Viessmann Boiler CC Fault Code

The Viessmann fault code CC relates to an air lock or blockage in the system and here we have Q & A or require an engineer for an emergency boiler repair.

The Viessmann Boiler Fault Code CC Error Common Q & A

Just below, we have a list of common questions relating to the CC fault code on the Viessmann Boiler.

What does the CC fault code mean on my Viessmann boiler?
If the CC fault code is displayed on my Viessmann boiler, can I fix this on a DIY basis?
Why would an air lock cause my boiler to display the CC fault code?
How can I remove air locks from radiators and towel rails?
My boiler pressure has dropped after releasing air from the system, what can I do to fix it?
What blockages can occur in my central heating system?
How can we combat limescale in our boiler and heating system?
If central heating sludge is the problem, how can we get rid of it?
My boiler engineer thinks there is a problem with my pump, does this sound right?
What other issues could my central heating pump have?
If my pump is leaking, could this contribute to the CC fault code being displayed?
If I need to replace the pump on my Viessmann boiler, how much is it likely to cost?

What does the CC fault code mean on my Viessmann boiler

All modern boilers have a fault code system built into the appliance. The printed circuit board (PCB) monitors a range of pressure and temperature sensors to determine what parts are working, when, and if they’re within working tolerance.

When a problem occurs, the boiler will lockout. Alongside the lockout, it’s likely an error code is going to be shown on the display panel. In the case of the CC fault code, it usually relates to an air lock or blockage in the system.

Whereby air locks and blockages aren’t the problem it’s likely the cause of the fault code being displayed is due to a pump failure. Due to lack of water circulation, this acts in a similar way to an air lock or blockage.

Whatever the fault, the burner is going to go into fault mode until the issue is found and fixed.

If the CC fault code is displayed on my Viessmann boiler, can I fix this on a DIY basis

There are very few fault codes that can be fixed on a DIY basis. And, that’s because most fault codes will require the boiler to be taken apart. Taking apart a gas boiler is a job for qualified professionals. So, you’ll need to call a Gas Safe registered repair company that has experience working with Viessmann boilers.

However, if the problem is an air lock that isn’t located in your boiler, there’s a chance you can fix this without the help of a heating company.

Another thing worth noting, is the reset function. The reset function isn’t designed to be used to fix a problem such as the CC fault. Instead, it’s going to be used by your Gas Safe boiler repair company once they’ve found and fixed the problem.

Why would an air lock cause my boiler to display the CC fault code

Air locks act much like a blockage; they can restrict the circulation of water throughout the heating system.

They can occur in any part of the central heating system, including:

Towel rails
Radiators
The boiler, specifically, the pump

If the air lock you are experiencing is on the pump, your boiler engineer will need to fix the problem. They’ll be able to locate the bleed screw on the pump to bleed air from the system.

However, it’s highly likely that there are major air locks in towel rails and radiators. And, this is a problem that you’re able to fix on a DIY basis.

How can I remove air locks from radiators and towel rails

Each towel rail and radiator will have a specifically designed bleed valve. And, you’ll be able to buy a radiator bleed key to open and close this valve, from most DIY stores or plumbing merchants.

Alongside the bleed key, you’ll need to ensure you have a container to catch water, and something to protect walls and floors (towels, rags etc).

Using the radiator bleed key, you can slowly open the valve on the radiator or towel rail. If air is in the system, you’ll hear a hissing noise. Once this hissing noise stops, the radiator will start dribbling water. This signifies that air has escaped from the system, and the valve can be closed.

You’ll want to wipe the bleed valve dry and check it after a few minutes to ensure it’s not leaking. Rinse and repeat for other towel rails and radiators in your property.

My boiler pressure has dropped after releasing air from the system, what can I do to fix it

Boilers work best at 1.3 bar, and air locks can produce inconsistent boiler pressure, leading to the appliance working intermittently.

Once the air lock has been released, it’s likely that your boiler pressure will have dropped. You’ll be able to top up your boiler to 1.3 bar (or to the pressure stated in your manufacturer’s handbook), using the filling loop. This is a braided hose usually located just beneath the boiler’s casing.

The filling loop lets water into the system incredibly quickly. So, if you do overfill the boiler’s pressure, you can release pressure by either:

Using the drain cock
Releasing water from the bleed valves on radiators

What blockages can occur in my central heating system

Heating system blockages are usually either due to:

Limescale build-up
Central heating sludge

To get rid of any sludge or limescale build up, you will need a central heating power flush.

How can we combat limescale in our boiler and heating system

Limescale is only common in hard water areas. It’s likely you’re in a hard water area if you use water softeners for dishwashers and so on.

Limescale can attach itself to pipework, radiators, and even parts in the boiler. And, when it does this, it creates a small blockage. At the very least, it’s going to restrict the boiler pump’s ability to circulate water.

Your boiler engineer can flush existing limescale from your system, by using specifically designed chemicals that are used to attack limescale. Once they’ve done this, they can fit a limescale filter that will catch any future limescale that’s circulating in your central heating system.

There are several top brands to choose from for limescale filters, including:

Boiler Mag
Magna Clean
Fernox
Scale Master

If central heating sludge is the problem, how can we get rid of it

Heating sludge tends to be more common than limescale, simply because it can occur in heating systems, even if they’re not in a hard water area.

Heating sludge is typically rust that’s broken off from boiler parts, radiators and pipework. Over time, it breaks down to create a thick and dirty heating water. But, particles that don’t get broken down are going to get lodged in expensive parts such as the pump, and cause blockages.

Like limescale, a hot flush using cleaning chemicals will remove most of the heating sludge. Once a hot flush has been completed, the next job is to dose the system with central heating inhibitor and fit a magnetic system filter.

The inhibitor will break down the sludge into small particles, ready for the system filter to remove them from your heating system.

My boiler engineer thinks there is a problem with my pump, does this sound right

The Viessmann boiler CC fault code can be related to a pump issue. This might be a blockage, or a faulty pump unit.

Pump blockages are typically in the form of heating sludge mentioned above. If a hot flush doesn’t clear the pump, it will need to be cleaned manually. It’s also likely your boiler engineer is going to bleed the pump of air. A combination of air and heating sludge is enough to cause a blockage and therefore, a circulation fault with your boiler’s pump.

What other issues could my central heating pump have

If your boiler engineer pinpoints the pump as the issue, there are a few things they’ll want to check.

To start, they’ll want to ensure that all wires and connections are in good condition and secure. Any loose or damaged connections will lead to the pump working intermittently. If after a visual inspection no problems arise, your engineer will be able to double check by testing all electrical wires and connections using a multi-meter.

The next step would be to ensure that the pump isn’t jammed. If it’s making loud humming noises and is incredibly warm, this is likely to be the case. Typically, after a hot flush clears small blockages in the pump, a gentle tap is going to free it to get it working again.

They’ll also want to check that the pump has been installed correctly. The pump should’ve been installed so that the shaft is 100% horizontal. Even being slightly offset is going to mean that the pump can’t work at its optimum. It’s also going to lead to premature wear, and a replacement being needed.

If my pump is leaking, could this contribute to the CC fault code being displayed

A leaking pump can cause a whole host of issues. Moisture in your boiler from leaks could cause havoc when it comes to electrical components, and result in hundreds of pounds worth of repair bills.

But, it’s also going to reduce the pump’s ability to operate correctly. If your boiler’s pump is leaking water, that’s water that’s not going to be circulated around the heating system.

Typically, we find that pumps leak due to old and worn seals. Most top brand pump manufacturers provide a servicing kit that includes seals.

After fitting the service kit, your boiler engineer can reset your boiler to fix the problem. This will clear the CC fault code from the display panel.

If I need to replace the pump on my Viessmann boiler, how much is it likely to cost

If your pump needs replacing, you should expect to pay around £250. This would be a top of the line pump from a leading brand such as Grundfos, including labour. The job will usually take around one day to complete.

Assuming this is the only repair that’s needed, it makes sense to repair your boiler rather than replace it. Typically, it’s only repairs that cost upwards of £500 that warrant investigating the price of a new boiler installation.

Other Viessmann boiler issues

For more boiler issues regarding the Viessmann Boiler then please visit the Ideal Boiler Problems And Cures page.

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