Residential Double-Wall Indirect Water Heaters

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Figure Number: Indirect Water Heaters

Product Function

Niles Steel Tank has many indirect water heaters to choose. All provide superior heat transfer capabilities when used with a boiler or other hydronic heating source such as a heat pump or solar. Our internal coils are designed for low pressure drops and high heat transfer capabilities, which make our indirect water heaters the most efficient on the market. Niles Steel Tank offers, single wall and double wall internal coils, residential and commercial products and stainless steel for areas where aggressive water is present. Choosing the correct indirect water heater for your application is easy. Refer to the list of specifications from the list on the left to help you decide which indirect water heater is right for you.

Model_Number Capacity A.
Floor to Heater Top
Jacket Diameter
Floor to T&P Conn.
Floor to Water Conn.
Floor to Floor to Boiler Return
Floor to Boiler Supply
Floor to Thermostat
Aprox. Shp. Wt.
U.S.Gal. in. in. in. in. in. in. in. lbs.
NDW-2-40L 38 41 22 34 3/4 41 7/8 5 3/8 27 1/2 11 1/2 195
NDW-2-50L 48 46 1/4 22 40 1/4 47 14 5 3/8 27 1/2 11 1/2 205
NDW-2-65L 64 59 22 53 1/8 60 5 3/8 27 1/2 11 1/2 235
NDW-2-80L 75 59 24 52 7/8 59 3/4 5 3/8 27 1/2 11 1/2 255

Regularly Furnished

Heat Exchanger-Double wall 1½” O.D. glass coated (Ultonium®) steel coil. The positive leak path between the two walls of the coil ensures the potable water will stay separate from the hydronic fluid. Low Heat Exchanger Head Loss-Up to 10 GPM flow, with less than 5 ft. of head loss. Greatly reduces the required pump size for heat exchange. Factory Installed Sparge Tube System-Cold water inlet sediment reducing device helps to minimize sediment build up in tank. Increases first hour delivery of hot water while minimizing temperature build up in tank. Ultonium® Lining-Niles Steel Tank water heater tanks are protected from the corrosive effects of hot water by an exclusive ceramic porcelain-like coating. The Niles Steel Tank high silica Ultonium® lining provides a tough interior surface for our hot water tanks. Fully Automatic Controls-Fast acting surface-mount thermostat for automatic temperature control. Supply and Return Connections-The 3/4″ NPT female connections are located on the front for both the boiler supply and boiler return. 2″ Non-CFC Foam Insulation-Covers the sides and top of tank to save energy by retarding loss of heat. Also increases jacket rigidity. Water Connections-3/4″ NPT factory installed true dielectric fittings extend water heater life and eases installation. Two Protective Aluminum Rods-Provide added protection against corrosion for long trouble-free service. Stand-by Heat Loss-Less than 1/2°F per hour (ASHRAE 90.1b current standard). Steel Tank-Heavy gauge steel automatically formed, rolled and welded to assure a continuous seam for glass lining. T&P Relief Valve Included-All models feature opening on side of tank. Brass Drain Valve. I=B=R Certified-These water heaters are rated by the Institute of Boiler and Radiation Manufacturers (I=B=R) to provide accurate performance data within the standards of the certification. The I=B=R rating is issued by the Hydronics Institute Division of GAMA and provides a recognized standard for proper comparison of hydronic appliances.

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