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An automatic thermostatically operating control device that controls the supply hydronic solution temperature to the snow melt area shall be installed in the system. A means shall be provided to prevent low return hydronic solution temperature, as specified in Section 1213.5. Snow melt auxiliary systems shall be protected from freezing with an approved hydronic solution. The circulating heat transfer fluid shall be a mixture of propylene glycol or ethylene glycol, and water. Automotive antifreeze shall not be used.
1220.3.1 Tube Placement
Snow melt tubing shall be installed in accordance with the manufacturer's installation instructions and with the tubing layout and spacing as specified in the system design. Except for distribution mains, tube spacing that is shown in the design as center-to-center and the individual loop lengths shall be installed with a variance of not more than ±10 percent from the design.

    The length of continuous tubing from a supply-and-return manifold arrangement shall not exceed the lengths specified by the manufacturer's installation instructions and system design or, in the absence of manufacturer's specifications, the lengths specified in Table 1220.3.1. Actual loop lengths shall be determined by spacing, flow rate, temperature, and pressure drop, as specified in the system design.

TABLE 1220.3.1
LOOP LENGTHS FOR SNOW MELT SYSTEMS1,2
SIZE
(inches)
AVERAGE ACTIVE LOOP
(feet)
TOTAL LOOP
(feet)
PE-RT and PEX Tubing
5/8 225 250
3/4 300 325
1 450 475
Copper Tubing3
1/2 - 140
3/4 - 280
For SI units: 1 inch = 25.4 mm, 1 foot = 304.8 mm

Notes:
1   The total PE-RT and PEX loop lengths consist of two separate sections, the active loop and the leader length. The active loop is installed within the heated slab. The leader length is the total distance to and from the manifold and heated slab, including any vertical distances.
2   The manifolds shall be installed as close to the snow melt area as possible.
3   In concrete use minimum Type L copper water tubing. In bituminous pavement use a Type K copper water tubing.
1220.3.2 Poured Concrete Slab Systems (Thermal Mass)
Where tubes are embedded in a concrete slab, such tubes shall not be larger in outside dimension than one-third of the overall thickness of the slab and shall be spaced not less than three diameters on center. The top of the tubing shall be embedded in the slab not less than 2 inches (51 mm) below the surface.
1220.3.3 Slab Penetration Tube and Joint Protection
Where embedded in or installed under a concrete slab, tubing shall be protected from damage at penetrations of the slab with a protective pipe sleeve. The space between the tubing and sleeve shall be sealed. The tubing at the location of a joint in a concrete slab shall be encased in a protective pipe sleeve that covers the tubing not less than 12 inches (305 mm) on either side of the joint or the tubing shall be installed below the slab.
1220.3.4 Concrete Slab Preparation
A solid foundation shall be prepared before the tubing is installed. Compaction shall be used for slabs, sidewalks, and driveways.
1220.3.5 Insulation
Where a poured concrete snow melt system is installed in contact with the soil, insulation that has a R-5 value shall be placed between the concrete and the compacted grade; extend as close as practical to the outside edges of the concrete; and be placed on vertical slab edges that are in contact with plants or landscaping.
1220.3.6 Testing
Testing of auxiliary systems shall be in accordance with Section 1205.2.