Ravenheat E22 Fault Code: Causes, Fixes & Repair Costs
What does the Ravenheat E22 fault code mean?
The E22 code (sometimes displayed alongside E23 on certain Ravenheat models) indicates that the boiler's control board has detected a problem with the flue sensor — either the flue is reaching temperatures above the safe operating limit, or the sensor itself has stopped providing a reliable signal. As a safety precaution, the boiler will lock out to prevent potential damage or danger. The flue sensor is an NTC thermistor: a component whose electrical resistance changes with temperature. It plays a critical role in protecting the plastic elements of the flue system by allowing the boiler to reduce its output or shut down when flue temperatures climb too high. Because Ravenheat produces several boiler ranges, the exact display format of this code can vary slightly by model — always cross-reference with your specific boiler's documentation if you are unsure.
General guidance only — not a substitute for professional advice, and not certified by a Gas Safe engineer. Always have your specific appliance assessed by a qualified professional. Any gas work must be carried out by a Gas Safe registered engineer. If you smell gas or suspect carbon monoxide, leave the property and call the National Gas Emergency line on 0800 111 999.
Common causes
- Faulty flue sensor (NTC thermistor) Common
The flue sensor itself is the most common culprit. Over time, NTC thermistors can drift out of their correct resistance range, develop internal faults, or fail completely. Limescale and heat cycling both accelerate wear on these components, and a failed sensor will trigger the E22 lockout even if the flue is perfectly healthy.
- Damaged or loose sensor wiring Common
The wiring connecting the flue sensor to the PCB can become corroded, pinched, or develop loose terminals. This causes intermittent or incorrect resistance readings that the PCB interprets as a sensor fault or overheating event, bringing up E22 without any genuine flue problem.
- Genuine flue overheating Sometimes
If a safety component elsewhere in the boiler has degraded — for example, a partially blocked heat exchanger or an overfiring gas valve — the flue can genuinely reach excessive temperatures. In this scenario the sensor is doing its job correctly, and the underlying cause must be identified by an engineer.
- Blocked or obstructed flue Sometimes
A flue that is partially blocked by debris, a bird nest, or physical damage restricts the flow of combustion gases. Heat can then back up and raise flue temperatures enough to trigger the sensor. Any visible staining around the flue terminal or unusual smells indoors are warning signs.
- PCB fault Rare
If the sensor and its wiring both test within specification, the PCB itself may be misinterpreting the incoming signal. This is the least common cause of E22 but should be considered after all other components have been ruled out.
How to fix it
- Reset the boiler once or twice DIY safe
Locate the reset button or mains on/off switch on your Ravenheat boiler and carry out a manual reset. If the E22 code clears and the boiler runs normally, monitor it closely over the next hour or two. A single transient spike can occasionally trigger a lockout. If the code returns after one or two resets, stop resetting and move on — repeated resets without investigation will not fix the underlying fault and could mask a genuine safety issue.
- Check for visible signs of flue obstruction from outside DIY safe
Go outside and look at where your flue terminal exits the building. Check for obvious blockages such as debris, a bird nest, or physical damage to the terminal grille. Do not attempt to clear anything from inside the flue or touch the flue pipe itself — simply note what you see and relay this to your engineer.
- Verify your gas supply is working DIY safe
Check that other gas appliances in your home (hob, gas fire) are working normally. If they are not, contact your gas supplier before doing anything else. If the supply is fine, the fault is isolated to the boiler.
- Call a Gas Safe registered engineer to test the flue sensor Gas Safe engineer
An engineer will use a multimeter to measure the sensor's resistance across a range of temperatures and compare these readings against the manufacturer's specification. A sensor that reads outside the expected range, or gives an open-circuit reading, confirms it has failed and needs replacing.
- Engineer to inspect sensor wiring and connections Gas Safe engineer
The engineer will check the wiring harness running from the flue sensor back to the PCB, looking for corrosion, chafing, loose terminals, or any signs of heat damage. Faulty wiring is repaired or the harness replaced as required.
- Engineer to inspect the flue for blockages and integrity Gas Safe engineer
A full flue inspection confirms that combustion gases are exhausting freely and that the flue is correctly installed and undamaged. If a blockage or flue fault is found, it must be rectified before the boiler is returned to service.
- Engineer to replace the flue sensor if faulty Gas Safe engineer
If the sensor has failed, the engineer will fit a correct replacement NTC thermistor, applying heat-resistant compound to the threads where applicable. The boiler is then tested to confirm the E22 code has cleared and that flue temperatures are within the normal operating range.
- Engineer to assess the PCB if all other components test correctly Gas Safe engineer
Should the sensor, wiring, and flue all prove to be in good order, the PCB is likely misreading the sensor signal. PCB diagnosis and replacement must be carried out by a Gas Safe engineer. Given the cost of a new PCB on an older Ravenheat boiler, the engineer may also advise whether replacement of the boiler makes better financial sense.
Parts you may need
- Flue NTC thermistor sensor · from £20
- Sensor wiring harness · from £30
- Flue terminal/grille · from £25
- PCB (control board) · from £280
The exact spare depends on your boiler's GC number (on the data badge). Check this against the part before buying.
Typical repair cost
Expect to pay roughly £120–£320, depending on the underlying cause.
Frequently asked questions
Can I fix the Ravenheat E22 fault myself?
Homeowners can safely try a boiler reset and check for obvious external flue blockages, but that is the limit of safe DIY action. Testing or replacing the flue sensor, inspecting internal wiring, and any work on the PCB or gas components must be carried out by a Gas Safe registered engineer. Working on gas appliances without the correct qualifications is illegal and dangerous.
How much does it cost to fix a Ravenheat E22 fault in the UK?
For most people, the repair involves replacing the flue sensor and checking the wiring, which typically costs £120–£200 including parts and labour. If the investigation reveals a more complex cause — such as a PCB fault — costs can rise to around £300–£400. PCB replacement alone can cost £180–£400 for parts, so on older Ravenheat boilers it is worth discussing with your engineer whether a full boiler replacement might be more economical.
What is the difference between the Ravenheat E22 and E23 codes?
On most Ravenheat models, E22 and E23 both relate to the flue sensor circuit — E22 typically indicates the sensor has detected excessive flue temperature or has failed, while E23 can indicate a related sensor or circuit fault depending on the specific model variant. Because Ravenheat's code definitions vary slightly across their range, you should cross-reference your boiler's manual. In practice, the diagnostic and repair process is very similar for both codes, and a Gas Safe engineer will test the sensor and wiring in the same way.
Why does my Ravenheat boiler keep showing E22 even after a reset?
If the code returns shortly after a reset, a temporary spike has been ruled out and there is a persistent fault — most likely a degraded flue sensor, damaged wiring, or a genuine flue restriction. Continuing to reset the boiler without investigation is not recommended, as the lockout is a safety mechanism. Book a Gas Safe engineer to diagnose the root cause rather than relying on resets to keep the boiler running.