RESIDENTIAL DOMESTIC WATER HEATING:
Maximum delivered water temperature must be 120°F or less. An anti-scald valve is required by most codes on the discharge of the water heater. Maintain the water heater at 140°F or higher to kill bacteria and virus.
Normal Family of 4, Modest Size House Larger Family in Larger House 40,000 BTUH recovery rate 75,000 BTUH recovery rate 50 to 75 gallon water heater 100 to 120 gallon water heater
HOT TUB HEATING:
Small (7’ to 10’ square x 4’ deep) insulated outdoor ho t tubes with an insulated cover generally require only 2,000 to 2,500 BTUH to maintain temperature when the tub is covered at outdoor temperatures of – 20°F. It is assumed that the hot tub is used for brief periods (say 1 to 2 hours per day) during which time the evaporative cooling of the water’s surface is the primary heat loss and may equal 6,000 to 9,000 BTUH. Any heat exchanger used to heat a hot tub should be sized for this larger value.
RADIANT FLOOR HEATING:
Normal temperature drop is 10°F to 20°F per tube length. Try not to exceed a floor surface temperature of 85°F (comfort and finish materials limitations). Always insulate beneath a radiant floor system whether on or above grade. 2” of blue, pink, green or yellow board (not white bead board or polyurethane) is strongly recommend for slab on grade concrete slabs and R13 is the minimum recommended for upper level wood floors.
Maximum Length of Individual Tube Run
Typical Maximum Number of Tubes per Manifold
Maximum Flow
1/2” PEX Tubing 5/8” PEX Tubing
0.575 gpm
300 ft 450 ft
8
1 gpm
12
GARN® recommends the use of oxygen-barried, PEX-a tubing. For more information visit: www.mrpexsystems.com www.uponor-usa.com www.comfortprosystems.com
OXYGEN-BARRIED PEX-A TUBING IS NECESSARY IN ORDER TO MINIMIZE THE POTENTIAL FOR CORROSION.
7
Hydronic System Design Manual ©DECTRA CORPORATION - March 2013
Made with FlippingBook - professional solution for displaying marketing and sales documents online