HVACopedia

Noritz · Tankless water heater troubleshooting

Heat exchanger replacement - Noritz NRC111 / NCC199

What is going on

Service procedure for replacing the stainless (secondary) and/or copper (primary) heat exchanger on NRC111 and NCC199 (N-0841MC / N-0842MC) units. For qualified service technicians only.

Likely causes

  • Leaking or failed heat exchanger

Check in this order

  1. Warning: Disconnect power, turn off gas and water, remove the inlet filter and drain the unit fully (open the bottom drain ports).
  2. Remove the front cover (4 screws), let the GFCI plate and circuit board hang out (remove ground wire, loosen the wire anchor).
  3. Remove the gas valve assembly C-clamp at the inlet, push the pipe up, unplug the manifold harness, remove 4 silver manifold screws.
  4. Unplug fan, thermal fuses, freeze heaters/sensors, neutralizer sensor, high limit, flame rods and ignition box; remove the neutralizer (3 spring clamps) and internal water pipes and 1/4 in. drain pipe.
  5. Remove the flue (4 screws), then the 2 burner set screws and upper set screws; lift out SS HE, CU HE, burner and fan as one assembly.
  6. Separate SS HE from CU HE (2 bracket screws, connecting pipe C-clamps, 9 rear screws); for the CU HE remove the 12 burner screws.
  7. Move freeze heaters, freeze sensor, high limit switch and thermal fuses to the new heat exchanger; replace the burner gasket, check the SS-CU gasket and fit new o-rings.
  8. Reassemble in reverse 12 burner screws, 9 SS HE screws, pipes fully inserted before the C-clamps, hooks into the case notches, neutralizer on its 3 key holes.
  9. Refit filter, close drains, open water slowly and check every C-clamp for leaks; turn on gas and leak test; refit cover and restore power.

Applies to: Noritz NRC111-SV/DV, NCC199-SV/DV, N-0841MC(-DV), N-0842MC(-DV)

More tankless water heater guides

Related

Noritz error codes · Noritz tips · Calculators and reference tables

Take it to the job

All guides, error codes and tips work offline in the HVACopedia app.

Open the app

Source: Noritz NRC111/NCC199 Heat Exchanger Replacement (N-0841MC/N-0842MC), p.1-17. Written in our own words; check the manual for your exact model.

For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.