Rinnai RL non-condensing tankless (RL75i/e, RL94i/e): quick sheet (diagnostic and electrical side)

Covers: RL75iN/iP, RL94iN/iP (indoor) and e (outdoor) versions; RLX94 is a Wi-Fi variant. Different from the V-series sheet.

Single sourceBrands: Rinnai3 components

Non-condensing tankless (UEF 0.81) with up to 180,000 (RL75) or 199,000 Btu/h (RL94), 3/4-in water connections, 20-150 psi. Freeze protection depends on power.

Safety first

Gas appliance: smell gas = stop, no switches or flames, leave and call the gas utility.
Gas valve, gas pressure, burner, orifice, gas line and venting changes are for a licensed gas technician only. This sheet covers inspection, codes, water side and the low-voltage / 120 V electrical side.
Venting problems (spillage, CO alarm, condensate backing up) are a shut-down-and-refer item.
Turn off power and gas and let the unit cool before opening the cabinet.

How it works

Flow-activated ignition with modulating gas valve.

Outdoor units rely on electric freeze-protection heaters.

Components & tests

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Official manufacturer documentation

Always confirm values against the tech sheet for the exact model.

OnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work. © 2026 OnCall Tech. Original content; not a reproduction of any manufacturer document.Generic part photos (not of this brand): Two wall-mounted tankless water heaters with expansion tanks on an exterior wall by Downtowngal, CC BY-SA 4.0

Diagnostic guides for this appliance

Guide · Water Heater

Heat-pump (hybrid) water heater: slow recovery, noise, errors

Hybrids need enough room air and a clean air filter, a working condensate drain and the right mode. Many complaints are mode settings or a dirty filter. Refrigerant faults are sealed-system work.

5 steps ~60 minmoderate

Guide · Water Heater

Tankless water heater descaling (flush)

Scale insulates the heat exchanger, causing overheat codes and fluctuating temperature. Flush with a pump and descaling solution through the isolation valves.

5 steps ~75 mineasy

Guide · Water Heater

Hot water recirculation pump problems

Check timer/settings, check valves, air in the loop and the pump itself. On tankless units with built-in pumps, a recirculation code may point to air or a leak in the loop.

5 steps ~60 minmoderate

Other water heaters manuals

Manual · Water Heater

Water heater brand families: A.O. Smith (State, American, Reliance, Lochinvar), Rheem (Ruud, Richmond, GE older), Bradford White (Jetglas) and store brands

US residential tank (gas and electric) water heaters under maker, sister and store brands, ~1998-2026; how to identify the builder from the rating plate.

2 components2 common failuresA.O. Smith, State, American, Reliance, U.S. Craftmaster, Lochinvar, Whirlpool, Kenmore, Rheem, Ruud, Richmond, GE, Bradford White, Jetglas

Manual · Water Heater

Rheem / Ruud / Richmond atmospheric gas tank with electronic thermopile control: quick sheet (diagnostic and electrical side)

Residential atmospheric-vent, standing-pilot gas tanks (Performance, Performance Plus, Professional Classic and the Ruud/Richmond equivalents, typically XG-prefix model numbers) built with the Guardian-style FVIR combustion chamber and a self-powered electronic gas control (White-Rodgers or Honeywell, depending on year). Power-vent and condensing Rheem tanks use different controls and are not covered here. Gas-side work (gas control, pilot, burner, thermopile replacement, venting) is diagnosis-and-refer only.

10 components8 common failuresRheem, Ruud, Richmond

Manual · Water Heater

A.O. Smith ProLine / Signature and State atmospheric gas tanks: quick sheet (diagnostic and electrical side)

Residential atmospheric-vent, standing-pilot FVIR gas tanks: A.O. Smith ProLine (plumber channel, e.g. GCR and GCG families), A.O. Smith Signature (sold at Lowe's) and comparable State models, with a thermopile-powered electronic gas control and status LED (Honeywell-type control on most current units). Power-vent, direct-vent and condensing models are excluded.

8 components7 common failuresA.O. Smith, State