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Boiler Not Firing Up – 9 Reasons Your Heating and Hot Water Boiler Won’t Start

A woman tries to start a boiler that's not firing up

You need about 15 minutes to realise that there is no heating or hot water after you have turned on the boiler. If that happens, then it’s more than just bad luck on a chilly Monday morning. Something is not quite right with it. Your boiler is obviously not firing up for central heating, but before you call a boiler engineer, try the simple checks that might save the day. This seemingly tedious situation might need a quick DIY fix if there is no power or gas supply to the boiler. 

Disclaimer: But if the issue is with the boiler burner, fan, or pilot light, you should leave it to the professionals to diagnose and repair. As you probably know, boiler problems may result in life-threatening situations and carbon monoxide leaks, so in order to avoid putting your life and property in danger, act quickly and call a Gas Safe registered engineer to fix your boiler for you.

So, if you are somebody who:

  • can’t get any heating or hot water because of boiler lockout; 
  • has moved into a new property but skipped the pre-purchase plumbing and gas check; 
  • wants professional help from a trusted tradesman;
  • has an old and unreliable boiler;

Then this article is for you. 

In this post, you will learn about the common reasons why your boiler won’t fire up, what does the error code on your boiler display means, and how to fix it.

Why is Your Boiler Not Firing Up

Reason #1: Boiler has no power

Your boiler needs a small amount of electricity to ignite. Keeping that in mind, here are the possible causes why your boiler might not have power:

  • there is a power outage during heavy snow, lightning, strong winds, and other harsh weather conditions;
  • You have manually changed your thermostat’s settings;
  • You have accidentally turned your boiler off;
  • The circuit was overloaded, and the breaker has tripped;
  • Your home has reached the preset temperature.

Error codes:

Boiler brandCommon boiler fuse lockout codes
WorcesterFD 231, C1 264, Thermal fuse lockout
BaxiE317, OFF OFF OFF, E13
Glow-wormGreen LED off, F17, F76, F83


  • Locate the reset button and press and hold it for 10s;
  • Wait for the boiler to ignite, which may take a few minutes. You will be able to tell if it’s ready if the indicator light is green and the error code has disappeared from the display;
  • Flick the fuse box switch back on if it has tripped;
  • Check that the isolation switch next to the boiler is on.

Reason #2: The gas supply to your home is interrupted or insufficient

Interrupted or insufficient gas supply is sure to block boiler ignition. There are a few reasons why your gas supply might be low or non-existent. 

First off, there might be an issue with the supply to your home, but unfortunately, there is very little you can do about it. Another possibility is that your gas meter is frozen, which leads to low gas pressure. Last but not least, the gas valve, which would normally open to provide more fuel, might be the culprit of your low gas supply issues. If it’s faulty or damaged, the gas cannot enter the chamber, so the boiler won’t ignite. 

Error codes:

Boiler brandCommon boiler faults concerning gas supply 
IdealIs the gas pressure available at the boiler (> 18mBar)


  • Keep outstanding payments to a minimum. Check if you have any unpaid bills.
  • Insulate your gas meter to keep it from freezing. The best way to do this is to lag it.
  • Make sure you have not turned the gas supply off. 
  • Did you recently update your old boiler to a high-efficient combi boiler? Your gas supplier might be responsible. The gas supply might be very old and insufficient for the new high-output combi boilers. A Gas Safe/Corgi registered plumber near you can test the outlet gas pressure. If it is low, you will need to contact your gas supplier directly.

Reason #3: The boiler timer is not working or boiler doesn’t respond to thermostat

If you have recently had a power outage or the clocks have changed, it may have reset your boiler to its factory default settings, which would cause it to fire at the wrong time. 

Another reason might be an old thermostat, which misjudges the temperature reading and causes an ignition problem. Also, when your thermostat is set too low or positioned near a heat source, your boiler will not ignite.

Error codes:

Boiler brandCommon boiler thermostat/timer error codes
WorcesterE9 224
BaxiE110, E20, E.04 – .08, E20, E28, E40, E50,E110,  E130, E163
VokeraA02, A77, E020, E077


  • Check that the time on the boiler is correct;
  • Reset the timer – keep in mind that after you do this, the timer will reset to midnight, so make sure you adjust it afterwards;
  • Turn up the thermostat and check if the boiler fires up;
  • Consider a new location for the thermostat if it is currently near a radiator, oven, towel rail, or another heat source;
  • Check if you or someone else has turned down the heating.

Reason #4: Air trapped in radiators

If you have noticed that the top part of your radiators is not heating up very well compared to the bottom, then you probably have air trapped in them. The way central heating works is by circulating hot water through the pipes and radiators. Over time, small pockets of air develop and since air is lighter than water, it rises to the top of the radiator, causing it to run inefficiently. This might lead to your boiler not firing.

Error codes:

Boiler brandCommon boiler faults 
Baxi110, E1, E2, E4
IdealOverheat lockout, Water pressure
Glow-wormF32, Boiler locks out within 10 seconds (air fault), F3, F02


Releasing the trapped air, more commonly known as radiator bleeding, will keep you home warm and cosy and save you money. Fortunately, bleeding the radiators is an easy DIY task.

If you would rather have a heating specialist, do it for you, book a radiator bleeding service now.

Reason #5: Frozen condensate pipe

The condensate pipe is the plastic pipe that drains the acidic wastewater away from your boiler. Sometimes it is connected to the wastewater system internally, however, more often than not, it is placed outside. That makes the pipe and the condensate inside it susceptible to freezing in winter. The boiler sensors will detect that there is a stoppage and stop the boiler to protect the system and the property. 

One way to tell if your condensate pipe is frozen is to listen for gurgling sounds coming from the boiler. If it was working fine yesterday, but today you can’t get it to fire and it’s freezing outside, then there’s a high chance that your condensate pipe is frozen. A foolproof way to tell whether that is the case is to check what the error code on the display means.

Error codes:

Boiler brandCommon boiler condensate pipe faults
WorcesterEA 229,  D5
BaxiE133,  E28
IdealIdeal boiler fires up for a short time, then turns off
Glow-wormF1, F29, F4, and F28


You can thaw your condensate pipe by using a couple of DIY methods. First, you need to find where the stoppage is. Usually, an ice blockage forms where the pipe bends or dips.

  • Apply heat to the frozen part continuously – hot water bottle, heating pack, etc.;
  • Apply warm water by pouring it over the pipe – might not work if it’s a big blockage; using boiling water will damage the plastic pipe, so it’s not recommended;

After you thaw the pipe, you should reset the boiler. Some boilers will do that automatically.

Some ways to prevent the condensate pipe from freezing include:

  • Covering the pipe with foam pipe insulation;
  • Checking with a Gas Safe engineer whether the slope of the pipe can be corrected;
  • Keeping the heating on during nights with extremely low temperatures.

Reason #6: Faulty diverter valve

If your boiler is working but there is no hot water or vice versa, then the issue most likely comes from a faulty diverter valve. It works like a traffic policeman, directing the flow of hot water to either the heating or the taps. Over time, general wear and tear cause the valve to stick.

Error codes:

Boiler brandCommon boiler gas valve faults
WorcesterFA, FA 364, FB 365, F0 238, EA 234
BaxiH.01 – .00, E.02 – .17 , E.04 – .17, E09,E15, E134, E09,  E15
Glow-wormF26 / F77, F26 / F77, F14, F.61, F.82


In this case, unfortunately, there isn’t a low-cost DIY method available. You will need to call a Gas Safe registered engineer to clean, replace or free a stuck diverter valve. 

Have the boiler engineer inspect all the components of the boiler, particularly if it’s 8-10 years old. Throwing money at an old boiler is sometimes money down the drain. If the engineer finds any other faults with the water heater, it might be more cost-effective to get a new one.

Reason #7: Pilot light on boiler not firing up – flame failure

The pilot light is the tiny flame inside the boiler that ignites the gas, which then consequently heats the water. When it goes out, there is no hot water and no heating. Most often the reason is debris that is blocking the jet. On rare occasions, a draught from a poorly sealed window or a faulty thermocouple might be the culprit behind the light going out.

In older boilers, you might see the light through the framework, but in newer models, the error code on the display will let you know if there is an issue with the pilot light.

Disclaimer: In normal circumstances, the light is crisp and blue. However, if you notice that the light is not blue, but yellow or orange, turn off your boiler immediately! This is a sign that carbon monoxide is being produced, which is a toxic, odourless gas that is lethal.  

Error codes:

Boiler brandCommon boiler flame failure codes
Worcester227 V , 228 V , 306 V , 2927 B, EA, F7, EA 227
BaxiE.04 – .10, E133, E128, E129, 3 Green Flashes
IdealL6, LN, F2, FN, L2, L6, Flame is on before gas on , Flame loss
VokeraA11, A01
Glow-wormF.27, F.29, F.88


We recommend that you call a certified expert to carry out the task:

  • To ignite the pilot light, you will need to turn off all gas appliances, all taps and showers, and the gas valve;
  • Wait for about 10mins for the gas fumes to dissipate. Remember to always keep a window open so clean air can come in as a safety precaution! 
  • Remove the cover and locate the pilot light jet;
  • Use a long candle or a BBQ lighter and hold it next to the pilot light tube;
  • Turn the gas valve to pilot. If your gas valve has only on and off options, it means that you have an automatic ignition system;
  • Press and hold the reset switch for about 30s after the flame has been ignited.

Reason #8: Boiler pressure is too low or too high when heating or hot water is on

Normally, when the heating is on, the boiler pressure is around 1.5-2 bar and around 1-1.5 when it’s off. Monitor the water pressure meter on the front of the boiler for any changes. If the pressure is higher than 2, your radiators might need bleeding or the pressure valve has come loose. When you have a boiler, that’s losing pressure – lower than 1, there may be a leak. It could also result from recent radiator bleeding. 

Disclaimer: Always check your boiler manual to find out what the optimal range for the specific model is. 

Error codes:

Boiler brandCommon boiler pressure sensor faults 
WorcesterCE 207, H07
BaxiE117, E78
VokeraA04, AL41, AL40
Glow-wormF32, F73 / F74, F9, F09, F.22, F.75, F.72


In short, when:

Reason #9: Faulty boiler burner

When the boiler burns gases, it produces CO2, which can clog up the burner, causing it to work inconsistently or not at all. The burner also ages over time and might need replacement.

Error codes:

Boiler brandCommon boiler pressure sensor faults 
WorcesterB7, F7 228, FA 306, 283, 235, 360, 9A 361, 9U 233 , B7 257, EA 261, EH 258, EC 256, F0 280
BaxiE.04 – .12
Glow-wormF.83, Poor burner pressure,


A qualified boiler engineer can clean out the carbon build-up or replace the burner. To count on an boiler servicing at least once per year will save you a lot of headaches and money down the road.

Heating and Hot Water Not Coming On Yet?

A professional team of Gas Safe Registered specialists can repair any boiler brand and model, or replace an outdated and inefficient unit with a new A-rated appliance.

It is hard to estimate exactly how much a repair of a fire-up issue might cost, given the range of repairs and replacement parts that might be needed. The service can cost you an hourly rate of £110.00, but it’s all worth it for the safety of your family. Fortunately, you can make your service much cheaper by being a member of the Fantastic Club.


There are a few major reasons why your boiler won’t fire for central heating and hot water, the most common of them being issues with:

  • The power supply
  • The gas supply
  • The boiler timer
  • Trapped air in the radiators
  • A frozen condensate pipe
  • A faulty diverter valve
  • The pilot light
  • The pressure
  • A faulty boiler burner

Some of these issues you can resolve yourself, but if you don’t feel confident, it is always best to call a boiler engineer in London in order to ensure the safety of your family and home.

Boiler Not Firing Up – 9 Reasons Your Heating and Hot Water Boiler Won’t Start

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