Worcester Bosch Boiler E9 Fault Code

The Worcester fault code E9 heat exchanger, sensors or thermostats Q & A or require an engineer for an emergency boiler repair.

The Worcester Boiler Fault Code E9 Error Common Q & A

Just below, we have a list of common questions relating to the E9 fault code on the Worcester Bosch Boiler.

QWhat does the E9 fault code mean on my Worcester Bosch boiler?
What do the E9 cause codes mean on my Worcester Bosch boiler?
What does the heat exchanger do in my Worcester Bosch Boiler?
What are the main causes of a heat exchanger overheat and the E9 219 cause code being displayed?
Will I need a new boiler if it’s displaying the E9 219 fault code?
How does limescale lead to the E9 fault code being displayed?
Can I fix the E9 219 fault code on a DIY basis by resetting the boiler?
How can an engineer fix my boiler and clear the E9 219 fault code?
How much will it cost to fit a new heat exchanger on my boiler?
How long will it take a boiler engineer to replace the heat exchanger on my boiler?
My boiler engineer says it’s the pump causing the problem, is this right?
What’s wrong with my heating pump that’s causing the E9 fault code to be displayed?
How can these heating pump problems be fixed?
What causes sensing issues on my Worcester boiler and the 220, 221 and 224 codes to be displayed?
What causes loose and damaged connections?
Why is water damage a culprit for the 220, 221 and 224 cause codes?
How can I protect my boiler in the future?

What does the E9 fault code mean on my Worcester Bosch boiler?

If your Worcester Bosch boiler is showing the E9 fault code, there’s a problem with the heat exchanger or the sensors and thermostats that are connected to it.

When your boiler shows the E9 fault code, it should also display a cause code.

This will be one of the following:

The fault code indicates the generic problem (a fault connected to the heat exchanger) and the cause code indicates the more specific problem at hand.

What do the E9 cause codes mean on my Worcester Bosch boiler?

The most common issue, is the heat exchanger overheating. This happens when the temperature sensor on the heat exchanger reads a temperature that exceeds 105°C.

If this is the case with your boiler it will be showing the 219 cause code.

However, it maybe a sensor issue. If the temperature sensor on the heat exchanger has failed, it will show the 220 fault code.

But, if your Worcester Bosch boiler is showing the 221 cause code, this indicates that the sensor isn’t being recognised by the PCB. It’s likely a fault or wiring issue.

Finally, the 224 cause code will be generated when the flue gas thermostat reaches maximum temperature.

What does the heat exchanger do in my Worcester Bosch Boiler?

The heat exchanger in a boiler is the component that transfers heat from the fuel source, to the water that heats up the central heating system.

As water passes through the heat exchanger, it’s heated and then pumped out of the boiler.

What are the main causes of a heat exchanger overheat and the E9 219 cause code being displayed?

There are two main causes that will lead to a heat exchanger overheating, by exceeding its maximum temperature of 105°C:

Limescale build-up
The pump isn’t running correctly

Will I need a new boiler if it’s displaying the E9 219 fault code?

Assuming this is the only problem with your boiler, it’s rare that a new boiler is needed.

Instead, a more effective solution is to get the boiler repaired.

The heat exchanger and pump are crucial and expensive parts in a boiler.

If there are other expensive parts showing signs of damage or excessive wear, that’s when a replacement becomes a more cost-effective option.

How does limescale lead to the E9 fault code being displayed?

Limescale comes from mineral deposits in water. Typically, modern heating systems should have chemicals and filters that break down this limescale and catch it.

If this isn’t the case, then limescale will start to affect a heating system. The mineral deposits will attach themselves to the inside of pipes, radiators and even boiler parts such as the heat exchanger.

Wherever limescale attaches itself, that area will burn hotter than it should.

In the case of an overheating heat exchanger that’s going to mean either:

The whole heat exchanger is overheating
A small section of the heat exchanger has limescale build-up that’s causing the temperature sensor to read over 105°C

Can I fix the E9 219 fault code on a DIY basis by resetting the boiler?

Resetting the boiler in this case, could damage internal components. Boilers will lock out and display a fault code when they notice a problem that could cause:

Damage to internal boiler parts
Safety concerns

In this case, the damage caused by running a boiler that’s over heating could run into the hundreds.

So, don’t reset the boiler.

All boiler repairs need to be completed by a Gas Safe engineer.

This isn’t just for safety reasons.

Parts like boiler heat exchangers are incredibly expensive. Diagnosing the wrong part or carrying out an incorrect installation could lead to you spending lots of cash, only for the problem to reoccur.

How can an engineer fix my boiler and clear the E9 219 fault code?

On some occasions, limescale can be removed manually from the heat exchanger.

However, when limescale attaches itself, it typically weakens the section of the heat exchanger that it attaches to. Over time, this causes a weak spot and eventually the heat exchanger cracks.

Unless this the first time this fault code has been displayed, it’s likely the heat exchanger is on the brink of cracking, and a replacement is going to be more effective than a repair.

There’s little point repairing the heat exchanger, only for it to break a few months down the line.

How much will it cost to fit a new heat exchanger on my boiler?

The only part more expensive on a boiler is the printed circuit board (PCB).

For a replacement heat exchanger on your Worcester Bosch boiler, you should expect to pay in the region of £500.

How long will it take a boiler engineer to replace the heat exchanger on my boiler?

Assuming the heat exchanger is in stock at your local plumbing merchant, your boiler should be fixed within 1 working day.

This allows for time to diagnose the problem, pick up parts and install them.

My boiler engineer says it’s the pump causing the problem, is this right?

Once the boiler’s heat exchanger has heated water to the correct temperature, it’s the pump’s job to get this water to towel rails and radiators.

The heat exchanger will continue to heat water, on the expectation that the pump will force hot water out, and cooler water in.

When the pump isn’t running correctly, this water sits in the heat exchanger body longer than it should, and kettling starts.

Eventually the water reaches its maximum temperature of 105°C and the temperature sensor sends the signal to the PCB, to lock out the boiler.

What’s wrong with my heating pump that’s causing the E9 fault code to be displayed?

If the pump on your boiler is new, there could be an obvious explanation.

Modern pumps like those from Grundfos have a range of speed settings.

If your pump isn’t on a high enough setting, it won’t be pumping water fast enough. That’s going to cause a backlog of hot water in the heat exchanger.

But, there are faults can lead to bad pump operation including:

Stuck or seized pump shaft/bearings
Central heating sludge build-up in the pump housing
Incorrect pump installation

How can these heating pump problems be fixed?

Your boiler engineer will need to take apart the pump to determine what the problem is.

First, they’ll check to see that the shaft and bearings move freely. If they don’t they’ll need to be freed, but in most cases they’ll need to be replaced.

If the pump is more than a few years old, it’s likely there’s a build-up of sludge. This dirt, grit and rust will need to be removed from the pump.

If the pump doesn’t need replacing, it will then need to be re-installed.

The engineer will need to check the installation is 100% correct, with the pump’s shaft horizontal. If a pump’s shaft isn’t horizontal, it can lead to the stuck bearings and shaft we’ve mentioned above.

What causes sensing issues on my Worcester boiler and the 220, 221 and 224 codes to be displayed?

If your boiler is showing a sensor issue (short or open circuit), there are two likely causes:

Loose or damaged connections to the sensors, or from the sensors to the PCB
Water damage

What causes loose and damaged connections?

When sensors on a boiler have loose or damaged connections, the signals they’re going to send will be incorrect, or intermittent. This is going to cause the boiler to act strangely, such as cycling on and off for no reason.

Typically, damaged connections will come from wear and tear. Small sections of wiring can be replaced to fix the problem.

However, it’s more common to find loose connections. After all, boilers vibrate, and years of vibrations can cause connections to work themselves loose.

An engineer will be able to re-secure the connections, reset the boiler, and then test to see if this has solved the E9 issue.

Why is water damage a culprit for the 220, 221 and 224 cause codes?

One of the main reasons a boiler gets water damage, is due to a cracked heat exchanger.

As the E9 fault code has a possible cause as being limescale build-up which can lead to cracks, water damage can’t be ruled out.

When a heat exchanger cracks, it will leak water onto electrical components. It won’t take long for these components to fail.

If you notice any water dripping from your boiler, turn it off straight away.

Sensors are relatively cheap to replace. But if this water finds its way onto parts such as a PCB, you could be looking at a repair bill of 2-3x of what you have currently.

How can I protect my boiler in the future?

Where the problem relates to limescale build-up, you should ask your engineer to flush the heating system out with limescale inhibitor.

The system should then be dosed with a heating inhibitor and a magnetic filter should be fitted.

Typically, limescale build-up occurs in hard water areas, so you’ll also need a limescale reducing filter fitted.

Other Worcester boiler issues

More more boiler issue regarding the Worcester Bosch the please visit the Worcester Boiler Problems And Cures page.

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