Viesmann boiler operation query

11 Jan 2015
Reaction score
United Kingdom
Hi all

Have finally replaced our ancient floor standing conventional boiler with a wall mounted open vented condensing boiler from Viesmann (35kW - Vitodens 100-W Open Vent).

It has been in for a day now and I have noticed that instead of just maintaining a steady burning state it keeps on going silent every say 10-15 minutes for 5 minutes and then slowly starts up again. The programmer and thermostat are both calling for heat.

Is this normal behavior ?

A few other points. We have kept the Horstmann programmer from our old system and also the Honeywell Thermostat and all other piping & zone valves etc. We have bought the climate sensor but it is not yet installed and we have not got the Viesmann Room Thermostat

The installer is coming back on Monday but I don't want to hassle him before then. He has been great but is under great pressure from many of his customers who have heating problems in this horrific weather. Yesterday his mobile hardly stopped and all I heard all day was "is it showing a fault code ?" Most of these were frozen condensate pipes apparently.

Any comments would be welcome.
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Please ignore the above post as it seems to have settled down with a constant droning noise. It could be that had turned the temperature control knob up too high and close to Reset.

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