Rinnai · Tankless water heater

FH Forced high-fire combustion

Normal status KCM (RUCS/RUS)

What the display is showing

Forced High combustion. Seen only during the gas pressure setting procedure that is done after certain components are replaced. Not part of normal use.

Applies to: Rinnai KCM tankless (RUCS65i/75i, RUS65e/75e) status monitor

Settings for these units

RSC supply connection sizes · SENSEI
RSC water quality limits · SENSEI
RSC clearances to combustibles · SENSEI
RSC temperature settings available · SENSEI
RX supply connection sizes · SENSEI RX/CX
RX water quality limits · SENSEI RX/CX

Other codes on the same units

(blank) Status monitor: standby
-- Status monitor: power just connected
Diag history Maintenance code history viewer (last 9 codes)
FL Forced low-fire combustion
LOC Controller locked (KCM)
Maint monitor KCM maintenance monitor (flow and outlet temperature)
Mute Controller key beeps on/off
ON Hot water running (controller installed)

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Source: Rinnai KCM Series Manual (U328-0700X04), Diagnostic Information (status monitor) p.56. Summarized in our own words; check the original manual for your 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.