Rheem 305, 505, 705 Error LC: Scale Build-up in Heat Exchanger (when checking maintenance code history, "00" is substituted for "LC")

Tankless water heater · taken from the manufacturer’s manual, pages cited

Fault codeLC

Scale Build-up in Heat Exchanger indicates lime buildup that requires flushing to prevent damage. The manual's first action is: “Refer to instructions in manual.”

Model
Rheem 305, 505, 705
Display shows
LC
Type
Fault code
Source
Manual p. 10

What LC means

Scale Build-up in Heat Exchanger (when checking maintenance code history, "00" is substituted for "LC") p. 10

Common causes

  • Flush heat exchanger. p. 10
  • Replace heat exchanger. p. 10
  • The unit is beginning to lime up. p. 10

What to do

  1. Refer to instructions in manual. p. 10
  2. Failure to flush the appliance will cause damage to the heat exchanger. Damage caused by lime build-up is not covered by the unit's warranty. p. 10
  3. After flushing, reset the LC fault code by turning off the power to the unit and turning the power back on. p. 10

Before you service the product, read the safety instructions in the manual p. 4.

If LC is still not resolved

  • Immediately call your gas supplier from a neighbor’s phone. p. 1
    “Immediately call your gas supp lier from a neighbor’s phone.”
  • If you cannot reach your gas supplier, call the fire department. p. 1
    “If you cannot reach your gas supplier, call the fire department.”
Open the manual at page 10 All 305, 505, 705 error codes Manual details & download

This page summarises what the manufacturer’s manual says about LC; each statement links to the page it comes from, and quoted lines are copied word for word. It is not a substitute for the manual or for a qualified installer. ManualLib is not affiliated with Rheem. Found a mistake? Report an error.