Takagi Code 111: Ignition Failure
On this page (4 sections)
The Short Answer: On current Takagi tankless heaters, code 111 means ignition failure: the heater tried to light and did not detect a flame. The most common owner-level causes are a closed gas valve, an empty propane tank, or a gas supply problem shared with other appliances. If gas supply is fine, the cause is inside the heater, and a technician needs to check it.
What Takagi says about 111
Takagi’s maintenance sheets for the T-H3P (opens in a new tab) and T-KJr3 (opens in a new tab) series list 111 as “Ignition failure.” The checks Takagi gives the service technician include:
- Gas supply and inlet gas pressure.
- Whether the hi-limit switch is working properly.
- Wiring connections and breaks, soot on the flame rod, and whether the overheat cut-off fuse (O.H.C.F.) has opened.
- Whether the igniter sparks and whether the gas valve opens (Takagi describes listening for a buzzing spark and a double “clunk” from the valve).
- Leaks from the heat exchanger, dust or lint in the burner nozzles, and the flame rod’s current.
On several Takagi sheets, 111 is marked as a code that clears when water flow stops in a single-unit installation. That makes it easy to reset by closing and reopening a tap, which is why repeated 111s are worth recording rather than ignoring.
The same sheets list 121 as “Loss of flame,” which means the burner lit and then went out. It shares many causes with 111 but is a different event. Older Takagi models with two-digit codes are not covered by these sheets; check the manual for your model.
What you can check safely
| Check | What it tells you |
|---|---|
| Gas valve to the heater is open (handle in line with the pipe) | A closed valve after service work is a common cause |
| Other gas appliances light normally | If they do not, the problem is the gas supply, not the heater |
| Propane tank has fuel and the regulator is not iced | Low or freezing LP starves ignition on cold mornings |
| The code returns on the next hot-water call | A single 111 after a supply interruption may not recur; repeated codes need service |
| Recent events: new installation, gas meter work, a power surge, a leak | Helps the technician narrow the cause |
After correcting an obvious cause, close the hot tap and open it again once. If 111 returns, stop and call a technician. Takagi’s reset steps are covered in how to reset a Takagi tankless water heater.
Do not remove the front cover, clean the flame rod, or press the hi-limit button yourself. These are inside the cabinet next to the gas valve and line-voltage wiring.
What the technician will do
A licensed tankless or gas technician will measure inlet and manifold gas pressure against the rating plate, watch the ignition sequence, and test the igniter and gas valve voltages as described in Takagi’s service appendix. They will inspect and clean the flame rod and burner, and check the hi-limit switch and overheat cut-off fuse. If the overheat fuse has opened, they also need to find out why the heater overheated before it is replaced.
On a new installation, an undersized gas line or connector is a frequent cause of 111 at high firing rates. That is corrected by resizing the gas supply, not by adjusting the heater.
For other Takagi codes and symptoms, see Takagi tankless water heater problems and the error codes hub.
Frequently Asked Questions
Q: Is 111 the same as Takagi code 11? A: Older Takagi models used two-digit codes, and 11 is often described as an ignition fault on those. Confirm in the manual for your model, since these sheets cover the three-digit models.
Q: Why did 111 appear only on a cold morning? A: Propane regulators can ice and cylinders lose pressure in the cold, and a gas line that is just adequate in summer may be short at full firing in winter. Mention the timing to the technician.
Manuals and supporting references
These links distinguish general safety information from model-specific documentation. A manual directory helps you locate your unit’s instructions; it does not establish that every model uses the same parts, codes, or test values.
- Takagi maintenance sheet 5M2054 (T-H3P series): error codes (opens in a new tab)Takagi T-H3P indoor and outdoor models.
- Takagi maintenance sheet 1W6010 (T-KJr3 series): error codes (opens in a new tab)Takagi T-KJr3 indoor and outdoor models.
- PG&E: recognizing and responding to a gas leak (opens in a new tab)Emergency actions for suspected fuel-gas leaks.
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