Rinnai Error Code 10

What the code is telling you

A tankless burner needs a steady flow of fresh air in and exhaust out. The combustion fan does that work, and the controller watches whether it's getting the airflow it expects. When it isn't, you get a Rinnai code 10 and cold water.

The neighbors help narrow it down. Rinnai lists code 11 as "No Ignition" and code 12 as "Flame Failure". A unit that throws a code 10 alongside those may have an air problem that's also stopping the burner from lighting or staying lit. Write down every code you see.

The usual causes

Rinnai's code 10 checklist covers venting first, then the fan:

• A blocked vent or intake. Rinnai's list starts with obstructions at the flue inlet or exhaust, and snow, leaves and nests are the usual ones.
• Water, condensation or debris in the vent pipe.
• A condensate line that isn't draining. Rinnai's troubleshooting guide puts this at the top of its code 10 list. Condensing models make water, and if it backs up, airflow suffers.
• A dirty inlet air filter. Rinnai's guide says to clean the inlet air filter under the front cover, in the top right of the cabinet.
• A vent run that's too long or built wrong. Rinnai checks that the vent is within the allowable equivalent vent length, uses approved materials and has properly seated joints.
• A crushed wall penetration. Rinnai's guide even checks that foam sealant hasn't collapsed the pipe where it passes through the wall.
• Terminal clearance problems. Vent caps too close to each other, to grade, an overhang or another obstruction.
• Fan, settings or board. A fan wheel full of debris, a stuck check valve, a wrong altitude or dip switch setting, or a failed fan motor or control board.

Safe checks you can do

1. Go outside and look at the vent and intake terminals. Clear snow, ice, leaves, cobwebs or a shrub that's grown over them. Don't reach into the pipe.
2. Look for damage. A cap knocked loose, a pipe pulled out of a joint, or a sag where water can sit are all things to tell the tech.
3. Check the condensate drain line on condensing models. It should run downhill to a drain or pump with no kinks, ice or caps, and the pump, if you have one, should be plugged in and working.
4. Think about recent changes. New siding, a deck, a fence or landscaping near the vent can put the terminal too close to an obstruction.
5. Reset once. Turn the heater off at the controller, turn it back on and open a hot tap. If the code clears and stays clear, keep an eye on the vent through the next snowfall.

The inlet air filter sits under the front cover. Opening the cabinet is a technician's job unless your owner's manual tells you how to reach it.

When to call a technician

Call if the vent is clear and the code returns. Rinnai's code 10 procedure includes checking vent length and joints, measuring manifold gas pressures, inspecting the burner and heat exchanger fins, and testing the fan motor and board. That's all inside the unit or behind the wall.

For budgeting, HomeGuide puts tankless water heater repairs at $300 to $1,300 on average. If the unit is also overdue for descaling, combine the visit with a flush; see how to flush a tankless water heater.

A note on new installs

If code 10 shows up on a heater that was just installed or just had its venting changed, call the installer first. Rinnai's code 10 checks focus heavily on vent materials, length, joints and clearances, which are installation details. A heater that has run for years and suddenly throws the code points more toward a blockage, a condensate problem or the fan.

More on Rinnai codes in our Rinnai tankless error codes guide.