Worcester Bosch Boiler E5 Fault Code
The Worcester fault code E5 Overheat Q & A or require an engineer for an emergency boiler repair.
The Worcester Boiler Fault Code E5 Error Common Q & A
Just below, we have a list of common questions relating to the E5 fault code on the Worcester Bosch Boiler.
- What does the E5 fault code mean on my Worcester boiler
- What happens if my boiler overheats?
- Is a boiler showing an E5 fault code dangerous?
- Will resetting my Worcester boiler fix the E5 fault code?
- Why is my Worcester boiler overheating and displaying the E5 fault code?
- How can the PRV contribute to the E5 fault code being displayed?
- Can the PRV be fixed to clear the E5 fault code on my Worcester boiler?
- What is a NTC thermistor and how can it contribute to the E5 fault code being displayed?
- How can a faulty heating pump cause the E5 fault code to be displayed?
- Can a seized heating pump be easily fixed?
- If I need a new heating pump, how much will it cost to replace?
- What is limescale build-up?
- What components commonly suffer from limescale build-up?
- What happens if limescale builds up on the flow NTC thermistor?
- What happens if limescale builds up on the heat exchanger?
- How much does it cost to replace a heat exchanger?
- What can be done to combat limescale?
What does the E5 fault code mean on my Worcester boiler?
The E5 fault code on Worcester Bosch boilers relates to an overheat.
There are two cause codes for this fault.
E5 218 relates to a general overheat, due to the flow temperature being too high.
E5 332 relates to the primary flow sensor logging temperatures that exceed 110°C.
What happens if my boiler overheats?
When a boiler overheats, it puts unnecessary strain on important internal components.
A typical example would be the heat exchanger. If this is boiling at a higher temperature than it should, it can weaken and crack the component.
Whereby there are electronic faults not allowing the boiler to lock out, the boiler will continue to operate, and these components will get damaged.
Fortunately, all modern boilers are fitted with a fail safe for such scenarios; a boiler lock out.
Is a boiler showing an E5 fault code dangerous?
If your boiler is showing an overheat fault code such as the E5, it’s only dangerous if it carries on running.
So, if your boiler hasn’t locked out it’s advisable to turn off the appliance until a boiler engineer can fix the problem.
If anything, this will save you money, as an overheat can cause damage to boiler parts.
Will resetting my Worcester boiler fix the E5 fault code?
Your boiler has locked out, because it would be harmful to internal components for it to continue to operate.
For that reason, you shouldn’t reset your boiler.
It may take a few minutes for the boiler to recognise that the problem hasn’t been fixed. During this time, it could cause damage before it’s able to lock out again.
You’ll need to employ a Gas Safe engineer to assess what damage has been caused, fix the problem that’s causing the overheat, and then they’ll reset the boiler for you.
Why is my Worcester boiler overheating and displaying the E5 fault code?
Boilers overheat for a variety of reasons. This may include:
- PRV (pressure release valve) blockage, or failure
- Faulty NTC thermistor
- Broken heating pump
- Limescale build-up
How can the PRV contribute to the E5 fault code being displayed?
The PRV in a central heating system allows excess pressure to escape when the boiler is up to temperature. As a boiler heats up, pressure in the system increases, and this escapes in a controlled manner via the PRV.
However, faulty PRVs can contribute to a sudden drop in boiler pressure.
Essentially, they allow pressure to escape when they shouldn’t. In some slightly shocking cases, it’s been known for engineers to block up the PRV to stop the leaks causing pressure loss.
This contributes to increased pressure and a boiler overheat.
Can the PRV be fixed to clear the E5 fault code on my Worcester boiler?
If the PRV is blocked, or has been blocked up, it can be fixed. The simple fix here is a replacement.
PRVs are relatively easy to access, cheap to purchase and therefore, the repair isn’t an expensive one.
Once a new PRV has been fitted, the boiler engineer will assess the rest of the boiler for other issues and reset the boiler to clear the overheat issue, and the E5 fault code.
What is a NTC thermistor and how can it contribute to the E5 fault code being displayed?
NTC thermistors are sensors that monitor the temperature of flow (water out of the boiler) and return (water back into the boiler).
These devices measure resistance in ohms, transfer their readings to the PCB, and the PCB converts this into a temperature reading.
It’s the NTC thermistor on the flow pipe that’s signalling the water temperature from the flow is too high. However, there’s nothing to say that it’s not the NTC thermistor providing a false reading, rather than the water temperature being too high.
The NTC thermistor can be tested using a multi-meter by a Gas Safe engineer. They’ll be able to determine if it’s the thermistor causing the issues. If it is, these can be easily replaced, the boiler reset, and the E5 fault code can be cleared.
How can a faulty heating pump cause the E5 fault code to be displayed?
The job of the heating pump is to work in tandem with the heat exchanger. As water is heated, it needs to be pumped out of the boiler and circulated around the heating system.
There are two common faults we find with old heating pumps:
- Leaking pump seals
- Seized bearings/shaft
In this case, leaking pump seals aren’t relevant. However, a seized bearing or shaft could be contributing to the E5 fault code being displayed.
If the pump is even slightly seized, it won’t be providing the flow rate needed to pump water from the heat exchanger.
That means hot water that should be travelling around the pipework and radiators in your heating system, is staying in the heat exchanger and pump for too long.
This can quickly cause an overheat issue, the boiler to lock out and the E5 fault code to be displayed.
Can a seized heating pump be easily fixed?
Seized bearings and shafts in heating pumps can cause terminal damage. If this isn’t the case, the individual parts can be replaced to fix the problem.
However, we tend to find that the pump’s shaft/bearings are too far gone. And, there’s little point investing cash into an old unit that’s already showing signs of weakness.
Instead, we prefer to replace the whole unit.
More importantly, the pump needs to be fitted so that the shaft is horizontal. Even a few degrees off horizontal can cause the shaft and bearings to wear and seize, which is likely to be what’s happened in the first place.
If I need a new heating pump, how much will it cost to replace?
There are lots of cheap heating pumps on the market. With a budget heating pump including labour, you could pay as little as £175.
However, we always advise our customers to fit a high-quality pump that’s going to last the test of time.
Typically, we’ll install Grundfos pumps, as these are the pumps that many boiler manufacturers now fit as standard in all their new boilers.
What is limescale build-up?
Limescale comes from minerals in water. Throughout the UK, the water system is rated from moderate-hard. The harder the water in an area, the higher the concentration of minerals there are in the water.
Ultimately, this means that homeowners in these areas are more likely to have problems with limescale.
These minerals are deposited throughout a central heating system. Sometimes they’ll deposit themselves in areas that create blockages, such as microbore pipe and radiator valves.
However, when an overheat fault code such as the E5 218 or E5 332 is displayed, these deposits are likely to have found their way onto important boiler components.
Once limescale has settled, it’s extremely hard to shift.
What components commonly suffer from limescale build-up?
The first culprit, will be the NTC thermistors we’ve mentioned above. With the second, being the heat exchanger.
What happens if limescale builds up on the flow NTC thermistor?
Wherever limescale builds up, that area of the heating system will burn slightly hotter than the rest.
Even the smallest amount of limescale build-up on or near NTC thermistors will cause that area to burn hotter. Throughout the rest of the central heating system, this isn’t a concern.
However, the NTC thermistor is monitoring the temperature of water into and out of the boiler.
If the NTC thermistor (wrongly, due to limescale build-up) notices a higher temperature than it should, it will cause the boiler to lockout.
So, even though the temperature of the flow water is within tolerance, the flow water near the NTC thermistor is burning hotter, and causing the thermistor to generate the wrong reading which is then passed back to the PCB.
What happens if limescale builds up on the heat exchanger?
Whilst the NTC thermistor problem causes an issue, it’s not a hugely expensive one to fix.
However, limescale build-up on the heat exchanger is a different story altogether.
Limescale build-up here will create the same hot spots we mentioned above. These hotspots don’t just contribute to the boiler overheat, they also weaken sections of the heat exchanger plate.
Eventually, this is going to lead to a cracked heat exchanger.
Unfortunately, a cracked heat exchanger will start to leak, can cause more internal boiler damage (due to leaks), and will need to be replaced.
How much does it cost to replace a heat exchanger?
A heat exchanger replacement including labour is likely to cost around £500, depending on your model of boiler.
And, this is the exact reason why you shouldn’t keep resetting your boiler until the issue is fixed; this problem could have been avoided.
What can be done to combat limescale?
A combination of limescale and central heating sludge can cause issues such as the overheat and E5 fault code we mention here.
To protect your boiler, it’s worth speaking to a heating engineer that’s Gas Safe registered to:
- Add the correct dosage of central heating inhibitor to your system to break down debris
- Fit a magnetic system filter to catch this debris
- Install a scale reducer which will catch minerals such as limescale, when a magnetic system filter doesn’t
Other Worcester boiler issues
More more boiler issue regarding the Worcester Bosch the please visit the Worcester Boiler Problems And Cures page.