Noritz Tankless With No Hot Water
The Short Answer: A Noritz with no hot water is four folders: no 120 V, no flow call, a lockout code, or gas/ignition. Photograph the controller or the PCB digits. Do not descale a dark display. No water moving is a different page. Lukewarm with fire is scale or fuel, not “no hot water.”
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Search Intent & The Real Problem
Every fixture is cold. Not slow. Not lukewarm. Cold. NRC, EZ, NRCP, NR, NCC, and outdoor cousins all need power, a flow signal, clean air, and gas. People paste Rinnai 11/12 tables onto a Noritz and sand the wrong rod. People flush vinegar through a unit that never fired. No water at the hot tap: Noritz no flow. Puddle under the case: Noritz from the bottom. Sister splitters: Rinnai no hot water, AO Smith tankless, Navien not getting hot.
What other guides get wrong
They start with a vinegar flush. Flushing a unit that never fires floods a mixer and does nothing for a 10. They dump every Noritz code into one blob so you clean a flame rod on a 90. They tell you to turn it to 140°F. A dead Noritz does not care about setpoint. They treat “no hot water” as “no water flow” and skip the burner.
Step-by-Step Troubleshooting
Step 1: Display, flow, and the exact cold
| What you have | Folder | Next |
|---|---|---|
| Blank display | Power / GFCI / PCB | Step 2 |
| Display on, unit never wakes when you open hot | No flow call | Screen, valves, min GPM — no flow |
| Wakes, fan, then a code, still cold | Lockout | Photograph; Step 4 |
| Wakes, flame, still cold at the tap | Mixing valve / crossover | Thermometer at the outlet |
| After a storm or freeze | Outage / rain / split | After rain, leaking after freeze |
- What to look for: Closest hot faucet as the test, not the master shower 60 feet away. Remote dark while the PCB still has digits — look at both.
- Required tools: Phone photo of the controller before you cycle power.
Step 2: 120 V — GFCI, disconnect, both legs of the story
- What to look for: Outdoor GFCI popped. Disconnect off. House breaker off. Remote cable unplugged. Freeze-protection on these units is electric — a dark outdoor NRC in 15°F weather is how the exchanger splits. Reset a GFCI once. If it trips again, leave it off. A breaker that will not reset is a short — do not hold it On.
- Required tools: Eyes, receptacle tester. Cover stays on if the cabinet is wet.
Step 3: Call for heat — valves, screen, activation flow
- What to look for: Isolation handles not parallel to the pipe. Cold-inlet screen packed with well-sand or Teflon scraps. Fixture mixing below activation (often ~0.4–0.5 GPM on these chassis — confirm the sticker). Recirc crossover that cancels net flow. Open a tub spout. If the unit never wakes, stay on flow. Do not start on gas.
- Required tools: Filter service with cold isolated, bucket.
House static over ~80 psi belongs on a PRV, not on the temperature buttons.
Step 4: Read the Noritz code — then stop guessing
Confirm against the sticker on that NRC / EZ / NR. Cousin digits (Rinnai/Takagi) are close, not identical.
| Code (common Noritz) | Meaning | First move |
|---|---|---|
| 10 | Combustion air / exhaust | Cap, nest, snow, fan — do not fire a silent blower |
| 11 | Ignition failure | Gas cock parallel, then licensed if it repeats |
| 12 | Flame lost after light | Wind, sense, pressure under load |
| 14 | Thermal fuse / overheat | Scale, low flow — licensed fuse |
| 16 | Outlet too hot | Open a tap, drop setpoint; repeating = scale |
| 61 | Fan motor | Licensed. Silent fan = no burner |
| 90 / 99 | Combustion abnormality | Licensed. Not a second reset |
| 76 | Remote communication | Cable, then licensed PCB |
| 92 / 93 (condensing) | Neutralizer / condensate | Drain, pump, trap |
- What to look for: One power cycle after the obvious cause (cap, hose, GFCI, cock). Same digit on the next shower is the end of DIY. Manifold pressure is licensed (about 3.5–7 in. w.c. natural gas / 10–11 in. w.c. LP — confirm the plate). Do not purge the line.
- Required tools: Jacket sticker. No manometer in a homeowner kit.
Sister ignition language: Takagi problems, Rinnai 12.
Step 5: Flame on, water still cold — not the burner
- What to look for: 120°F at the Noritz outlet, 100°F at the fixture = mixing valve or a shower cartridge dumping cold into hot. Gas on, fan on, water never rises: scale-insulated exchanger — licensed flush with service valves, or parts. A unit that goes hot then cold mid-shower is tankless hot-to-cold, not this dead-cold page.
- Required tools: Contact thermometer at the outlet vs the faucet.
Do not set 140°F to chase a mixer. Never cap the T&P.
When DIY Ends: Calling a Licensed Pro
You may restore one GFCI, rinse the inlet screen, open isolation valves, photograph a code, and power-cycle once. Stop at gas odor, a wet cabinet, a silent fan, a freeze-split, a repeating 10/11/12/14, and any jumper. Combustion, gas pressure, flame rod, PCB, and exchanger work are licensed. A cold Noritz with a packed screen is a rinse. A cold Noritz with an 11 that returns is a service truck.
Frequently Asked Questions
Q: Why does my Noritz tankless have no hot water? A: No 120 V, flow below activation, a lockout code (10/11/12/14/16/61/90), or a mixing valve hiding a hot outlet. Photograph the display before you cycle power.
Q: How do I reset a Noritz with no hot water? A: Photograph the code, fix the obvious cause, power off 10–30 seconds. One try. A code that returns is licensed. Do not reset a wet cabinet or a unit that smells like gas.
Q: Should I flush a Noritz that will not heat at all? A: Not first. Flushing treats scale on a unit that fires. A dark controller, a 10, or a 61 needs power or air — not acid.