- Boilers
- Gas boiler
A15
Ferroli A15 gas boiler: air signal protection lockout
Risk level
High
Professional inspection is recommended.
Urgency
High
Quick answer
Permanent shutdown A15 on Ferroli DIVAtop MICRO LN F boilers indicates air signal protection activation after fault F05 occurred 5 times in the last 15 minutes. Never open the sealed chamber; try at most one 1-second press of RESET and call an authorised engineer if the lockout returns.
Safety first
Stop and check this first
- Do not attempt to bridge or bypass the air pressure transducer (297), open the sealed chamber (5), or repeat resets after an A15 lockout, because if one 1-second press of RESET does not resolve the fault you must turn the boiler off and contact an authorised engineer.
- If you detect any smell of gas, ventilate the room immediately by opening windows, close the gas shut-off valve if safe, avoid operating electrical switches or naked flames, leave the property, and call the gas emergency number from outside.
Safe checks you can perform
- Check cold system pressure (around 1 bar) and stable power supply on the display
- Try one single reset by pressing the RESET button for 1 second
- Professional check of air pressure transducer (297) wiring and flue ducting
Leave these tasks to a qualified professional
- Do not attempt this professional task: Clean the flue system and verify equivalent length against Tables 2 and 3
- Do not attempt this professional task: Inspect and repair the air pressure transducer (297) wiring and connections
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.
Clean the flue system and verify equivalent length against Tables 2 and 3
What they doInspect the intake and exhaust ducts for debris or blockage and verify that the installation respects maximum lengths (5 m for 60/100 coaxial, 10 m for 80/125 coaxial, or 60 meq and 48 meq for ø 80 separate pipes).
They must show youAny debris removed from the flue termination and the calculated equivalent length of the ducting.
In writingVerified flue diameter, equivalent length in m or meq, and confirmation that flue draught is unobstructed.
Inspect and repair the air pressure transducer (297) wiring and connections
What they doTest electrical continuity and terminal seating between the air pressure transducer (component 297) and the main control board, as well as the pressure sensing ports at the fume manifold (28).
They must show youThe inspected connectors on air pressure transducer 297 and confirmation that the air signal registers within 25 seconds.
In writingWiring continuity results and part number if air pressure transducer 297 required replacement.
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.
Check cold system pressure (around 1 bar) and stable power supply on the display
- Who:
- you, no tools.
- How:
- Look at the display (item 21 in figure 1) and the water pressure gauge (145, item 2 in figure 16) to check that cold water pressure is near 1 bar (minimum working pressure 0.8 bar) and that no supply voltage warnings such as F34 (below 170 V) or F35 occurred.
- Result that matters:
- Cold system pressure is around 1 bar and the 230 Vac 50 Hz electrical supply is steady.
- If pressure is below 0.8 bar with fault F37, top up via the filling cock (74) to 1 bar and close it; if F34 or F35 appeared, report the voltage drop to the technician.
- If pressure and power are normal, proceed to the single permitted reset attempt.
- Evidence to keep:
- Photo of the display flashing A15 with fault symbol 22 and the reading on pressure gauge 145.
Evidence: Ferroli DIVAtop MICRO LN F instrucciones de uso instalación y mantenimiento
Try one single reset by pressing the RESET button for 1 second
- Who:
- you, at the panel.
- How:
- Press the RESET button (item 8 in figure 1) for 1 second (or press RESET on the optional remote timer control 139) once only, then listen to see whether the fan starts and the burner ignites within 25 seconds.
- Result that matters:
- Code A15 clears and the boiler runs without logging F05 again over the next 15 minutes.
- If the appliance fails to prove air signal within 25 seconds and displays F05 or A15 again, stop immediately, switch the boiler off, and call an authorised service engineer.
- If the boiler ignites and heats normally, monitor it over the next 15 minutes without opening any panels.
- Evidence to keep:
- Note of the exact time of the single 1-second reset and whether F05 or A15 returned within 25 seconds or 15 minutes.
Evidence: Ferroli DIVAtop MICRO LN F instrucciones de uso instalación y mantenimiento
Professional check of air pressure transducer (297) wiring and flue ducting
- Who:
- Ferroli engineer.
- How:
- After isolating the 230 Vac supply, the technician opens the sealed chamber (5), checks the wiring harness and sensing ports of the air pressure transducer (297) at fume manifold (28) and outlet collar (29), and verifies that the flue is clean and within Table 2 and Table 3 limits (max 5 m on 60/100 coaxial with 1 m reduction per 90° bend and 0.5 m per 45° bend, or 10 m on 80/125 coaxial).
- Result that matters:
- Transducer 297 wiring is sound and the air intake and exhaust ducts are clean and properly sized.
- If the flue pipe is partially blocked or exceeds the allowed pressure loss (60 meq on DIVAtop MICRO LN F 24 or 48 meq on model 32 with ø 80 pipes), the technician clears the obstruction or corrects the flue run.
- If flue length and fan 16 performance are correct but transducer 297 still fails to register within 25 seconds, the transducer is replaced with an original Ferroli spare.
- Evidence to keep:
- Written job sheet detailing transducer 297 wiring continuity and measured equivalent flue length.
Opening the sealed chamber (5) and working on flue components or 230 Vac wiring affects combustion gas safety and must be performed only by a qualified gas engineer.
Evidence: Ferroli DIVAtop MICRO LN F instrucciones de uso instalación y mantenimiento
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
- Ferroli
- Product type
- Gas boiler
Known code variants
- A 15
- caldera Ferroli A15
- error A15 Ferroli
- Ferroli A15
- Ferroli boiler A15
- Ferroli error A15
What it means
In the official bilingual Ferroli manual for DIVAtop MICRO LN F 24 and DIVAtop MICRO LN F 32 (Table 5), code A15 means 'Air signal protection activation' triggered when fault F05 is generated 5 times in the last 15 minutes. Fault F05 occurs when the air pressure transducer (component 297) does not receive a sufficient minimum value within 25 seconds after the modulating fan (16) starts. Because it carries the letter A, A15 is a permanent shutdown flashing alongside the spanner symbol (item 22 in figure 1). Code A15 by itself never proves that a component is defective, because loose transducer wiring or a blocked or oversized flue duct will produce the exact same symptom.
Warnings and stop conditions
- Highsource verified
Do not attempt to bridge or bypass the air pressure transducer (297), open the sealed chamber (5), or repeat resets after an A15 lockout, because if one 1-second press of RESET does not resolve the fault you must turn the boiler off and contact an authorised engineer.
Evidence: Ferroli DIVAtop MICRO LN F instrucciones de uso instalación y mantenimiento
- Highsource verified
If you detect any smell of gas, ventilate the room immediately by opening windows, close the gas shut-off valve if safe, avoid operating electrical switches or naked flames, leave the property, and call the gas emergency number from outside.
Evidence: Ferroli DIVAtop MICRO LN F instrucciones de uso instalación y mantenimiento
Symptoms and causes
Probable causes · in order
- Flue obstructed or exceeding maximum permissible equivalent lengthCommon
Table 5 of the Ferroli manual lists 'Flue obstructed or not correctly sized', such as exceeding 5 m on 60/100 coaxial ducts, 10 m on 80/125 coaxial ducts, or 60 meq (model 24) and 48 meq (model 32) on ø 80 separate ducts.
Evidence: Ferroli DIVAtop MICRO LN F instrucciones de uso instalación y mantenimiento
- Incorrect or loose air pressure transducer (297) wiringCommon
The manufacturer table explicitly cites 'Incorrect air pressure transducer wiring', where poor electrical contact between transducer 297 and the PCB prevents a valid signal within the 25-second window.
Evidence: Ferroli DIVAtop MICRO LN F instrucciones de uso instalación y mantenimiento
- Faulty air pressure transducer (297) or modulating fan (16) inside sealed chamberPossible
When the flue is clear and wiring is intact, the air pressure transducer (297) at the fume manifold (28) or the modulating fan (16) inside the sealed chamber (5) may fail to develop or sense the required air differential.
Evidence: Ferroli DIVAtop MICRO LN F instrucciones de uso instalación y mantenimiento
Virtual technician
Does A15 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
Ferroli DIVAtop MICRO LN F instrucciones de uso instalación y mantenimiento
Ferroli · 2015 · manual
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