Vaillant Turbomax, high CH temperature fluctuation

[fluorescence]

Hi all,

My Vaillant Turbomax 828e seems to be doing an odd thing with the way it heats the central heating (CH) circuit as follows:

• CH demand from thermostat, boiler fires up ok
• CH circuit heats up as it should until the temperature display on the boiler reaches the setpoint (currently set to 65°C)
• The burners then cut out and the pump keeps running circulating flow as it should, this is where the issue begins....
• The boiler then merely circulates like this for a long time without firing up the burners again, reaching a temperature readout of well below 40°C before the burners eventually fire up again. By this point the radiators in the house barely feel warm, obviously affecting the temperature rise in the property that should be happening!

My question; is this normal, and if not is there a setting to adjust to make the temperature fluctuate less?

Many thanks in advance.

 

[CBW]

Hello,

No this doesn’t seem “normal”. Do you have a room thermostat? If so what’s this set to? and where isit located? Has it always behaved like this?

 

[fluorescence]

Room Thermostat (Hive) is set up ok and CH demand is active.

We've had the boiler serviced since writing this and the engineer changed the pump speed from 2 to 3 which seems to have helped somewhat, I still think the 'run on' (if that's what it is?) Is too long, but it's a lot better than it was!