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Heat Transfer Plates
HRTP3 Heat Transfer Plates are used in Sub-Floor HRH systems to enhance the general system performance by decreasing the time to heat the floor.
For 16 floor joist spacing, two runs of tubing are installed on 8 centers. With this set-up, the plates are positioned approx. 1 - 1/8 from the edge of the joists with 3 3/4 side-space between the plates.
Position the heat transfer plates approx. 12 from the ends of the joist cavity to allow for the tubing to loop back into the next plate, and leave a 4 ,or less, end gap between the plates.
We use the following general formula for determining how many heat transfer plates to use for a heated area:
Square Footage x .7 OR
Linear footage of tubing x .44
A 28' x 24' room = 672 sq ft: 672 x .7 = 470 plates
A 28' x 24' room = 1068 ln feet of tubing (based on 8" tubing spacing, 672 x 1.5): 1068 x .44 = 470 plates
This formula generally works out pretty well considering a 4" gap between plates and the plates stopping 12" from the end of the joist cavity.
If you want to figure the exact number of plates for your project (assuming 12" end space and a 4" gap between plates), subtract 2' from the linear footage of the joist cavity, then divide that number by 2' (which is the 20" length of the plate, plus a 4" gap between plates, 20" + 4" = 24" divided by 12), then round down and multiply by 2 (assuming 2 tubing runs per joist cavity). For example, a 28' x 24' room with 28' joist cavities: 28' - 2' = 26'; 26'/2' = 13 (no rounding required); 13 x 2 = 26 plates per joist cavity. Then, 24' x 12" = 288"; 288" / 16" joist spacing = 18 joist cavities. 26 plates per joist cavity x 18 joist cavities = 468 plates.
Please note that these formulas and examples do not take into consideration 'dead areas' within the heated area that plates are not used (under cabinets, tubs, showers, interior closets, etc), and the amount of tubing leaders where plates are not installed (the tubing between the heated area and the manifolds). Generally, these 'dead areas' and leaders require a 15 to 30 percent reduction in the number of plates used, but may be more or less depending on your specific application.