Heating Breakdown in Paris: 5 Checks Before You Call

If your heating has stopped, start with five safe checks: the boiler's circuit breaker, the pressure gauge (1 to 1.5 bar when cold), the thermostat, air in the radiators, and the reset button. Many breakdowns end there. A smell of gas, suspected carbon monoxide or a major leak means you stop and call straight away.

It is cold, you turn up the thermostat, and nothing happens. The radiators stay lukewarm, a red light is flashing on the boiler, and the hot water has gone. It is one of the most common breakdowns of a Paris winter, and it nearly always comes at the worst moment: during the first real cold spell, when the boiler goes back to full power after months of rest. That sudden restart is what exposes the weaknesses built up over the year.

This guide helps you work out what is going on, carry out the safe checks yourself, and recognise the situations where you should call without waiting.

No heating right now? Réseau Tubulure works across Paris and the inner suburbs, 7 days a week, 24 hours a day. Call 01 89 70 15 36 or see our heating engineer service.

Identify the problem in two minutes

First, work out which kind of breakdown you have. The three families below have different causes and different levels of urgency.

Total breakdown: no heat at all

Symptoms. The boiler is off, every radiator is cold, and there is no sound of it running.

Common causes: a power problem (circuit breaker, fuse), water pressure too low on a gas boiler, a faulty thermostat, the boiler locking out in safety mode, or a pilot light failure on older models.

Urgency: high in winter. Below 10 °C outside, allow 24 to 48 hours before the flat becomes genuinely uncomfortable, and before pipes start to be at risk of freezing.

Partial breakdown: the heating is not keeping up

Symptoms. The boiler runs but some radiators stay cold, or all of them are lukewarm instead of hot.

Common causes: air in the radiators, sludge in the circuit, a failing circulation pump, a stuck thermostatic valve, or a boiler that is too small for the home.

Urgency: medium. The flat still gets some heat, but you are uncomfortable and paying for wasted energy. If the problem is in the radiators themselves, our guide to radiators that do not heat properly covers bleeding and flushing (désembouage).

The boiler starts and stops in a loop

Symptoms. The boiler fires up, heats for five to ten minutes, stops, restarts, and stops again.

Common causes: a thermostat that is badly set or badly placed, unstable pressure, a clogged circulation pump, or a faulty temperature sensor.

Urgency: medium to high, depending on the outside temperature. This short cycling usually ends in a permanent safety lockout, and it wears the boiler out.

The boiler goes into safety mode

Symptoms. A red light, an error code on the display, and a complete stop.

Safety mode is a protection, not a fault in itself: the boiler shuts down to avoid damage. The most common cause is low pressure (covered below), but it is not the only one. An ignition fault from a dirty electrode, overheating caused by a sludged-up circuit, a flue blocked by a nest or leaves, a sensor sending false readings: from the outside, all of these look like the same red light.

The five checks to make before you call

These five checks are safe and solve a good share of breakdowns. Do them in this order.

1. The power supply

Open your fuse box (the "tableau électrique") and find the circuit breaker for the boiler, usually labelled "chaudière" or "chauffage". If it is down, push it back up and keep an eye on the boiler for an hour.

If it trips again straight away, do not keep trying. A breaker that trips immediately points to a short circuit, and forcing it is genuinely dangerous. On the other hand, a one-off power surge (a storm, a brief cut on the grid) can trip the breaker without the boiler being at fault.

2. The system pressure

A boiler heats water in a closed circuit that feeds the radiators. To circulate properly, that water has to stay under pressure. On most boilers, normal pressure is between 1 and 1.5 bar when cold, shown on a needle gauge or a digital display.

Below about 0.5 bar, the boiler can no longer heat the water safely and it locks out. At the other end, above 2.5 bar another safety device trips and the pressure relief valve may discharge water.

Get into the habit of glancing at the gauge now and then, even when everything works. Knowing your system's usual pressure lets you spot a problem immediately. A small difference between cold and hot is normal, because water expands as it heats. A sharp drop is not.

3. The thermostat

Check it is set above the room temperature. If it is programmable, make sure it has not been left on "away" or "night" mode. If it is wireless, change the batteries: weak batteries cut the link with the boiler without any other symptom. Then raise the setting by 5 °C for a moment to force the boiler to fire.

This matters more than it sounds: a large share of heating "breakdowns" turn out to be a wrong setting or flat batteries. In some buildings with shared heating, each flat also has its own heat meter; check that its display is working and its batteries are not flat.

4. Bleeding the radiators

If some radiators are cold at the top while the bottom is warm, there is air in the circuit.

Open the bleed valve (the small screw at the top of the radiator) with a radiator key, let the air out until water comes through, then close it straight away. Repeat on each cold radiator, then check the boiler pressure again: bleeding lowers the pressure in the circuit, and it is a very common reason for a boiler to lock out just after bleeding.

Do this once a year, in October or November, before the heating season starts.

5. The reset button and the error code

If the boiler shows a code, write it down before you touch anything. Then press the "reset" button (sometimes marked "réarmement"), usually red or orange.

If the boiler restarts and runs normally for two to three hours, the fault was a one-off. If it goes back into error immediately or within half an hour, the breakdown is confirmed, and the code you noted will save the engineer real time.

How to repressurise your boiler, step by step

This is the most useful thing in this guide, and you can do it yourself.

Step 1: switch the boiler off and let it cool

Turn the boiler off and wait for it to cool, ideally around thirty minutes. Working on a cold circuit gives you a reliable reading and avoids any risk of burns. Note the starting value on the gauge so you know how far you need to go.

Step 2: find the filling valve

Under the boiler or just beside it is the filling valve, sometimes called the filling loop (in French, "robinet de remplissage" or "disconnecteur"). It is often a small handle or a key-operated tap linking the heating circuit to the cold water supply. Some models have two, which you open together. The boiler manual, usually available online, will help you find it.

Step 3: open slowly until you reach the right pressure

Open it slowly. You will hear water coming in and see the needle rise gradually. Close it as soon as the pressure reaches 1 to 1.5 bar. Take your time: it is easy to overfill, and pressure that is too high trips another safety device and means draining some water back out.

Step 4: close the valve and restart

Close the valve completely; this is essential. A valve left slightly open keeps pushing the pressure up and causes another lockout. Then switch the boiler back on: in most cases the fault clears within a few minutes.

If the pressure drops again, find out why

Topping up the pressure from time to time is normal on an ageing system. Having to do it every week is not.

Pressure does not drop by chance. The usual causes are a recent bleed that let water out, a small leak somewhere on the circuit (often invisible, sometimes at a joint or a radiator), a tired expansion vessel, or a worn pressure relief valve letting a trickle of water escape all the time.

Watch how often it happens. A slow loss over several months is ordinary and a simple top-up fixes it. A drop that keeps coming back points to a leak or a faulty part, and topping up only postpones the real problem.

Understanding error codes

Modern boilers show a code when they lock out. The code is there to inform you, not to alarm you. Each manufacturer has its own references (a letter and a number, such as "F28" or "E03"), but the same families come up: a code for pressure, one for ignition, one for overheating, one for the temperature sensor.

Note exactly what is displayed before doing anything. Keep the manual within reach too: it often includes a table of codes and first steps. A restart sometimes clears a passing code; if it comes straight back, the cause is real.

When to call a heating engineer urgently

Real emergencies: do not try anything yourself

A smell of gas. Our full instructions are in what to do if you smell gas. In short: open all the windows. Do not switch anything on or off, and do not use a phone in the room. Turn off the gas at the meter, leave the flat, call the GRDF gas emergency line on 0 800 47 33 33 (24 hours a day), then call a heating engineer.

Suspected carbon monoxide. Headaches, nausea or dizziness affecting several people in the home at the same time: open the windows, get out immediately, and call the fire brigade (18) or the SAMU emergency medical service (15). Do not use the boiler again until it has been checked.

A major water leak from the boiler. Turn off the water supply and the electricity to the boiler, put containers under the leak, and call urgently: the risk of water damage now comes on top of the breakdown.

Call within a day or two

• It is below freezing outside and you have no heating.
• The five checks above have not worked.
• The error code persists after a reset.
• You hear unusual noises: high-pitched whistling, banging, rumbling.
• Smoke or soot appears around the boiler. Switch it off immediately.
• The pressure drops several times a week.
• You have neither heating nor hot water during a cold spell. If only the hot water is missing, see our guide to emergency water heater repair instead.
• The boiler is over fifteen years old and keeps breaking down: this is the point to weigh repair against replacement (see the end of this guide).

The five most common breakdowns

Listed from most to least frequent during the heating season.

1. Pressure too low. Small leaks, a recent bleed, natural loss over time. Often fixed by the repressurising steps above; if it keeps happening, the leak has to be found.

2. A failing circulation pump. The boiler heats but the radiators stay cold, or only the ones nearest the boiler get warm. The pump is blocked by sludge or worn out. Replacement takes one to two hours.

3. A faulty thermostat or sensor. The boiler will not start, or starts and stops for no apparent reason. Replacement takes about an hour.

4. A stuck three-way valve. You have hot water at the taps but no heating, or the other way round. The valve that sends hot water either to the radiators or to the taps is stuck. Freeing or replacing it takes one to two hours.

5. A scaled-up heat exchanger, more common in Paris. Lukewarm hot water, weak heating, a bubbling or kettling noise. Descaling or replacing the exchanger takes two to four hours.

Boiler leaking, pressure rising or a noise like a plane

Boiler leaking water

A puddle under the boiler does not always have the same cause. First find where the water comes from:

• The safety valve pipe is dripping: the system pressure is too high and the valve is releasing the excess. Check the pressure gauge (see below).
• Water beads at a fitting under the boiler: a seal or nut to tighten or replace.
• Water runs from inside the casing: a holed heat exchanger, pump or boiler body. Do not open the cover.
• Water comes from the condensate pipe of a condensing boiler: the pipe is blocked or has come loose.

While you wait for the heating engineer, switch the boiler off, close its cold water inlet valve if the leak is heavy, put a container underneath and mop up. If water is near the electrics, switch off the circuit breaker. A small leak that lowers the pressure day after day will end up putting the boiler into safety mode: have it fixed before then.

Boiler pressure keeps rising

If the gauge needle goes well above the usual range (1 to 1.5 bar when cold) and gets close to 3 bar when heating, the extra water has to go somewhere: often the safety valve starts dripping. Three causes come up most often:

• the filling valve has been left slightly open or no longer closes fully;
• the expansion vessel has lost its air charge and no longer absorbs the expansion of hot water;
• on a boiler that also heats your tap water, a holed domestic hot water exchanger lets mains water into the heating circuit.

Check that the filling valve is fully closed. Bleeding a radiator brings the pressure down, but if it climbs again, the heating engineer needs to check the expansion vessel and the exchanger. Never block the safety valve.

Boiler making a noise like a plane

A loud whoosh or roar, which many people compare to a plane taking off, usually comes from one of these:

• the flue fan of a room-sealed boiler, dirty or with a worn bearing;
• the burner, badly adjusted, roaring on ignition;
• a scaled heat exchanger that boils the water in spots: the noise then sounds like a kettle;
• air in the circuit, or a pump set too high.

Bleed the radiators and check the pressure. If the noise continues, have the boiler checked: a fan or burner that is straining is a breakdown waiting to happen, and a badly adjusted burner is also a safety matter. In small Paris kitchens, where the boiler hangs close to the living space, the noise is hard to miss: use it as a reason to act early.

Heating in Paris: three local factors

Shared heating: is the problem only in your flat?

In an older building with shared heating ("chauffage collectif"), a breakdown in your flat is not necessarily a breakdown for the whole building. Ask your neighbours whether they are cold too. If it is building-wide, the syndic (the building's managing agent) is the one who calls out the heating engineer. If it is only your flat, the problem is on your part of the circuit: radiators, valves, or your individual meter.

Thermostatic valves stuck in the closed position are a classic: your radiator stays cold while the shared system works perfectly. If the whole building is badly heated, our article on inadequate shared heating explains your options.

Hard Paris water

Paris tap water measures 20 to 30 °f (French degrees of hardness), which noticeably speeds up scaling in the heat exchanger. Descaling every three to five years is recommended; without it, the loss of efficiency becomes noticeable at around eight to ten years. An anti-scale treatment on the closed heating circuit limits the problem.

Boilers on the roof or in the cellar

In Paris, many boilers sit on the top floor, in former maids' rooms ("chambres de bonne"), or in the cellar. Two consequences: a risk of freezing below minus 5 °C (our guide to frozen pipes in Paris explains how to prevent and deal with it), and access that can be awkward for an urgent call-out. If you go away in winter, always leave the frost protection mode on: it holds the temperature at 7 to 8 °C and protects both the boiler and the circuit. For a longer absence, our article on turning off the water before a winter holiday covers the other precautions.

While you wait: staying warm safely

Electric heaters. No more than 1,500 to 2,000 W per socket, never on a power strip, kept away from curtains and furniture, with five minutes of fresh air every hour.

Gas, paraffin or ethanol heaters: avoid them in a flat. The risk of carbon monoxide poisoning is real. If you have no other choice: constant ventilation, a CO detector, and never while you sleep.

Keep the heat in. Close the shutters at night (this cuts heat loss by around 20 %), block the gaps under doors, shut rooms you are not using, and open the curtains on the sunny side during the day.

Protect the pipes from freezing if the indoor temperature falls below 10 °C: leave a thin trickle of cold water running, and open the cupboard doors under sinks so room heat reaches the pipes.

Heating engineer or plumber: who should you call?

The two trades are often confused and they do overlap, but they are not the same. A plumber works on water systems: leaks, taps, pipes, water heaters. A heating engineer ("chauffagiste") specialises in producing and distributing heat: boilers, radiators, underfloor heating, heat pumps.

The difference matters most for anything involving gas and combustion, which requires a specific qualification, and for work that qualifies for French energy-renovation grants, which must be done by a contractor holding the right label. Our guide to the certifications to check before hiring a tradesperson explains each label and how to verify it.

Our article on the difference between a plumber and a heating engineer goes into both trades in detail.

Preventing the next breakdown

Most winter breakdowns would be avoided by regular servicing, and for a gas or oil boiler annual servicing is a legal requirement. It clearly reduces the risk of a breakdown and improves efficiency.

The best time is autumn, before the first big cold snap, when engineers are less stretched. Our full guide to gas boiler servicing in Paris covers the legal obligations, what the visit involves, and how to plan it.

Three simple habits complete the servicing: bleed the radiators once a year in October or November, check the pressure once a month during the heating season, and leave the frost protection mode on when you are away. Our plumbing checklist before winter brings together all the start-of-season checks.

Finally, watch for early warning signs: a new noise, less steady hot water, radiators taking longer to warm up. They often come before an outright breakdown. If your boiler is over fifteen years old and breaking down more and more often, replacement becomes a real question: our article on when to replace your boiler compares the cost of repair with the cost of replacement.

Frequently asked questions

What is the right pressure for a boiler? Between 1 and 1.5 bar when cold. It rises a little when the boiler is running, which is normal. Check your boiler's manual, as the values vary slightly between models.

How often can I top up the pressure myself? Occasionally, as often as needed. If you have to do it every week, there is a leak or an expansion vessel at the end of its life, and topping up only hides the problem.

Is it dangerous to leave a boiler in safety mode? No. Safety mode is precisely a protection. Forcing repeated restarts without dealing with the cause, however, wears the boiler and can hide a more serious problem.

Can I repair my boiler myself? Beyond the checks described here, no. Any work on a gas boiler is a job for a qualified professional, because of the risks of a gas leak, carbon monoxide and explosion.

My landlord is not answering. What can I do? Heating is one of the features a rented home must have to be considered decent housing (Article 1719 of the Civil Code and Article 6 of the law of 6 July 1989). If your landlord cannot be reached for more than 48 hours in winter, you can call out a heating engineer yourself and ask to be reimbursed. Keep the invoices, photos and proof of your attempts to get in touch.

Who can I call at night or at the weekend? Out-of-hours emergencies go through an on-call system. Our article on the on-call plumber in Paris explains how it works and what to check before you call. Réseau Tubulure takes calls 7 days a week, 24 hours a day on 01 89 70 15 36.

Heating breakdown? We can help

You have done the checks and the heating is still off? Do not stay in the cold. We take calls 7 days a week, 24 hours a day. Many of our plumbers speak English.

Réseau Tubulure works in Paris and the inner suburbs: Paris (75), Hauts-de-Seine (92), Seine-Saint-Denis (93) and Val-de-Marne (94) (see our service area), on all types of heating: gas, oil and electric boilers, and heat pumps.

01 89 70 15 36 (from abroad: +33 1 89 70 15 36). Request a visit · See our prices