- Boilers
- Gas boiler
304
Chaffoteaux 304 on a gas boiler: over 5 resets within 15 minutes
Risk level
Medium
Proceed carefully and stop if the check is unclear.
Urgency
Medium
Quick answer
Chaffoteaux 304 appears when RESET has been pressed more than 5 times in 15 minutes. Cut the power at the external switch to unlock, write down the code that showed before and, if that lockout returns, call a technician.
Safety first
Stop and check this first
- If you notice a strong smell of gas: Chaffoteaux says to close the gas tap, open the windows and call the technician. Do not operate switches or anything that sparks: leave the home and call your gas distributor's emergency number from outside.
- If there is a burning smell or smoke coming out: disconnect the power, close the gas tap, open the windows and call the technician, as Chaffoteaux says. Carbon monoxide has no smell; with a headache, dizziness or nausea, get out of the home. A CO alarm near the boiler gives early warning.
- Do not keep pressing RESET: Chaffoteaux limits unlocks to 5 in 15 minutes for safety. If the lockout repeats often, ask for an authorised technical service centre to attend.
Safe checks you can perform
- Which code was showing before 304
- Gas tap and pressure gauge
- Unlock by cutting the power
- Error history and repair by the technician
Leave these tasks to a qualified professional
- Do not attempt this professional task: Reading parameter 8 6 0
- Do not attempt this professional task: Ionisation current and flame safety
- Do not attempt this professional task: Combustion analysis and flue
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Reading parameter 8 6 0
What they doThe technician checks the boiler error history, which stores the last 10 with their code, and finds the one repeating before 304.
They must show youthe Err 0 to Err 9 list with the repeated code.
In writingwhich code caused the lockouts and what was repaired.
Ionisation current and flame safety
What they doIf the underlying lockout is a flame fault, the technician reads the ionisation current in parameter 8 7 5 and checks the no gas or no flame safety, as the maintenance section asks.
They must show youthe ionisation current measured against the manufacturer's specification.
In writingthe value, what was checked and the parts replaced.
Combustion analysis and flue
What they doAfter the repair, the technician carries out the combustion analysis Chaffoteaux recommends, checks the tightness of the flue and air intake, and that the condensate trap holds water.
They must show youthe analyser printout.
In writingthe values measured against the manufacturer's specification and the condition of the trap.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Which code was showing before 304
- Who:
- you.
- How:
- think back or check your photos: which number was flashing on the display before the RESET presses. On the Pigma Advance, ignition and flame faults start with 5, such as 5 01.
- Result that matters:
- identifying the lockout that kept repeating.
- If you remember it:
- that is the key fact for the technician; 304 only counts the RESETs.
- If you do not:
- the technician finds it in the history of the last 10 errors, with its date.
- Evidence to keep:
- photo of 304 on the display and, if you have it, of the earlier code.
Evidence: Chaffoteaux Pigma Advance 25, 30 y 35, instrucciones de instalación y de utilización
Gas tap and pressure gauge
- Who:
- you.
- How:
- check that the boiler gas tap is open and read the pressure gauge with the system cold. Chaffoteaux asks for 0.6 to 1.5 bar and, if it is lower, to top up using the filling procedure in the manual.
- Result that matters:
- ruling out a lack of gas or pressure as the source of the repeated lockout.
- If the tap was closed or the pressure low:
- correct it before unlocking.
- If everything is correct:
- the underlying lockout has another cause; go on to the unlock.
- Evidence to keep:
- photo of the gauge and a note of the tap position.
Evidence: Chaffoteaux Pigma Advance y Pigma Ultra, manual de usuario
Unlock by cutting the power
- Who:
- you.
- How:
- after the sixth RESET within 15 minutes, Chaffoteaux says the boiler can only be unlocked by disconnecting it. Set the external electrical switch to OFF, back to ON, and let it try to start without pressing RESET.
- Result that matters:
- whether it runs normally or the same lockout returns.
- If it runs:
- note the day and time; an isolated lockout is not a problem.
- If the lockout reappears:
- switch off, external switch to OFF, close the gas tap and call a technician.
- Evidence to keep:
- a note of the unlock time and the code that reappears.
Evidence: Chaffoteaux Pigma Advance y Pigma Ultra, manual de usuario · Chaffoteaux Pigma Advance 25, 30 y 35, instrucciones de instalación y de utilización
Error history and repair by the technician
- Who:
- Chaffoteaux authorised technical service centre.
- How:
- opens parameter 8 6 0 in the technical menu, which shows the last 10 errors from Err 0 to Err 9, and diagnoses the one that kept repeating.
- Result that matters:
- the code that led to the RESETs and why it repeats.
- If it is in group 5, ignition and flame detection:
- checks ignition, ionisation and gas.
- If it is in another group, such as main circuit or flue:
- checks that system.
- Evidence to keep:
- job sheet with the code found in the history and the repair made.
Chaffoteaux says to cut the power with the external double-pole switch and close the gas tap before opening the boiler. The inside, the burner and the gas section are technician-only work.
Evidence: Chaffoteaux Pigma Advance 25, 30 y 35, instrucciones de instalación y de utilización
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- Boilers
- Brand
- Chaffoteaux
- Product type
- Gas boiler
Known code variants
- 3 04
- Ariston 3 04
- Chaffoteaux 3 04
- Clas One 304
- Error 304 Ariston
- Error 304 Chaffoteaux
- Genus One 304
- Pigma 304
- Pigma Advance 304
What it means
In the Pigma Advance code table, 3 04 sits in the internal electronics group and means too many reset attempts, more than 5, in 15 minutes. Lockout stops are non-volatile errors cleared with the RESET button; for safety the boiler allows 5 reactivations in that time and, on the sixth attempt, it can only be unlocked by disconnecting it. 304 points to no part: it warns that another lockout has repeated, and that is the one the technician must look for in the error history.
Warnings and stop conditions
- Criticaleditorial warning
If you notice a strong smell of gas: Chaffoteaux says to close the gas tap, open the windows and call the technician. Do not operate switches or anything that sparks: leave the home and call your gas distributor's emergency number from outside.
Evidence: Chaffoteaux Pigma Advance y Pigma Ultra, manual de usuario · Chaffoteaux Pigma Advance 25, 30 y 35, instrucciones de instalación y de utilización
- Higheditorial warning
If there is a burning smell or smoke coming out: disconnect the power, close the gas tap, open the windows and call the technician, as Chaffoteaux says. Carbon monoxide has no smell; with a headache, dizziness or nausea, get out of the home. A CO alarm near the boiler gives early warning.
Evidence: Chaffoteaux Pigma Advance y Pigma Ultra, manual de usuario · Chaffoteaux Pigma Advance 25, 30 y 35, instrucciones de instalación y de utilización
- Highsource verified
Do not keep pressing RESET: Chaffoteaux limits unlocks to 5 in 15 minutes for safety. If the lockout repeats often, ask for an authorised technical service centre to attend.
Evidence: Chaffoteaux Pigma Advance 25, 30 y 35, instrucciones de instalación y de utilización
Symptoms and causes
Probable causes · in order
- A non-volatile lockout that comes back after every RESETCommon
The most likely case: a lockout type fault, for example 501 no flame, reappears each time. 304 comes afterwards and hides that code, which is the one that needs repairing.
Evidence: Chaffoteaux Pigma Advance y Pigma Ultra, manual de usuario · Chaffoteaux Pigma Advance 25, 30 y 35, instrucciones de instalación y de utilización
- RESET button pressed many times in a short periodPossible
It fits if the boiler starts normally after being disconnected and does not lock again. Chaffoteaux states that an occasional or isolated lockout is not a problem.
Evidence: Chaffoteaux Pigma Advance 25, 30 y 35, instrucciones de instalación y de utilización
Virtual technician
Does 304 still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
- 1
Chaffoteaux Pigma Advance y Pigma Ultra, manual de usuario
Chaffoteaux · 2018 · manual
- 2
Chaffoteaux Pigma Advance 25, 30 y 35, instrucciones de instalación y de utilización
Chaffoteaux · 2019 · manual
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