not increase energy usage such as liquid refrigerant piping.
5. Piping having an outside diameter of 1 inch (25 mm) or less, associated with strainers, control valves, and balancing valves.

1. The proportions apply to all nominal pipe diameters greater than ¹/₄ inch and less than or equal to 2 inches. For nominal pipe diameters larger than 2 inches, outside diameter, the minimum wall thickness of the insulation shall be equal to the wall thickness required for 2-inch pipe.
2. These thicknesses are based on energy-efficiency considerations only.