The Causes Of Boiler Lockouts, And What To Do Next
Are boiler lockouts causing you grief? No problem. In our 5-minute guide, we’ll cover what a boiler lockout is, what happens during a lockout, and what to do next.
Table of Contents
What Does Lockout Mean on a Boiler?
A boiler lockout is a safety feature that initiates a shut-down procedure when a boiler is not working within certain tolerances.
Boilers can lock out due to various problems, such as low/high water pressure, lack of, or no fuel supply (gas, LPG or oil), a blockage in the system, or the lack of power to electronic components.
What Happens During Boiler Lockouts?
Though the lockout process varies between boiler manufacturers, you can expect to see either red or green flashing lights, and the boiler will begin to shut down.
Newer boilers with a display panel will show a fault code, which should give you an indication of what the problem is.
What to Do When Your Boiler Locks Out
If you’re experiencing boiler lockouts for the first time, or intermittently, there are a few things you can do.
Step 1: Determine What the Fault Code Means
Alongside flashing lights on the display panel, you’ll notice a fault code.
Take note of the fault code, and reference your owner’s manual to determine what the code means.
Step 2: Find and Fix the Fault
Resetting your boiler at this stage will do nothing. You need to fix the problem before going any further.
Common Faults That Lead to Boiler Lockouts
Try to match your fault code to one of the faults below. We’ve outlined solutions for clearing these fault codes and preventing boiler lockouts.
#1 – A Faulty Pump
Pumps can blow seals and seize. If your fault code relates to pump failures, or water circulation, read our article on fixing boiler pump problems.
#2 – Ignition Lockout
If you experience an ignition lockout, your boiler has probably attempted to fire up 3 times — and failed. If this happens, you’ll see an ignition lockout fault on the boiler’s display.
Ignition lockout fault codes depend on the brand and model. For instance, an ignition lockout on an Ideal boiler triggers the L2 error, whereas a Worcester would respond with a slowly flashing light and a flashing lockout reset button.
If you’re getting an ignition lockout fault from your boiler, ask a Gas Safe engineer to check the ignition leads and probe.
You can also learn more about ignition lockout faults in our thorough guide here.
#3 – Low/High Water Pressure
Reference your owner’s manual to determine the pressure your boiler should operate at.
1.3 bar is normal, and most boilers will lock out if they are below 0.6 bar, or above 3 bar.
To increase pressure, add water via the boiler filling loop. But keep in mind that a loss in pressure typically means a leak in the central heating system, and you’ll have to fix this leak first.
To reduce water pressure, bleed radiator valves with a bleed key.
#4 – No Power
Getting no power to a boiler is a common lockout cause that could be due to a failed display board, a blown fuse, or tripped electrics in your property.
#5 – System Blockage
Make sure your condensate pipe isn’t frozen, especially on chilly mornings and during winter.
Other common blockages come from heating sludge buildup in the radiators and pipework.
#6 – Heat Exchanger Blockage
If you’ve noticed a whistling noise coming from your boiler, there’s a good chance there’s limescale build up on the heat exchanger. This buildup will cause excessively high water temperatures, and your boiler will lock out.
#7 – Fan Problems
Your boiler’s fan vents gases from your boiler via the flue. If the fan isn’t working correctly, it’ll be dangerous for your boiler to operate and it’s going to lock out.
Step 3: How To Reset a Boiler After a Lockout
Modern boilers have a reset button on the display button. Once you’ve resolved the underlying issue, simply press and hold the button to reset the boiler after a lockout.
For older boilers (or boilers that don’t have a reset button on the front of the boiler) refer to the manual to determine the reset procedure.
Step 4: What to Do if Your Boiler’s Locked Out and Won’t Reset
But what if your boiler won’t reset after a lockout, even after you’ve fixed the problem relating to the fault code?
Unfortunately, a boiler’s computing power isn’t like that of a PC or laptop. It will try and determine the most relevant fault code. But, that doesn’t mean it’s correct, or the only fault with the system.
So, you’ll need to run through some checks to find other potential faults before resetting again.
#1 – Check If the Pump Is Working
Can you feel small vibrations and humming from the pump? This signals the motor is working.
If it is, is it too hot to touch? A hot pump suggests seized internal parts. A gentle tap can sometimes free them.
#2 – Adjust Boiler Pressure
The pressure on your boiler should be 1.3-1.5 bar. If it’s not, this could cause a lockout.
#3 – Determine if the PCB Is Working
The PCB (Printed Circuit Board) is the heart of a boiler. Is the display panel showing any lights or codes, or is it completely blank?
A boiler will immediately lockout without a working PCB, as this unit facilitates communication between all electrical components of the boiler.
#4 – Check for Power
Check the condition of the fuse. If the fuse hasn’t blown, try plugging in the boiler elsewhere. And, of course, check to see if your property’s electricity has tripped.
#5 – Monitor Heat Flow
There’s a flow and return water pipe on each boiler. One should be piping hot, the other slightly cooler.
Flow is the hot water leaving the system; it travels around, and returns via the return. Naturally, the water will lose some heat as it travels around radiators and pipes; but it shouldn’t be exactly cold.
If the flow is hot, but the return is cold, that’s a sign of a blockage. Most likely, it’s limescale and heating sludge that needs to be removed with a power flush.
Boiler Still Won’t Work?
Does your old boiler keep locking out despite repairs? If so, it may be time to consider a replacement.
You can start by getting a fixed-price online quote from Heatable — they typically have excellent deals available on top boilr brands, such as Worcester Bosch, Viessmann, Ideal, and others. All you have to do is fill out their anonymous questionnaire about your existing central heating system, and you’ll get a range of boiler recommendations, along with installation quotes. Then, you can use Heatable’s quote as a benchmark when you call your local boiler installers — this will raise your chances of finding a good boiler deal.
Thanks for reading out 5-minute guide to boiler lockouts.
Still haven’t fixed yours? Check out our guide to boiler troubleshooting here.
Still have a boiler that is locking out, and have questions? Drop a comment below and we’ll get back to you as soon as possible.