Residential Double-Wall Indirect Water Heaters

Designed to give homeowners efficiency and peace-of-mind, our double-wall indirect water heaters come with a limited lifetime warranty on the tank and heat exchanger.
Standard features:
  • 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 water while minimizing temperature build up in tank.
  • Ultonium® Glass Lining with Microban® – Applied to the interior surface of the steel for superior protection against corrosion. Microban® antimicrobial technology helps prevent the growth of bacteria, mold and mildew on the surface of the tank lining.
  • 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 Water Heater Diagram

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-2-80L 75 59 24 52 7/8 59 3/4 5 3/8 27 1/2 11 1/2 255