How to Replace the Heat Exchanger in an Indirect Water Heater

Heat Exchanger Operation

• Heat exchangers are designed to move heat efficiently from one place to another. Made of metal alloys, the heat exchanger of an indirect water heater not only keeps the combustion chamber separate from the water in the closed loop, but its fins and broad surfaces allow thermal energy to easily pass through. While they are made to be durable, heat exchangers can develop cracks or flaws over time, which may leak or endanger the burner if not fixed.

Preparation

• Begin by carefully labeling all connecting wires and tubing so you know where they go. Turn off the gas line with an external shut off valve, and make sure the electricity going to the furnace is also shut down. Shut down the water supply, and consult your manual to see if you need to drain the closed loop or boiler tank. Remove the furnace doors, and turn the inner gas valve (if present) off. This will keep you safe when you start to disassemble the burner. Keep a wrench, screwdrivers and pliers handy to disconnect attachments.

Removal

• The heat exchanger is typically buried underneath a number of other components. You may find trap and pressure switches, collector boxes, inducer assemblies and even second heat exchangers in your way. These are connected with fasteners and screws, which are relatively easy to take off but still need to be handled carefully. Remove components one at a time and lay them out on sheets in the precise order you disconnected them. Clean away any gasket residue and oils as you work.

Installation

• Once it is unscrewed from the tank and the looped water pipes, the primary heat exchanger should slide out. You may need to remove cell panels or covers and attach them to the new exchanger before sliding the new version into place. After the replacement, return all components in reverse order. Here is where your layout and wire-labeling become very important, because you must use all the proper gaskets and screws to complete the installation. Once the new exchanger is installed, you can turn your power supply back on.