The gas boiler does not start

Nothing is more frustrating than a gas boiler that won’t start when winter really gets in. A broken boiler, the beating heart of your house’s heating system, can leave you cold, both literally and metaphorically. Knowing the reason behind your boiler’s failure to ignite is essential to bringing warmth and comfort back to your home, regardless of whether you use it for radiant heating, hot water, or both.

There could be a number of reasons why your gas boiler isn’t working. It could be something as straightforward as a blown fuse or something more complicated like an internal boiler component issue. Prior to losing your cool or contacting an expert, it’s advisable to troubleshoot the issue methodically.

First, review the fundamentals. Make sure the pilot light on the boiler is lit; this is frequently the easiest fix for a boiler that refuses to start. To safely relight it if the pilot light is out, adhere to the manufacturer’s instructions. It’s time to look into more serious reasons if the boiler won’t ignite even with the pilot light on.

Lack of fuel is a common cause of a gas boiler that won’t start. Verify that the gas valve on your boiler is open and that your gas supply is turned on. Make sure there is enough oil or propane in your tank before using it. Sometimes a straightforward mistake, such as a closed valve, can spare you needless aggravation and repair expenses.

A broken thermostat could be an additional problem. The boiler may remain inactive if the thermostat isn’t signaling it to begin heating. To check if your thermostat is igniting the boiler, try turning it up a few degrees above the room temperature. If not, the thermostat might need to be replaced or calibrated.

Additionally, take into account the potential for an electronic control module malfunction or an ignition system issue. In contemporary gas boilers, these parts are in charge of starting the ignition sequence. No matter what else is going on, if they’re broken, the boiler won’t start. In these situations, seeking professional assistance may be required to identify and address the issue.

In conclusion, having a gas boiler that won’t start can be a difficult situation, particularly in the chilly winter months. Nonetheless, you can frequently identify the issue and take the necessary action by methodically looking for common problems like pilot light status, fuel supply, thermostat functionality, and ignition system integrity. Always remember that safety comes first when working with gas appliances, and always seek the advice of a trained technician if in doubt.

Why the gas boiler goes out and how to fix the problem with your own hands

When heating equipment, like a gas boiler, breaks down in the middle of winter in a private residence, it can be very unpleasant. Murphy’s law states that on the coldest days, the heat source begins to lose heat. When it does, the system’s heat transfer medium quickly cools down, which in turn causes the building as a whole to rapidly cool down.

Immediately calling a master who can solve your problem comes to mind. The concept is sound, but there are a number of reasons why a specialist’s arrival could be hours or even days away. Rather than letting it freeze slowly, attempt to identify the cause of the gas boiler’s failure and solve it on your own. We’ll advise you on what to do in this circumstance.

Why the burner of the gas boiler goes out

The solution is straightforward: all heating units that use natural or liquefied gas have dependable automation installed on them that cuts off the fuel supply. There will be a disconnect in any one of the three scenarios:

  • reduced or no draught in the chimney;
  • the gas pressure in the supply line has fallen below normal;
  • the flame of the burner itself has gone out.

As a point of reference. Gas valves manufactured in Italy by American Honeywell or EuroSIT are the devices that automatically shut off.

Automatics can be activated by outside forces as well as by any component of the heat generator breaking. Energy-independent floor standing boilers with straightforward designs are easier to maintain in this sense because there is practically nothing to break in them and the burner is more likely to fade from outside factors than from malfunctions. Among these brands are Ross, Danko, Zhitomir, Aton, and other producers of gas-powered appliances from the former USSR.

Gas valves from Honeywell (left) and EuroSit (right)

A more contemporary wall-mounted electric gas boiler with a closed combustion chamber functions as a mini boiler room and has extra safety features that cut off the fuel supply in certain circumstances:

  • movement of coolant in the heating system has stopped (flow sensor is triggered);
  • air supply has decreased or stopped, which is signaled by the pressostat (another sensor);
  • there are voltage surges in the house power supply;
  • power failure.

Note: Currently, only one Russian manufacturer, Neva, sells high-quality wall-mounted boilers; imported brands from Korea and Europe make up the majority of the market.

Different types of natural gas-burning home heaters

It is difficult to fix a wall-mounted heat generator when it starts to malfunction, but there are a few issues that can be fixed by hand. Read on to learn how to do it correctly.

This post about diagnosing a gas boiler that won’t start will look at common causes of this problem and workable fixes. It can be annoying and uncomfortable when your gas boiler won’t light, especially in the winter. The problem may be caused by a number of things, such as problems with the electrical components, gas supply, or pilot light. You can frequently fix the issue on your own without hiring a specialist by methodically inspecting these possible offenders and carrying out simple maintenance duties. In order to keep your house warm and cozy, this article attempts to offer clear instructions that will assist you in identifying and resolving the problem.

Attenuation of boilers with an open combustion chamber

By default, we take into account the scenario in which the heating system has operated faultlessly for a few seasons but has recently begun to malfunction for unknown reasons. The following is a longer list of factors that trigger the automatic valve to cut off the gas supply:

  • The draught in the chimney has disappeared;
  • there were problems with the supply of natural gas, from which its pressure in the pipe fell below normal;
  • the boiler lacks air for combustion, causing the flame to go out;
  • The burner is blown out by a strong wind outside or the flame breaks off in a strong draught inside the house;
  • hardware faults of the gas boiler – failure of the draught sensor or thermocouple.

A poetic aside. The damping of the gas burner device might not be noticed by the homeowners right away, particularly if it is installed in a separate room. Once the private home’s air temperature has dropped, the issue is identified.

The boiler burner has extinguished, causing the radiators to cool.

Therefore, if your boiler’s main burner goes out, follow the steps below to find the cause. Start by looking for a chimney draught. Let’s examine each step in greater detail.

Problems with the draught

Checking the draught is the first thing atmospheric gas boiler owners should do when the burner fades out. Light a candle or a box of matches, carry it over to the viewing window, and watch how the flame behaves. If it deflected in the direction of the opening, the draft is in good condition and you can move on to the next step.

In the event that the flame does not deflect, the chimney is not draught-free.

The flame doesn’t move, indicating that the chimney draft has disappeared and the burner’s cause has been identified. What you did:

  1. Open a window in the boiler room to ensure that there is a guaranteed air supply into the room.
  2. Disconnect the section of the chimney connected to the outlet pipe of the heating unit, then check the presence of draught in the chimney itself. If there is one, you need to disassemble and clean the gas boiler itself, which is described in a separate article .
  3. If the draft is not detected in the main duct, it is probably clogged. Locate the maintenance and cleaning hatch, it is located in the boiler room below the connection point or outside. Open the manhole and slip a mirror inside to see the exit hole. If it is not visible, the chimney should be cleaned.
  4. Inspect the header of the pipe from the outside, during the summer period there could be a bird"s nest. Another option is a solid frosting of the hood covering the chimney cutoff. This happens in severe frosts, when ice blocks the working cross-section of the chimney.

Hooded, icy chimneys

Crucial! Placement of umbrellas over chimney pipes is expressly forbidden by the operating regulations of gas-using installations. You need to take off that cap if you have one.

A succinct rundown of the reasons why chimney blockages occur:

  • uninsulated brick walls are destroyed by condensate, which causes the passage section to be clogged with construction debris;
  • In cheap sandwich chimneys, the zinc coating may peel off from the inner wall and block the channel in the form of a thin film;
  • To one chimney connected 2 boilers – gas and solid fuel, so it is clogged with soot;
  • Foreign objects from bird activity can get into the pipe.

Not only can a lot of soot accumulate in the chimney stack, but birds can also

When low outside temperatures cause the pipe walls to freeze through, pipe cleaning may not be successful. The truth is that the gas heat generator’s combustion products only reach a temperature of 120 °C, which is too low to heat the chimney and produce a steady draught. The only option left is to purchase a disposable torch with a can, light it, and insert it into the open cleaning hatch because you won’t be doing insulation in the middle of winter. Start the boiler as soon as the frozen channel begins to warm up; do not turn it off abruptly or else you will need to repeat the process.

Something to think about. Situations arise when a nearby plot begins construction on a two- or three-story cottage close to your home. Because of this, the chimney may enter the adjacent building’s leeward zone. This reduces the draft, which causes the gas boiler to go out of service. It is not possible to stop your neighbors from building, so you will need to raise the chimney by one to two meters to remove it from the stagnant zone.

Additional factors contributing to the poor draught in the chimney and wind blowing (from the left to the right) include the chimney cut’s low location, tree obstructions, and downward air flow.

The easiest and least expensive solution to stop wind from entering a troublesome chimney is to install a screen over the gas boiler’s outlet. Its position will need to be adjusted, though, when the weather changes, as a partially closed section of the channel heater will not operate at its best and could release carbon monoxide into the house. Therefore, extending the chimney by one or two meters is the most effective way to prevent draft tipping.

Reduction of gas pressure in the mains

Checking the fuel supply is the next step to take after you are certain there is a draft in the chimney. The burner is fading for no apparent reason, but the flame on the boiler’s igniter is still burning. This is an indication of low gas pressure at the inlet. Actions that you can take:

  1. Check how well the gas flows from the pipeline. First, close the door to the boiler room, open the window and unscrew the supply hose from the pipe of the heat generator. Open the gas tap briefly. A sign of a good supply is a loud hiss from the hose and a strong odor of odorized methane. Put the hose back in place and check the tightness of the joint with a soap solution.
  2. If the fuel supply is poor, clean the gas strainer and then try to ignite the wick and the main burner of the boiler. If the result is negative, call the appropriate service and call a master – gas technician.

Caution! Make sure you use the cut-off valve to turn off the gas before making any changes to the fuel line!

The main line could be clogged inside the gas meter before it reaches your heating unit. This occurs when rust or welding scale seeps into outdoor pipelines that have been repaired. However, disassembling the metering device for cleaning is not permitted; in this case, calling a master will be of assistance.

On the supply pipe, the meter and the filter

The fuel supplier is required to check the mains’ pressure and increase the amount of gas supplied at the start of the heating season, when thermal equipment is widely installed in private homes. There may not be enough fuel for customers who are at a dead end in the network when the service responds slowly at times. Here, your only options are to call the supplier’s company in a furious manner or, if there is one, turn on the second boiler using wood or electricity.

Insufficient and excessive air

The possibility of the gas boiler catching fire at any time arises from any one of these phenomena. The furnace room needs fresh air from other rooms or from a ventilation duct in order to function properly. Strong drafts should also be prevented as they have the potential to blow out a burner that is in low power.

It is easy to confirm that there is not enough oxygen present: just open the closest window and watch how the flame behaves. The cause of the fading is evident if the burner’s operation has stabilized. Let’s examine the causes of it:

  • you have installed airtight plastic windows and the air supply inside the house has stopped;
  • one or more interior doors have been replaced and the gaps between the sashes and the floor, where air used to pass through, have been greatly reduced;
  • you have installed a powerful kitchen extractor hood, pulling part of the air flow to itself;
  • The same effect is observed when installing a forced extractor hood in the toilet and bathroom.

Diagram schematic for an atmospheric burner

When purchasing different exhaust devices, keep in mind that the air removed must be balanced by the air entering the system; otherwise, the chimney’s draught will lessen or possibly tilt in the other direction. Then, the issue of what to do if the wind blows the gas boiler comes up. Special air inlets must be installed on plastic windows, and a mechanical inflow from the street must be arranged to offset the forced exhaust.

A tip: The cost of purchasing and installing an air inlet unit is high. Organizing natural inflow to areas with excess heat (like the kitchen or the boiler room directly) can serve as a compromise because the outside air will have time to warm up.

On a different level, there are convectors and parapet gas boilers with a short coaxial chimney that exits through the wall. Since the byproducts of combustion pass through them organically, it is common to witness the burner being blown by the wind when the flue outlet is located in an unfavorable location. Finding the direction of the yard’s draught and securely shutting the windward side grille will solve the issue.

How to handle wind entering a coaxial chimney

Atmospheric boiler malfunctions

Certain components in non-volatile floor-standing heat generators can malfunction after many years of use. The following are indicators that they are failing:

  1. When trying to ignite the igniter, it extinguishes immediately after releasing the button on the valve. This means that the thermocouple, which is heated by the wick and keeps the gas supply solenoid valve open, has failed.
  2. The floor gas boiler does not ignite at all, not even the ignition burner. This indicates a failure of the draught sensor.
  3. When the main burner ignites with difficulty, operates intermittently and pops, and the color of the flame is yellow, the main fuel injector is clogged.

Draught sensors and thermocouple (left) from various manufacturers

The thermocouple is a copper tube that has a capillary attached to the gas valve coming out of the other end that is sealed. The heat-sensitive fluid inside the element expands as a result of the igniter flame washing it clean. The thermocouple can only be replaced; it cannot be repaired.

As a point of reference. There are two thermocouples in some boiler models (Lemax, for example).

The draught sensor is an accessory that resembles a tablet. It is mounted on the combustion product outlet and is wired in tandem with the gas valve. Checking the operability is simple: just close the contacts where these wires are connected, try lighting the burner, and replace the sensor if it works. Old connecting wires that create a high resistance can occasionally be the cause of the fault because it supplies a negligible voltage. Replacing them solves the problem.

The igniter’s flame cleans the thermocouple, which is fixed on the same flange.

It is not advised to use your hands to remove the boiler’s gas burner device in order to clean the jaculator. If there isn’t any other choice, remember to turn off the gas before beginning any work and then loosen the fasteners. Reassemble the gas line joints and use a soap solution to check for leaks. Try not to disassemble any unnecessary joints.

Furthermore. When the circulation pump outside the boiler breaks, the floor heating unit’s burner won’t light up. After heating the water in the boiler tank, it will turn off and wait for the coolant to cool.

Repair of wall-mounted and turbo units

Open and closed combustion chamber wall-mounted gas boilers are more sophisticated appliances with contemporary electronics and safety features. Yet, some issues can also be resolved on their own in this situation. For atmospheric heat generators with wall-mounted designs, all of the previously mentioned adjustments involving the inspection of the draught, fuel supply, and sensors are equally pertinent.

The product instruction manual and a Phillips screwdriver are all you need to locate problems with the wall-mounted electric gas boiler; other instruments are probably not necessary. The heater display’s fault codes are specified in the technical passport, and removing the front panel requires a screwdriver.

The heat generator is in three non-operational states:

  1. The boiler is switched off completely, no indicator light is on.
  2. The unit is switched on, the display and mains indicator are lit, but no automatic ignition occurs.
  3. There are attempts to start the main burner, but after ignition it immediately goes out.

Advice: Always make sure the wall-mounted boiler is powered on in case of a total failure when it comes to powering the house. One possibility is that the switchboard’s tripped circuit breaker is the root of the issue. Second moment: nearly all imported units are phase-sensitive, and reversing the plug in the socket to reverse the positions of the contacts frequently fixes the problem.

The boiler’s electronic board contains the fuse block.

We can address condition #1 after confirming that the heater is powered on. Using a screwdriver or star wrench, unscrew the gas boiler’s front panel and remove it, or tilt the front cover, depending on the model, to accomplish this. The algorithm then looks like this:

  1. Find the fuse box and check each of them with a multimeter or visually. There will probably be one blown fuse.
  2. As a rule, the spare fuse is glued from the inside to the front panel. Replace the burnt-out one or buy a new one (of exactly the same rating)!).
  3. Try to start the heating unit. If it works, the repair is complete, put the cover back in place.
  4. The unit turned on and then "died" again? It remains only to call a master, because the malfunction is more serious.

Advice: After prying open the panel, thoroughly examine every component of the heat generator to check for burned-out parts on the board, broken or missing wires, and leaky joints. In the event that the latter is found, contact a specialist right away. Our expert Vladimir Sukhorukov will provide more information in his video regarding the wall-mounted gas boiler’s troubleshooting algorithm:

When one of the other two inoperative states occurs, the display indicates an error code that can be used to look up the malfunction in the product passport. The specialist suggests doing the following: You should take action when the error code is accompanied by the words "call for service" in the documentation because you are incapable of handling the breakdown on your own. You can get rid of these mistakes by yourself:

  1. Clogged strainer filtering the coolant from the heating system. Disconnect the heat generator from the house power supply, close the taps and clean the mesh of the element.
  2. The built-in circulation pump does not work. Causes – rotor jamming or air lock. In both cases, unscrew the large screw (centered on the pump) and bleed the air or turn the rotor with a screwdriver. Proceed carefully, a little water will leak out of the hole.
  3. When the boiler pressure gauge shows low pressure, and there are no leaks in the heating system, you need to pump air into the expansion tank, mounted inside the heating unit. The pressure on the air side of the diaphragm must be lower by 0.2 Bar than in the system. Read more about pumping the tank here .
  4. If a leak is detected at low pressure, it must be repaired and then water must be added to the system.

Note: If the room thermostat’s electrical circuit or the gas boiler’s own thermostat is damaged, the display won’t indicate a problem. Additional details are provided by our expert in the second segment of the video:


Undoubtedly, the typical user will not be able to resolve a significant heat generator malfunction. In the event that a minor issue causes the gas boiler to malfunction, you can intervene to not only restore heat to the house but also avoid incurring additional costs for calling a service technician. The most important thing is to approach the task with confidence, pay attention to advice, and avoid making needless movements that could further harm the heat source.

We recommend:

The most affordable gas boilers for heating homes How to install a draught regulator on a solid fuel boiler and what does it entail? How should a hot water boiler be selected for a warm floor and connected to the comb correctly?

Boilers and burners > Reasons for gas boiler failure and do-it-yourself solutions

How to start the gas two-circuit boiler after an emergency stop?

Good day. I turn to you with such a problem. We have a two-circuit boiler with a coaxial system in our house. During the repair of the heating system was drained of all water. At this point, my wife decided to wash the dishes and turned on the hot water tap. The boiler, of course, reacted, and as a result there was an emergency shutdown of the device. The alarm sensor was triggered. When the pipe repair was completed and the system was filled with water, the boiler failed to start up. The emergency light was on and the heating system did not start up. We can not invite specialists, as the nearest service is 100 km away. Help to start the boiler correctly. The boiler brand is Viessmann.

After a gas boiler emergency shutdown, you must fill the radiators and pipes with water to turn on the heating system. Prior to doing so, check the boiler’s technical passport to determine the minimum and maximum working pressure of the water in the system, then fill in the spaces around these numbers. Verify the pressure level on the sensor, which is mounted on the device’s front panel (depending on the brand, it may be at the side or bottom).

The temperature and pressure sensor is displayed as a red arrow with two scales on it. The pressure is on the lower scale, and the system heating temperature is on the upper scale.

Check the gas connection after that. The gas supply tap is unblocked and all connecting hoses are in their proper locations.

Press the boiler’s "mains" button to restart the system if everything is in working order.

Unlocking the boiler emergency condition

  1. Use the heating temperature regulator knob on the boiler dashboard to set the temperature to maximum.
  2. Then sharply turn off the temperature regulator to zero.
  3. Repeat the procedure 2-3 times, turning the sensor from maximum to minimum.
  4. Leave the regulator in the position at the maximum temperature and wait for automatic unlocking of the boiler. The system must start automatically.
  5. Wait for the emergency stop light to go out.
  6. After these manipulations, we set the regulator mode of the desired temperature.
Problem The gas boiler does not start
Possible Cause 1. No gas supply
2. Pilot light is out
3. Faulty thermostat
4. Electrical issues
Solution 1. Check gas supply and valve
2. Relight pilot light according to manufacturer instructions
3. Test and replace thermostat if necessary
4. Inspect electrical connections and components, repair or replace as needed

It can be annoying and inconvenient to have a gas boiler that won’t start, especially in the winter. But in order to find and fix the underlying problems, you must approach the situation with a systematic troubleshooting mindset.

Check the essentials first: make sure the boiler’s gas supply is turned on and that there are no problems with the gas meter or supply line. An easy mistake in these areas can occasionally be the cause of a boiler that won’t start.

Examine the boiler’s ignition system next, if the gas supply appears to be operating normally. Typical parts of this system include the igniter, flame sensor, and pilot light. Make sure all of these parts are clean and operating properly. A malfunctioning ignition system is frequently the reason why boilers don’t start up.

Don’t forget to take into account the potential of a broken thermostat. It might be necessary to replace or calibrate the thermostat if it is not informing the boiler to begin heating. There are occasions when checking and adjusting the thermostat settings will fix the problem.

The ventilation system of the boiler must also be inspected. Inadequate airflow caused by blocked vents or flues can cause ignition issues. To aid in the combustion process, remove any obstacles and make sure the ventilation system is operating properly.

It could be necessary to bring in a qualified technician if you’ve tried all the above solutions and the boiler still won’t start. They are equipped with the knowledge and resources necessary to identify more complicated boiler problems, like broken internal mechanisms or defective electrical parts. Without the necessary skills, attempting to fix these problems can be risky and worsen the boiler’s damage.

In summary, resolving a non-starting gas boiler necessitates a systematic approach and meticulous attention to detail. You can usually find and fix the issue by methodically inspecting the gas supply, ignition system, thermostat, and ventilation. The safest course of action to guarantee the effective and secure operation of your boiler is to seek assistance from a qualified technician if troubleshooting attempts prove to be fruitless.

Video on the topic

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Does not start the gas boiler "Zhitomir". Problem and solution.

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If the gas boiler does not start

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Sergey Ivanov

I like to help people create comfort and comfort in their homes. I share my experience and knowledge in articles so that you can make the right choice of a heating and insulation system for your home.

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