Quick answer
Bosch tankless error code EA means ignition failure: water is flowing but the control unit did not recognize a burner flame. The heater will not fire until it is reset. Check that every manual gas shut-off valve is open, reset the code and run a hot tap. If EA returns, a licensed gas technician needs to purge the line and check inlet gas pressure.
Bosch tankless error code EA means the heater tried to light and the control unit never saw a flame. A hot tap opened, water started flowing, the unit ran its ignition sequence, and the flame was not recognized, so it shut the gas and put the code on the display. You get cold water and nothing else. The meaning comes from the error table in Bosch's Greentherm installation manual; codes vary between Bosch models, so if the label or manual for your heater says something different, the label wins.
What EA is telling you: gas, air or the ignition parts
EA is a no-flame code, not a water-side code. The heater needs three things in the first few seconds of a call for hot water: gas at the right pressure, a spark from the igniter, and a flame sensor that reports the burner lit. Lose any one and the control reads the same thing, no flame, and posts EA. That is why the fix ranges from opening a valve to replacing a part, and why the order you check things in matters.
Is it safe to keep resetting a Bosch heater showing EA?
The heater is safe sitting in EA: it has closed its gas valve and will not fire. What you should limit is the resetting. Bosch's own service bulletin on EA says that after new gas-line work, resetting and opening a hot tap a few times is how trapped air gets pushed out of the line, and that is normal on a new install. On a heater that has worked for years, repeated resets are not a fix, and a unit that will not light after two or three tries is telling you the cause is still there.
If you smell gas at any point, stop. Leave the house and follow the steps in what to do if you smell gas before anyone touches the heater again.
The one check a homeowner can make: gas valves, then one reset
- Find the manual gas shut-off on the pipe feeding the heater. The handle should sit in line with the pipe; a handle turned crosswise is closed.
- Check the other shut-offs between the meter and the heater. A valve closed for a range or dryer hookup sometimes gets left that way.
- Confirm other gas appliances work. If the furnace and range are dead too, the problem is at the meter or the supply, and that is a call to Enbridge Gas instead of a heater repair.
- On a propane property, read the tank gauge. Rural lots around Lowville, Kilbride, Campbellville and Carlisle sit past the natural gas mains, and a tank that has run low starves the burner the same way a closed valve does.
- Reset the code on the control panel as the manual describes, open a hot tap fully and let the heater try again.
Stop there. Do not remove the front cover, and do not loosen any gas fitting to bleed air yourself: purging a gas line is work for a TSSA-licensed gas technician in Ontario.
What causes EA, most likely first
- A closed or partly closed gas shut-off. The most common cause after any plumbing, renovation or appliance work in the house.
- Air in the gas line. New piping, a meter change or a line that was opened for another appliance leaves air that has to be purged before the burner sees clean gas.
- Low inlet gas pressure. A tankless heater draws far more gas at once than the tank it replaced. If EA shows up mostly on cold mornings when the furnace is running too, the line may be too small to feed both; see whether a tankless needs a bigger gas line.
- The wrong gas type. A heater set up for natural gas will not light properly on propane, or the reverse. This shows up at start-up on a new install or after a move from one fuel to the other, and the conversion is a technician's job.
- An igniter or flame-sensor fault. A worn or fouled igniter gives a weak spark; a coated flame sensor cannot report a flame that is there. Less common than a gas-supply cause, more common as the heater ages.
What a technician does about EA, and what it costs
Bosch directs that when EA persists, a licensed gas technician purges the line and checks inlet pressure. In practice that means a manometer on the heater's gas inlet, read with the unit off and then firing, and again with the furnace and other gas appliances running. A pressure that sags under load points to the piping or regulator, not the heater; pipe sizing follows the tables in CSA B149.1, the gas code Ontario uses. If pressure holds, the igniter and flame sensor are inspected and tested next.
- Diagnosis: $90–$150, deducted from the repair once you say go.
- Water heater repairs in general: $150–$800, depending on the part.
- Upsizing a gas run that is too small for the heater: $400–$1,200.
- Purging and re-commissioning after gas-line work: priced on the visit, with the figure in writing before work starts.
ZK Mechanical services Bosch tankless heaters from the Burlington shop, and every technician holds a TSSA gas licence. Other Bosch codes are listed in the Bosch tankless error code guide, and the general no-ignition checks sit on why a tankless water heater is not igniting. To have EA diagnosed properly, see tankless water heater repair or send us the model and the code; the phone is (647) 801-1252.