Some boiler and heating issues are simple and can be sorted at home by you, without an engineer.
If you’re not confident or suspect there may be a fault with your boiler or central heating system, do call us out.
0 operation mode
The boiler is in standby mode awaiting for the central heating or hot water to be switched on
C operation mode
The central heating has been switched on but the boiler has already reached the desired temperature set.
D operation mode
The boiler has a call for hot water but the appliance has reached the desired temperature set on the boiler.
C operation mode, burner on
The boiler is operating in central heating mode.
D operation mode, burner on
The boiler is operating in hot water mode.
F operation mode, burner on
The boiler is operating in frost mode.
The boiler display will flash a warning triangle and fault code. At the same time a (static) cause code will also be displayed. Manual intervention (Pressing the reset button on the boiler fascia) is required following clearance of the fault.
The boiler will stop operating with no fault data displayed. The cause code, in the info menu, is accessed by pressing the spanner/return button. The condition will clear automatically when the associated fault clears e.g. waiting for an area to cool. In some cases a blocking error has a defined time duration prior to changing to a locking condition.
Alpha numeric code indicating the fault group.
Three digit number. During a blocking error (or normal operating status) it is not displayed, but accessed in the info menu via the spanner/return button. During a locking error the cause code flashes on the display.
These are displayed with the letter H followed by a number. The code advises of a situation that will need some attention but is not a fault that will stop the boiler from functioning. Some of the common ones are listed:
Hot water outlet sensor defect, hot water can still be delivered but with less control.
H13 A time has been set in the Service interval function i.e. 1 to 72 months and that time has expired. Menu 2.5F allows this feature to be set (1 to 72), a 0 will disable this function.
Viessmann have a total of 58 fault codes on their website. Instead of listing all of these on our website we thought it would be easier for you to follow a link to their website. Depending on what Viessmann boiler you have, the diagnosis for the code may differ so they have organised each fault code to the boiler model it may appear on with the system behaviour and the diagnosis.
Click the link below for all Viessmann Fault & Status codes:
The water from combi boilers is heated directly from the mains, so the only time the water is released to the atmosphere is when it comes out of the tap. This means that during heating, the calcium bicarbonate which is present in the water changes to calcium carbonate. This creates carbon dioxide, which is seen as millions of bubbles when viewed close up. It is not sediment and is not harmful. If you run some hot water into a glass and let it cool, it will slowly clear.
We recommend the use of suitable water treatment in the form of an inhibitor to the heating water system, in accordance with the water treatment manufacturer’s instructions. The concentration level of the water inhibitor should be checked every 12 months or sooner if system content is lost.
There are times when a white plume or discharge can be seen coming from the flue terminal on condensing boilers. This is due to the flue gases being cooler than in non-condensing boilers. With standard efficiency (non-condensing) boilers, flue gases are hotter and cool down further away from the flue’s terminal and dissipate differently. The flue gases of condensing boilers exhaust at around 55ºC, cool quicker in the atmosphere and in certain outside temperatures cause a plume similar in effect to breath on a cold morning.
Upgrading to a condensing boiler can offer the following benefits:
We don’t need you to be there when the work is being carried out, but we ask that you make yourself available for at least one hour at the start and end of the work. This will enable our heating engineer to confirm all the details of the installation before we start and show you the benefits of your heating system when it is finished.
This will depend on how complex your heating system is, but we will give you an estimate before the work begins.
Your gas, electricity and cold water supply can normally be isolated in the areas where we are working, so you should be able to use these utilities for most of the time.