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Ferroli specialists
Modena, Optimax, Bluehelix and the older Domiproject. Twenty years on Ferroli boilers, rates agreed beforehand, and parts guaranteed for a year.
Answered 24 hours a day by a technical customer service member.
On a Ferroli the letter matters more than the number. An A is a lockout, an F can clear on its own.
No heating or hot water right now? Call 0203 868 6134. We will tell you the earliest realistic slot rather than the one you want to hear.
Two details to start. Add the fault code and your postcode and we can usually tell you the likely part before we attend.
Three steps, no sales pitch, and you will know where you stand before an engineer is booked.
A Ferroli that started working again has not necessarily been repaired. F codes are blocking faults, which means the boiler stops while a condition is out of range and starts again once it improves. So the fault clears, the heating comes back, and the cause is still sitting there waiting for the next cold night. Write the code down before it disappears, because on this make the evidence does not wait for you.
Ferroli faults divide cleanly between the gas side, which locks out, and the water side, which blocks. Six parts cover most of what we attend.
Ferroli use two prefixes and they mean genuinely different things. An A is a lockout that has stopped the boiler and needs somebody to reset it. An F is a blocking fault that can release itself once the condition causing it improves. Read the letter first.
What the boiler is saying: pressure has dropped below the level it needs to run safely. The most common Ferroli code and the only one most householders can clear themselves.
What you can safely do: use the filling loop to add water slowly until the gauge reads between 1.2 and 1.3 bar, close both valves firmly, then hold the reset for five to ten seconds.
Because it is an F code, it may clear on its own the moment pressure comes back, which is exactly why people top up, see the heating return and never find out why the pressure fell.
The related codes: F40 is the opposite, pressure too high, usually a filling loop somebody left open. F41 and F47 point at the pressure sensor rather than the pressure.
Has it dropped again since you last filled it? That answer is the diagnosis.
The boiler tried to light the burner and the flame sensor could not confirm a stable flame, so it locked out. The most common A code across every Ferroli range.
Do the hob test first. Try lighting a gas hob. If that will not light either, the problem is your gas supply rather than the boiler, and no amount of resetting will help.
In winter: excessive condensate in the pipe can block the burner area. That white plastic pipe running outside freezes, and pouring warm water along it, never boiling, often clears the fault.
What it usually is otherwise: a dirty or worn ignition electrode, low gas pressure at the meter, or the gas valve.
Because it is an A code, it will not clear itself. The boiler stays locked out until somebody resets it, which at least means the evidence is still on the display when an engineer arrives.
Does the hob light? Ten seconds, and it changes the answer entirely.
The water went past the temperature the safety system allows and the boiler locked out. An A code, so it stays locked out until reset.
What this normally turns out to be: circulation rather than the burner. A jammed pump, a seized valve, sludge or trapped air, all of which leave the boiler making heat faster than the system carries it away.
What this is not: the heat exchanger, which is what the word overheat makes people fear. It is the last thing to suspect rather than the first.
Read it alongside F43. If you have seen both, they are describing the same problem from two directions and the underlying cause is almost certainly poor flow.
What helps most: not a part. Getting the system properly clean deals with the cause where a component swap usually does not.
Leave it off to cool and tell us whether any radiator was cold beforehand.
Different from A01 and the difference decides the repair. A01 never lit. A06 means a flame was there and the boiler could not maintain a stable signal from it.
Why that matters: failing to light points at the spark side and the gas supply. Failing to hold points at the sensing electrode, at gas pressure sagging once the boiler draws properly, or at the flue.
A02 sits alongside it, meaning an incorrect flame was detected, which is a different order of problem and one to stop resetting.
What this is not: worth spending money on parts before the gas pressure has been measured at the appliance while it is running. A boiler starved under load produces this on perfectly healthy components.
Does it fire and run for a few seconds first? That is A06 rather than A01.
The air pressure switch confirms that the fan is moving air properly before the boiler will light. F05 means it did not get that confirmation.
What is genuinely Ferroli about this one: a wrongly sized or incorrectly fitted flue baffle obstructs the flow and produces this fault on an appliance where nothing has actually broken. If the code appeared soon after somebody worked on the flue, say so.
The other causes: the switch itself, the small tubes connecting it, a fan losing speed, or a flue terminal blocked by leaves or nesting material.
Related: F15 is a fan tachometer fault, where the signal from the fan is interrupted or debris has got into it.
Why these deserve respect: the fan and flue carry combustion products safely out of the building. This is not a code to keep resetting past.
Has anybody worked on the flue recently? That detail matters here.
This is not an overheat and it is worth understanding as its own thing. F43 means the exchanger protection has activated, so the boiler has stopped deliberately to prevent damage to the most expensive part inside it.
What triggers it: no circulation through the exchanger. Air in the system, sludge, or a pump that is not moving water.
Why it is good news: the boiler is doing exactly what it should. Left running in that state, the heat exchanger is what fails, and that is usually the end of the appliance.
Why it is bad news: it is an F code, so it can clear once things cool and circulation improves slightly. People see the heating come back and assume it fixed itself. It did not.
What to do: bleed the radiators, check the pressure, and get the system cleaned. A magnetic filter on the return catches the magnetite that causes this before it reaches the exchanger.
Seen this one more than once? Then it has not fixed itself.
This is the single most useful thing to know about a Ferroli, and it is not on most code lists.
A codes are lockout faults. The boiler has stopped and will not restart until somebody clears it manually. A01, A02, A03 and A06 are all in this group, and they mostly concern ignition, flame and gas. The boiler stays down, so the fault is still on the display when help arrives.
F codes are blocking faults. The boiler stops while a condition is out of range, then releases itself when the condition improves. F37, F05, F43 and the sensor codes are in this group, and they mostly concern pressure, sensors, circulation and the electrical supply.
Why that distinction matters to you: an F code can disappear on its own. The heating comes back, everybody relaxes, and the cause is untouched. Whatever caused an F43 or an F37 is still there whether or not the code is.
What to do about it: note the display the moment you see a code, before you touch anything. On this make that note is often the only record that the fault happened at all.
Did it clear before anybody saw it? Tell us what the code was.
| Code | What the boiler is saying | What it usually turns out to be |
|---|---|---|
| A02 | Incorrect flame detected | Moisture on the electrode, or a valve passing |
| F10 / F11 / F14 | Flow, hot water or outlet sensor fault | The sensor or its wiring, not the exchanger |
| F15 | Fan tachometer signal interrupted | Debris in the fan, or a broken connection |
| F34 | Supply voltage under 170 volts | Your electricity supply, not the boiler |
| F35 | Irregular mains frequency | The electrical supply again, worth an electrician |
| F40 | System pressure too high | A filling loop left open, usually |
| F41 / F47 | Pressure sensor fault | The sensor, when the gauge itself reads normal |
| F50 / F51 | Modureg fault | The gas valve modulation coil |
| A61 to A64 | Controller communication | The control board or the link to the gas valve |
A Ferroli reset button has to be held for five to ten seconds. A quick press, which is what works on most other makes, does nothing at all. That is why people conclude the reset is broken, or that the boiler is beyond help, when the button is usually marked with an R or a flame symbol and simply needs holding. It is worth trying properly once before booking anybody, though only once, because repeated resetting hides the fault underneath.
Because F codes clear themselves, a fair number of Ferroli problems arrive with nothing on the display and a story about what happened last week.
This is the classic Ferroli call. No heating on Tuesday morning, working again by the evening, nothing on the display, and a nagging sense that something is wrong.
What happened: an F code. The boiler blocked because a condition was out of range, then released itself once that condition improved. Pressure that dipped and recovered, circulation that improved once the house cooled, a sensor reading that came back into tolerance.
Why it will happen again: nothing has been repaired. The boiler simply stopped complaining. On the coldest night of the year, when demand is highest and the margin is smallest, it will block again and probably stay blocked.
What is worth doing: write down the date and time each time it happens. A pattern of early mornings points at one cause, a pattern regardless of time points at another. That note is worth more than any guess we could make on the phone.
Has it done this more than once? Then it is a fault, not a glitch. Call 0203 868 6134.
On most combis, poor hot water comes down to one of two components: a plate heat exchanger that has scaled, or a diverter valve that has stopped switching cleanly.
Where Ferroli differs: some of their ranges are built without a separate plate heat exchanger and without a diverter valve, using a single exchanger design instead. On those, the two faults that account for most combi hot water problems elsewhere simply cannot happen.
Why this is worth checking rather than assuming: it varies by range, and it changes the diagnosis completely. Being quoted for a diverter valve on a boiler that does not have one is not a hypothetical.
What to do: give us the range name and we will tell you which design yours uses before anybody quotes for a part. On the ranges that do have a plate exchanger, London water scales it as fast as it scales anybody else's.
Tell us the range and we will say which parts yours actually has. Call 0203 868 6134.
Ferroli boilers monitor the electricity arriving at the property and stop if it falls outside what they can work with. F34 is triggered below roughly 170 volts, and F35 covers irregular mains frequency.
What that means: the fault is in the supply rather than the appliance, and replacing boiler parts will change nothing.
Where it turns up: properties on a long shared supply, houses with elderly wiring, and anywhere something large on the same circuit pulls the voltage down when it starts.
The clue to look for: whether anything else in the property misbehaves at the same time. Lights dimming when a shower or a washing machine starts is the same information from a different direction.
Who to call: an electrician rather than us, at least first. We will tell you honestly if that is where the problem is, and there is no charge for saying so on the phone.
Modena, Optimax, Bluehelix, Divacondens, Domiproject, Domina and the i-Series are not variations on a theme. Code meanings shift between them, and several are sold in combi, system and heat only versions with different part numbers.
Where it goes wrong: a code is looked up against the wrong range, a plausible answer comes back, and the wrong part is ordered. On this make that is a common way to end up paying for two visits.
On parts availability: the current ranges are well supported. The older ones are where availability starts to decide whether a repair happens at all, and that question is worth asking before anybody charges to attend.
What to do: read us the whole label rather than just the range name. The serial number is what gets an engineer to the right fault table and the right parts list.
Working again does not mean repaired
F codes are blocking faults, so the boiler releases itself once conditions improve and the cause is untouched. The heating comes back, everybody relaxes, and it blocks again on the coldest night. note what the display shows before you touch anything.
The label is behind the front panel. On this make the range name decides both which fault table applies and which internal design you are looking at.
Ferroli name the range, then the output, then a letter for the type. A Modena 32C is a Modena rated 32 kilowatts.
If your letter is S, there is stored hot water somewhere in the property and the cylinder is as likely to be the fault as the boiler is.
Modena is one of their largest ranges and the one most often on London walls, in combi and system versions.
Bluehelix is the newer range, built around fewer components on the principle that there is less to go wrong.
Optimax and Optimax HE Plus are the previous generation and still very much in service.
Domiproject, Divacondens and Domina are older, and on those availability rather than cost tends to decide whether a repair happens.
Codes vary slightly between all of these, which is why the range name belongs in the same sentence as the code.
Ferroli have revised ranges repeatedly and sold several under names that sound alike. A code that means one thing on a Modena can mean something slightly different on a Domiproject.
The serial number and GC number on the label identify exactly which revision is on your wall, and they are what gets an engineer to the correct fault table rather than a general one.
Read us the whole label when you ring. On this brand it is also the fastest way to settle whether your boiler has a plate heat exchanger and a diverter valve at all. The same holds for every make we work on, which is all of them.
London is a hard water city almost everywhere, and that is the single biggest difference between repairing a Ferroli here and repairing one in Manchester or Glasgow.
Chalk is the reason. The Thames and the Lea both run through it in the Chilterns and the North Downs before the water reaches your tap, and the result is roughly 277 milligrams of calcium carbonate per litre, ranging from about 250 to over 350 depending on the district. Inside a combi that means one thing: the plate heat exchanger furs up faster than the manual's service intervals allow for.
It is the same story in Hampstead Garden Suburb and Finchley as it is in Purley and Kenley. The water is hard, the plate heat exchanger scales, and the only question is whether anybody checks it before condemning the boiler.
Hardness is not uniform, and it does not follow borough boundaries. It varies by supply zone and can change over a short distance, so your supplier publishes a figure for your own postcode and it is worth reading before anybody guesses.
Scale drops out of solution faster the hotter the water gets. A combi set to deliver taps at 65 degrees furs up its plate heat exchanger noticeably faster than one set to 50, which is still hot enough to scald. Turning that dial down costs nothing and is the most effective thing a householder in a hard water area can do. This applies to the tap setting, not to a cylinder, which must reach 60 degrees for safety.
Stored hot water is normal in larger London houses, and no combi replaces it whatever the output figure says.
A great many London firms will only touch combis, which is awkward in a city with this much older housing stock. A Ferroli system or heat only boiler feeds a separate cylinder carrying its own thermostat, immersion element and, where it is unvented, its own safety devices. Two appliances rather than one, which is why no hot water so often turns out to have nothing to do with the boiler at all.
The cylinder sensor lives in a pocket on the tank. If it fails or works loose the boiler stops heating the cylinder while every radiator stays warm, which is the single clearest sign the fault is not in the appliance.
The motorised valve sends the heat to the radiators, the cylinder or both. When its motor or microswitch goes you get heating with no hot water, hot water with no heating, or both at once, and the head usually changes without draining anything.
The immersion element furs up in London water and then either trips out or stops working. Test it before condemning a tank, because the element is a fraction of the cost. In larger houses across Kingston, Coombe and Surbiton we generally fit a scale reducer on the same visit.
An unvented cylinder runs at mains pressure and is protected by an expansion vessel, a pressure reducing valve, an expansion relief valve and a temperature and pressure relief valve, discharging through a tundish. If water is running at that tundish, one of those devices has failed. It is not something to leave and certainly not something to cap.
Unvented work is notifiable and needs a G3 qualification alongside Gas Safe registration. Our engineers carry both, which keeps the boiler side and the cylinder side on one visit. That is the reason unvented cylinder repair sits with the boiler work here.
People swap a cylinder for a combi to gain a cupboard, then ask us to put it back. A combi makes hot water as it flows rather than holding a tankful, so two showers at once is beyond it whatever the badge claims. In a three bathroom house, keeping the cylinder is usually the honest recommendation, replacing it if it is tired rather than taking it out.
Age is the wrong question. Which part failed is the right one, and we would rather tell you to keep the boiler than quote you for a new one.
| What has failed | Under 8 years | 8 to 14 years | 15 years and older |
|---|---|---|---|
| Pressure sensor, temperature sensors | Repair | Repair | Repair if parts exist |
| Ignition and sensing electrodes | Repair | Repair | Repair if parts exist |
| Expansion vessel, pump | Repair | Repair | Repair |
| Fan, air pressure switch | Repair | Repair | Depends on the rest of the boiler |
| Modureg coil, diverter valve | Repair | Repair | Repair if the part is still made |
| Gas valve | Repair | Depends on the rest of the boiler | Replace |
| Control card | Check the guarantee first | Borderline, we will be straight with you | Replace |
| Main heat exchanger | Guarantee claim if registered | Usually replace | Replace |
At this age the parts are current and the fault is a component, not the appliance giving up. A Ferroli under ten years old with one fault is a repair, and the great majority of what we see on this brand at that age is an electrode, a sensor or a pressure switch.
Ask about guarantee cover when you ring, us included. Ferroli registered guarantees run for a set term from installation and are usually conditional on annual servicing.
Quoted for a replacement at this age? Ask which one part failed, and what that part costs by itself. The gap between those two answers is usually the whole conversation.
Still a clear repair: electrodes, sensors, pump, fan, air pressure switch, expansion vessel, Modureg coil. Ordinary wear items that say nothing about the rest of the boiler.
The pattern that matters on this make: because F codes clear themselves, a Ferroli can be failing repeatedly without anybody registering it as a fault history. Several different codes recurring across a season is a stronger signal than a single dramatic failure, and it is the point at which replacement starts to enter the conversation.
The expensive ones: a control card, a gas valve or a heat exchanger. Any of those on a boiler that has also been blocking repeatedly changes the arithmetic considerably.
Past this point availability takes over from cost. The older Ferroli ranges are where parts start to decide the outcome, and a Domiproject or a Divacondens can be mechanically sound and still finished because one component is no longer made.
Where the part does still exist, an older Ferroli is often worth keeping, and the current ranges are well enough supported that this is a smaller problem than it used to be.
Before you spend anything on a diagnosis, we will find out whether the part can still be had. That question is free and on an older Ferroli it is the one worth asking first. There is more on what drives the price in our guide to repair and replacement costs.
Boiler problem? We're here 24/7
Emergency boiler repairs across London, north and south of the river
Call 0203 868 6134London, north and south of the river. These are the districts we work in most.
These are where we work most, not a boundary. An engineer attends anywhere in north London and south London. Tell us where you are and we will say plainly when we can get to you.
If you smell gas: do not touch any switches. Open the windows, leave the property, then call the National Gas Emergency Service on 0800 111 999. That line is free and open 24 hours. Call them before you call us.
If a carbon monoxide alarm is sounding: get everyone out immediately, then call 999 if anyone feels unwell. Do not go back in until the property has been ventilated and checked.
If the boiler locks out repeatedly: try one reset. If it locks out again straight away, stop. Repeated resets hide a fault that is still there, and on a gas appliance that is not a risk worth taking.
Under the Gas Safety (Installation and Use) Regulations 1998, only a Gas Safe registered engineer may work on gas appliances. Never open the boiler casing yourself.
An A code is a lockout. The boiler has stopped and will not restart until somebody resets it manually, and these mostly concern ignition, flame and gas. An F code is a blocking fault, which means the boiler stops while a condition is out of range and releases itself once that improves, and these mostly concern pressure, sensors, circulation and the electrical supply. The practical consequence is that an F code can vanish on its own with the cause untouched, so note what the display shows before you touch anything.
Usually, yes. F37 means system water pressure has dropped below the minimum needed to run safely, and it is the most common Ferroli code. Use the filling loop to add water slowly until the gauge reads between 1.2 and 1.3 bar, close both valves firmly, then hold the reset button for five to ten seconds. If the pressure drops again within a few days without anybody bleeding radiators, there is a leak and it needs tracing rather than topping up repeatedly.
Because it probably needs holding rather than pressing. A Ferroli reset button has to be held for five to ten seconds, and a quick press, which works on most other makes, does nothing at all. The button is usually marked with an R or a flame symbol. Try it properly once before booking anybody, but only once, because repeated resetting hides the fault underneath and on an ignition fault it wears the electrodes while fixing nothing.
A01 means the boiler tried to light the burner and the flame sensor could not confirm a stable flame, so it locked out. It is the most common code across all Ferroli models. Do the hob test first: if a gas hob will not light either, the problem is your gas supply rather than the boiler. In cold weather, excessive condensate in the pipe can block the burner area, and thawing that pipe with warm water often clears it. Otherwise it is usually a dirty ignition electrode, low gas pressure or the gas valve.
No. That is an F code releasing itself once the condition that caused it improved, and nothing has been repaired. Pressure that dipped and recovered, circulation that improved as the house cooled, or a sensor reading that came back into tolerance will all do it. The cause is still there and it will block again, usually on the coldest night when demand is highest. Note the date and time each time it happens, because the pattern is what identifies the cause.
F43 means the exchanger protection has activated, so the boiler has stopped deliberately to protect the most expensive part inside it from damage. The trigger is no circulation through the heat exchanger, caused by air in the system, sludge, or a pump not moving water. The boiler is doing the right thing, but because it is an F code it can release itself once things cool, which makes people think it resolved. Bleed the radiators, check the pressure, and get the system cleaned.
The label is behind the front panel. Ferroli name the range then the output then a letter, so a Modena 32C is a Modena combi rated 32 kilowatts, and S marks a system boiler with a cylinder somewhere in the property. Read us the serial when you ring rather than just the name, because code meanings shift between Modena, Bluehelix, Optimax and the older ranges, and the serial number is what gets an engineer to the right fault table. We work on every make of boiler.
We will not put a number on a repair before knowing what has failed, and you should be wary of anybody who will. Three things drive it: which component has gone, whether it is on the van or has to be ordered, and how long the work takes. On a Ferroli the letter tells us whether the boiler has locked out, which decides how urgently anybody needs to attend. The rate is agreed beforehand and parts we fit are guaranteed for a year, so nothing is carried out on the assumption that you will approve it afterwards. There is no charge for telling you a repair is not the right call. There is more on what drives the price in our guide to repair and replacement costs.
Ferroli is one of the few makes that separates lockout faults from blocking faults in the code itself, which is worth knowing when comparing a fault list against any other brand.
No gas supply? Plenty of London flats run without one, and we also cover electric boiler repair.
A Ferroli that started working again has not necessarily been fixed. When you ring, give us the letter, the number and the range name, and what the display showed if you saw it before it cleared.
Gas Safe registered. Unvented cylinder qualified. Parts guaranteed for a year. Covering London, north and south of the river, 24 hours a day.
