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Common Biasi Boiler Problems


Biasi boiler started as a thermomechanical business in 1938, and it was founded by Leopoldo Biasi. However, after a couple of decades, the company started dealing with gas boilers, and it has grown to be the industry leader we know today.

Though boilers are designed to last long, they break down once in a while. You’ve probably had to suffer through boiler banging noises throughout the night or shower with cold water. These are a few examples of common boiler problems.

To help you find quick fixes, we’ve compiled a list of all Biasi boiler fault codes along with their causes and fixes.

Boiler won’t ignite

Your Biasi boiler will show an ER01 fault code. And since this is a problem related to the boiler ignition, it might be dangerous if the boiler continued to run. As such, boilers are designed to lockout. You shouldn’t reset the boiler until the problem is diagnosed and fixed.

Possible ER01 fault code causes include:

  • Blocked condensate pipe
  • Faulty gas valve operation
  • Blocked burner
  • Faulty fan


Condensate pipes transport gases and wastewater from the boiler. During winter, these gases and water freeze and block the pipe. Luckily, this problem is easily fixed by thawing the pipe with warm water. Once the ice block is melted, reset the boiler.

However, if it’s a faulty gas valve, you’ll need to call in a Gas Safe engineer to free it or replace it. Usually, engineers will recommend a replacement to avoid future breakdowns and repair costs. A gas valve replacement costs between £250 and £300.

Lastly, if it’s a blocked burner, the engineer will need to unblock it or replace it if the process takes a long time to complete.

Faulty thermostat and overheating

This problem is associated with the ER02 fault code. It points to an overheating boiler or a problem with the thermostat. The list of causes is long, and as such, a Gas Safe engineer will need to perform thorough troubleshooting before diagnosis.

Once they inspect the thermostat and ascertain that it’s in good condition, the wiring is fine and it’s getting sufficient power, they will have to check:

  • The condensate pipe for blockage.
  • Limescale build-up in the boiler system.
  • Sludge build up in the central heating.


As explained above, unblocking a condensate pipe is simple. You can thaw it without the help of an engineer.

However, if a sludge and limescale build-up is causing the heat exchanger to overheat, the engineer will Powerflush the system.

General boiler lockout

This boiler problem is unusually common and a little complicated than most. Unlike most Biasi boiler errors, the ER03 fault code isn’t specific. It could be caused by a number of faults in the system, including:

  • A faulty PCB
  • Low boiler pressure
  • Faulty fan
  • Blocked condensate pipe
  • Limescale and sludge build-up
  • Airlocks in the boiler pumps, towel rails, and radiators

Boiler lockout is a built-in self-preservation and safety mechanism. When the boiler senses a problem, it locks out the boiler to prevent further damage.


The Gas Safe engineer needs to be intentional with the troubleshooting process. As such, he will go through every component to ensure it’s in good condition.

If it’s a block, they will Powerflush the system, and if it’s a faulty boiler component (e.g. the PCB or pump), he will repair or replace the component.

Low water pressure/no water in the system

This boiler problem is represented by an ER04 fault code. This error code is more specific than the ER04. The error points to low pressure or circulation problem.

As such, the first place a Gas Safe engineer will check is the pressure gauge. The optimal boiler pressure is between 1 and 1.5 bar. If the boiler pressure is at 0.5 bar, then the boiler will lockout. Usually, low boiler pressure is caused by a leak in the radiator or pipes.

When the PCB recognizes the pressure drop, it shuts down the boiler to prevent the boiler components from overworking. But if the boiler pressure is in the green zone, it’s probably an airlock in the system or limescale and sludge build-up.


To restore boiler pressure, add water to the system through the external filling loop. If the pressure drops again, call a Gas Safe engineer to find a leak and seal it.  But if its sludge and limescale build-up, a Powerflush will work wonders.

Faulty Fan

Your Biasi boiler will display an ER05 fault code. If this code pops up and the boiler has not locked out, you should turn it off until a Gas Safe engineer inspects it.

A boiler fan is an important boiler safety component. It creates a draft that pushes harmful boiler gases into the flue for expulsion. If the fan is faulty, it means the boiler is filling up with harmful gases. When this happens, the PCB will recognize it and shut off the boiler. Do not try to reset the boiler.


You should call a Gas Safe engineer to fix the fan fault. As they attempt to solve the problem, they will ask:

  • Is the fan slow? If it is, they will increase the speed to generate a stronger draft and push the gases into the flue.
  • Is the wiring intact? Poor wiring and loose electrical connections cause intermittent signals to the PCB. This means the fan gets the wrong commands.
  • Is the fan faulty and beyond repair? Usually, fans can be fixed. However, if this is not an option, a replacement will cost between £250 and £300.

Central heating temperature probe

The code for this boiler problem is ER06. There are two possible causes for this problem:

  • Faulty temperature heating temperature probe.
  • Incorrect readings from the probe thus leading to unnecessarily high-water temperatures.

If the probe is broken, it will give incorrect readings and feedback to the boiler PCB. The PCB will think the optimal temperatures have been hit and shut down the heating.


If the probe is faulty, the Gas Safe engineer will replace it and reset the boiler. But if the probe is intact but giving incorrect readings, the Gas Safe engineer will need to inspect the:

  • PCB
  • Radiators
  • Central heating pump

The pump could be blocked by sludge or limescale or set to the wrong speed. The speed is easy to adjust, and the block is removed using chemicals. But if it’s faulty or worn out, it will be replaced.

If it’s a PCB fault, the PCB will be replaced. But since it costs between £400 and £500, if your boiler is outside its warranty, the engineer will recommend a new boiler installation.

Direct hot water probe fault

This problem is similar to the central heating temperature probe. However, it is represented by an ER07 fault code.

If the boiler is displaying multiple codes, it means there’s a problem with the general temperature readings. The possible causes could include no circulation and a faulty PCB.


Call a Gas Safe engineer to test the probe and its connections using a multi-meter. If the probe is faulty, it will be replaced. However, if it’s a wiring problem, retightening and repairing some parts will do. Once this is done the boiler will be reset to clear the fault code.

Faulty pump

An ER14 error is displayed. A faulty pump leads to circulation problems. Usually, if the pump speed is too slow, the water will linger in the boiler’s heat exchanger. The problem can also be a block in the pump. The pump can be blocked by air or debris, including sludge and limescale.

The last pump fault could be a leak. A pump leak will cause a drop-in boiler pressure. Consequently, the pump will have to work harder to retain optimum circulation.


If it’s a bloc, the Gas Safe engineer hired will flush the system using chemicals or a Powerflush. They will also install a magnetic filter to prevent future blockage.

If it’s a leak, they will replace the pump seals or the pump as a whole. And lastly, if it’s low pump speed, increasing the speed will work.

No Hot Water

When you don’t have hot water or heating, you should check the diverter valve. Faulty diverter valves result in issues including:

  • No heating even when there’s hot water.
  • On hot water when there’s heating.
  • Radiators are hotter when the showers and taps are turned on.

Boiler diverter valves control water used for hot water or heating. Since it’s a moving part, a diverter valve can get stiff and stuck. It could get stuck on heating, on hot water, or between the two.

Getting stuck in either of the sides explains why you have heating and no hot water or the reverse.


If the diverter isn’t faulty, it means the Gas Safe engineer needs to free it. But usually, a replacement is a better economic choice.

Loud banging noises

Boilers develop strange noises with time. Usually, it’s an annoying banging. If your Biasi boiler makes banging noises when turned on and has an ER01 fault code, the problem is a blocked burner or blocked condensate pipe.


Call in a Gas Safe engineer to unclog or replace the burner. You can unblock the condensate pipe yourself using warm water.

Other faults codes and troubleshooting

Fault code ER25 – Flame detection

How to fix: Reset the boiler or repair the PCB fault

Fault code ER69 – Wiring fault

How to fix: Repair and relay the connections

Fault code ER13 – DT delivery return

How to fix: Call a Gas Safe engineer for repair or replacement of boiler component

How to improve your boilers life?

Biasi boiler warranty

Biasi offers free 2-year warranties to save you on cash if problems arise after installation. Depending on the Biasi boiler model you purchase, you’ll get a warranty ranging between 2 and 7 years.

The warranty covers electrical and mechanical breakdown as a result of defective material or workmanship during manufacturing. However, for the warranty to apply, you need to register with Biasi within 30 days of the installation. Also, to sustain the warranty, you’ll need to get a Gas Safe engineer to perform an annual service.

The registration process requires that you have the boiler’s serial number at hand.

Biasi boiler cover

When the warranty expires, consider getting a boiler cover. You are under no obligation to do so, but it saves you money in case of a boiler breakdown. When choosing an insurance company, get one that includes safety inspections and annual servicing.

Biasi boiler service

An annual boiler service is mandatory to sustain the boiler warranty. Also, it should be performed by a Gas Safe boiler engineer who shall provide a certificate as proof.

In addition to sustaining your warranty, regular boiler service also:

  • Helps you to catch problems in their early stages
  • Saves on heating bills
  • Ensures boiler safety
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