Residential Double-Wall Indirect Water Heaters

  • NDW-2-50-LHeat 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.
  • Limited Lifetime Warranty on tank and heat exchanger.
  • 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.

Residential Double Wall Indirect

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