Worcester Bosch Boiler D1 Fault Code
The Worcester fault code D1 NTC thermistor Q & A or require an engineer for an emergency boiler repair.
The Worcester Boiler Fault Code D1 Error Common Q & A
Just below, we have a list of common questions relating to the D1 fault code on the Worcester Bosch Boiler.
- What does the D1 fault code mean on my Worcester boiler?
- What is the return NTC thermistor?
- Is the D1 fault code one that’s likely to mean I need a new boiler?
- My boiler is displaying the D1 240 or D1 241 cause code, what does this mean?
- Is my boiler dangerous if it’s showing the 240 or 241 cause code?
- How would the NTC thermistor get water damaged?
- Can the NTC thermistor on the return be fixed to clear the D1 fault code on my Worcester boiler?
- Why do connections come loose on the NTC thermistors?
- My boiler is showing the D1 286 cause code, what does it mean?
- What can cause the return pipe to get too hot?
- How could the heating pump be contributing to the D1 286 cause code?
- How can lockshields and TRVs cause the D1 286 fault code to occur?
What does the D1 fault code mean on my Worcester boiler?
The Worcester boiler D1 fault code relates to a return NTC thermistor error, or a return temperature that’s too high.
There are three different cause codes for the D1, including:
- 240 – The thermistor is faulty, or has moisture damage
- 241 – The thermistor is damaged, or has been disconnected
- 286 – The return NTC reading is too high
It’s likely your boiler will show one of these cause codes on the display panel, and then lock out until it’s reset.
You shouldn’t reset your boiler until the problem has been found and fixed.
What is the return NTC thermistor?
Boilers have NTC thermistors on the flow and the return.
The flow is water that’s been heated and is leaving the boiler, whereas the return is water that’s travelled around the heating system and has made its way back to the boiler to be reheated.
The NTC thermistors monitor the temperatures of the water on the flow and return and report the readings back to the PCB.
The readings are in resistance (ohms), which the PCB will then convert into a temperature reading.
The idea of these thermistors is to detect problems with overheating, which could cause internal damage to crucial boiler components.
Is the D1 fault code one that’s likely to mean I need a new boiler?
Good news, this isn’t one of the fault codes that ends up with a new boiler being the fix.
The problem at hand can cause your boiler to come to an almost complete standstill, but the fix is usually simple and easy.
My boiler is displaying the D1 240 or D1 241 cause code, what does this mean?
The 240 and 241 cause code relates to a NTC thermistor error, rather than a temperature reading that is too high.
The thermistor has been subject to water damage, disconnected, or is completely faulty. If this is the case, it won’t be able to provide a reading to the PCB.
The PCB relies on sensors like the thermistors to determine that the boiler is operating safely. When this isn’t the case (i.e. no readings are being received), it will lock out and display the relevant fault code.
Is my boiler dangerous if it’s showing the 240 or 241 cause code?
As the thermistor has been damaged, or is faulty, there’s no way to tell what temperature the water via the flow is running at. That’s why the boiler locks out, as a safety precaution.
If your boiler hasn’t locked out, it’s advisable to turn off your central heating and hot water, turn off the appliance, and wait for a boiler engineer to find and fix the problem.
How would the NTC thermistor get water damaged?
Usually we find that electronic components in a boiler get water damage from either a leaking heat exchanger, or a leaking boiler pump.
These are separate issues to the D1 fault code. Whilst they may have contributed to the D1 code being shown, the damage has already been done. So, fixing these components won’t clear the D1 code; both issues need to be dealt with separately.
Can the NTC thermistor on the return be fixed to clear the D1 fault code on my Worcester boiler?
The pump/heat exchanger needs to be fixed so that they’re no longer leaking.
Your boiler engineer will need find and fix the leak, ensuring the pump/heat exchanger are functional. They’ll then need to diagnose the fault with the NTC thermistor.
If it’s loose connections that are causing the issue, these can easily be re-secured.
However, we tend to find that replacing the NTC thermistor is a better option, as the part itself is relatively cheap.
Why do connections come loose on the NTC thermistors?
All boilers, particularly older ones, will vibrate.
These vibrations over time can cause parts to work themselves free, including the connections to the NTC thermistors.
My boiler is showing the D1 286 cause code, what does it mean?
This is a more common cause of the D1 fault code. When the 286 cause code is displayed, it’s highlighting an issue whereby the return pipe water on the boiler is too hot.
Boilers pump out hot water. Radiators, towel rails and pipework will absorb some of this heat, meaning that when the water returns to the boiler, it’s going to be much cooler.
The NTC thermistor on the return is looking for a differential in temperature between the flow and return readings.
When this is minimal (i.e. the return is too hot), it will send the signal to the printed circuit board, which will then shut the boiler down.
What can cause the return pipe to get too hot?
Generally, we’d be looking at anything that moderates the flow of the water in your heating system.
Heating components that moderate flow include the:
- Heating pump
- Lockshield valves
- TRVs/li>
How could the heating pump be contributing to the D1 286 cause code?
The heating pump is usually the culprit here.
Most modern heating pumps will have a speed/flow rate setting on them. For example, many Grundfos pumps have three speed settings.
The highest of these settings is designed to be used in large properties with a long heating run and lots of radiators.
The lowest of these settings is designed to be used in much smaller properties with fewer radiators.
So, if you have a small property and the flow rate is set on the maximum, hot water is rushing around the system too quickly. It’s not allowing the radiators to absorb the heat and therefore, the return temperature is too hot.
In this scenario, the engineer will first need to determine this is the case. If it is, they can reduce the flow rate to suit your property. This means water flows slower, allowing heat to be extracted and the return pipe/water temperature will then drop.
How can lockshields and TRVs cause the D1 286 fault code to occur?
The pump moderates the flow of water out of the boiler, but the lockshield and TRV valves moderate the flow into each radiator.
First, your engineer will need to check your radiators are correctly balanced. If they’re not, they could be allowing too much water flow.
Next, they’ll need to check the operation of each valve.
If your valves are particularly old, there’s a good chance they are seized. If they are stuck open, the water will rush through radiators so quickly, it might as well be bypassing them.
So, a combination of radiator balancing and replacement valves (where necessary) will help to clear the D1 286 fault code in this case.
Other Worcester boiler issues
More more boiler issue regarding the Worcester Bosch the please visit the Worcester Boiler Problems And Cures page.