If your Viessmann boiler won’t fire up, there could be a few reasons:

Central Heating Works but No Hot Water

If your heating is working but there’s no hot water, there could be a fault with the diverter valve. The diverter valve on Viessmann boilers opens and closes depending on whether hot water is being called for by your taps or radiators. A broken diverter valve is a job for a professional boiler engineer. 

Low Boiler Pressure

Low boiler pressure will stop your central heating from functioning properly. If you’re finding that you have to keep re-pressurising your boiler, there may be a leak in your heating system.  It could be something as simple as a loose radiator valve, but more serious problems such as a broken internal component could cause your boiler to short circuit.  It’s always best to seek expert advice from a qualified engineer. WaterGuys will diagnose where the leak is and fix it promptly. 

Blocked Condensate Pipe

A blocked condensate pipe often happens when temperatures plummet. The waste gas produced by Viessmann condensing boilers turns to water as it cools and is drained outside to the condensate pipe. In very cold conditions, this water can freeze and block the pipe. It’s a fairly simple job to thaw the pipe and doesn’t normally require an engineer visit.

Viessmann Boiler Overheating

Occasionally, as with any other make, Viessmann boilers can overheat and shut down.  The built-in safety features will prevent anything dangerous happening but it is essential to find out why the boiler overheated and rectify the problem. The most common causes of a boiler overheating are: